d World Of Nano Technology

Step Forward For Nanotechnology: Controlled Movement Of Molecules

2009-10-02T00:06:00.001-07:00

In a step forward for nanotechnology, scientists are reporting an advance that allows the controlled movement of individual molecules without help from outside forces. Shown is a model of the atomic structure of a silicon nanocrystal.
Scientists in the United Kingdom are reporting an advance toward overcoming one of the key challenges in nanotechnology: Getting molecules to move quickly in a desired direction without help from outside forces.
Their achievement has broad implications, the scientists say, raising the possibility of coaxing cells to move and grow in specific directions to treat diseases. It also could speed development of some long-awaited nanotech innovations. They include self-healing structures that naturally repair tears in their surface and devices that deliver medication to diseased while sparing healthy tissue.

The study is scheduled for the October issue of ACS Nano, a monthly journal.

Mark Geoghegan and colleagues note long-standing efforts to produce directed, controlled movement of individual molecules in the nano world, where objects are about 1/50,000ththe width of a human hair. The main solutions so far have involved use of expensive, complex machines to move the molecules and they have been only partially successful, the scientists say.

The scientists used a special surface with hydrophobic (water repelling) and hydrophilic (water-attracting) sections. The region between the two sections produced a so-called "energy gradient" which can move tiny objects much like a conveyor belt. In lab studies, the scientists showed that plastic nanoparticles (polymer molecules) moved quickly and in a specific direction on this surface. "This could have implications in many technologies such as coaxing cells to move and grow in given directions, which could have major implications for the treatment of paralysis," the scientists said

Better Control Of Carbon Nanotube 'Growth' Promising For Future Electronics

2009-10-01T23:57:00.000-07:00

Researchers have learned how to more fully control the formation of carbon nanotubes so that they have either metallic or semiconducting properties. The findings could help overcome a major obstacle in efforts to use the tiny structures to create a new class of electronics that would be faster and smaller than conventional silicon-based transistors. The researchers learned that if helium is used instead of argon in the formation of nanotubes, tiny iron catalyst particles have a specific size and shape and also have pronounced facets, shown in this electron microscope image. The facets apparently are related to the creation of the metallic nanotubes.
Researchers have overcome a major obstacle in efforts to use tiny structures called carbon nanotubes to create a new class of electronics that would be faster and smaller than conventional silicon-based transistors.

Carbon nanotubes, which were discovered in the early 1990s, could make possible more powerful, compact and energy-efficient computers, as well as ultra-thin "nanowires" for electronic circuits. The nanotubes might be ideal for future electronics because they conduct electricity more efficiently than any other metal, but their practical application requires that they be manufactured to specific standards.

Now scientists in the Materials Science Division at the Honda Research Institute USA Inc., Purdue University and the University of Louisville have learned how to control the formation of carbon nanotubes so that they have either metallic or semiconducting properties.

"This problem of how to control whether you have a metal or a semiconductor is the key stumbling block in making transistors out of carbon nanotubes," said Eric Stach, an associate professor of materials engineering at Purdue. "Solid-state electronics is built around the fact that you can control the semiconducting properties of silicon."

Findings will be detailed in a research paper appearing Oct. 2 in the journal Science. The research is led by Avetik Harutyunyan, principal scientist at the Honda Research Institute USA Inc. in Columbus, Ohio.

"This is the first report that shows we can control pretty systematically whether carbon nanotubes are metallic or semiconducting," Harutyunyan said. "We have a 91 percent success rate of producing metallic nanotubes."

Silicon-based transistors control the flow of electrons by using specific combinations of metals and semiconductors. Researchers are working to learn how to precisely control the properties of carbon nanotubes so that they can be used as both the semiconductor and metal components of transistors.

"Generally, carbon is not a metal, but carbon nanotubes with a particular configuration are," Stach said.

Semiconductors, such as silicon, sometimes behave as conductors and sometimes as insulators, whereas metals always behave as conductors. Researchers have known for several years that carbon nanotubes randomly form so that they are sometimes metallic and sometimes semiconductor, but until now they have not known the precise reasons why.

Carbon nanotubes can be visualized as sheets of carbon atoms one layer thick and rolled up into tubes. Much like the pitch of a screw, they can have a different configuration depending on how they roll up, and this configuration determines whether they conduct like a metal or a semiconductor.

The nanotubes are "grown" in a vacuum chamber by exposing iron particles to methane gas. The gas contains carbon and hydrogen, and the iron particles act as a catalyst to liberate carbon from the gas. The particles are heated to about 800 degrees Celsius, or more than 1,400 degrees Fahrenheit. With increasing exposure, the iron eventually contains too much carbon and becomes "supersaturated." As a result, the carbon precipitates as a solid, causing the nanotube to begin forming.

Honda researchers learned recently that they could control whether the carbon nanotubes become metal or semiconductor by using either argon or helium as "carrier gases" to aid in flowing the methane into the chamber in the presence of water.

Researchers at Louisville used the technique to produce large quantities of nanotubes and made careful electrical measurements to confirm whether the nanotubes were metallic or semiconductor.

Purdue researchers took high-resolution images using an instrument called a transmission electron microscope to determine why the process works.

"The instrument enables you to take images while the nanotubes are forming," Stach said. "We can see the atomic structure of the materials while also looking at how the environment affects them."

The Purdue portion of the research is based at the Birck Nanotechnology Center in the university's Discovery Park.

"These findings provide a window into the intimate relationship between the atomic structure of the catalyst nanoparticle and the carbon nanotube that grows from that catalyst nanoparticle," said Timothy D. Sands, the Mary Jo and Robert L. Kirk Director of the Birck Nanotechnology Center. "The results also show that the atomic structure of the catalyst nanoparticle can be controlled by the ambient carrier gas, a linkage that may represent the first step toward a solution to one of the most vexing challenges in nanotechnology."

The Purdue researchers learned that if helium is used instead of argon, the iron particles have a specific size and shape and also have pronounced facets, but the facets diminish and the particle size varies when argon is used.

"The facets form nearly at right angles, but when you switch from helium to argon those facets round out," Stach said. "The helium and the presence of these strong facets, together with the size of the iron particles, appears to be what allows the creation of the metallic nanotubes.

"Our results indicate that you might be able to control the size and shape of the catalyst sufficiently to control the structure and thus the conductivity of the nanotubes. It is the first demonstration of a deterministic relationship between the catalyst state and the resulting nanotube structure."

Researchers aren't sure what role the water plays in the process.

"The water might promote the formation of the facets, and the argon might somehow prevent the water from doing so, but more research is needed to determine this," Stach said.

The work is ongoing and is funded by Honda.

The paper was written by Honda researchers Harutyunyan, Gugang Chen, Elena M. Pigos and Oleg A. Kuznetsov; Louisville researchers Tereza M. Paronyan, Gamini U. Sumanasekera and Kapila Hewaparakrama; and Purdue researchers Seung Min Kim, Dmitri Zakharov and Stach.

Nanotech Particles Affect Brain Development In Mice

2009-08-02T02:30:00.000-07:00

Two nine day old baby mice. Maternal exposure to nanoparticles of titanium dioxide (TiO2) affects the expression of genes related to the central nervous system in developing mice. Researchers found that mice whose mothers were injected with the nanoparticles while pregnant showed alteration in gene expression related to neurological dysfunction
Maternal exposure to nanoparticles of titanium dioxide (TiO2) affects the expression of genes related to the central nervous system in developing mice. Researchers found that mice whose mothers were injected with the nanoparticles while pregnant showed alteration in gene expression related to neurological dysfunction.
Ken Takeda led a team of researchers from the Tokyo University of Science, Japan, who carried out the tests. He said, "Nanotechnology and the production of novel man-made nanoparticles are increasing worldwide. Titanium dioxide in its nanoparticle form has a high level of photocatalytic activity, and can be used for air and water purification and self-cleaning surfaces. Our findings, however, add to the current concern that this specific nanomaterial may have the potential to affect human health".

For this study, the researchers injected pregnant mice with Ti02 nanoparticles. The brains were obtained from male fetuses/pups on the 16th day of gestation and at several points after birth. Comparing these brains to those of control animals, the researchers were able to demonstrate changes in expression of hundreds of genes. According to Takeda, "Diseases associated with these genes include those we normally consider to develop in childhood, such as autistic disorder, epilepsy and learning disorders, and also others that arise mainly in adulthood or old age, such as Alzheimer's disease, schizophrenia and Parkinson's disease."

Nanotechnology deals with engineering at the molecular scale. Materials reduced to nanoparticles behave in ways dissimilar to those we're used to - altering their reactivity, surface area to volume and any number of other properties. While larger TiO2 particles are commonly used in paints and sunblocks, nanoparticles of TiO2 are specially created for new applications in coatings and self-cleaning surfaces and their effects on living tissue are only beginning to be understood. It should be noted that this gene expression data cannot be interpreted as a direct health effect. In addition, the nanoparticles were deliberately injected at a high dose, so the relevance to real-life exposure may be limited.

Nanotubes Spin As They Grow

2009-08-02T02:27:00.000-07:00

Researchers at Rice University and France's Université Lyon1/CNRS have found nanotubes spin as they grow
New video showing the atom-by-atom growth of carbon nanotubes reveals they rotate as they grow, much like the halting motion of a mechanical clock's second hand.
Published online this month in the American Chemical Society's journal Nano Letters by researchers at France's Université Lyon1/CNRS and Houston's Rice University, the research provides the first experimental evidence of how individual carbon atoms are added to growing nanotubes.

"The key issue for realizing the potential of carbon nanotubes has always been better control of their growth," said team lead Stephen Purcell of the Université Lyon1/CNRS. "Our findings offer new insights for better measurement, modeling and control of nanotube growth."

Carbon nanotubes are long, hollow cylinders of pure carbon. They are hair-like in shape but are about 100,000 times smaller than human hair. They are also about six times stronger than steel, conduct electricity as well as copper and are almost impervious to radiation and chemical destruction. As a result, scientists are keen to use them in superstrong, "smart" materials, but they need to better understand how to produce them.

"The images from Dr. Purcell's lab show the atom-by-atom 'self assembly' of a nanotube," said Rice co-author Boris Yakobson, professor in mechanical engineering and materials science and of chemistry. "The video offers compelling evidence of the rotational motion that accompanies nanotube growth. It brings to mind Galileo's famous quote, 'And yet, it does turn.'"

In February, Yakobson offered a new theory suggesting that nanotubes grow like tiny, woven tapestries, with new atoms attaching to twisting atomic threads. The new video appears to support the theory, indicating that atoms are added in pairs as the tube spins and grows.

To create the images, Purcell's team at LPMCN (Laboratoire de Physique de la Matière Condensée et Nanostructures) used a field emission microscope (FEM). A few atoms of metal catalyst were placed on the tip of the FEM's needle-like probe, and carbon nanotubes grew atop the metal catalyst. An electric current was passed lengthwise through the probe and nanotube, and it projected a bright, top-down image of the nanotube onto a phosphor screen. The bright spot was filmed by a video camera, which revealed the nanotube's rotation during growth.

In one case, a nanotube turned approximately 180 times during its 11-minute growth. A frame-by-frame analysis of the video showed that the rotation proceeded in discrete steps -- much like the halting motion of the second hand on a mechanical clock -- with about 24 steps per rotation.

"The results support our predictions of how nanotubes grow," Yakobson said. "The video shows rotational movement during growth, as carbon atoms are added in pairs to the twisting, chiral network of carbon atoms that comprise the nanotube."

Co-authors include Mickaël Marchand, Catherine Journet, Dominique Guillot and Jean-Michel Benoit, all of Université Lyon. The research was supported by the Programme en Nanosciences et Nanotechnologies of France's L'Agence Nationale de Recherche, the National Science Foundation and the Air Force Research Laboratory.

Breakdown In Planck's Law: Bringing Objects Close Together Can Boost Radiation Heat Transfer

2009-08-02T02:24:00.000-07:00

Professor Gang Chen with the vacuum chamber used in this research.
A well-established physical law describes the transfer of heat between two objects, but some physicists have long predicted that the law should break down when the objects are very close together. Scientists had never been able to confirm, or measure, this breakdown in practice. For the first time, however, MIT researchers have achieved this feat, and determined that the heat transfer can be 1,000 times greater than the law predicts.
The new findings could lead to significant new applications, including better design of the recording heads of the hard disks used for computer data storage, and new kinds of devices for harvesting energy from heat that would otherwise be wasted.

Planck's blackbody radiation law, formulated in 1900 by German physicist Max Planck, describes how energy is dissipated, in the form of different wavelengths of radiation, from an idealized non-reflective black object, called a blackbody. The law says that the relative thermal emission of radiation at different wavelengths follows a precise pattern that varies according to the temperature of the object. The emission from a blackbody is usually considered as the maximum that an object can radiate.

The law works reliably in most cases, but Planck himself had suggested that when objects are very close together, the predictions of his law would break down. But actually controlling objects to maintain the tiny separations required to demonstrate this phenomenon has proved incredibly difficult.

"Planck was very careful, saying his theory was only valid for large systems," explains Gang Chen, MIT's Carl Richard Soderberg Professor of Power Engineering and director of the Pappalardo Micro and Nano Engineering Laboratories. "So he kind of anticipated this [breakdown], but most people don't know this."

Part of the problem in measuring the way energy is radiated when objects are very close is the mechanical difficulty of maintaining two objects in very close proximity, without letting them actually touch. Chen and his team, graduate student Sheng Shen and Columbia University Professor Arvind Narayaswamy, solved this problem in two ways, as described in a paper to be published in the August issue of the journal Nano Letters (available now online). First, instead of using two flat surfaces and trying to maintain a tiny gap between them, they used a flat surface next to a small round glass bead, whose position is easier to control. "If we use two parallel surfaces, it is very hard to push to nanometer scale without some parts touching each other," Chen explains, but by using a bead there is just a single point of near-contact, which is much easier to maintain. Then, they used the technology of the bi-metallic cantilever from an atomic-force microscope to measure the temperature changes with great precision.

"We tried for many years doing it with parallel plates," Chen says. But with that method, they were unable to sustain separations of closer than about a micron (one millionth of a meter). By using the glass (silica) beads, they were able to get separations as small as 10 nanometers (10 billionths of a meter, or one-hundredth the distance achieved before), and are now working on getting even closer spacings.

Professor Sir John Pendry of Imperial College London, who has done extensive work in this field, calls the results "very exciting," noting that theorists have long predicted such a breakdown in the formula and the activation of a more powerful mechanism.

"Experimental confirmation has proved elusive because of the extreme difficulty in measuring temperature differences over very small distances," Pendry says. "Gang Chen's experiments provide a beautiful solution to this difficulty and confirm the dominant contribution of near field effects to heat transfer."

In today's magnetic data recording systems - such as the hard disks used in computers - the spacing between the recording head and the disk surface is typically in the 5 to 6 nanometer range, Chen says. The head tends to heat up, and researchers have been looking for ways to manage the heat or even exploit the heating to control the gap. "It's a very important issue for magnetic storage," he says. Such applications could be developed quite rapidly, he says, and some companies have already shown a strong interest in this work

The new findings could also help in the development of new photovoltaic energy conversion devices to harness photons emitted by a heat source, called thermophovoltaic, Chen says. "The high photon flux can potentially enable higher efficiency and energy density thermophovoltaic energy converters, and new energy conversion devices," he says.

The new findings could have "a broad impact," says Shen. People working with devices using small separations will now have a clear understanding that Planck's law "is not a fundamental limitation," as many people now think, he says. But further work is needed to explore even closer spacings, Chen says, because "we don't know exactly what the limit is yet" in terms of how much heat can be dissipated in closely spaced systems. "Current theory will not be valid once we push down to 1 nanometer spacing."

And in addition to practical applications, he says, such experiments "might provide a useful tool to understand some basic physics."

The work was funded by the U.S. Department of Energy and the Air Force Office of Scientific Research.

New Method To Encapsulate Substances In Nanospheres

2009-07-17T05:36:00.000-07:00

Nanoparticles. Encapsulating substances and then controlling when and how much is released is one of the most recently developed strategies in the fields of chemistry, medicine, material science and environmental technologies.
A group of researchers at the Catalan Institute of Nanoscience and Nanotechnology (CIN2), belonging to the Catalan Institute of Nanotechnology and the Spanish National Research Council (CSIC) located at the UAB Research Park, and the UAB Department of Chemistry have developed and patented a method which obtains minute organometallic capsules ranging from micrometric to nanometric sizes. These will encapsulate substances in nanospheres containing intrinsic metal properties, such as magnetism, fluorescence or conductivity, which could be useful when applied to radiodiagnostics, electronics or sensors.
Encapsulating substances and then controlling when and how much is released is one of the most recently developed strategies in the fields of chemistry, medicine, material science and environmental technologies. This strategy pursues the idea of the "magic bullet", which has been discussed for a long time, especially in the field of medicine: being able to transport therapeutic substances to the specific place where they are needed.

Until now this technique was possible with liposomes (commonly used in cosmetics), dendrimers (polymeric macromolecules) or polymeric organic particles. In these cases, the capsules are formed by organic molecules. However, encapsulating substances within metal-containing particles had not been achieved until now.

And that is precisely what has been done by the research group at the Catalan Institute of Nanoscience and Nanotechnology (CIN2) - belonging to the Catalan Institute of Nanotechnology and the Spanish National Research Council (CSIC) located at the UAB Research Park - and the UAB Department of Chemistry. Researchers have developed and patented a method to obtain minute organometallic capsules (i.e. formed by a partially organic, partially metallic material) ranging from micrometric to nanometric sizes. The incorporation of metal implies that the nanospheres will contain intrinsic metal properties, such as magnetism, fluorescence or conductivity, which can be useful in medical applications, e.g. radiodiagnostics, electronics or sensors.

The authors of this method are Daniel Maspoch, Inhar Imaz, and Daniel Ruiz-Molina, researchers of the NanoStructured Functional Materials (NanoSFun) group at CIN2, and Jordi Hernando, researcher at the UAB Department of Chemistry. Their names are all included in the article which will be published in the journal Angewandte Chemie International Edition, and which can be found online as one of the journal's highlights.

Efficient and easily scalable method

The method allows for the creation of micro and nanospheres by joining two units: an organic or binding molecule, which acts as an "adhesive", and a metal ion. Generally, the organic molecule shares an electron pair with a metal ion and this gives them the tendency to join. Described simply, the method consists in mixing a solution made up of metal ions, organic molecules and the active principle which is to be encapsulated. When the solution is shaken, either mechanically or with ultrasounds, the metal ions join the organic molecules to form spheres, thus capturing within them the active principle present in the solution. The system is therefore relatively simple and does not present any particular problems with regard to its use at industrial level.

"This simplicity however does not mean that it cannot be used for a variety of purposes. Depending on the composition of the mixture, its concentration, how fast and how long it is shaken, and the speed at which each of the components is added, the size of the nanospheres can be varied, as can characteristics such as the fluorescence or porosity. All these factors can be controlled and varied depending on which application is needed. Thus, porosity is relevant in nanospheres which are programmed to release the substance they contain through the capsule's pores," scientists explain.

In many other cases however, the substance is released during the degradation of the nanosphere, which "disintegrates" at a specific moment (which can also be programmed) and liberates its contents. The units forming the nanosphere (metal ion and organic molecule) can also be changed depending on the type of application desired. Thus, a hypothetic application could be made up of a sphere containing gadolinium, which would enable it to be used as a contrasting agent in radiodiagnostics and at the same time transport the active principal directly to the cells which need to be treated, thanks to the incorporation of an antibody which would detect target cells.

The possibilities are almost unlimited and the selection of molecules not only will depend on the application but on the stability that is expected from the sphere. In the article researchers detail the results achieved with spheres formed with zinc which, according to laboratory tests, can be maintained stable when stored in alcohol for five or six months. This period is reduced to a few days when they are stored in water or blood. Scientists explain that they are nevertheless working on making them more stable.

The advantage of encapsulation versus conventional drug administration processes resides in the fact that it limits the number of side effects by selectively releasing the drug in the specific area where the treatment is needed. Therefore, the amount of drug required is reduced and the necessary levels of the drug are maintained for a longer period of time. This strategy is already being applied to treatments for cancer and other lung diseases. It is calculated that in the United States alone, this business moved approximately 117 billion dollars in the year 2000, a figure which is expected to rise to 366 billion dollars in 2010.

New Optical Forces Revealed

2009-07-15T11:16:00.000-07:00

Using advanced fabrication technologies, including DUV (Deep Ultraviolet) lithography and critical-point-drying, the researchers created two parallel waveguides on a silicon-on-insulator chip. The waveguides are freestanding, acting as movable strings. They have a width of 445nm, a height of 220nm, a length of approximately 25µm and they are separated by a 220nm gap.
The University of Ghent (UGent) and the nanoelectronics research center IMEC demonstrated repulsive and attractive nanophotonic forces, depending on the spatial distribution of the light used. These fundamental research results might have major consequences for telecommunication and optical signal.
Photon impulse is usually considered to be relatively weak. In our macroscopic world, photons bumping into an object exert an almost negligible force on this object. Nevertheless, this picture changes dramatically when the object size is shrunk to nanoscale dimensions. When light is confined to very small cross-sections and large gradients exist in the spatial field distribution of the light, the optical gradient force induced per photon increases dramatically.

Using advanced fabrication technologies, including DUV (Deep Ultraviolet) lithography and critical-point-drying, the researchers created two parallel waveguides on a silicon-on-insulator chip. The waveguides are freestanding, acting as movable strings. They have a width of 445nm, a height of 220nm, a length of approximately 25µm and they are separated by a 220nm gap.

By sending laser light through the waveguides the researchers generated optical forces between them. Depending on the spatial distribution of the light (both in amplitude and phase) the strings were attracting or repulsing each other. The repulsive force that had never been demonstrated before makes this experiment of fundamental scientific importance.

The experiment might eventually have a major impact to achieve very high speed telecommunication for optical forces provide an interesting option for implementing all-optical signal processing functions on a chip. All-optical routing is one of the key challenges in developing faster communication networks (such as the internet) and the new technique opens up new routes towards solutions for this bottleneck.

Strong Freestanding Nanoparticle Films Created Without Fillers

2009-06-21T02:11:00.000-07:00

Image of the surface of an iron oxide nanoparticle film made with an atomic force microscope that shows individual nanoparticles.
Nanoparticle films are no longer a delicate matter: Vanderbilt physicists have found a way to make them strong enough so they don’t disintegrate at the slightest touch.
In the last 25 years, ever since scientists figured out how to create nanoparticles – ultrafine particles with diameters less than 100 nanometers – they have come up with a number of different methods to mold them into thin films which have a variety of interesting potential applications ranging from semiconductor fabrication to drug delivery, solid state lighting to flexible television and computer displays.

Until now these films have had a common problem: lack of cohesion. Nanoparticles typically consist of an inorganic core coated with a thin layer of organic molecules. These particles are not very sticky so they don’t form coherent thin films unless they are encapsulated in a polymer coating or mixed with molecules called chemical “cross-linkers” that act like glue to stick the nanoparticles together.

“Adding this extra material can complicate the fabrication of nanoparticle films and make them more expensive. In addition, the added material, usually a polymer, can modify the physical properties that make these films so interesting,” says James Dickerson, assistant professor of physics at Vanderbilt, who headed the research group that created the freestanding nanoparticle films without any additives.

The properties of the new films and the method that the researchers use to create them is described in the article “Sacrificial layer electrophoretic deposition of freestanding multilayered nanoparticle films” published online in the journal Chemical Communications on May 27, 2009.

“Our films are so resilient that we can pick them up with a pair of tweezers and move them around on a surface without tearing,” says Dickerson. “This makes it particularly easy to put them into microelectronic devices, such as computer chips.”

Dickerson considers the most straightforward applications for his films to be in semiconductor manufacturing to aid in the continued miniaturization of digital circuitry and in the production of flexible television and computer screens.

A key component in the transistors in integrated circuits is an insulating layer that separates the gate, which turns current flow on and off, from the channel through which the current flows. Traditionally, semiconductor manufacturers have used silicon dioxide for this purpose. As transistors have shrunk, however, they have been forced to make this layer thinner and thinner until they reached the point where electrons leak through and sap the power from the device. This has led semiconductor manufacturers to retool their process to use “high-k” dielectric materials, such as hafnium oxide, because they have much higher electrical resistance.

“We have made high-k nanoparticle films that could be cheaper and more effective than the high-k materials the manufacturers are currently using,” Dickerson says.

In addition, the physicist argues that the films have properties that make them ideal for flexible television and computer screens. They are very flexible and don’t show any signs of cracking when they are flexed repeatedly. They are also made using a technique called electrophoretic deposition (EPD) that is well suited for creating patterned material and is compatible with fluorescent materials that can form the red, green and blue pixels used in flat panel television screens and computer displays.

EDP is a wet method. Nanoparticles are placed in a solution along with a pair of electrodes. When an electric current is applied, it creates an electrical field in the liquid that attracts the nanoparticles, which coat the electrodes. Using colloids, mixtures with particles 10 to 1,000 times larger than nanoparticles, EDP is widely used to apply coatings to complex metal parts such as automobile bodies, prosthetic devices, appliances and beverage containers. It is only recently that researchers like Dickerson have begun applying the technique to nanoparticles.

“The science of colloidal EDP is well known but the particles are substantially larger than the solvent molecules. Many nanoparticles, however, are about the same size as the solvent molecules, which makes the process considerably more complicated and difficult to control,” Dickerson explains.

To get the method to work, in fact, Dickerson and his colleagues had to invent of new form of EDP, which they call sacrificial layer electrophoretic deposition. They added a spun-cast layer of polymer to the electrodes that serves as a pattern that organizes the nanoparticles as they are deposited. Then, after the deposition process is completed, they dissolve (sacrifice) the polymer layer to free the nanoparticle film.

According to the researchers, films made in this fashion stick together because the electrical field slams the nanoparticles into the film with sufficient force to pack the particles together tightly enough to allow naturally attractive inter-particle forces to bind the particles together.

So far the Dickerson group has used the technique to make films out of two different types of nanoparticles – iron oxide and cadmium selenide – and they believe the technique can be used with a wide variety of other nanoparticles.

“The technique is liberating because you can make these films from the materials you want and use them where you want,” Dickerson says.

The co-authors on the paper are graduate students Saad A. Hasan and Dustin W. Kavich. The research was funded by a grant from Vanderbilt University.

New Nanoparticles Could Lead To End Of Chemotherapy

2009-06-16T23:05:00.000-07:00

Dr. Manuel Perez and his team have been investigating the use of nanoparticles for medicine for years.
Nanoparticles specially engineered by University of Central Florida Assistant Professor J. Manuel Perez and his colleagues could someday target and destroy tumors, sparing patients from toxic, whole-body chemotherapies.
Perez and his team used a drug called Taxol for their cell culture studies, recently published in the journal Small, because it is one of the most widely used chemotherapeutic drugs. Taxol normally causes many negative side effects because it travels throughout the body and damages healthy tissue as well as cancer cells.

The Taxol-carrying nanoparticles engineered in Perez's laboratory are modified so they carry the drug only to the cancer cells, allowing targeted cancer treatment without harming healthy cells. This is achieved by attaching a vitamin (folic acid) derivative that cancer cells like to consume in high amounts.

Because the nanoparticles also carry a fluorescent dye and an iron oxide magnetic core, their locations within the cells and the body can be seen by optical imaging and magnetic resonance imaging (MRI). That allows a physician to see how the tumor is responding to the treatment.

The nanoparticles also can be engineered without the drug and used as imaging (contrast) agents for cancer. If there is no cancer, the biodegradable nanoparticles will not bind to the tissue and will be eliminated by the liver. The iron oxide core will be utilized as regular iron in the body.

"What's unique about our work is that the nanoparticle has a dual role, as a diagnostic and therapeutic agent in a biodegradable and biocompatible vehicle," Perez said.

Perez has spent the past five years looking at ways nanotechnology can be used to help diagnose, image and treat cancer and infectious diseases. It's part of the quickly evolving world of nanomedicine.

The process works like this. Cancer cells in the tumor connect with the engineered nanoparticles via cell receptors that can be regarded as "doors" or "docking stations." The nanoparticles enter the cell and release their cargo of iron oxide, fluorescent dye and drugs, allowing dual imaging and treatment.

"Although the results from the cell cultures are preliminary, they are very encouraging," Perez said.

A new chemistry called "click chemistry" was utilized to attach the targeting molecule (folic acid) to the nanoparticles. This chemistry allows for the easy and specific attachment of molecules to nanoparticles without unwanted side products. It also allows for the easy attachment of other molecules to nanoparticles to specifically seek out particular tumors and other malignancies.

Perez's study builds on his prior research published in the prestigious journal Angewandte Chemie Int. Ed. His work has been partially funded by a National Institutes of Health grant and a Nanoscience Technology Center start-up fund.

"Our work is an important beginning, because it demonstrates an avenue for using nanotechnology not only to diagnose but also to treat cancer, potentially at an early stage," Perez said.

Perez, a Puerto Rico native, joined UCF in 2005. He works at UCF's NanoScience Technology Center and Chemistry Department and in the Burnett School of Biomedical Sciences in the College of Medicine. He has a Ph.D. from Boston University in Biochemistry and completed postdoctoral training at Massachusetts General Hospital, Harvard Medical School's teaching and research hospital.

Tunable Graphene Bandgap Opens The Way To Nanoelectronics And Nanophotonics

2009-06-12T03:41:00.000-07:00

One of the most unusual features of single-layer graphene (top) is that its conical conduction and valence bands meet at a point -- it has no bandgap. Symmetrical bilayer graphene (middle) also lacks a bandgap. Electrical fields (arrows) introduce asymmetry into the bilayer structure (bottom), yielding a bandgap (Δ) that can be selectively tuned.
Graphene is the two-dimensional crystalline form of carbon, whose extraordinary electron mobility and other unique features hold great promise for nanoscale electronics and photonics. But there's a catch: graphene has no bandgap.
"Having no bandgap greatly limits graphene's uses in electronics," says Feng Wang of the U.S. Department of Energy's Lawrence Berkeley National Laboratory, where he is a member of the Materials Sciences Division. "For one thing, you can build field-effect transistors with graphene, but if there's no bandgap you can't turn them off! If you could achieve a graphene bandgap, however, you should be able to make very good transistors."

Wang, who is also an assistant professor in the Department of Physics at the University of California at Berkeley, has achieved just that. He and his colleagues have engineered a bandgap in bilayer graphene that can be precisely controlled from 0 to 250 milli-electron volts (250 meV, or .25 eV).

Moreover, their experiment was conducted at room temperature, requiring no refrigeration of the device. Among the applications made possible by this breakthrough are new kinds of nanotransistors and – because of its narrow bandgap – nano-LEDs and other nanoscale optical devices in the infrared range.

The researchers describe their work in the June 11 issue of Nature.

Constructing a bilayer graphene transistor

As with monolayer graphene, whose carbon atoms are arranged in "chickenwire" configuration, bilayer graphene – which consists of two graphene layers lying one on the other – also has a zero bandgap and thus behaves like a metal. But a bandgap can be introduced if the mirror-like symmetry of the two layers is disturbed; the material then behaves like a semiconductor.

Previously, in 2006, researchers at Berkeley Lab's Advanced Light Source (ALS) observed a bandgap in bilayer graphene in which one of the layers was chemically doped by adsorbed metal atoms. But such chemical doping is uncontrolled and not compatible with device applications.

"Creating and especially controlling a bandgap in bilayer graphene has been an outstanding goal," says Wang. "Unfortunately chemical doping is difficult to control."

Researchers then tried to tune the bilayer graphene bandgap by doping the substrate electrically instead of chemically, using a perpendicularly applied, continuously tunable electrical field. But when such a field is applied with a single gate (electrode), the bilayer becomes insulating only at temperatures below one degree Kelvin, near absolute zero – suggesting a bandgap value much lower than predicted by theory.

Says Wang, "With these results it was hard to understand exactly what was happening electronically, or why."

Wang and his colleagues made two key decisions that led to their successful attempt to introduce and determine a bandgap in bilayer graphene. The first was to build a two-gated bilayer device, fabricated by Yuanbo Zhang and Tsung-Ta Tang of the UC Berkeley Department of Physics, which allowed the team to independently adjust the electronic bandgap and the charge doping.

The device was a dual-gated field-effect transistor (FET), a type of transistor that controls the flow of electrons from a source to a drain with electric fields shaped by the gate electrodes. Their nano-FET used a silicon substrate as the bottom gate, with a thin insulating layer of silicon dioxide between it and the stacked graphene layers. A transparent layer of aluminum oxide (sapphire) lay over the graphene bilayer; on top of that was the top gate, made of platinum.

The other key decision the researchers made was to get a better grasp of what was really going on in the device as they varied the voltage. Rather than try to measure the bandgap by measuring the device's electrical resistance, or transport, they decided to measure its optical transmission.

"The problem with transport measurements is that they are too sensitive to defects," says Wang. "A tiny amount of impurity or defect doping can create a big change in the resistance of the graphene and mask the intrinsic behavior of the material. That's why we decided to go with optical measurements at the Advanced Light Source."

Using infrared beamline 1.4 at the ALS, under the direction of ALS physicist Michael Martin and Zhao Hao of the Earth Sciences Division, Wang and his colleagues were able to send a tight beam of synchrotron light, focused on the graphene layers, right through the device. As the researchers tuned the electrical fields by precisely varying the voltage of the gate electrodes, they were able to measure variations in the light absorbed by the gated graphene layers. The absorption peak in each spectrum provided a direct measurement of the bandgap at each gate voltage.

"In principle we could have used a tunable laser to measure the optical transmission, but the 1.4 beamline is very bright and can be focused down to the diffraction limit – an important consideration when the graphene-flake target is so small," Wang says. "Also, compared to a laser, the beamline provides a wider range of frequencies all at once, so we don't have to painstakingly tune to each absorption frequency we're trying to measure."

The malleable electronic structure of bilayer graphene

The results from the ALS measurements were obtained with relative ease and efficiency, and showed that by independently manipulating the voltage of the two gates, the researchers could control two important parameters, the size of the bandgap and the degree of doping of the graphene bilayer. In essence, they created a virtual semiconductor from a material that is not inherently a semiconductor at all.

In ordinary semiconductors, the gap between the conduction band (unoccupied by electrons) the valence band (occupied by electrons) is finite, and fixed by the crystalline structure of the material. In bilayer graphene, however, as Wang's team demonstrated, the bandgap is variable and can be controlled by an electrical field. Although a pristine graphene bilayer has zero bandgap and conducts like a metal, a gated bilayer can have a bandgap as big as 250 milli-electron volts and behave like a semiconductor.

With precision control of its bandgap over a wide range, plus independent manipulation of its electronic states through electrical doping, dual-gated bilayer graphene becomes a remarkably flexible tool for nanoscale electronic devices.

Wang emphasizes that these first experiments are only the beginning. "The electrical performance of our demonstration device is still limited, and there are many routes to improvement, for example through extra measures to purify the substrate."

Nevertheless, he says, "We've demonstrated that we can arbitrarily change the bandgap in bilayer graphene from zero to 250 milli-electron volts at room temperature, which is remarkable in itself and shows the potential of bilayer graphene for nanoelectronics. This is a narrower bandgap than common semiconductors like silicon or gallium arsenide, and it could enable new kinds of optoelectronic devices for generating, amplifying, and detecting infrared light."

"Direct observation of a widely tunable bandgap in bilayer graphene," by Yuanbo Zhang, Tsung-Ta Tang, Caglar Girit, Zhao Hao, Michael C. Martin, Alex Zettl, Michael F. Crommie, Y. Ron Shen, and Feng Wang, appears in the June 11, 2009 issue of Nature. Zhang, Tang, and Girit are members of UC Berkeley's Department of Physics, in the groups of Professors Crommie, Shen, and Zettl respectively; Zettl, Crommie, and Shen are also members of Berkeley Lab's Materials Sciences Division.

Thinnest Superconducting Metal Ever Created

2009-06-12T03:36:00.000-07:00

This is a scanning tunneling microscope image of the 2-atom thick lead film. The inset is a zoomed view showing the atomic structure.
A superconducting sheet of lead only two atoms thick, the thinnest superconducting metal layer ever created, has been developed by physicists at The University of Texas at Austin.
Dr. Ken Shih and colleagues report the properties of their superconducting film in the June 5 issue of Science.

Superconductors are unique because they can maintain an electrical current indefinitely with no power source. They are used in MRI machines, particle accelerators, quantum interference devices and other applications.

The development of the thin superconducting sheets of lead lays the groundwork for future advancements in superconductor technologies.

"To be able to control this material—to shape it into new geometries—and explore what happens is very exciting," says Shih, the Jane and Roland Blumberg Professor in Physics. "My hope is that this superconductive surface will enable one to build devices and study new properties of superconductivity."

In superconductors, electrons move through the material together in pairs, called Cooper pairs.

One of the innovative properties of Shih's ultra-thin lead is that it confines the electrons to move in two dimensions, or one "quantum channel," like ballroom dancers gliding across the floor. Uniquely, the lead remains a good superconductor despite the constrained movement of the electrons through the metal.

Shih and his colleagues used advanced materials synthesis techniques to lay the two-atom thick sheet of lead atop a thin silicon surface. The lead sheets are highly uniform with no impurities.

"We can make this film, and it has perfect crystalline structure—more perfect than most thin films made of other materials," Shih says.

New Memory Material May Hold Data For One Billion Years

2009-05-27T10:02:00.000-07:00

Packing more digital images, music, and other data onto silicon chips in USB drives and smart phones is like squeezing more strawberries into the same size supermarket carton. The denser you pack, the quicker it spoils. The 10 to 100 gigabits of data per square inch on today's memory cards has an estimated life expectancy of only 10 to 30 years. And the electronics industry needs much greater data densities for tomorrow's iPods, smart phones, and other devices.
Scientists are reporting an advance toward remedying this situation with a new computer memory device that can store thousands of times more data than conventional silicon chips with an estimated lifetime of more than one billion years. Their discovery is scheduled for publication in the June 10 issue of the American Chemical Society's Nano Letters, a monthly journal.

Alex Zettl and colleagues note in the new study that some of today's highest-density experimental storage media can retain ultra-dense data for only a fraction of a second. They note that William the Conqueror's Doomsday Book, written on vellum in 1086 AD, has survived 900 years. However, the medium used for a digital version of the book, encoded in 1986, failed within 20 years.

The researchers describe development of an experimental memory device consisting of an iron nanoparticle (1/50,000 the width of a human hair) enclosed in a hollow carbon nanotube. In the presence of electricity, the nanoparticle can be shuttled back and forth with great precision. This creates a programmable memory system that, like a silicon chip, can record digital information and play it back using conventional computer hardware. In lab and theoretical studies, the researchers showed that the device had a storage capacity as high as 1 terabyte per square inch (a trillion bits of information) and temperature-stability in excess of one billion years.

Inexpensive Plastic Used In CDs Could Improve Aircraft, Computer Electronics

2009-05-17T09:50:00.000-07:00

CDs. The inexpensive plastic now used to manufacture CDs and DVDs may one day soon be put to use in improving the integrity of electronics in aircraft, computers and iPhones.
If one University of Houston professor has his way, the inexpensive plastic now used to manufacture CDs and DVDs will one day soon be put to use in improving the integrity of electronics in aircraft, computers and iPhones.
Thanks to a pair of grants from the U.S. Air Force, Shay Curran, associate professor of physics at UH, and his research team have demonstrated ultra-high electrical conductive properties in plastics, called polycarbonates, by mixing them with just the right amount and type of carbon nanotubes.

Curran, who initially began this form of research a decade ago at Trinity College Dublin, started to look at high-conductive plastics in a slightly different manner. Curran's team has come up with a strategy to achieve higher conductivities using carbon nanotubes in plastic hosts than what has been currently achieved. By combining nanotubes with polycarbonates, Curran's group was able to reach a milestone of creating nanocomposites with ultra-high conductive properties.

"While its mechanical and optical properties are very good, polycarbonate is a non-conductive plastic. That means its ability to carry an electrical charge is as good as a tree, which is pretty awful," Curran said. "Imagine that this remarkable plastic can now not only have good optical and mechanical properties, but also good electrical characteristics. By being able to tailor the amount of nanotubes we can add to the composite, we also can change it from the conductivity of silicon to a few orders below that achieved by metals."

Making this very inexpensive plastic highly conductive could benefit electronics in everything from military aircraft to personal computers. Computer failure, for instance, results from the build up of thermal and electrical charges, so developing these polymer nanotube composites into an antistatic coating or to provide a shield against electromagnetic interference would increase the lifespan of computing devices, ranging from PCs to PDAs.

The next step of this research is to develop ink formulations to paint these polycarbonate nanocomposites onto various electrical components. Normally, metal plates are used to dissipate electrical charge, so it's not surprising that the availability of a paintable ink would be particularly appealing to the Air Force for its lightweight properties, resulting in lighter aircraft that guzzle less gas.

Another key component of this latest research is that pristine nanotubes disbursed in this polycarbonate were found to possess an even higher conductivity than acid-treated carbon nanotubes. Traditionally, the tubes are sonicated, or treated with acid, to clean them and remove soot to get a higher conductivity. This, however, damages the tubes and exposes them to defects. Instead, Curran and his group were able to centrifuge, or swirl, them. This takes a little longer, but increases the potential to have higher conductivities. He attributes this to the incredibly clean samples of carbon nanotubes obtained from fellow collaborator David Carroll in the physics department at Wake Forest University.

In addition to Curran and Carroll, the team behind these remarkable findings includes Donald Birx, professor of electrical engineering and vice president for research at UH, two of Curran's former post-doctoral students, Jamal Talla and Donghui Zhang, and a current Curran student, Sampath Dias.

Coincidentally, Curran's former thesis supervisor Werner Blau and his group in the department of physics at Trinity College Dublin have come out with similar findings recently in the journal ACS Nano. Both groups really have been pushing hard in the area of polymer nanotube composites during the course of the last decade. Curran said his group at UH achieved the highest conductivity levels so far, but also is encouraged by Blau's success and said repeating these types of outcomes will open doors for even higher values.

"While these are phenomenal results, finding these unusual highly conductive properties has not even begun to scratch the surface," Curran said. "There is hard science behind it, so developing it further will require significant investment. And we are very thankful to the Air Force for giving us this auspicious start."

New Fuel Cell Catalyst Uses Two Metals: Up To Five Times More Effective

2009-05-16T10:02:00.000-07:00

Material scientists at Washington University in St. Louis have developed a technique for a bimetallic fuel cell catalyst that is efficient, robust and two to five times more effective than commercial catalysts. The novel technique eventually will enable a cost effective fuel cell technology, which has been waiting in the wings for decades, and should give a boost for cleaner use of fuels worldwide.
Younan Xia, Ph.D., the James M. McKelvey Professor of Biomedical Engineering at Washington University led a team of scientists at Washington University and the Brookhaven National Laboratory in developing a bimetallic catalyst comprised of a palladium core or "seed" that supports dendritic platinum branches, or arms, that are fixed on the nanostructure, consisting of a nine nanometer core and seven nanometer platinum arms. They synthesized the catalysts by sequentially reducing precursor compounds to palladium and platinum with L-ascorbic acid (that is, Vitamin C) in an aqueous solution. The catalysts have a high surface area, invaluable for a number of applications besides in fuel cells, and are robust and stable.

Xia and his team tested how the catalysts performed in the oxygen reduction reaction process in a fuel cell, which determines how large a current will be generated in an electrochemical system similar to the cathode of a fuel cell. They found that their bimetallic nanodendrites, at room temperature, were two-and-a-half times more effective per platinum mass for this process than the state-of-the-art commercial platinum catalyst and five times more active than the other popular commercial catalyst. At 60 C(the typical operation temperature of a fuel cell), the performance almost meets the targets set by the U.S. Department of Energy.

The Department of Energy has estimated for widespread commercial success the "loading" of platinum catalysts in a fuel cell should be reduced by four times in order to slash the costs. The Washington University technique is expected to substantially reduce the loading of platinum, making a more robust catalyst that won't have to be replaced often, and making better use of a very limited and very expensive supply of platinum in the world.

The study was published in Science online on May 14.

"There are two ways to make a more effective catalyst," Xia says. "One is to control the size, making it smaller, which gives the catalyst a higher specific surface area on a mass basis. Another is to change the arrangement of atoms on the surface. We did both. You can have a square or hexagonal arrangement for the surface atoms. We chose the hexagonal lattice because people have found that it's twice as good as the square one for the oxygen reduction reaction.

"We're excited by the technique, specifically with the performance of the new catalyst."

Xia says seeded growth has emerged recently as a good technique for precisely controlling the shape and composition of metallic nanostructures prepared in solutions. And it's the only technique that allowed Xia and his collaborators to come up with their unconventional shape.

"When you have something this small, the atoms tend to aggregate and that can reduce the surface area,' Xia says. "A key reason our technique works is the ability to keep the platinum arms fixed. They don't move around. This adds to their stability. We also make sure of the arrangement of atoms on each arm, so we increase the activity."

Xia and his collaborators are exploring the possibility of adding other noble metals such as gold to the bimetallic catalysts, making them trimetallic. Gold has been shown to oxidize carbon monoxide, making for even more robust catalysts that can resist the poisoning by carbon monoxide – a reduction byproduct of some fuels.

"Gold should make the catalysts more stable, durable and robust, giving yet another level of control," Xia says.

Progress Toward Artificial Tissue?

2009-05-16T09:58:00.000-07:00

A team of Australian and Korean researchers led by Geoffrey M. Spinks and Seon Jeong Kim has now developed a novel, highly porous, sponge-like material whose mechanical properties closely resemble those of biological soft tissues. It consists of a robust network of DNA strands and carbon nanotubes.
For modern implants and the growth of artificial tissue and organs, it is important to generate materials with characteristics that closely emulate nature. However, the tissue in our bodies has a combination of traits that are very hard to recreate in synthetic materials: It is both soft and very tough.
A team of Australian and Korean researchers led by Geoffrey M. Spinks and Seon Jeong Kim has now developed a novel, highly porous, sponge-like material whose mechanical properties closely resemble those of biological soft tissues. It consists of a robust network of DNA strands and carbon nanotubes.

Soft tissues, such as tendons, muscles, arteries, and skin or other organs, obtain their mechanical support from the extracellular matrix, a network of protein-based nanofibers. Different protein morphologies in the extracellular matrix produce tissue with a wide range of stiffness. Implants and scaffolding for tissue growth require porous, soft materials -- which are usually very fragile. Because many biological tissues are regularly subjected to intense mechanical loads, it is also important that the implant material have comparable elasticity in order to avoid inflammation. At the same time, the material must be very strong and resilient, or it may give out.

The new concept uses DNA strands as a matrix; the strands completely “wrap” the scaffold-forming carbon nanotubes in the presence of an ionic liquid, networking them to form a gel. This gel can be spun: just as silk and synthetic fibers can be wet-spun for textiles, the gel can be made into very fine threads when injected into a special bath. The dried fibers have a porous, sponge-like structure and consist of a network of intertwined 50 nm-wide nanofibers. Soaking in a calcium chloride solution further cross-links the DNA, causing the fibers to become denser and more strongly connected.

These spongy fibers resemble the collagen fiber networks of the biological extracellular matrix. They can also be knotted, braided, or woven into textile-like structures. This results in materials that are as elastic as the softest natural tissues while simultaneously deriving great strength from the robust DNA links.

An additional advantage is the electrical conductivity of the new material, which can thus also be used in electrodes for mechanical actuators, energy storage, and sensors. For example, the researchers were able to produce a hydrogen peroxide sensor. The carbon nanotubes catalyze the oxidation of hydrogen peroxide, which results in a measurable current. Hydrogen peroxide plays a role in normal heart function and certain heart diseases. A robust sensor with elasticity similar to the heart muscle would be of great help in researching these relationships.

Discovery Of An Unexpected Boost For Solar Water-splitting Cells

2009-04-26T08:14:00.000-07:00

A research team from Northeastern University and the National Institute of Standards and Technology (NIST) has discovered, serendipitously, that a residue of a process used to build arrays of titania nanotubes—a residue that wasn’t even noticed before this—plays an important role in improving the performance of the nanotubes in solar cells that produce hydrogen gas from water.
Their recently published results indicate that by controlling the deposition of potassium on the surface of the nanotubes, engineers can achieve significant energy savings in a promising new alternate energy system.

Titania (or titanium dioxide) is a versatile chemical compound best known as a white pigment. It’s found in everything from paint to toothpastes and sunscreen lotions. Thirty-five years ago Akira Fujishima startled the electrochemical world by demonstrating that it also functioned as a photocatalyst, producing hydrogen gas from water, electricity and sunlight. In recent years, researchers have been exploring different ways to optimize the process and create a commercially viable technology that, essentially, transforms cheap sunlight into hydrogen, a pollution-free fuel that can be stored and shipped.

Increasing the available surface area is one way to boost a catalyst’s performance, so a team at Northeastern has been studying techniques to build tightly packed arrays of titania nanotubes, which have a very high surface to volume ratio. They also were interested in how best to incorporate carbon into the nanotubes, because carbon helps titania absorb light in the visible spectrum. (Pure titania absorbs in the ultraviolet region, and much of the ultraviolet is filtered by the atmosphere.)

This brought them to the NIST X-ray spectroscopy beamline at the National Synchrotron Light Source (NSLS)*. The NIST facility uses X-rays that can be precisely tuned to measure chemical bonds of specific elements, and is at least 10 times more sensitive than commonly available laboratory instruments, allowing researchers to detect elements at extremely low concentrations. While making measurements of the carbon atoms, the team noticed spectroscopic data indicating that the titania nanotubes had small amounts of potassium ions strongly bound to the surface, evidently left by the fabrication process, which used potassium salts. This was the first time the potassium has ever been observed on titania nanotubes; previous measurements were not sensitive enough to detect it.

The result was mildly interesting, but became much more so when the research team compared the performance of the potassium-bearing nanotubes to similar arrays deliberately prepared without potassium. The former required only about one-third the electrical energy to produce the same amount of hydrogen as an equivalent array of potassium-free nanotubes. “The result was so exciting,” recalls Northeastern physicist Latika Menon, “that we got sidetracked from the carbon research.” Because it has such a strong effect at nearly undetectable concentrations, Menon says, potassium probably has played an unrecognized role in many experimental water-splitting cells that use titania nanotubes, because potassium hydroxide is commonly used in the cells. By controlling it, she says, hydrogen solar cell designers could use it to optimize performance.

*The NSLS is part of the Department of Energy’s Brookhaven National Laboratory.

New Security And Medical Sensor Devices Made Possible By Fundamental Physics Development In Metallic Nanostructures

2009-04-14T10:32:00.000-07:00

Scientists have designed tiny new sensor structures that could be used in novel security devices to detect poisons and explosives, or in highly sensitive medical sensors, according to research published tomorrow (8 April) in Nano Letters.
The new ‘nanosensors’, which are based on a fundamental science discovery in UK, Belgian and US research groups, could be tailor-made to instantly detect the presence of particular molecules, for example poisons or explosives in transport screening situations, or proteins in patients’ blood samples, with high sensitivity.

The researchers were led by Imperial College London physicists funded by the Engineering and Physical Sciences Research Council. The team showed that by putting together two specific ‘nanostructures’ made of gold or silver, they can make an early prototype device which, once optimised, should exhibit a highly sensitive ability to detect particular chemicals in the immediate surroundings.

The nanostructures are each about 500 times smaller than the width of a human hair. One is shaped like a flat circular disk while the other looks like a doughnut with a hole in the middle. When brought together they interact with light very differently to the way they behave on their own. The scientists have observed that when they are paired up they scatter some specific colours within white light much less, leading to an increased amount of light passing through the structure undisturbed. This is distinctly different to how both structures scatter light separately. This decrease in the interaction with light is in turn affected by the composition of molecules in close proximity to the structures. The researchers hope that this effect can be harnessed to produce sensor devices.

Lead researcher on the project Professor Stefan Maier from Imperial’s Department of Physics, and an Associate of Imperial’s Institute for Security Science and Technology, said:

"Pairing up these structures has a unique effect on the way they scatter light

– an effect which could be very useful if, as our computer simulations suggest, it is extremely sensitive to changes in surrounding environment. With further testing we hope to show that it is possible to harness this property to make a highly sensitive nanosensor."

Metal nanostructures have been used as sensors before, as they interact very strongly with light due to so-called localised plasmon resonances. But this is the first time a pair with such a carefully tailored interaction with light has been created.

The device could be tailored to detect different chemicals by decorating the nanostructure surface with specific ‘molecular traps’ that bind the chosen target molecules. Once bound, the target molecules would change the colours that the device absorbs and scatters, alerting the sensor to their presence. The team’s next step is to test whether the pair of nanostructures can detect chosen substances in lab experiments.

Professor Maier concludes: "This study is a beautiful example of how concepts from different areas of physics fertilise each other – in essence our nanosensor system is a classical analogue of electromagnetically induced transparency, a famous phenomenon from quantum mechanics."

Biocompatible Materials For Rapid Prototyping

2009-04-14T10:30:00.000-07:00

The implantation of integrated biomedical devices to the human body provides challenges to engineering materials science and biology. The demand for metallic and polymeric biomaterials is greatly increasing because of the rapid growth of the world’s population, the increasing proportion of older people and the high functional requirements of younger people.
Rapid prototyping (RP) of medical devices and custom-made prosthetic implants is also an area of growing interest and subject to intensive research during the last decades. The unique advantages of layer additive manufacturing open the way for design and development of multi-tasking functional tools with a wide range of applications from dentistry to regenerative medicine and tissue engineering. The current materials of choice for RP are metals, ceramics and limited range of biocompatible polymers. Photopolymers are most attractive for biomedical applications offering mechanical properties versatility and unlimited options in functionalization.

Custom-fit project has been developing during the last 4 years new bio-compatible materials which can be used in its machines. As the machines developed into the project framework have achieved the rapid manufacturing of Multi-Materials Graded Structures, one of the project’s partners, DSM from the Netherlands, has been developing new bio-compatible materials which can be printed with these techniques.

They have achieved the development of photo-curable resins, based on either bio-stable or biodegradable oligomers. These materials are readily processable on commercial RP machines, yielding high quality, biocompatible polymers and demonstrating the versatility and prospective of RP as method of choice for fabrication of biomedical devices. The biostable resins comprised polyester/polyether oligomers bearing acrylate or methacrylate functions while the biodegradable composites have been prepared from methacrylate-functionalized, biocompatible polyesters. The chemical composition, purity and molecular weight distribution of the synthesized oligomers were proven by means of 1H NMR, IR spectroscopy and gel permeation chromatography. The conversion of (meth)acrylate functions after the photo-curing process was estimated by FT-IR. Standard mechanical tests were performed on 40 mm long tensile bars produced by Envisiontec perfactory machine.

Applying polyester/polyether backbone oligomers and reactive diluents DSM adapted composites to the optimal viscosity requirements of the Envisiontec machine. This made it possible to use the full machine capacity and to obtain precise RP-parts as small as 50 microns. Such accuracy was essentially important when targeting a custom-fitting artificial implant. Furthermore the RP processing afforded a high (meth)acrylate conversion of the cured polymers and resulted in materials with a broad range of mechanical properties. The results demonstrated the flexibility of both the composite materials and the production method in fabrication of parts of desired mechanical properties.

In order to obtain biodegradable RP-parts, DSM prepared also methacrylate functionalized biodegradable oligomers and incorporated them in RP-processable composites. Applying different biodegradable polyesters they fine tuned the degradation rate of the final, photo-cured material.

The production method ensured a high conversion of the methacrylate functions. This finding is supported also by the toxicological studies on the cured material where no harmful extractables were found. The tested material meets the requirements of the Intracutaneous Test according ISO 10993-10 guidelines.

Engineers Create DNA Sensors That Could Identify Cancer Using Material Only One Atom Thick

2009-04-14T10:25:00.000-07:00

Kansas State University engineers think the possibilities are deep for a very thin material.
Vikas Berry, assistant professor of chemical engineering, is leading research combining biological materials with graphene, a recently developed carbon material that is only a single atom thick.

"The biological interfacing of graphene is taking this material to the next level," Berry said. "Discovered only four years ago, this material has already shown a large number of capabilities. K-Staters are the first to do bio-integrated research with graphene."

To study graphene, researchers rely on an atomic force microscope to help them observe and manipulate these single atom thick carbon sheets.

"It's a fascinating material to work with," Berry said. "The most significant feature of graphene is that the electrons can travel without interruptions at speeds close to that of light at room temperature. Usually you have to go near zero Kelvin -- that's about 450 degrees below zero Fahrenheit -- to get electrons to move at ultra high speeds."

One of Berry's developments is a graphene-based DNA sensor. When electrons flow on the graphene, they change speed if they encounter DNA. The researchers notice this change by measuring the electrical conductivity. The work was published in Nano-Letters.

"Most DNA sensors are optical, but this one is electrical," Berry said. "We are currently collaborating with researchers from Harvard Medical School to sense cancer cells in blood."

Another area he is exploring is loading graphene with antibodies and flowing bacteria across the surface.

"Most researchers focus on pristine graphene, but we're making it dirty," he said.

Berry and Nihar Mohanty, a graduate student in chemical engineering, used a type of bacteria commonly found in rice and interfaced it with graphene. They found that the graphene with tethered antibodies will wrap itself around an individual bacterium, which remains alive for 12 hours.

Berry said that possible applications include a high-efficiency bacteria-operated battery, where by using geobater, a type of bacteria known to produce electrons, can be wrapped with graphene to produce electricity. The research was presented at the annual American Physical Society conference in Pittsburgh and the American Institute for Chemical Engineers conference in Philadelphia.

"Materials science is an incredible field with several exploitable quantum effects occurring at molecular scale, and biology is a remarkable field with a variety of specific biochemical mechanisms," Berry said. "But for the most part the two fields are isolated. If you join these two fields, the possibilities are going to be immense. For example, one can think of a bacterium as a machine with molecular scale components and one can exploit the functioning of those components in a material device."

For his doctoral research, Berry used bacteria to make a humidity sensor.

"That was only possible through combining materials science with biological science," he said.

Another area of his current research is compressing and stretching molecular-junctions between nanoparticles. Berry said that his group has developed a molecular-spring device where they can compress and stretch molecules, which then act like springs, allowing researchers to study how they relax back. He said that this technology could be used to create molecular-timers in which the spring action from a decompressed molecule on a chip could trigger a circuit, for instance.

Berry said for stretching the molecules, Kabeer Jasuja, a doctoral student in chemical engineering, came up with the idea to place the device on a centrifuge to stretch the molecules with centrifugal force.

Pentagonal Ice Discovered: Could Be Used To Modify Weather

2009-04-08T10:31:00.000-07:00

Scientists at the University of Liverpool have discovered a five-sided ice chain structure that could be used to modify future weather patterns.
Researchers, in collaboration with University College London and the Fritz-Haber Institut in Berlin, created the first moments of water condensing on matter – a process vital for the formation of clouds in the atmosphere – by analysing how the two interact on a flat copper surface. Ice has rarely been viewed at the nanoscale before and the team discovered a one-dimensional chain structure built from pentagon-shaped rings, rather than the more commonly seen hexagonal structures of ice formations like those seen in snowflakes.

This discovery could lead to scientists developing new materials for seeding clouds and causing rain. Cloud seeding is a form of weather modification, where the amount or type of precipitation that falls from clouds is altered by dispersing substances into the air which modify cloud particles. This process can increase amounts of rain and snow but can also be used to suppress hail and fog. The substances currently used to seed clouds are chosen to bind to hexagonal ice, but this work suggests that the process could work equally well with materials which bind to other structures.

Professor Andrew Hodgson, from the University’s Surface Science Research Centre, said: “Water is a ubiquitous material that is central to many biological and chemical reactions, but its influence is often indirect and difficult to understand. Water usually takes on hexagonal arrangements, like those seen in snowflakes, yet this research has shown that the intricate, nanoscale structure of ice can actually be built from one-dimensional pentagons.

“Ice crystals form against flat, solid surfaces and watching the microscopic process take place on copper has provided detailed information on how ice forms at interfaces. The research will help to improve our understanding of how ice patterns form and how water is structured at metal interfaces.

“Many important chemical reactions take place at interfaces so understanding the structure of water in these environments will allow scientists to make better models of these processes. With a better understanding of how ice crystals form in the upper atmosphere, new and cheaper materials could now be developed that could be used across the globe to seed clouds and modify weather patterns."

Better Way To Manufacture Fast Computer Chips Developed

2009-04-08T10:25:00.000-07:00

Engineers at Ohio State University are developing a technique for mass producing computer chips made from the same material found in pencils.
Experts believe that graphene -- the sheet-like form of carbon found in graphite pencils -- holds the key to smaller, faster electronics. It might also deliver quantum mechanical effects that could enable new kinds of electronics.

Until now, most researchers could only create tiny graphene devices one at a time, and only on traditional silicon oxide substrates. They couldn’t control where they placed the devices on the substrate, and had to connect them to other electronics one at a time for testing.

In a paper published in the March 26 issue of the journal Advanced Materials, Nitin Padture and his colleagues describe a technique for stamping many graphene sheets onto a substrate at once, in precise locations.

“We designed the technique to mesh with standard chip-making practices,” said Padture, College of Engineering Distinguished Professor in Materials Science and Engineering.

“Graphene has huge potential -- it’s been dubbed ‘the new silicon,’” said Padture, who is also director of Ohio State’s Center for Emergent Materials. “But there hasn’t been a good process for high-throughput manufacturing it into chips. The industry has several decades of chip-making technology that we can tap into, if only we could create millions of these graphene structures in precise patterns on predetermined locations, repeatedly. This result is a proof-of-concept that we should be able to do just that.”

Graphene is made of carbon atoms arranged in a hexagonal pattern resembling chicken wire. In graphite, many flat graphene sheets are stacked together.

“When you write with a pencil, you leave graphene sheets behind on the paper,” Padture said. Each sheet is so thin -- a few tenths of a nanometer (billionths of a meter) -- that researchers think of it as a two-dimensional crystal.

Researchers have shown that a single sheet, or even a few sheets, of graphene can exhibit special properties. One such property is very high mobility, in which electrons can pass through it very quickly -- a good characteristic for fast electronics. Another is magnetism: magnetic fields could be used to control the spin of graphene electrons, which would enable spin-based electronics, also called spintronics.

Yet another characteristic is how dramatically graphene’s properties change when it touches other materials. That makes it a good candidate material for chemical sensors.

In this method, Padture and his Ohio State colleagues carved graphite into different shapes -- a field of microscopic pillars, for example -- and then stamped the shapes onto silicon oxide surfaces.

“Think of a stack of graphene sheets in graphite as a deck of cards. When you bring it contact with the silicon oxide and pull it away, you can ‘split the deck’ near the point of contact, leaving some layers of graphene behind. What we found through computer simulations was that the graphene surface interacts so strongly with the silicon oxide surface that the chemical bonds between the graphene layers weaken, and the lower layers split off,” Padture said.

In this first series of experiments, the Ohio State researchers were able to stamp high-definition features that were ten layers thick, or thicker. The graphite stamp can then be used repeatedly on other predetermined locations on the same or other substrates, making this a mass-production method, potentially.

They used three different kinds of microscopes -- a scanning electron microscope, optical microscope, and atomic force microscope -- to measure the heights of the features, and assure that they were placed precisely on the substrate.

They eventually hope to stamp narrow features that are only one or two layers thick, by stamping on materials other than silicon oxide.

In computer simulations, they found that each material interacts differently with the graphene. So success might rely on finding just the right combination of substrate materials to coax the graphene to break off in one or two layers. This would also tailor the properties of the graphene.

Padture’s co-authors on the paper include Dongsheng Li, a postdoctoral researcher, and Wolfgang Windl, associate professor of materials science and engineering.

This work was partially funded by the Center for Emergent Materials at Ohio State, which is a Materials Research Science & Engineering Center (MRSEC) sponsored by the National Science Foundation. Partial funding was also provided by Ohio State’s Institute for Materials Research.

Chemists Create Bipedal, Autonomous DNA Walker

2009-04-07T01:02:00.000-07:00

Chemists at New York University and Harvard University have created a bipedal, autonomous DNA "walker" that can mimic a cell's transportation system. The device, which marks a step toward more complex synthetic molecular motor systems, is described in the most recent issue of the journal Science.
Two fundamental components of life's building blocks are DNA, which encodes instructions for making proteins, and motor proteins, such as kinesin, which are part of a cell's transportation system. In nature, single strands of DNA—each containing four molecules, or bases, attached to backbone—self-assemble to form a double helix when their bases match up. Kinesin is a molecular motor that carries various cargoes from one place in the cell to another. Scientists have sought to re-create this capability by building DNA walkers.

Earlier versions of walkers, which move along a track of DNA, did not function autonomously, thereby requiring intervention at each step. A challenge these previous devices faced was coordinating the movement of the walker's legs so they could move in a synchronized fashion without falling off the track.

To create a walker that could move on its own, the NYU and Harvard researchers employed two DNA "fuel strands." These fuel strands push the walker (blue) along a track of DNA, thereby allowing the walker and the fuel strands to function as a catalytic unit.

The forward progress of the system is driven by the fact that more base pairs are formed every step—a process that creates the energy necessary for movement. As the walker moves along the DNA track, it forms base pairs. Simultaneously, the fuel strands move the walker along by binding to the track and then releasing the walker's legs, thereby allowing the walker to take "steps".

The track's length is 49 nanometers—if the track was one meter long, an actual meter, enlarged proportionally, would be the approximate diameter of the earth.

For a video demonstration of the walker, go to http://www.nyu.edu/public.affairs/videos/qtime/biped_movie.mov.

The walker was created in the laboratory of NYU Chemistry Professor Nadrian Seeman, one of the article's co-authors. The paper's other authors were Tosan Omabegho, a doctoral candidate at Harvard's School of Engineering and Applied Sciences, and Ruojie Sha, a senior research associate in the NYU Chemistry Department.

Flexible, Transparent Supercapacitors Could Pave Way To E-Paper

2009-04-07T00:56:00.000-07:00

It is a completely transparent and flexible energy conversion and storage device that you can bend and twist like a poker card.
It continues a line of prototype devices created at the USC Viterbi School of Engineering that can perform the electronic operations now usually handled by silicon chips using carbon nanotubes and metal nanowires set in indium oxide films, and can potentially do so prices competitive with these existing technologies.

The latest device is a supercapacitor, a circuit component that can temporarily store large amounts of electrical energy for release when needed. Its creators believe the device points the way to further applications, such as flexible power supply components in “e-paper” displays and conformable products.

The device stores an energy density of 1.29 Watt-hour/kilogram with a specific capacitance of 64 Farad/gram. By contrast, conventional capacitors usually have an energy density of less than 0.1 Wh/kg and a storage capacitance of several tenth millifarads.

Zhou, who holds the Jack Munushiun Early Career Chair at the USC Ming Hsieh Department of Electrical Engineering, worked with USC graduate students Po-Chiang Chen and Sawalok Sukcharoenchoke, and post-doc Guozhen Shen. The group incorporated metal oxide nanowires with carbon nanotubes (CNTs) to form heterogeneous films and further optimized the film thickness attaching on transparent plastic substrates to maintain the mechanical flexibility and optical transparency of the supercapacitors.

According to Zhou, the work, based on combing CNTs with metal nanowiers represents an advance on earlier attempts to produce supercapacitors using just CNTs or graphite. Such efforts resulted in only modest performance compared to those using transition metal oxide materials, including such oxides of iron, manganese and rubidium. Moreover, energy storage devices made by these materials have neither mechanical flexibility nor optical transparency, which have confined their applications in the flexible and transparent electronics.

The critical improvement in performance, according to the research, can be attributed to the incorporation of metal oxide nanowires with CNT films. Indium oxide nanowire, with the properties of wide band gap, high aspect ratio, and short diffusion path length, can be one of the best candidates for transparent electrochemical capacitors. Professor Zhou’s lab has pioneered this material over the past several years.

These new devices, by contrast, "demonstrated enhanced specific capacitance, power density, energy density, and long operation cycles, compared to those supercapacitors made only by CNTs,” says the new release.

“We successfully produced a prototype of flexible and transparent supercapacitors built on two important nanostructured materials (including metal oxide nanowires and CNTs).

The researchers not only created metal oxide nanowire / CNT heterogeneous films as active materials and current collecting electrodes for the supercapacitors, but also examined the stability of the transparent and flexible supercapacitors through a large cycle number of charge/discharge measurements.

The paper contains description of how the new devices are made.

"CNT films were fabricated by vacuum filtration method. An adhesive and flat poly (dimethysiloxane) (PDMS) stamp was adapted to peel the CNT film off of the filtration membrane and then released it onto a polyethylene terephtalate (PET) substrate. In2O3 nanowires with a diameter of ~ 20 nm and a length of ~ 5 μm were synthesized by a pulsed laser deposition (PLD) method. The

as-grown nanowires were sonicated into IPA solutions and then dispersed upon transferred CNT films to form In2O3 nanowire /CNT heterogeneous film for transparent and flexible supercapacitor study.

"In addition, with the increasing amount of In2O3 nanowires dispersed upon CNT films, the specific capacitance of the heterogeneous supercapacitor can be dramatically improved up from 25.4 Farad/gram to 64 Farad/gram. In comparisons to supercapacitors made by other transition metal oxide nanostructured materials, this observation indicates a good stability of In2O3 nanowire / CNT heterogeneous films for long-term capacitor applications."

DNA-based Assembly Line For Precision Nano-cluster Construction

2009-04-07T00:47:00.000-07:00

Building on the idea of using DNA to link up nanoparticles — particles measuring mere billionths of a meter — scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have designed a molecular assembly line for predictable, high-precision nano-construction.
Such reliable, reproducible nanofabrication is essential for exploiting the unique properties of nanoparticles in applications such as biological sensors and devices for converting sunlight to electricity. The work was published online March 29, 2009, by Nature Materials.

The Brookhaven team has previously used DNA, the molecule that carries life’s genetic code, to link up nanoparticles in various arrangements, including 3-D nano-crystals. The idea is that nanoparticles coated with complementary strands of DNA — segments of genetic code sequence that bind only with one another like highly specific Velcro — help the nanoparticles find and stick to one another in highly specific ways. By varying the use of complementary DNA and strands that don’t match, scientists can exert precision control over the attractive and repulsive forces between the nanoparticles to achieve the desired construction. Note that the short DNA linker strands used in these studies were constructed artificially in the laboratory and don’t “code” for any proteins, as genes do.

The latest advance has been to use the DNA linkers to attach some of the DNA-coated nanoparticles to a solid surface to further constrain and control how the nanoparticles can link up. This yields even greater precision, and therefore a more predictable, reproducible high-throughput construction technique for building clusters from nanoparticles.

“When a particle is attached to a support surface, it cannot react with other molecules or particles in the same way as a free-floating particle,” explained Brookhaven physicist Oleg Gang, who led the research at the Lab’s Center for Functional Nanomaterials. This is because the support surface blocks about half of the particle’s reactive surface. Attaching a DNA linker or other particle that specifically interacts with the bound particle then allows for the rational assembly of desired particle clusters.

“By controlling the number of DNA linkers and their length, we can regulate interparticle distances and a cluster’s architecture,” said Gang. “Together with the high specificity of DNA interactions, this surface-anchored technique permits precise assembly of nano-objects into more complex structures.”

Instead of assembling millions and millions of nanoparticles into 3-D nanocrystals, as was done in the previous work, this technique allows the assembly of much smaller structures from individual particles. In the Nature Materials paper, the scientists describe the details for producing symmetrical, two-particle linkages, known as dimers, as well as small, asymmetrical clusters of particles — both with high yields and low levels of other, unwanted assemblies.

“When we arrange a few nanoparticles in a particular structure, new properties can emerge,” Gang emphasized. “Nanoparticles in this case are analogous to atoms, which, when connected in a molecule, often exhibit properties not found in the individual atoms. Our approach allows for rational and efficient assembly of nano-‘molecules.’ The properties of these new materials may be advantageous for many potential applications.”

For example, in the paper, the scientists describe an optical effect that occurs when nanoparticles are linked as dimer clusters. When an electromagnetic field interacts with the metallic particles, it induces a collective oscillation of the material’s conductive electrons. This phenomenon, known as a plasmon resonance, leads to strong absorption of light at a specific wavelength.

“The size and distance between the linked particles affect the plasmonic behavior,” said Gang. By adjusting these parameters, scientists might engineer clusters for absorbing a range of wavelengths in solar-energy conversion devices. Modulations in the plasmonic response could also be useful as a new means for transferring data, or as a signal for a new class of highly specific biosensors.

Asymmetric clusters, which were also assembled by the Brookhaven team, allow an even higher level of control, and therefore open new ways to design and engineer functional nanomaterials.

Because of its reliability and precision control, Brookhaven’s nano-assembly method would be scalable for the kind of high-throughput production that would be essential for commercial applications. Brookhaven Lab has applied for a patent on the assembly method as well as several specific applications of the technology. (For information about the patent or licensing this technology, contact Kimberley Elcess at (631) 344-4151.)

In addition to Gang, the team included materials scientist Dmytro Nykypanchuk, summer student Marine Cuisinier, and biologist Daniel (Niels) van der Lelie, all from Brookhaven, and former Brookhaven chemist Matthew Maye, now at Syracuse University. Their work was funded by DOE’s Office of Science and through a Goldhaber Distinguished Fellowship sponsored by Brookhaven Science Associates.

First Ever Video Of Dynamics Of Carbon Atoms Makes Spintronic-based Computing Look More Promising

2009-04-03T01:11:00.001-07:00

Science fiction fans still have another two months of waiting for the new Star Trek movie, but fans of actual science can feast their eyes now on the first movie ever of carbon atoms moving along the edge of a graphene crystal. Given that graphene – single-layered sheets of carbon atoms arranged like chicken wire – may hold the key to the future of the electronics industry, the audience for this new science movie might also reach blockbuster proportions.
Researchers with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), working with TEAM 0.5, the world’s most powerful transmission electron microscope, have made a movie that shows in real-time carbon atoms repositioning themselves around the edge of a hole that was punched into a graphene sheet. Viewers can observe how chemical bonds break and form as the suddenly volatile atoms are driven to find a stable configuration. This is the first ever live recording of the dynamics of carbon atoms in graphene.

“The atom-by-atom growth or shrinking of crystals is one of the most fundamental problems of solid state physics, but is especially critical for nanoscale systems where the addition or subtraction of even a single atom can have dramatic consequences for mechanical, optical, electronic, thermal and magnetic properties of the material,” said physicist Alex Zettl who led this research. “The ability to see individual atoms move around in real time and to see how the atomic configuration evolves and influences system properties is somewhat akin to a biologist being able to watch as cells divide and a higher order structure with complex functionality evolves.”

Zettl holds joint appointments with Berkeley Lab’s Materials Sciences Division (MSD) and the Physics Department at the University of California (UC) Berkeley, where he is the director of the Center of Integrated Nanomechanical Systems. He is the principal author of a paper describing this work which appears in the March 27, 2009 issue of the journal Science. The paper is entitled, “Graphene at the Edge: Stability and Dynamics.” Co-authoring this paper with Zettl were Çağlar Girit, Jannik Meyer, Rolf Erni, Marta Rossell, Christian Kisielowski, Li Yang, Cheol-Hwan Park, Michael Crommie, Marvin Cohen and Steven Louie.

In their paper, the authors credit the unique capabilities of TEAM 0.5 for making their movie possible. TEAM stands for Transmission Electron Aberration-corrected Microscope. The newest instrument at Berkeley Lab’s National Center for Electron Microscopy (NCEM) - a DOE national user facility and the country’s premier center for electron microscopy and microcharacterization - TEAM 0.5 is capable of producing images with half angstrom resolution, which is less than the diameter of a single hydrogen atom.

Said NCEM director Ulrich Dahmen of this achievement with TEAM 0.5, “The real-time observation of the movements of edge atoms could lead to a new level of understanding and control of nanomaterials. With further advances in electron-optical correctors and detectors it may become possible to increase the sensitivity and speed of such observations, and begin to see a live view of many other reactions at the atomic scale.”

Rubbing graphene off the end of a pencil tip and suspending the specimen in an observation grid, Zettl and his colleagues used prolonged irradiation from TEAM 0.5’s electron beam (set at 80 kV) to introduce a hole into the graphene’s pristine hexagonal carbon lattice. Focusing the beam to a spot on the sheet blows out the exposed carbon atoms to create the hole. Since atoms at the edge of the hole are continually being ejected from the lattice by electrons from the beam the size of the hole grows. The researchers used the same TEAM 0.5 electron beam to record for analysis a movie showing the growth of the hole and the rearrangement of the carbon atoms.

“Atoms that lose their neighbors become highly volatile, and move around rapidly, continually repositioning themselves from one metastable configuration to the next,” said Zettl. “Although configurations come and go, we found a zigzag configuration to be the most stable. It occurs more often and over longer length scales along the edge than the other most common configuration, which we called the armchair.”

Understanding which of these atomic configurations is the most stable is one of the keys to predicting and controlling the stability of a device that utilizes graphene edges. The discovery of strong stability in the zigzag configuration is particularly promising news for the spintronic dreams of the computer industry.

Two years ago, co-authors Cohen and Louie, theorists who hold joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley, calculated that nanoribbons of graphene can conduct a spin current and could therefore serve as the basis for nanosized spintronic devices. Spin, a quantum mechanical property arising from the magnetic field of a spinning electron, carries a directional value of either “up” or “down” that can be used to encode data in the 0s and 1s of the binary system. Spintronic devices promise to be smaller, faster and far more versatile than today’s devices because – among other advantages – data storage does not disappear when the electric current stops.

Said Cohen, “Our calculations showed that zigzag graphene nanoribbons are magnetic and can carry a spin current in the presence of a sufficiently large electric field. By carefully controlling the electric field, it should be possible to generate, manipulate, and detect electron spins and spin currents in spintronics applications.”

Said Louie, “If electric fields can be made to produce and manipulate a 100-percent spin-polarized carrier system through a chosen geometric structure, it will revolutionize spintronics technology.”

The theorists were enthusiastic about actually being able to see their predictions in action.

Said Cohen, “This work is an excellent example of the power of attacking a fundamental problem through a combination of theory, experiment and cutting edge instrumentation. The instrument is one of the world’s best and allows us to see atoms move, the theory allows us to make realistic models, and the experiment was performed through the magic hands of Alex Zettl to ensure that the right measurement was done in the right way.”

Said Louie, “As the old saying goes - seeing is believing. The visual verification of the formation and stability of zigzag edges in the live atomic images from TEAM 0.5 is very satisfying. Furthermore, the ability to simultaneously see atomic structure and perform physical measurements, using the kind of set-up that the Zettl group has at NCEM, should greatly accelerate the cycle of discovery, theoretical understanding, applications and further discovery.”

For Zettl and his movie-making collaborators, next up they will correlate the atomic dynamics in graphene that they can now observe in real time with such properties as electrical conduction, optical response and magnetism. This will be a major advance towards fully understanding and applying graphene to spintronic technology as well as other electronic and photovoltaic devices.

“While, graphene is particularly exciting, our experimental methods should be applicable to other materials, including other 2-D systems as well,” Zettl said. “We are vigorously pursuing these areas of research in collaboration with the theorists and the staff at NCEM.”

Said NCEM principal investigator and co-author of this paper, Kisielowski, “The ability to observe the dynamics of single carbon atoms is a dream come true that reaches beyond investigations of graphene. In fact it gets us one step closer to understanding artificial photosynthesis, which is considered to be an ultimate energy technology and is being pursued at Berkeley Lab through the Helios Project.”

More on TEAM

TEAM 0.5 features state-of-the-art technical advances including an extremely bright electron source, ultra-stable electronics to reduce drift and, perhaps most importantly, the ability to provide optical corrections for spherical aberration (blurring). By making points of light look like disks, spherical aberrations have been the prime limiting factors in the resolution of transmission electron microscopy. Its ability to correct spherical aberrations makes TEAM 0.5 highly versatile. It can be used for broad-beam “wide-angle” imaging as well as for scanning transmission electron microscopy (STEM), in which the tightly focused electron beam is moved across a sample as a probe. In the STM mode, TEAM 0.5 is capable of performing spectroscopy on one atom at a time — an ideal way to precisely locate impurities in an otherwise homogeneous sample, such as individual dopant atoms in a semiconductor. Aberration correction also enables TEAM 0.5 to produce high resolution images at relatively low electron beam energies. Because of their longer wavelengths, lower energy electrons are more difficult to focus than higher energy electrons. Aberration correction overcomes this problem.

TEAM 0.5 was designed and constructed through a collaboration led by Berkeley Lab and including DOE’s Argonne and Oak Ridge National Laboratories, the Frederick Seitz Materials Laboratory of the University of Illinois, and two private companies specializing in electron microscopy, the FEI Company headquartered in Portland, Oregon, and CEOS of Heidelberg, Germany.

The TEAM project is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Zettl’s research was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division, of the U.S. Department of Energy.

Fitter Frames: Nanotubes Boost Structural Integrity Of Composites

2009-04-03T01:06:00.000-07:00

A new research discovery at Rensselaer Polytechnic Institute could lead to tougher, more durable composite frames for aircraft, watercraft, and automobiles.
Epoxy composites are increasingly being incorporated into the design of new jets, planes, and other vehicles. Composite material frames are extremely lightweight, which lowers the overall weight of the vehicle and boosts fuel efficiency. The downside is that epoxy composites can be brittle, which is detrimental to its structural integrity.

Professor Nikhil Koratkar, of Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, has demonstrated that incorporating chemically treated carbon nanotubes into an epoxy composite can significantly improve the overall toughness, fatigue resistance, and durability of a composite frame.

When subjected to repetitive stress, a composite frame infused with treated nanotubes exhibited a five-fold reduction in crack growth rate as compared to a frame infused with untreated nanotubes, and a 20-fold reduction when compared to a composite frame made without nanotubes.

This newfound toughness and crack resistance is due to the treated nanotubes, which enhance the molecular mobility of the epoxy at the interface where the two materials touch. When stressed, this enhanced mobility enables the epoxy to craze – or result in the formation of a network of pillar-like fibers that bridge together both sides of the crack and slow its growth.

“This crazing behavior, and the bridging fibers it produces, dramatically slows the growth rate of a crack,” Koratkar said. “In order for the crack to grow, those fibers have to first stretch, deform plastically, and then break. It takes a lot of energy to stretch and break those fibers, energy that would have otherwise gone toward enlarging the crack.”

Results of the study were just published in the journal Small.

Epoxy composites infused with carbon nanotubes are known to be more resistant to cracks than pure epoxy composites, as the nanotubes stitch, or bridge, the two sides of the crack together. Infusing an epoxy with carbon nanotubes that have been functionalized, or treated, with the chemical group amidoamine, however, results in a completely different bridging phenomenon.

At the interface of the functionalized nanotubes and the epoxy, the epoxy starts to craze, which is a highly unusual behavior for this particular type of composite, Koratkar said. The epoxy deforms, becomes more fluid, and creates connective fibers up to 10 microns in length and with a diameter between 100 nanometers and 1,000 nanometers.

“We didn’t expect this at all. Crazing is common in certain types of thermoplastic polymers, but very unusual in the type of epoxy composite we used,” Koratkar said. “In addition to improved fatigue resistance and toughness, the treated nanotubes also enhanced the stiffness, hardness, and strength of the epoxy composite, which is very important for structural applications.”

Koratkar said the aircraft, boat, and automobile industries are increasingly looking to composites as a building material to make vehicle frames and components lighter. His research group plans to further investigate crazing behavior in epoxy composites, in order to better understand why the chemical treatment of nanotubes initiates crazing.

Co-authors of the paper include Rensselaer Associate Professor Catalin Picu, of the Department of Mechanical, Aerospace, and Nuclear Engineering; Rensselaer doctoral students Wei Zhang and Iti Srivastava; and Yue-Feng Zhu, professor in the Department of Mechanical Engineering at Tsinghua University in China.

Virus-built Battery Could Power Cars, Electronic Devices

2009-04-03T01:02:00.000-07:00

For the first time, MIT researchers have shown they can genetically engineer viruses to build both the positively and negatively charged ends of a lithium-ion battery.
The new virus-produced batteries have the same energy capacity and power performance as state-of-the-art rechargeable batteries being considered to power plug-in hybrid cars, and they could also be used to power a range of personal electronic devices, said Angela Belcher, the MIT materials scientist who led the research team.

The new batteries, described in the April 2 online edition of Science, could be manufactured with a cheap and environmentally benign process: The synthesis takes place at and below room temperature and requires no harmful organic solvents, and the materials that go into the battery are non-toxic.

In a traditional lithium-ion battery, lithium ions flow between a negatively charged anode, usually graphite, and the positively charged cathode, usually cobalt oxide or lithium iron phosphate. Three years ago, an MIT team led by Belcher reported that it had engineered viruses that could build an anode by coating themselves with cobalt oxide and gold and self-assembling to form a nanowire.

In the latest work, the team focused on building a highly powerful cathode to pair up with the anode, said Belcher, the Germeshausen Professor of Materials Science and Engineering and Biological Engineering. Cathodes are more difficult to build than anodes because they must be highly conducting to be a fast electrode, however, most candidate materials for cathodes are highly insulating (non-conductive).

To achieve that, the researchers, including MIT Professor Gerbrand Ceder of materials science and Associate Professor Michael Strano of chemical engineering, genetically engineered viruses that first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conductive material.

Because the viruses recognize and bind specifically to certain materials (carbon nanotubes in this case), each iron phosphate nanowire can be electrically "wired" to conducting carbon nanotube networks. Electrons can travel along the carbon nanotube networks, percolating throughout the electrodes to the iron phosphate and transferring energy in a very short time.

The viruses are a common bacteriophage, which infect bacteria but are harmless to humans.

The team found that incorporating carbon nanotubes increases the cathode's conductivity without adding too much weight to the battery. In lab tests, batteries with the new cathode material could be charged and discharged at least 100 times without losing any capacitance. That is fewer charge cycles than currently available lithium-ion batteries, but "we expect them to be able to go much longer," Belcher said.

The prototype is packaged as a typical coin cell battery, but the technology allows for the assembly of very lightweight, flexible and conformable batteries that can take the shape of their container.

Last week, MIT President Susan Hockfield took the prototype battery to a press briefing at the White House where she and U.S. President Barack Obama spoke about the need for federal funding to advance new clean-energy technologies.

Now that the researchers have demonstrated they can wire virus batteries at the nanoscale, they intend to pursue even better batteries using materials with higher voltage and capacitance, such as manganese phosphate and nickel phosphate, said Belcher. Once that next generation is ready, the technology could go into commercial production, she said.

Lead authors of the Science paper are Yun Jung Lee and Hyunjung Yi, graduate students in materials science and engineering. Other authors are Woo-Jae Kim, postdoctoral fellow in chemical engineering; Kisuk Kang, recent MIT PhD recipient in materials science and engineering; and Dong Soo Yun, research engineer in materials science and engineering.

The research was funded by the Army Research Office Institute of the Institute of Collaborative Technologies, and the National Science Foundation through the Materials Research Science and Engineering Centers program.

New Nanogenerator May Charge IPods And Cell Phones With A Wave Of The Hand

2009-03-29T04:14:00.000-07:00

Imagine if all you had to do to charge your iPod or your BlackBerry was to wave your hand, or stretch your arm, or take a walk? You could say goodbye to batteries and never have to plug those devices into a power source again.
In research presented at the American Chemical Society's 237th National Meeting in Salt Lake City, Utah on March 26, scientists from Georgia describe technology that converts mechanical energy from body movements or even the flow of blood in the body into electric energy that can be used to power a broad range of electronic devices without using batteries.

"This research will have a major impact on defense technology, environmental monitoring, biomedical sciences and even personal electronics," says lead researcher Zhong Lin Wang, Regents' Professor, School of Material Science and Engineering at the Georgia Institute of Technology. The new "nanogenerator" could have countless applications, among them a way to run electronic devices used by the military when troops are far in the field.

The researchers describe harvesting energy from the environment by converting low-frequency vibrations, like simple body movements, the beating of the heart or movement of the wind, into electricity, using zinc oxide (ZnO) nanowires that conduct the electricity. The ZnO nanowires are piezoelectric — they generate an electric current when subjected to mechanical stress. The diameter and length of the wire are 1/5,000th and 1/25th the diameter of a human hair.

In generating energy from movement, Wang says his team concluded that it was most effective to develop a method that worked at low frequencies and was based on flexible materials. The ZnO nanowires met these requirements. At the same time, he says a real advantage of this technology is that the nanowires can be grown easily on a wide variety of surfaces, and the nanogenerators will operate in the air or in liquids once properly packaged. Among the surfaces on which the nanowires can be grown are metals, ceramics, polymers, clothing and even tents.

"Quite simply, this technology can be used to generate energy under any circumstances as long as there is movement," according to Wang.

To date, he says that there have been limited methods created to produce nanopower despite the growing need by the military and defense agencies for nanoscale sensing devices used to detect bioterror agents. The nanogenerator would be particularly critical to troops in the field, where they are far from energy sources and need to use sensors or communication devices. In addition, having a sensor which doesn't need batteries could be extremely useful to the military and police sampling air for potential bioterrorism attacks in the United States, Wang says.

While biosensors have been miniaturized and can be implanted under the skin, he points out that these devices still require batteries, and the new nanogenerator would offer much more flexibility.

A major advantage of this new technology is that many nanogenerators can produce electricity continuously and simultaneously. On the other hand, the greatest challenge in developing these nanogenerators is to improve the output voltage and power, he says.

Last year Wang's group presented a study on nanogenerators driven by ultrasound. Today's research represents a much broader application of nanogenerators as driven by low-frequency body movement.

The study was funded by the Defense Advanced Research Projects Agency, the Department of Energy, the National Institutes of Health and the National Science Foundation.

Hollow Gold Nanospheres Show Promise For Biomedical And Other Applications

2009-03-29T04:11:00.000-07:00

A new metal nanostructure developed by researchers at the University of California, Santa Cruz, has already shown promise in cancer therapy studies and could be used for chemical and biological sensors and other applications as well.
The hollow gold nanospheres developed in the laboratory of Jin Zhang, a professor of chemistry and biochemistry at UCSC, have a unique set of properties, including strong, narrow, and tunable absorption of light. Zhang is collaborating with researchers at the University of Texas M. D. Anderson Cancer Center, who have used the new nanostructures to target tumors for photothermal cancer therapy. They reported good results from preclinical studies earlier this year (Clinical Cancer Research, February 1, 2009).

Zhang will describe his lab's work on the hollow gold nanospheres in a talk on Sunday, March 22, at the annual meeting of the American Chemical Society in Salt Lake City.

"What makes this structure special is the combination of the spherical shape, the small size, and the strong absorption in visible and near infrared light," Zhang said. "The absorption is not only strong, it is also narrow and tunable. All of these properties are important for cancer treatment."

Zhang's lab is able to control the synthesis of the hollow gold nanospheres to produce particles with consistent size and optical properties. The hollow particles can be made in sizes ranging from 20 to 70 nanometers in diameter, which is an ideal range for biological applications that require particles to be incorporated into living cells. The optical properties can be tuned by varying the particle size and wall thickness.

In the cancer studies, led by Chun Li of the M. D. Anderson Cancer Center, researchers attached a short peptide to the nanospheres that enabled the particles to bind to tumor cells. After injecting the nanospheres into mice with melanoma, the researchers irradiated the animals' tumors with near-infrared light from a laser, heating the gold nanospheres and selectively killing the cancer cells to which the particles were bound.

Cancer therapy was not the goal, however, when Zhang's lab began working several years ago on the synthesis and characterization of hollow gold nanospheres. Zhang has studied a wide range of metal nanostructures to optimize their properties for surface-enhanced Raman scattering (SERS). SERS is a powerful optical technique that can be used for sensitive detection of biological molecules and other applications.

Adam Schwartzberg, then a graduate student in Zhang's lab at UCSC, initially set out to reproduce work reported by Chinese researchers in 2005. In the process, he perfected the synthesis of the hollow gold nanospheres, then demonstrated and characterized their SERS activity.

"This process is able to produce SERS-active nanoparticles that are significantly smaller than traditional nanoparticle structures used for SERS, providing a sensor element that can be more easily incorporated into cells for localized intracellular measurements," Schwartzberg, now at UC Berkeley, reported in a 2006 paper published in Analytical Chemistry.

The collaboration with Li began when Zhang heard him speak at a conference about using solid nanoparticles for photothermal cancer therapy. Zhang immediately saw the advantages of the hollow gold nanospheres for this technique. Li uses near-infrared light in the procedure because it provides good tissue penetration. But the solid gold nanoparticles he was using do not absorb near-infrared light efficiently. Zhang told Li he could synthesize hollow gold nanospheres that absorb light most efficiently at precisely the wavelength (800 nanometers) emitted by Li's near-infrared laser.

"The heat that kills the cancer cells depends on light absorption by the metal nanoparticles, so more efficient absorption of the light is better," Zhang said. "The hollow gold nanospheres were 50 times more effective than solid gold nanoparticles for light absorption in the near-infrared."

Zhang's group has been exploring other nanostructures that can be synthesized using the same techniques. For example, graduate student Tammy Olson has designed hollow double-nanoshell structures of gold and silver, which show enhanced SERS activities compared to the hollow gold nanospheres.

The ability to tune the optical properties of the hollow nanospheres makes them highly versatile, Zhang said. "It is a unique structure that offers true advantages over other nanostructures, so it has a lot of potential," he said.

Water Acts As Catalyst In Explosives

2009-03-22T02:04:00.000-07:00

The most abundant material on Earth exhibits some unusual chemical properties when placed under extreme conditions
Lawrence Livermore National Laboratory scientists have shown that water, in hot dense environments, plays an unexpected role in catalyzing complex explosive reactions. A catalyst is a compound that speeds chemical reactions without being consumed. Platinum and enzymes are common catalysts. But water rarely, if ever, acts as a catalyst under ordinary conditions.

Detonations of high explosives made up of oxygen and hydrogen produce water at thousands of degrees Kelvin and up to 100,000 atmospheres of pressure, similar to conditions in the interiors of giant planets.

While the properties of pure water at high pressures and temperatures have been studied for years, this extreme water in a reactive environment has never been studied. Until now.

Using first-principle atomistic simulations of the detonation of the high explosive PETN (pentaerythritol tetranitrate), the team discovered that in water, when one hydrogen atom serves as a reducer and the hydroxide (OH) serves as an oxidizer, the atoms act as a dynamic team that transports oxygen between reaction centers.

"This was news to us," said lead researcher Christine Wu. "This suggests that water also may catalyze reactions in other explosives and in planetary interiors."

This finding is contrary to the current view that water is simply a stable detonation product.

"Under extreme conditions, water is chemically peculiar because of its frequent dissociations," Wu said. "As you compress it to the conditions you'd find in the interior of a planet, the hydrogen of a water molecule starts to move around very fast."

In the molecular dynamic simulations using the Lab's BlueGene L supercomputer, Wu and colleagues Larry Fried, Lin Yang, Nir Goldman and Sorin Bastea found that the hydrogen (H) and hydroxide (OH) atoms in water transport oxygen from nitrogen storage to carbon fuel under PETN detonation conditions (temperatures between 3,000 Kelvin and 4,200 Kelvin). Under both temperature conditions, this "extreme water" served both as an end product and as a key chemical catalyst.

For a molecular high explosive that is made up of carbon, nitrogen, oxygen and hydrogen, such as PETN, the three major gaseous products are water, carbon dioxide and molecular nitrogen.

But to date, the chemical processes leading to these stable compounds are not well understood.

The team found that nitrogen loses its oxygen mostly to hydrogen, not to carbon, even after the concentration of water reaches equilibrium. They also found that carbon atoms capture oxygen mostly from hydroxide, rather than directly from nitrogen monoxide (NO) or nitrogen dioxide (NO_). Meanwhile water disassociated and recombines with hydrogen and hydroxide frequently.

"The water that comes out is part of the energy release mechanism," Wu said. "This catalytic mechanism is completely different from previously proposed decomposition mechanisms for PETN or similar explosives, in which water is just an end product. This new discovery could have implications for scientists studying the interiors of Uranus and Neptune where water is in an extreme form."

The research appears in the premier issue (April 2009) of the new journal Nature Chemistry.

Nanoscopic Probes Can Track Down And Attack Cancer Cells

2009-03-22T02:02:00.000-07:00

A researcher has developed probes that can help pinpoint the location of tumors and might one day be able to directly attack cancer cells.
Joseph Irudayaraj, a Purdue University associate professor of agricultural and biological engineering, developed the nanoscale, multifunctional probes, which have antibodies on board, to search out and attach to cancer cells.

A paper detailing the technology was released last week in the online version of Angewandte Chemie, an international chemistry journal.

"If we have a tumor, these probes should have the ability to latch on to it," Irudayaraj said. "The probe could carry drugs to target, treat as well as reveal cancer cells."

Scientists have developed probes that use gold nanorods or magnetic particles, but Irudayaraj's nanoprobes use both, making them easier to track with different imaging devices as they move toward cancer cells.

The magnetic particles can be traced through the use of an MRI machine, while the gold nanorods are luminescent and can be traced through microscopy, a more sensitive and precise process. Irudayaraj said an MRI is less precise than optical luminescence in tracking the probes, but has the advantage of being able to track them deeper in tissue, expanding the probes' possible applications.

The probes, which are about 1,000 times smaller than the diameter of a human hair, contain the antibody Herceptin, used in treatment of metastatic breast cancer. The probes would be injected into the body through a saline buffering fluid, and the Herceptin would find and attach to protein markers on the surface of cancer cells.

"When the cancer cell expresses a protein marker that is complementary to Herceptin, then it binds to that marker," Irudayaraj said. "We are advancing the technology to add other drugs that can be delivered by the probes."

Irudayaraj said better tracking of the nanoprobes could allow doctors to pinpoint the location of known tumors and better treat the cancer.

The novel probes were tested in cultured cancer cells. Irudayaraj said the next step would be to run a series of tests in mice models to determine the dose and stability of the probes.

The research was funded through a National Institute of Health grant, as well as by the Purdue Research Foundation. Irudayaraj is head of a biological engineering team that includes postdoctoral researcher Chungang Wang and graduate student Jiji Chen.

Nanotech Batteries For A New Energy Future

2009-03-22T01:59:00.000-07:00

Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available.
In order to save money and energy, many people are purchasing hybrid electric cars or installing solar panels on the roofs of their homes. But both have a problem -- the technology to store the electrical power and energy is inadequate.

Battery systems that fit in cars don't hold enough energy for driving distances, yet take hours to recharge and don't give much power for acceleration. Renewable sources like solar and wind deliver significant power only part time, but devices to store their energy are expensive and too inefficient to deliver enough power for surge demand.

Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available. The results of their research are available in a recent issue of Nature Nanotechnology.

"Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded," said Gary Rubloff, director of the University of Maryland's NanoCenter. "Conventional devices to store and deliver electrical energy -- batteries and capacitors -- cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future."

Researchers working with Professor Rubloff and his collaborator, Professor Sang Bok Lee, have developed a method to significantly enhance the performance of electrical energy storage devices.

Using new processes central to nanotechnology, they create millions of identical nanostructures with shapes tailored to transport energy as electrons rapidly to and from very large surface areas where they are stored. Materials behave according to physical laws of nature. The Maryland researchers exploit unusual combinations of these behaviors (called self-assembly, self-limiting reaction, and self-alignment) to construct millions -- and ultimately billions -- of tiny, virtually identical nanostructures to receive, store, and deliver electrical energy.

"These devices exploit unique combinations of materials, processes, and structures to optimize both energy and power density -- combinations that, taken together, have real promise for building a viable next-generation technology, and around it, a vital new sector of the tech economy," Rubloff said.

"The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power)," he continued.

Electrical energy storage devices fall into three categories. Batteries, particularly lithium ion, store large amounts of energy but cannot provide high power or fast recharge. Electrochemical capacitors (ECCs), also relying on electrochemical phenomena, offer higher power at the price of relatively lower energy density. In contrast, electrostatic capacitors (ESCs) operate by purely physical means, storing charge on the surfaces of two conductors. This makes them capable of high power and fast recharge, but at the price of lower energy density.

The Maryland research team's new devices are electrostatic nanocapacitors which dramatically increase energy storage density of such devices - by a factor of 10 over that of commercially available devices - without sacrificing the high power they traditionally characteristically offer. This advance brings electrostatic devices to a performance level competitive with electrochemical capacitors and introduces a new player into the field of candidates for next-generation electrical energy storage.

Where will these new nanodevices appear? Lee and Rubloff emphasize that they are developing the technology for mass production as layers of devices that could look like thin panels, similar to solar panels or the flat panel displays we see everywhere, manufactured at low cost. Multiple energy storage panels would be stacked together inside a car battery system or solar panel. In the longer run, they foresee the same nanotechnologies providing new energy capture technology (solar, thermoelectric) that could be fully integrated with storage devices in manufacturing.

This advance follows soon after another accomplishment, the dramatic improvement in performance (energy and power) of electrochemical capacitors (ECC's), thus 'supercapacitors,' by Lee's research group, published recently in the Journal of the American Chemical Society. Efforts are under way to achieve comparable advances in energy density of lithium (Li) ion batteries but with much higher power density.

"The University of Maryland's successes are built upon the convergence and collaboration of experts from a wide range of nanoscale science and technology areas with researchers already in the center of energy research," Rubloff said.

The Research Team

Gary Rubloff is Minta Martin Professor of Engineering in the materials science and engineering department and the Institute for Systems Research at the University of Maryland's A. James Clark School of Engineering. Sang Bok Lee is associate professor in the Department of Chemistry and Biochemistry at the College of Chemical and Life Sciences and WCU (World Class University Program) professor at KAIST (Korea Advanced Institute of Science and Technology) in Korea. Lee and Rubloff are part of a larger team developing nanotechnology solutions for energy capture, generation, and storage at Maryland. Their collaborators on electrical energy storage include Maryland professors Michael Fuhrer (physics), associate director of the Maryland Nanocenter Reza Ghodssi (electrical and computer engineering), John Cumings (materials science engineering), Ray Adomaitis (chemical and biomolecular engineering), Oded Rabin (materials science and engineering), Janice Reutt-Robey (chemistry), Robert Walker (chemistry), Chunsheng Wang (chemical and biomolecular engineering), Yu-Huang Wang (chemistry) and Ellen Williams (physics), director of the Materials Research Science and Engineering Center at the University of Maryland.

This work was partially supported by the Laboratory for Physical Sciences and by the university's Materials Research Science and Engineering Center under a grant from the National Science Foundation

Hot Electrons In Carbon: Graphite Behaves Like Semiconductor

2009-03-14T08:01:00.000-07:00

Scientists have found that graphite behaves like a semiconductor in ultrafast time scales. The results are of fundamental importance for future electronic devices based on carbon, in which high electrical fields or frequencies are processed.
Nanomaterials like carbon possess unique properties, which have led to first applications in novel electronic devices and sensors. These materials are based on ordered, atomically thin layers of carbon atoms, for example in the form of a single layer as so-called “graphene”, or rolled-up in carbon nanotubes. The electronic properties of such structures are closely related to those of graphite, which consists of a stack of graphene sheets.

Despite intensive research in the past, the fundamental behavior of electrons in this material are not fully understood and still controversially debated.

Markus Breusing, Claus Ropers und Thomas Elsaesser, three scientists from the Max-Born-Institute in Berlin, have now investigated the behavior of electrons in thin graphite films in real time.

As they now report in Physical Review Letters,* they recorded the dynamics of electrons with an unprecedented temporal resolution of only 10 femtoseconds (one femtosecond is a millionth of a billionth of a second). Electrons were excited to high energy states with ultrashort laser pulses, and their return to equilibrium was observed. The individual steps of this process are temporally resolved, and the momentary distribution of electrons in the material is identified. Within 30 femtoseconds, electrons form a hot gas with temperatures of 2500 °C, which cools down to about 200 °C in only 500 femtoseconds. The energy dissipated in this process is transferred to the crystal lattice. After this process, the electrons slowly return to their initial states.

For the first time, the study shows conclusively that, on ultrashort time scales, graphite behaves like a semiconductor, such as silicon or gallium arsenide, and not like a metal.

The observed dynamics have significant consequences for electrical transport, such as currents flowing through the material at high frequencies. The results are of fundamental importance for future electronic devices based on carbon, in which high electrical fields or frequencies are processed

First High-resolution Images Of Bone, Tooth And Shell Formation

2009-03-14T07:59:00.000-07:00

Researchers at Eindhoven University of Technology (TU/e) have for the first time made high-resolution images of the earliest stages of bone formation. They used the world’s most advanced electron microscope to make three-dimensional images of the nano-particles that are at the heart of the process.
The results provide improved understanding of bone, tooth and shell formation. For industrial applications, they promise better materials and processes based on nature itself. The findings are published in the journal Science, March 13.

Led by dr. Nico Sommerdijk, the researchers imaged small clusters with a cross-section of 0.7 nanometer in a solution of calcium carbonate (the basic material of which shells are made). They showed for the first time that these clusters, each consisting of only about ten ions, are the beginning of the growth process through which the crystalline biomineral is ultimately formed.

To do this they used the very high resolution of a special electron microscope: the cryoTitan (of FEI Company). This enabled them, as the first in their field of research, to make three-dimensional images of very rapidly frozen samples. These showed how the clusters in the solution nucleate into larger, unstructured nano-particles with an average diameter of around thirty nanometers.

An organic surface applied by the researchers ensures that these nano-particles can grow into larger particles, in which crystalline regions can later form by ordering of the ions. The TU/e researchers also demonstrated a second function of the organic layer: it controls with great precision the direction in which the mineral can grow into a fully fledged biomineral. They now hope to show that the mechanism they have identified also applies to the formation of other crystalline biominerals, and perhaps even to other, inorganic materials.

This is important for research into bone growth and bone-replacement materials. In addition it could be used in nanotechnology, to allow the growth of nano-particles to be controlled in the same way as seems to be the case in nature: through subtle interactions between organic and inorganic materials.

About biomineralization

Biomineralization is the formation of inorganic materials in a biological environment, as it is found in bones, teeth and shells. In this process the formation of the mineral is controlled with great precision by specialized organic biomolecules such as sugars and proteins. Although the underlying mechanisms have already been studied for a long time, the process is still not fully understood.

A widely used strategy is the use of so-called biomimetic studies, in which the process of biomineralization is simulated by a simplified system in a laboratory. This allows parts of the mineralization process to be studied individually.

With this approach and by using the unique electron microscope referred to above, Sommerdijk’s research group in the Chemical Engineering and Chemistry department at TU/e have been able to image the earliest stages of such a biomimetically controlled mineralization reaction.

Nico Sommerdijk carried out this work with a Vidi grant from the Netherlands Organisation for Scientific Research (NWO). The cryoTEM equipment was financed partly by an NWO Large Investment Subsidy.

Twin Nanoparticle Shown Effective At Targeting, Killing Breast Cancer Cells

2009-03-14T07:56:00.000-07:00

Breast cancer patients face many horrors, including those that arise when fighting the cancer itself. Medications given during chemotherapy can have wicked side effects, including vomiting, dizziness, anemia and hair loss. These side effects occur because medications released into the body target healthy cells as well as tumor cells.
The trick becomes how to deliver cancer-fighting drugs directly to the tumor cells. Brown University chemists think they have an answer: They have created a twin nanoparticle that specifically targets the Her-2-positive tumor cell, a type of malignant cell that affects up to 30 percent of breast cancer patients.

The combination nanoparticle binds to the Her-2 tumor cell and unloads the cancer-fighting drug cisplatin directly into the infected cell. The result: Greater success at killing the cancer while minimizing the anti-cancer drug's side effects.

"Like a missile, you don't want the anti-cancer drugs to explode everywhere," explained Shouheng Sun, a chemistry professor at Brown University and an author on the paper published online in The Journal of the American Chemical Society. "You want it to target the tumor cells and not the healthy ones."

The researchers created the twin nanoparticle by binding one gold (Au) nanoparticle with an iron-oxide (Fe3O4) nanoparticle. On one end, they attached a synthetic protein antibody to the iron-oxide nanoparticle. On the other end, they attached cisplatin to the gold nanoparticle. Visually, the whole contraption looks like an elongated dumbbell, but it may be better to think of it as a vehicle, equipped with a very good GPS system, that is ferrying a very important passenger.

In this case, the GPS comes from the iron-oxide nanoparticle, which homes in on a Her-2 breast-cancer cell like a guided missile. The attached antibody is critical, because it binds to the antigen, a protein located on the surface on the malignant cell. Put another way, the nanoparticle vehicle "docks" on the tumor cell when the antibody and the antigen become connected. Once docked, the vehicle unloads its "passenger," the cisplatin, into the malignant cell.

"It's like a magic bullet," said Chenjie Xu, a Brown graduate student and the lead author on the paper. Baodui Wang, a visiting scientist at Brown and now an associate professor at Lanzhou University in China, contributed to the paper.

In a neat twist, the Brown-led team used a pH-sensitive covalent bond to connect the gold nanoparticle with the cisplatin to ensure that the drug was not released into the body but remained attached to the nanoparticle until it was time for it to be released into the malignant cell.

In laboratory tests, the gold-iron oxide nanoparticle combination successfully targeted the cancer cells and released the anti-cancer drugs into the malignant cells, killing the cells in up to 80 percent of cases. "We made a Mercedes Benz now," Sun joked. "It's not a Honda Civic anymore."

The research builds on previous work in Sun's lab where researchers created peptide-coated iron-oxide nanoparticles that, in tests with mice, successfully located a brain tumor cell called U87MG.

The researchers will test the breast-cancer nanoparticle system in laboratory tests with animals. They also plan to create twin nanoparticles that can release the drug via remote-controlled magnetic heating.

The breast-cancer nanoparticle research was funded by the National Institutes of Health.

Models Present New View Of Nanoscale Friction

2009-03-10T09:13:00.000-07:00

To understand friction on a very small scale, a team of University of Wisconsin-Madison engineers had to think big.
Friction is a force that affects any application where moving parts come into contact; the more surface contact there is, the stronger the force. At the nanoscale — mere billionths of a meter — friction can wreak havoc on tiny devices made from only a small number of atoms or molecules. With their high surface-to-volume ratio, nanomaterials are especially susceptible to the forces of friction.

But researchers have trouble describing friction at such small scales because existing theories are not consistent with how nanomaterials actually behave. Through computer simulations, the group demonstrated that friction at the atomic level behaves similarly to friction generated between large objects. Five hundred years after Leonardo da Vinci discovered the basic friction laws for large objects, the UW-Madison team has shown that similar laws apply at the nanoscale.

The team, which was led by Izabela Szlufarska, an assistant professor of materials science and engineering, and included materials science and engineering graduate student Yifei Mo and mechanical engineering assistant professor Kevin Turner, published its findings in the Feb. 26 issue of the journal Nature.

Current nanoscale friction theories are based on the idea that nanoscale surfaces are smooth, but, in reality, the surfaces resemble a mountain range, where each peak corresponds to an atom or a molecule.

The UW-Madison team performed computer simulations that looked at nanoscale materials as a collection of atoms, monitoring their positions and interactions throughout the entire sliding process. "For the first time, we modeled friction at length scales very similar to experiments, while maintaining atomic resolution and realistic interactions between atoms," say Szlufarska.

The team discovered simple laws of nanoscale friction. They found that friction is proportional to the number of atoms that interact between two nanoscale surfaces. The researchers' simulations showed that, at the nanoscale, materials in contact behave more like large rough objects rubbing against each other, rather than as two perfectly smooth surfaces, as was previously imagined. "When you look at it closely, the surface is made of atoms, so the contact is actually rough," says Szlufarska.

The team's simulation data correlates very well with recorded experimental data — something that previous models have failed to accomplish. Szlufarska hopes to use the simulations as a tool to understand what mechanisms contribute to friction on both the nano- and macroscale.

"Nobody is able to predict friction or design materials with desired friction properties — we measure a lot of friction coefficients for different materials, but it's not really clear how to relate them to the properties of the material," she explains. "The origin of friction is really an open and growing research field."

Quantum Doughnuts Slow And Freeze Light At Will: Fast Computing And 'Slow Glass'

2009-03-10T02:44:00.000-07:00

Research led by the University of Warwick has found a way to use doughnut shaped by-products of quantum dots to slow and even freeze light, opening up a wide range of possibilities from reliable and effective light-based computing to the possibility of "slow glass."
The key to this new research is the “exciton.” This describes the pairing of an electron that has been kicked into a higher energy state by a photon, with a hole or gap it (or another electron) leaves within the shell or orbit around the nucleus of an atom. Despite its new high energy state, the electron remains paired with one of the holes or positions that has been vacated by electrons moving to a higher energy state. When an electron’s high energy state decays again, it is drawn back to the hole it is linked to and a photon is once again emitted.

That cycle usually happens very quickly, but if one could find a way to freeze or hold an exciton in place for any length of time, one could delay the reemitting of a photon and effectively slow or even freeze light.

The researchers, led by PhD researcher Andrea Fischer and Dr. Rudolf A. Roemer from the University of Warwick’s Department of Physics, looked at the possibilities presented by some tiny rings of matter accidentally made during the manufacture quantum dots. When creating these very small quantum dots of a few 10-100nm in size, physicists sometimes cause the material to splash when depositing it onto a surface, leaving not a useful dot, but a doughnut-shaped ring of material. Though originally created by accident, these “Aharonov-Bohm nano rings” are now a source of study in their own right, and in this case seemed just the right size for enclosing an exciton. However, simply being this useful size does not, in itself, allow them to contain or hold an exciton for any length of time.

However, remarkably the Warwick led research team have found that if a combination of magnetic and electric fields is applied to these nano-rings, they can actually then simply tune the electric field to freeze an exciton in place or let it collapse and re-emit a photon.

While other researchers have used varying exotic states of matter to dramatically slow the progress of light, this is the first time a technique has been devised to completely freeze and release individual photons at will.

Dr Roemer said: “This has significant implications for the development of light based computing which would require an effective and reliable mechanism such as this to manipulate light. “

The technique could also be used to develop a “buffer” of incoming photons which could re-release them in sequence at a later date, thus creating an effect not unlike the concept of “Slow Glass” first suggested by science fiction author Bob Shaw several decades ago.

The new research paper is entitled “Exciton storage in a nanoscale Aharonov-Bohm ring with electric field tuning," by University of Warwick PhD student Andrea M.Fischer, Dr Rudolf Roemer (University of Warwick) Vivaldo L. Campo Jr. (Universidade Federal de Sao Carlos-UFSCar, Brazil), and Mikhail E. Portnoi (University of Exeter), and has just been published in Physical Review Letters (PRL).

New Genre Of Sugar-coated 'Quantum Dots' For Drug Delivery

2009-03-10T02:40:00.000-07:00

Scientists in Switzerland are reporting an advance that could help tap the much-heralded potential of "quantum dots"— nanocrystals that glow when exposed to ultraviolet light — in the treatment of cancer and other diseases.
They are publishing the first study showing that giving quantum dots an icing-like cap of certain sugars makes these nanoparticles accumulate in the liver but not other parts of the body. That selective targeting could be used to deliver anti-cancer drugs to one organ, without causing the body-wide side-effects that occur with existing cancer drugs, they suggest.

Their study is in the Feb. 18 issue of the Journal of the American Chemical Society, a weekly publication.

In the new report, Peter H. Seeberger and colleagues note that quantum dots, about 1/5,000th the width of a human hair, are used in solar cells, medical diagnostic imaging, and electronics. Scientists believe these particles also show promise for drug delivery for treating cancer and other diseases. However, researchers still have not found an ideal way to target these dots to specific tissues or organs in order to maximize their effectiveness and limit toxicity.

They describe development of a new type of quantum dot coated with certain sugar molecules that are attracted to receptors in specific tissues and organs. In a study with laboratory mice, the scientists coated quantum dots with either mannose or galactosamine, two sugars that accumulate selectively in the liver. The sugar-coated dots became three times more concentrated in the mice livers than the regular dots, demonstrating their higher specificity, the researchers say.

First Measurement Of The Ability Of A Very Long Molecular Wire To Conduct Electric Current

2009-03-08T21:25:00.000-07:00

For the first time, researchers from CNRS, the Free University of Berlin and Humboldt University (Berlin) have measured the ability of a single, very long molecular wire to carry electric current. Until now, there were only statistical measurements on a collection of wires a few nanometers long. Now, thanks to an ingenious experiment using a scanning tunneling microscope, the researchers have characterized individual polymer chains of known length, up to 20 nanometers long.
They confirm what is predicted by theory: the ability to conduct electric current decreases exponentially with the length of the wire.

Tomorrow's electronic circuits will be made up of individual molecules, connected to each other by means of 'molecular electric wires' (themselves consisting of a single, long molecule). But first, researchers need to understand how electric current flows through this type of wire. On the macroscopic scale, the ability to carry current, called conductance, varies linearly as a function of the length and cross-sectional area of the wire. On the scale of a molecule, this rule is no longer valid.

Consequently, it is necessary to measure the electric current that flows through a single molecular wire connected to two electrodes and determine how it varies as a function of the length of the wire. Until now, all the experimental studies focused on very short wires (a few nanometers long) or were based exclusively on statistical measurements.

At the Free University of Berlin, in collaboration with CNRS's Center for Materials Elaboration and Structural Studies (Centre d’élaboration de matériaux et d’études structurales) (CEMES) in Toulouse and with Humboldt University (Berlin), researchers carried out an ingenious experiment to measure the conductance of a single molecule with a perfectly defined length. First they placed small molecules on a gold surface, which they bonded chemically to each other by means of a surface polymerisation reaction, which brought about the formation of long molecular chains.

They then selected one of the chains by making images of the surface with a scanning tunneling microscope and chemically bonded one end of the chain to the microscope's metal tip, which thus made up one of the two electrodes, while the other end of the polymer remained in position on the gold surface, making up the second electrode. By moving the tip away from the surface, the researchers gradually lifted up the chain, thus forming a molecular electric wire that became longer as the tip moved away from the surface. The scanning tunneling microscope was used both to measure the length of the selected molecular electric wire (since the resolution of the image is on the atomic scale it can, for example, be used to count the number of monomers) and to measure the current flowing through it. For the first time, the charge transport through a single polymer chain was measured for different lengths (up to 20 nanometers) between the two electrical contacts.

The results are in agreement with theoretical predictions: the current decreases exponentially with the length of the molecular electric wire. After the success of this innovative experiment, it is now up to chemists to come up with more conductive molecules that can be used to develop molecular wires able to carry current over even greater distances.

Chemists Find Secret To Increasing Luminescence Efficiency Of Carbon Nanotubes

2009-03-08T21:23:00.000-07:00

Chemists at the University of Connecticut have found a way to greatly increase the luminescence efficiency of single-walled carbon nanotubes, a discovery that could have significant applications in medical imaging and other areas.
Increasing the luminescence efficiency of carbon nanotubes may someday make it possible for doctors to inject patients with microscopic nanotubes to detect tumors, arterial blockages and other internal problems. Rather than relying on potentially harmful x-rays or the use of radioactive dyes, physicians could simply scan patients with an infrared light that would capture a very sharp resolution of the luminescence of the nanotubes in problem areas.

UConn's process of increasing the luminescence efficiency of single-walled carbon nanotubes will be featured in the journal Science on March 6, 2009. The research was performed in the Nanomaterials Optoelectronics Laboratory at the Institute of Materials Science at the University of Connecticut, in Storrs, CT. A patent for the process is pending.

University of Connecticut Chemist Fotios Papadimitrakopoulos describes the discovery as a major breakthrough and one of the most significant discoveries in his 10 years of working with single-walled carbon nanotubes. Assisting Papadimitrakopoulos with the research were Polymer Program graduate student Sang-Yong Ju (now a researcher at Cornell University) and William P. Kopcha, a former Chemistry undergraduate assistant in the College of Liberal Arts and Sciences who is now a first-year graduate student at UConn.

Although carbon is used in many diverse applications, scientists have long been stymied by the element's limited ability to emit light. The best scientists have been able to do with solution-suspended carbon nanotubes was to raise their luminescence efficiency to about one-half of one percent, which is extremely low compared to other materials, such as quantum dots and quantum rods.

By tightly wrapping a chemical 'sleeve' around a single-walled carbon nanotube, Papadimitrakopoulos and his research team were able to reduce exterior defects caused by chemically absorbed oxygen molecules.

This process can best be explained by imagining sliding a small tube into a slightly larger diameter tube, Papadimitrakopoulos says. In order for this to happen, all deposits or protrusions on the smaller tube have to be removed before the tube is allowed to slip into the slightly larger diameter tube. What is most fascinating with carbon nanotubes however, Papadimitrakopoulos says, is the fact that in this case the larger tube is not as rigid as the first tube (i.e. carbon nanotube) but is rather formed by a chemical "sleeve" comprised of a synthetic derivative of flavin (an analog of vitamin B2) that adsorbs and self organizes onto a conformal tube.

Papadimitrakopoulos claims that this process of self-assembly is unique in that it not only forms a new structure but also actively "cleans" the surface of the underlying nanotube. It is that active cleaning of the nanotube surface that allows the nanotube to achieve luminescence efficiency to as high as 20 percent.

"The nanotube is the smallest tube on earth and we have found a sleeve to put over it," Papadimitrakopoulos says. "This is the first time that a nanotube was found to emit with as much as 20 percent luminescence efficiency."

Papadimitrakopoulos has been working closely with the UConn Center for Science and Technology Commercialization (CSTC) in transferring his advances in research into the realm of patents, licenses and corporate partnerships. The CSTC was created several years ago as a way to help expand Connecticut's innovation-based economy and to help create new businesses and jobs around new ideas.

This is the second major nanotube discovery at UConn by Papadimitrakopoulos in the past two years. Last year, Papadimitrakopoulos and Sang-Young Ju, along with other UConn researchers, patented a way to isolate certain carbon nanotubes from others by seamlessly wrapping a form of vitamin B2 around the nanotubes. It was out of that research that Papadimitrakopoulos and Sang-Yong Ju began wrapping nanotubes with helical assemblies and probing their luminescence properties.

The more luminescent the nanotube, the brighter it appears under infrared irradiation or by electrical excitation (such as that provided by a light-emitting diode or LED). A number of important applications may be possible as a result of this research, Papadimitrakopoulos says. Carbon nanotube emissions are not only extremely sharp, but they also appear in a spectral region where minimal absorption or scattering takes place by soft tissue. Moreover, carbon nanotubes display superb photo bleaching stability and are ideally suited for near-infrared emitters, making them appropriate for applications in medicine and homeland security as bio-reporting agents and nano-sized beacons. Carbon nanotube luminescence also has important applications in nano-scaled LEDs and photo detectors, which can readily integrate with silicon-based technology. This provides an enormous repertoire for nanotube use in advanced fiber optics components, infrared light modulators, and biological sensors, where multiple applications are possible due to the nanotube's flavin-based (vitamin B2) helical wrapping.

Potential On-off Switch For Nanoelectronics

2009-03-03T22:07:00.000-08:00

As electronic circuits shrink from finely etched lines in silicon wafers to nearly elusive proportions, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Columbia University are studying how electrons flow through a molecular junction-a nanometer scale circuit element that contacts gold atoms with a single molecule.

Their findings reveal the electrical resistance through this junction can be turned ‘on’ and ‘off’ simply by pushing and pulling the junction-a feature that could be used as a switch in nanoscale electronic devices.

“To design circuit elements at the molecular scale, we need to understand how the intrinsic properties of a molecule or junction are actually connected to its measured resistance,” said Jeff Neaton, Facility Director of the Theory of Nanostructured Materials Facility in the Molecular Foundry, a U.S. Department of Energy User Facility located at Berkeley Lab that provides support to nanoscience researchers around the world. “Knowing where each and every atom is in a single-molecule junction is simply beyond what’s possible with experiments at this stage. For these sub-nanometer scale junctions-just a handful of atoms-theory can be valuable in helping interpret and understand resistance measurements.”

In traditional electronic devices, charge-carrying electrons diffuse through circuits in a well-understood fashion, gaining or losing energy through transactions with impurities or other particles they encounter. Electrons at the nanoscale, however, can travel by a mechanism called quantum tunneling in which, due to the small length scales involved, it becomes possible for a particle to disappear through an energy barrier and suddenly appear on the other side, without expending energy.

Tracking such ‘tunneling’ of electrons through individual molecules in nanoscale devices has proven difficult. “For more than a decade, researchers have been ‘wiring up’ individual molecules and measuring their electrical conductance,” said Neaton. “Forming reliable contacts between nanostructures and ‘alligator clip’ electrical leads is extremely challenging. This made experiments difficult to interpret, and as a result, reported conductance values-in experiment and theory-often varied by an order of magnitude or more. The time was ripe for a quantitative comparison between theory and an experiment with well-defined contacts.”

Through the Molecular Foundry user program, Su Ying Quek, a postdoctoral researcher, worked with Neaton and Latha Venkataraman, an experimental researcher at Columbia University, using a scanning tunneling microscope (STM), which probes changes in current across a material’s surface with a conductive gold tip. Previous work had shown a gold STM tip could be repeatedly be plunged into a gold surface containing a solution of molecules and retracted, until the contact area between the tip and gold surface reduces to a single strand, like a necklace.

When this strand finally breaks, nearby molecules can hop into the gap between strands and contact the gold electrodes, resulting in a sudden change in conductance. Using this technique, Venkataraman and colleagues, including Mark Hybertsen at Brookhaven National Lab, had recently discovered that the conductance of molecules containing amines (a group of molecules related to ammonia) in contact with gold electrodes could be reliably measured.

“We now had a reproducible and consistent data set to benchmark our theory,” said Quek. “Comparing with this data set, we discovered important electron correlation effects previously missing. When we added these, we found-for the first time-quantitative agreement with experimental results.”

Using their new theoretical approach, Quek and Neaton, together with Hybertsen and collaborators Steven G. Louie of University of California Berkeley and Hyoung Joon Choi of Yonsei University in Korea, began to study the conductance of a junction between gold electrodes and bipyridine-a benzene-like ring molecule containing nitrogen. The experimental data showed two stable conductance states, unlike anything seen previously. Working closely with Venkataraman and collaborators, Quek hypothesized the peaks corresponded to two states with different structures within the junction. During the next year, Quek and Neaton meticulously constructed a theory that could describe the conductance of junctions arranged vertically between two gold molecules and sandwiched at angles.

The story that emerged was surprisingly detailed: if bipyridine bonded at an angle, more current could flow compared with when the bipyridine bonded vertically. This suggests the conductance of bipyridine was linked to the molecule’s orientation in the junction, explained Quek. In the STM experiment, as you pull, just after the final strand of gold atoms breaks and snaps back, the vertical gap is not big enough for bipyridine, so it bonds at an angle. As the gap increases, the molecule jumps to a vertical configuration, causing the conductance to plummet abruptly. Eventually, the molecule straightens even more, and the contact breaks. “Once we determined this, we wondered, ‘could you reverse this behavior?’” said Quek.

Teaming with Venkataraman and collaborators, Quek and Neaton demonstrated why pushing the junction to an angle and pulling it straight could repeatedly alter the conductance, creating a mechanical switch with well defined ‘on’ and ‘off’ states. “One of the fascinating things about this experiment is the degree to which it is possible to control the ‘alligator clips’,” said Neaton. “For this particular molecule, bipyridine, experiments can reproducibly and reliably alter these atomic-scale features back and forth to switch the conductance of the junction.”

Quek and Neaton hope to refine and apply their theoretical framework to more complex molecular junctions for study of systems promising for solar energy conversion, such as organic photovoltaics.

“Understanding how electrons move through single-molecule junctions is the first step,” said Neaton. “Organic-inorganic interfaces are everywhere in nanoscience, and developing a better picture of charge transport in hybrid materials systems will certainly lead to the discovery of new and improved electronic devices.”

Nanoparticles Double Their Chances Of Getting Into Sticky Situations, And Boost Potential Uses

2009-02-28T22:12:00.000-08:00

Chemistry researchers at the University of Warwick have found that tiny nanoparticles could be twice as likely to stick to the interface of two non mixing liquids than previously believed. This opens up a range of new possibilities for the uses of nanoparticles in living cells, polymer composites, and high-tech foams, gels, and paints. The researchers are also working on ways of further artificially enhancing this new found sticking power.
University of Warwick researchers reviewed molecular simulations of the interaction between a non-charged nanoparticle and an "ideal" liquid-liquid interface. They were surprised to find that very small nanoparticles (of around 1 to 2 nanometres) varied considerably in their simulated ability to stick to such interfaces from what was expected in the standard model.

The researchers found that it took up to 50 percent more energy to dislodge the particles from the liquid-liquid interface for the smallest particle sizes. However as the radius of the particles increased this deviation from the standard model gradually faded out.

The researchers, Dr ir Stefan A. F. Bon and Dr David L. Cheung, believe that previous models failed to take into account the action of "capillary waves" in their depiction of the nanoparticles behaviour at the liquid to liquid interfaces.

Dr ir Stefan A. F. Bon said, " This new understanding on the nano-scale gives us much more flexibility in the design of everything from high-tech composite materials, to the use of quantum dots, cell biochemistry, and the manufacture of new "armored" polymer paint particles."

The researchers are now working on ways to build on this newly found natural stickiness of nanoparticles by designing polymer nanoparticles with opposing hydrophobic and hydrophilic surfaces that will bind even more strongly at oil/water liquid interfaces.

The research was funded by the Engineering and Physical Sciences Research Council (EPSRC)

Nano-origami Used To Build Tiny Electronic Devices

2009-02-28T22:08:00.000-08:00

Folding paper into shapes such as a crane or a butterfly is challenging enough for most people. Now imagine trying to fold something that's about a hundred times thinner than a human hair and then putting it to use as an electronic device.
A team of researchers led by George Barbastathis, associate professor of mechanical engineering, is developing the basic principles of "nano-origami," a new technique that allows engineers to fold nanoscale materials into simple 3-D structures. The tiny folded materials could be used as motors and capacitors, potentially leading to better computer memory storage, faster microprocessors and new nanophotonic devices.

Traditional micro- and nano-fabrication techniques such as X-ray lithography and nano-imprinting work beautifully for two-dimensional structures, and are commonly used to build microprocessors and other micro-electrical-mechanical (MEMS) devices. However, they cannot create 3-D structures.

"A lot of what's done now is planar," says Tony Nichol, a mechanical engineering graduate student working on the project. "We want to take all of the nice tools that have been developed for 2-D and do 3-D things."

The MIT team uses conventional lithography tools to pattern 2-D materials at the nanoscale, then folds them into predetermined 3-D shapes, opening a new realm of possible applications.

Smaller, faster

The researchers have already demonstrated a 3-D nanoscale capacitor, developed in collaboration with MIT Professor Yang Shao-Horn, which was presented at the 2005 meeting of the Electrochemical Society. The current model has only one fold but the more folds that are added, the more energy it will be able to store. Extra layers also promote faster information flow, just as the human brain's many folds allow for quicker communication between brain regions, says Nader Shaar, a mechanical engineering graduate student working on the project.

Getting the materials to fold back and forth into an accordion-like structure has been one of the researchers' biggest challenges, along with getting the faces and edges to line up accurately.

They have worked out several ways to induce the nanomaterials to fold, including:

* Depositing metal (usually chromium) onto the surface where you want the fold to be. This causes the material to curl upward, but it does not allow for right angles or accordion-type folds.
* Directing a beam of helium ions onto the desired fold location. The beams imprint patterns that will cause the material to fold once it's removed from the surface. High-energy beams go to the bottom of the material and cause it to fold up; ions from low-energy beams accumulate at the top of the material and make it fold down.
* Embedding gold wires in the material. A current running along the gold wires interacts with an external magnetic field, creating a Lorentz force that lifts the face. This technique is a form of directed self-assembly, where the designer provides the template and then lets the device assemble itself.

The folded shapes can be fabricated with a few different types of material, including silicon, silicon nitride (a type of ceramic) and a soft polymer known as SU-8.

Once the material is folded, the tricky part is getting the faces to align properly. The researchers have developed a few ways to do this successfully: one uses magnets; another involves attaching polymers to a certain spot on the faces and melting them with an electric current, sealing the two faces together.

They're still working on getting faces and edges of a folded cube to line up with nanoscale precision, but Shaar, co-supervised by associate professor of mechanical engineering Carol Livermore, has devised a promising method that uses three pairs of matching holes and protrusions to pull the edge and face into alignment.

The researchers are deep in the development phase of their nano-folded devices, but they are starting to think about how the technology could be used in the future. "We've got the core components figured out, and now we're just having fun with figuring out some applications," says Nichol.

Sophisticated Nano-structures Assembled With Magnets

2009-02-22T09:00:00.000-08:00

What do Saturn and flowers have in common?
As shapes, both possess certain symmetries that are easily recognizable in the natural world. Now, at an extremely small level, researchers from Duke University and the University of Massachusetts have created a unique set of conditions in which tiny particles within a solution will consistently assemble themselves into these and other complex shapes.

By manipulating the magnetization of a liquid solution, the researchers have for the first time coaxed magnetic and non-magnetic materials to form intricate nano-structures. The resulting structures can be "fixed," meaning they can be permanently linked together. This raises the possibility of using these structures as basic building blocks for such diverse applications as advanced optics, cloaking devices, data storage and bioengineering.

Changing the levels of magnetization of the fluid controls how the particles are attracted to or repelled by each other. By appropriately tuning these interactions, the magnetic and non-magnetic particles form around each other much like a snowflake forms around a microscopic dust particle.

"We have demonstrated that subtle changes in the magnetization of a fluid can create an environment where a mixture of different particles will self-assemble into complex superstructures," said Randall Erb, fourth-year graduate student. He performed these experiments in conjunction with another graduate student Hui Son, in the laboratory of Benjamin Yellen, assistant professor of mechanical engineering and materials science and lead member of the research team.

The results of the Duke experiments appear in Feb. 19 issue of the journal Nature.

The nano-structures are formed inside a liquid known as a ferrofluid, which is a solution consisting of suspensions of nanoparticles composed of iron-containing compounds. One of the unique properties of these fluids is that they become highly magnetized in the presence of external magnetic fields. The unique ferrofluids used in these experiments were developed with colleagues Bappaditya Samanta and Vincent Rotello at the University of Massachusetts.

"The key to the assembly of these nano-structures is to fine-tune the interactions between positively and negatively magnetized particles," Erb said. "This is achieved through varying the concentration of ferrofluid particles in the solution. The Saturn and flower shapes are just the first published examples of a range of potential structures that can be formed using this technique."

According to Yellen, researchers have long been able to create tiny structures made up of a single particle type, but the demonstration of sophisticated structures assembling in solutions containing multiple types of particles has never before been achieved. The complexity of these nano-structures determines how they can ultimately be used.

"It appears that a rich variety of different particle structures are possible by changing the size, type and or degree of magnetism of the particles," Yellen said.

Yellen foresees the use of these nano-structures in advanced optical devices, such as sensors, where different nano-structures could be designed to possess custom-made optical properties. Yellen also envisions that rings composed of metal particles could be used for antenna designs, and perhaps as one of the key components in the construction of materials that display artificial "optical magnetism" and negative magnetic permeability.

In the Duke experiments, the nano-structures were created by applying a uniform magnetic field to a liquid containing various types of magnetic and non-magnetic colloidal particles contained between transparent glass slides to enable real-time microscopic observations of the assembly process. Because of the unique nature of this "bulk" assembly technique, Yellen believes that the process could easily be scaled up to create large quantities of custom-designed nano-structures in high-volume reaction vessels. However, the trick is to also be able to glue the structures together, because they will fall apart when the external field is turned off, he said.

"The magnetic forces assembling these particles are reversible," Yellen said. "We were able to lock these nano-structures in their intended shapes both by using chemical glues and by simple heating."

The Duke team plans to test different combinations of particles and ferrofluids developed by the University of Massachusetts team to create new types of nano-structures. They also want to try to make even smaller nano-structures to find the limitations of the assembly process, and study the interesting optical properties which are expected from these structures.

"While we have shown that we can get small magnetic particles to form complex and beautiful structures, we believe that based on theory and the results of preliminary experiments, we should be able manipulate even smaller particles by using other magnetic particles and ferrofluids," Yellen said.

The research was supported by the National Science Foundation.

New Silver-based Nanoparticle Ink Could Lead To Better Flexible, Printed Electronics

2009-02-22T08:58:00.001-08:00

A new ink developed by researchers at the University of Illinois allows them to write their own silver linings.
The ink, composed of silver nanoparticles, can be used in electronic and optoelectronic applications to create flexible, stretchable and spanning microelectrodes that carry signals from one circuit element to another. The printed microelectrodes can withstand repeated bending and stretching with minimal change in their electrical properties.

In a paper to be published Feb. 12, by Science Express, the online version of the journal Science, Jennifer Lewis, the Thurnauer Professor of Materials Science and Engineering and director of the university's Frederick Seitz Materials Research Laboratory, and her collaborators demonstrate patterned silver microelectrodes by omnidirectional printing of concentrated nanoparticle inks with minimum widths of about 2 microns on semiconductor, plastic and glass substrates.

"Unlike inkjet or screen printing, our approach enables the microelectrodes to be printed out-of-plane, allowing them to directly cross pre-existing patterned features through the formation of spanning arches," Lewis said. "Typically, insulating layers or bypass electrode arrays are required in conventional layouts."

To produce printed features, the researchers first prepare a highly concentrated silver nanoparticle ink. The ink is then extruded through a tapered cylindrical nozzle attached to a three-axis micropositioning stage, which is controlled by computer-aided design software.

When printed, the silver nanoparticles are not yet bonded together. The bonding process occurs when the printed structure is heated to 150 degrees Celsius or higher. During thermal annealing, the nanoparticles fuse into an interconnected structure. Because of the modest processing temperatures required, the printed features are compatible with flexible, organic substrates.

To demonstrate the versatility of the printing process, the researchers patterned both planar and out-of-plane silver microelectrodes; produced spanning interconnects for solar microcell and light-emitting-diode arrays; and bonded silver wires to fragile, three-dimensional devices.

"Unlike conventional techniques, our approach allows fine silver wires to be bonded to delicate devices using minimal contact pressure," said postdoctoral researcher Bok Yeop Ahn, the lead author of the paper.

"Our approach is capable of creating highly integrated systems from diverse classes of electronic materials on a broad range of substrates," said graduate student Eric Duoss, a co-author of the paper. "Omnidirectional printing overcomes some of the design constraints that have limited the potential of printed electronics.

In addition to Lewis, Ahn and Duoss, the paper's co-authors include chemistry professor Ralph Nuzzo and materials science and engineering professor John Rogers, as well as members of their research groups.

Nanoscale Materials Grow With The Flow

2009-02-22T08:55:00.000-08:00

Imagine unloading a pile of bricks onto the ground and watching the bricks assemble themselves into a level, straight wall in only a few minutes. While merely a fantasy for builders in the everyday world, these types of self-assembled structures are a reality for those who build materials in the nanoworld.
Michael C. Tringides, a senior physicist at the U.S. Department of Energy's Ames Laboratory, has shown that nanoscale "straight wall" lead islands on silicon are spontaneously and quickly created by unusually mobile atoms.

Several years ago, Tringides' research group was the first to observe that lead atoms deposited on a silicon surface at low temperatures self-organize into uniform-height island nanostructures. The laws of quantum mechanics – specifically, Quantum Size Effects – determine why lead atoms stack up to create uniform islands while other nanostructure systems organize into islands that vary in height.

How the lead-on-silicon islands organized into uniform-height islands remained a mystery until Tringides' team made the surprising discovery that when lead atoms move along the surface of a silicon substrate, the lead atoms exhibit a liquid-like motion instead of the typical random-type diffusion observed in other systems. The liquid-like motion of atoms was observed using scanning tunneling microscopy at Ames Lab and low energy electron microscopy performed by collaborators in Hong Kong.

"One big surprise was that the atoms were moving a lot at such a low temperature: 150 degrees Kelvin or minus 123 degrees Celsius," said Tringides. "The other surprise was that the atoms weren't moving randomly like individual atoms as we would expect. In this particular case, it seemed like the whole layer of lead atoms was moving like a liquid.

Fluid-like motion of the lead atoms explains why the layer moves so easily and forms uniform islands so quickly.

"When applying nanotechnology, it's very important to be able to make nanostructures of the same dimension using a method that others can easily replicate," said Tringides. "And, it's important that the growth process is fast."

Tringides' work succeeds in terms of uniformity and speed. The lead islands self-organize on silicon in only two to three minutes. Also, better understanding of how the lead islands grow will help researchers see if other systems show the same liquid-like behavior at low temperatures.

With such promising findings in hand, Tringides' team, which includes associate scientist Myron Hupalo and graduate students Steven Binz and Jizhou Chen, further investigated the possible use of these unusual lead islands on silicon as templates to study typical atomic processes, such as adsorption, nucleation and atom bonding. These processes are important in the study of reactivity and catalysis.

During those experiments, Tringides' group made another unexpected discovery. Normally atomic processes depend on an element's chemical nature, but the group found that when it came to lead islands, quantum mechanics had another surprise in store: The atomic processes depend dramatically on whether the island height is odd or even rather than its chemical nature. Tringides' group made this intriguing observation in a large lead island that had formed over a step on the original silicon surface. The top of the large island was flat as expected.

"But, the part of the island sitting on the higher terrace of silicon was four layers high, and the other part of the island sitting on the lower terrace was five layers," said Tringides.

The group studied nucleation on this unusual island by adding a very small amount of lead to its surface, creating many new small islands on top of the large island. Examination revealed that the density of the new islands was 60 times higher on the four-layer part of the island than on the five-layer part even though the two parts of the island were connected, suggesting that atom bonding is easier on the four-layer islands.

"The island was made up of the same element, lead, throughout," said Tringides. "So, we would expect the two parts of the island to communicate with each other, and atoms should be able to easily move from left to right and right to left among both halves of the island, so the density of the new small islands should have been the same in both parts."

Instead, the two halves of the island behaved like two separate islands. The four-layer section of the island has similar characteristics to independent four-layer islands, and the five-layer section behaved like other five-layer islands.

"For the purpose of growing materials, the two-part island indicates that we may not have to change the element to create variation in material properties," said Tringides. "Instead, we may be able to just change the height of the island."

"This is promising because it's easier to change the geometry of an island than to go out and find a new, exotic material," he added.

Tringides plans further experiments using gas adsorption to test the relationship between material reactivity and island height.

The Department of Energy's Office of Science, Basic Energy Sciences Office funded the work.

Nanoparticles Delivering Drugs Can Kill Skin, Breast Cancer Cells

2009-02-07T22:38:00.000-08:00

Researchers in Pennsylvania are reporting for the first time that nanoparticles 1/5,000 the diameter of a human hair encapsulating an experimental anticancer agent, kill human melanoma and drug-resistant breast cancer cells growing in laboratory cultures.
The discovery could lead to the development of a new generation of anti-cancer drugs that are safer and more effective than conventional chemotherapy agents, the scientists suggest.

The research is scheduled for the Dec. 10 issue of ACS' Nano Letters, a monthly journal.

In the new study, Mark Kester, James Adair and colleagues at Penn State's Hershey Medical Center and University Park campus point out that certain nanoparticles have shown promise as drug delivery vehicles. However, many of these particles will not dissolve in body fluids and are toxic to cells, making them unsuitable for drug delivery in humans. Although promising as an anti-cancer agent, ceramide also is insoluble in the blood stream making delivery to cancer cells difficult.

The scientists report a potential solution with development of calcium phosphate nanocomposite particles (CPNPs). The particles are soluble and with ceramide encapsulated with the calcium phosphate, effectively make ceramide soluble. With ceramide encapsulated inside, the CPNPs killed 95 percent of human melanoma cells and was "highly effective" against human breast cancer cells that are normally resistant to anticancer drugs, the researchers say.

Penn State Research Foundation has licensed the calcium phosphate nanocomposite particle technology known as "NanoJackets" to Keystone Nano, Inc. MK and JA are CMO and CSO, respectively.

New Knowledge About Thermoelectric Materials Could Give Better Energy Efficiency

2009-02-07T22:37:00.000-08:00

Researchers at the University of Århus, Risø-DTU and the University of Copenhagen stand jointly behind new data, just published in Nature Materials, that describes properties of thermoelectric materials, which is of great importance for their practical application.
In the long term the new knowledge can be used to develop motors that are more fuel-efficient and for more environmentally friendly cooling methods.

Thermoelectric materials can be assembled into units, which can transform the thermal difference to electrical energy or vice versa - electrical current to cooling. An effective utilization requires however that the material supplies a high voltage and has good electrical, but low thermal conductivity.

"The new knowledge explains exactly why some thermoelectric materials can have the desired low thermal conductivity without degrading the electrical properties. This can be crucial for the conversion of wasted heat, for example, from vehicle exhaust emissions. Leading car manufacturers are now working to develop this possibility and the first models are close to production. The technology is expected to give the cars considerably improved fuel economy," explains Bo B. Iversen, Professor at iNANO at the University of Århus.

The new knowledge can also contribute to the development of new cooling methods, so that one avoids the most common, but very environmentally damaging greenhouse gas (R-134a). All of which is a gain for the environment.

In the Nature Materials article the researchers have studied one of the most promising thermoelectric materials in the group of clathrates, which create crystals full of ‘nano-cages'.

"By placing a heavy atom in each nano-cage, we can reduce the crystals' ability to conduct heat. Until now we thought that it was the heavy atoms random movements in the cages that were the cause of the poor thermal conductivity, but this has been shown to not be true," explains Asger B. Abrahamsen, senior scientist at Risø-DTU.

The researchers have used the technique of neutron scattering, which gives them opportunity to look into the material and see the atoms' movements.

"Our data shows that, it is rather the atoms' shared pattern of movement that determines the properties of these thermoelectric materials. A discovery that will be significant for the design of new materials that utilize energy even better," explains Kim Lefmann, associate professor at the Nano-Science Center, the Niels Bohr Institute at the University of Copenhagen.

Nano-scale Electromechanical Sensors In Handheld Devices

2009-02-07T22:35:00.000-08:00

Clemson physics professor Apparao Rao and his team are researching nano-scale cantilevers that have the potential to read and alert us to toxic chemicals or gases in the air. Put them into a small handheld device and the potential is there for real-time chemical alerts in battle, in industry, in health care and even at home.
“The ability to build extremely small devices to do this work has been something we’ve only seen so far in science-fiction movies,” Rao said.

The width of a human hair or smaller, the micro- and nano-scale cantilevers look like tiny diving boards under an electron microscope. The researchers have advanced the method of oscillating cantilevers that vibrate much like a guitar string and measure amplitude and frequency under different conditions, creating highly reliable sensors that can relay a message that there’s trouble in the air.

“The current way of sensing involves an optical method that uses a relatively bulky and expensive laser beam that doesn’t translate well to use in nano-scale cantilevers. Our method is fully electrical and uses a small AC voltage to vibrate the cantilever and simple electronics to detect any changes in the vibration caused by gaseous chemical or biological agents,” Rao said. “This method enables the development of handheld devices that would beep or flash as they read gas and chemical levels on site.”

The potential applications are varied, he said. In addition to simultaneously reading multiple kinds of toxins in the environment, these electromechanical sensors have been shown to measure changes in humidity and temperature.

Preliminary results indicate that this fully electrical sensing scheme is so sensitive that it can differentiate between hydrogen and deuterium gas, very similar isotopes of the same element. Since the whole process is electrical, the size limitations that plague competing detection methods are not a problem here. The cantilevers can be shrunk down to the nano-scale and the operating electronics can be contained on a single tiny chip. Rao’s research has shown that a single carbon nanotube can be used as a vibrating cantilever.

Rao credits Clemson Professor Emeritus of Physics Malcolm Skove, who discovered that measuring the resonant frequency of a cantilever at the second or higher harmonies would get rid of the so-called parasitic capacitance, an unwanted background that obscures the signal and has been a major stumbling block to the advancement of similar technology.

“When we operate at these higher harmonics of the resonant frequency, we get extremely clean signals. It makes a tremendous difference, and the National Institute for Standards and Technology is interested in promoting the Clemson method as one of the standard methods for measuring the stiffness of cantilevered beams,” said Rao.

The research was funded for $500,000 over four years from the National Science Foundation and the Department of Defense.

Test Tube Chemistry Inside A Carbon Nanotube

2009-02-07T22:33:00.000-08:00

At the University of Surrey, test tube chemistry just took a leap down in size to the nano-scale, with new test-tubes measuring only about one billionth of a metre across. The scaling factor is like scaling up from a normal test tube to one a hundred kilometres across.
When chemistry is performed in a conventional manner in laboratory test tubes, the reactions that occur are a result of billions and billions of molecules reacting with each other and with anything else we put into the tube. Being able to watch or control chemical reactions between individual molecules at this scale is like understanding and then controlling the interaction between two people on a tube train while you are sitting in the International Space Station!

An international team of researchers led by Dr. Hidetsugu Shiozawa of the Advanced Technology Institute at Surrey have been able to see individual events at atomic scale, as molecules react inside the confines of a nano-test tube. In the study the researchers show how a cerium organometallic compound reacts with individual atoms in the walls of the nano-test-tube made from a one-atom-thick sheet of carbon atom ‘chicken-wire’, called a carbon nanotube. They followed the reaction by measuring changes in the electrical properties of the tube when the molecule reacts with it.

Dr. Shiozawa says: "The excitement of this nano-test-tube chemistry experiment is the strong electronic interaction observed at the elemental level when compounds are confined within carbon nanotubes. The quantized electronic states of the tube allow specific molecules and compounds to interact, so we can tell the difference between molecules. We see a change in the properties of the tube from insulating to conducting when electrons hop from the molecule to the tube. This is a fundamental breakthrough, seen experimentally using the Synchrotron facilities in Berlin."

Professor Ravi Silva, Director of the Advanced Technology Institute, stated: "Our results are world leading and will tell researchers and technologists working on the next generation of nanoelectronic devices some of the fundamental issues that must be taken into account in their design. We have shown that single atoms stuck on the surface of a carbon nanotube can have a tremendous effect on its electrical characteristics. The implications are widespread because these tubes are proposed to be used as wires in nano-scale integrated circuit chips within the next decade."

This research was sponsored by a Portfolio Partnership award by the Engineering and Physical Sciences Research Council (EPSRC), UK.

Nanotube's 'Tapestry' Controls Its Growth

2009-02-05T20:10:00.000-08:00

Rice University materials scientists have put a new "twist" on carbon nanotube growth. The researchers found the highly touted nanomaterials grow like tiny molecular tapestries, woven from twisting, single-atom threads
Carbon nanotubes are hollow tubes of pure carbon that measure about one nanometer, or one-billionth of a meter, in diameter. In molecular diagrams, they look like rolled-up sheets of chicken wire. And just like a roll of wire or gift-wrapping paper, nanotubes can be rolled at an odd angle with excess hanging off the end.

Though nanotubes are much-studied, their growth is poorly understood. They grow by "self assembly," forming spontaneously from gaseous carbon feedstock under precise catalytic circumstances. The new research, which appears online in the Proceedings of the National Academy of Sciences, finds a direct relationship between a nanotube's "chiral" angle -- the amount it's twisted -- and how fast it grows.

"Our study offers some clues about this intimate 'self assembly' process," said Rice's Boris Yakobson, professor in mechanical engineering and materials science and of chemistry. New theory suggests that each tube is 'woven' from many twisting threads. Each grows independently, with new atoms attaching themselves to the exposed thread ends. The more threads there are, the faster the whole tapestry grows.

Yakobson, the lead researcher on the project, said the new formula's predictions have been borne out by a number of laboratory reports. For example, the formula predicts that nanotubes with the largest chiral angle will grow fastest because they have the most exposed threads -- something that's been shown in several experiments.

"Chirality is one of the primary determinants of a nanotube's properties," said Yakobson. "Our approach reveals quantitatively the role that chirality plays in growth, which is of great interest to all who hope to incorporate nanotubes into new technologies."

The study was co-authored by former Rice research scientist Feng Ding, now assistant professor at Hong Kong Polytechnic University, and Avetik Harutyunyan of the Honda Research Institute USA in Columbus, Ohio. The research was supported by the National Science Foundation, the Welch Foundation and the Department of Defense.

Beaming New Light On Life: From Beetles To Aircraft, Nanoparticles Aid Microscope Views

2009-02-05T20:07:00.000-08:00

University of Utah physicists and chemists developed a new method that uses a mirror of tiny silver "nanoparticles" so microscopes can reveal the internal structure of nearly opaque biological materials like bone, tumor cells and the iridescent green scales of the so-called "photonic beetle."
The method also might be used for detecting fatigue in materials such as carbon-fiber plastics used to build the latest generation of aircraft fuselages, tails and wings, says John Lupton, an associate professor of physics and leader of the new study.

The study will be published online Feb. 5 and in the March 2009 issue of Nano Letters, the leading nanoscience journal of the American Chemical Society. Nanoscience is the study of ultrasmall materials, structures or devices on a molecular or atomic scale.

The researchers are seeking a patent on the new method.

Lupton conducted the new study with Michael Bartl, an assistant professor of chemistry; Debansu Chaudhuri, a postdoctoral researcher in physics; and graduate students Jeremy Galusha in chemistry and Manfred Walter and Nicholas Borys in physics.

From the invention of the optical microscope in the 17th century, microscopy has grown to the point where there are scores of different methods available.

In an optical microscope, white light is passed through a specimen to view it. But the method is limited in how much detail and contrast can be seen within the specimen.

Electron microscopes can view tiny structures, but they are expensive, not always readily available and cannot be used on all types of samples, Lupton says.

A widely used method is known as laser or fluorescence microscopy, in which a laser is used to make a specimen emit light, either because the specimen does so naturally or because it has been injected or "labeled" with fluorescent dye. The trouble is that such dyes – when excited by laser light – generate toxic chemicals that kill living cells.

"It would be much better to place the cell, without any labels, on top of metal nanoparticles and measure the transmission of light," Lupton says.

The new method developed by Lupton and colleagues is a variation of fluorescence microscopy, but involves using an infrared laser to excite clusters of silver nanoparticles placed below the sample being studied. The particles form "plasmonic hotspots," which act as beacons, shooting intensely focused white light upward through the overlying sample.

The spectrum or colors of transmitted light reveal information about the composition and structure of the substance examined.

The Photonic Beetle Meets the Microscope

Development of the new method began after Bartl, Galusha and others published a study last May revealing that a beetle from Brazil – a weevil named Lamprocyphus augustus – has shimmering green scales with an ideal "photonic crystal" structure.

Scientists thus far have been unable to build an ideal photonic crystal to manipulate visible light – something they say is necessary to develop ultrafast optical computers that would run on light instead of electricity.

Ideal photonic crystals also are sought as a way to make solar power cells more efficient, catalyze chemical reactions and generate tiny laser beams that would serve as light sources on optical computer chips.

But first, researchers want to know more about the naturally occurring photonic crystals within the beetle's scales.

"A normal light microscope generally won't do the trick," Lupton says, because visible light is easily scattered by the scales, thwarting efforts to view their internal structure.

"We found that we can put silver nanoparticles – a fancy word for a silver mirror – beneath the beetle," he adds. "When illuminated with very intense infrared light, the silver starts to emit white light, but only at very discrete positions on the mirror."

Those "beacons" of intense light were transmitted upward through the beetle scale, allowing scientists to view the scale's internal structure, including tiny differences in the angles of crystal "facets" or faces and the existence of vertical stacks of crystals invisible to other microscope methods.

To the untrained eye, an image created using silver nanoparticle beacons – say, the image of the photonic beetle's scale – looks like a blotchy bunch of spots.

But Lupton says that each of those spots contains a spectrum of colors that reveal information about the scale's internal structure because the light has interacted with that structure.

A New Tool for Biologists, Doctors and Maybe Materials Scientists

"There really does not appear to be any other useful technique to look at these natural photonic crystals microscopically," Lupton says. "The silver nanoparticle approach to microscopy potentially could be very versatile, allowing us to view other highly scattering samples such as tumor cells, bone samples or amorphous materials in general." Amorphous materials are those without a crystal structure.

While Lupton believes the new method will be of interest mainly to biologists, he also says it could be useful for materials science.

For example, silver nanoparticles could be embedded in the carbon-fiber plastic in modern aircraft. The integrity of the fuselage or other aircraft components could be inspected regularly by exciting the embedded particles with a laser, and measuring how much light from the particles is transmitted through the fuselage material. Changes in transmission of the light would indicate changes in the fuselage structure, a warning that closer inspections of fuselage integrity are required.

So why does the new method work?

Lupton says the structure within the beetle's scales scatters light very strongly, like driving through a snowstorm: "Once your windshield gets wet, headlights appear all fuzzy, and different features get mixed up."

Using the tiny silver nanoparticles as light sources to see crystal structure within the beetle's scale is like "peering through your smudged windshield at a tiny white spot," Lupton adds. "It would not appear smeared out."

Microswimmers Make Big Splash For Improved Drug Delivery

2009-01-14T22:59:00.000-08:00

They may never pose a challenge to Olympic superstar Michael Phelps, but the "microswimmers" developed by researchers in Spain and the United Kingdom could break a long-standing barrier to improving delivery of medications for cancer and other diseases.
They describe the development of tiny, magnetically controlled particles, called "microswimmers," that doctors could use to precisely deliver medicine to diseased tissue.

In the new study, Pietro Tierno and colleagues note that scientists tried for years to develop tiny engines that can move micro and nanomachines through tight spaces, such as blood vessels and lab-on-a chip devices. But existing engines are slow, difficult to maneuver, and must undergo alterations in their shape, chemistry or temperature in order to work. The design of simple, more practical engines to power these tiny, robotic machines remains a major challenge, the researchers say.

The scientists describe a solution — tiny beads, about 1/25,000 of an inch in diameter, made of plastic and magnetic materials. When exposed to a magnetic field, the particles spun like a gyroscope and could be easily directed to move though narrow channels of liquids inside a glass plate, the researchers say. The scientists could control the speed of the "microswimmers" by varying the strength of the magnetic field

Super Sensitive Gas Detector Goes Down The Nanotubes

2009-01-14T22:58:00.000-08:00

When cells are under stress, they blow off steam by releasing minute amounts of nitrogen oxides and other toxic gases. In a recent paper, researchers at the National Institute of Standards and Technology (NIST) described a new method for creating gas detectors so sensitive that some day they may be able to register these tiny emissions from a single cell, providing a new way to determine if drugs or nanoparticles harm cells or to study how cells communicate with one another.
Based on metal oxide nanotubes, the new sensors are a hundred to 1,000 times more sensitive than current devices based on thin films and are able to act as multiple sensors simultaneously.

Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. Thus, the more surface available, the more sensitive the sensor will be. Scientists are interested in developing gas sensors based on nanotubes because, having walls that are only a few nanometers thick, they are almost all surface.

Although nanotubes have proven to be well suited for gas sensing applications, fabricating the devices themselves is a difficult, imprecise and time-consuming process, according to Kurt Benkstein, an author of the paper. Older methods include randomly scattering free nanotubes on a surface with preformed electrical contacts (the hope being that a least a few of the nanotubes would tumble into place) or laying contacts over the top of the nanotubes after they had been dispersed, among others. These methods, though they can result in functional devices, preclude researchers from knowing where exactly the reactions are happening on the substrate. This makes it impossible to do multiple simultaneous tests. Also, these sensors are not as sensitive as they could be because there is no way to ensure that the gas is reacting with the interior of the tube.

To address these problems, the NIST group built upon another design using a sheet of aluminum oxide about the thickness of a human hair and perforated with millions of holes about 200 nanometers wide. With the nanosized pores serving as a mold, the researchers dipped the aluminum oxide sheet in a solution of tungsten ions, coating the interior of the pores and casting the nanotubes in place. After the nanotubes were formed, the team deposited thin layers of gold on the top and bottom of the aluminum oxide membrane to act as electrical contacts. View schematic of the nanotube sensor at http://patapsco.nist.gov/ImageGallery/details.cfm?imageid=620.

The sensor’s high sensitivity derives from its design, which ensures that any sensor response is the result of the gas interacting with the interior of the nanotube. The researchers also note that this same technique can easily be adapted to form nanotubes of other semiconductors and metal oxides so long as the ends of the nanotubes remain open.

'Stress Tests' Probe Nanoscale Strains In Materials

2008-12-06T00:31:00.000-08:00

Researchers at the National Institute of Standards and Technology (NIST) have demonstrated their ability to measure relatively low levels of stress or strain in regions of a semiconductor device as small as 10 nanometers across. Their recent results not only will impact the design of future generations of integrated circuits but also lay to rest a long-standing disagreement in results between two different methods for measuring stress in semiconductors.
Mechanical stress and strain in semiconductors and other devices is caused by atoms in the crystal lattice being compressed or stretched out of their preferred positions, a complex—and not always harmful—phenomenon. Stress in the underlying structure of light-emitting diodes and lasers can shift output colors and lower the device’s lifetime. Stress in microelectromechanical systems can lead to fracture and buckling that also truncates their lifespan. On the other hand, stress is deliberately built into state-of-the-art microcircuits because properly applied it can increase the speed of transistors without making any other changes to the design. “Stress engineering has allowed the semiconductor industry to increase the performance of devices well beyond what was expected with the current materials set,” said NIST research physicist Robert Cook, “thus avoiding the significant engineering problems and expense associated with changing materials.”

Both the good and the bad stresses need to be measured, however, if they’re to be controlled by device designers. As the component size of microcircuits has become smaller and smaller, this has become more difficult—particularly since two different and widely used methods of stress measurement have been returning disparate results. One, electron back scattered diffraction (EBSD), deduces underlying stress by observing the patterns of electrons scattered back from the crystal planes. The other, confocal Raman microscopy (CRM), measures minute shifts in the frequency of photons that interact with the atomic bonds in the crystal—shifts that change depending on the amount of stress on the bond. The NIST team used customized, highly sensitive versions of both instruments in a series of comparison measurements to resolve the discrepancies.

The key issue, they found, was depth of penetration of the two techniques. Electron beams sample only the top 20 or 30 nanometers of the material, Cook explained, while the laser-generated photons used in CRM might penetrate as deep as a micrometer or more. The NIST researchers found that by varying the wavelength of the Raman photons and positioning the focus of the microscope they could select the depth of the features measured by the Raman technique—and when the CRM was tuned for the topmost layers of the crystal, the results were in close agreement with EBSD measurements.

The NIST instruments also demonstrate the potential for using the two techniques in combination to make reliable, nanoscale measurements of stress in silicon, which enables device developers to optimize materials and processes. EBSD, although confined to near-surface stress, can make measurements with resolutions as small as 10 nanometers. CRM resolution is about 10 times coarser, but it can return depth profiles of stress.

Boosting The Power Of Solar Cells

2008-12-06T00:29:00.000-08:00

New ways of squeezing out greater efficiency from solar photovoltaic cells are emerging from computer simulations and lab tests conducted by a team of physicists and engineers at MIT.Using computer modeling and a variety of advanced chip-manufacturing techniques, they have applied an antireflection coating to the front, and a novel combination of multi-layered reflective coatings and a tightly spaced array of lines — called a diffraction grating — to the backs of ultrathin silicon films to boost the cells' output by as much as 50 percent.

The carefully designed layers deposited on the back of the cell cause the light to bounce around longer inside the thin silicon layer, giving it time to deposit its energy and produce an electric current. Without these coatings, light would just be reflected back out into the surrounding air, said Peter Bermel, a postdoctoral researcher in MIT's physics department who has been working on the project.

"It's critical to ensure that any light that enters the layer travels through a long path in the silicon," Bermel said. "The issue is how far does light have to travel [in the silicon] before there's a high probability of being absorbed" and knocking loose electrons to produce an electric current.

The team began by running thousands of computer simulations in which they tried out variations in the spacing of lines in the grid, the thickness of the silicon and the number and thicknesses of reflective layers deposited on the back surface. "We use our simulation tools to optimize overall efficiency and maximize the power coming out," Bermel said.

"The simulated performance was remarkably better than any other structure, promising, for 2-micrometer-thick films, a 50 percent efficiency increase in conversion of sunlight to electricity," said Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, who directed the project.

The simulations were then validated by actual lab-scale tests. "The final and most important ingredient was the relentless dedication of graduate student Lirong Zeng, in the Department of Materials Science and Engineering, to refining the structure and making it," Kimerling said. "The experiments confirmed the predictions, and the results have drawn considerable industry interest."

The team will report the first reduction to practice of their findings on Dec. 2 at the Materials Research Society's annual meeting in Boston. A paper on their findings has been accepted for publication in Applied Physics Letters.

The work is just a first step toward actually producing a commercially viable, improved solar cell. That will require additional fine-tuning through continuing simulations and lab tests, and then more work on the manufacturing processes and materials. "If the solar business stays strong," Kimerling said, "implementation within the next three years is possible."

The MIT Deshpande Center selected the project for an "i-team" study to evaluate its business potential. The team analyzed the potential impact of this efficient thin solar cell technology and found significant benefits in both manufacturing and electrical power delivery, for applications ranging from remote off-grid to dedicated clean power.

And the potential for savings is great, because the high-quality silicon crystal substrates used in conventional solar cells represent about half the cost, and the thin films in this version use only about 1 percent as much silicon, Bermel said.

This project, along with other research work going on now in solar cells, has the potential to get costs down "so that it becomes competitive with grid electricity," Bermel said. While no single project is likely to achieve that goal, he said, this work is "the kind of science that needs to be explored in order to achieve that."

In addition to Kimerling, Bermel and Zeng, the work was done by John Joannopoulos, the Francis Wright Davis Professor of Physics, and by research engineer Bernard A. Alamariu, research specialist Kurt A. Broderick, both of the Microsystems Technology Laboratories; postdoctoral associate Jifeng Liu; Ching-yin Hong and research associate Xiaoman Duan, both of the Materials Processing Center. Funding was provided by the Thomas Lord Chair in Materials Science and Engineering, the MIT-MIST Initiative, the Materials Research Science and Engineering Center Program of the NSF and the Army Research Office through the Institute for Soldier Nanotechnologies.

Researchers Channel Microcapsules Into Tumour Cells And Release Their Contents Using A Laser Impulse

2008-11-30T20:40:00.000-08:00

Medicines are most helpful when they directly affect the diseased organs or cells - for example, tumour cells. Scientists at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, and Ludwig-Maximilian-University in Munich, have come one step closer to that goal: they have intentionally released a substance in a tumour cell. The scientists placed the substance in a tiny capsule which gets channelled into cancer cells, and is then "unpacked" with a laser impulse. The laser light cracks its polymer shell by heating it up and the capsule’s contents are released. (Angewandte Chemie, July 2006).
Treating malignant tumours is difficult. Doctors have to destroy the tumour, but healthy tissue needs to be preserved. Chemotherapy tends to kill diseased cells, at the same time causing great damage to the body in general. So scientists are looking for ways to destroy only the rampant tumour cells. One way to achieve this is to transport substances inside of microcapsules into the tumour cells and release them there. Researchers led by André Skirtach and Gleb Sukhorukov at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, along with Wolfgang Parak at Ludwig-Maximilian-University in Munich, have now used a laser as a means of opening microcapsules inserted into a tumour cell. The capsules subsequently release their contents, a fluorescent test substance, into the cell. The scientists used a light microscope to monitor how the luminous materials distribute themselves within the cell.

The vehicle that the researchers used was a polymer capsule only a few micrometres in diameter. The walls of the capsules were built from a number of layers of charged polymers, alternating positive and negative. In the laboratory, at least, this is an established way of producing transport containers for medicines, cosmetics, or nutrients, which can also pass through cell membranes. André Skirtach and his colleagues equipped the capsules with a kind of "open sesame". But it didn't require any magic - just nanoparticles made of gold or silver atoms. The scientists mixed together charged metal nanoparticles along with the polymers composing the walls of the vesicle. The tumour cells absorbed the microcapsules and then the scientists aimed an infrared laser at them. Metal nanoparticles are particularly good at absorbing the laser light and transmitting the heat further into their surroundings, heating up the walls. They became so hot that the bonds broke between the polymers and the shell and the capsules eventually opened.

For the time being, the scientists have only been trying out their methods on isolated tumour cells. "In principle, however, active substances could be released into the body this way," says Helmuth Möhwald, director of the Max Planck Institute of Colloids and Interfaces, and one of the participating scientists. This has to (do) with the fact that infrared laser light can penetrate at least one centimetre deep into the tissue. The cells of the body heat up negligibly because laser light at this wavelength is insignificantly absorbed in the tissue. It is the metal particles in the walls of the microcapsules only that absorb the light - even when the microcapsules are in a cell, because the laser affects only them.

Besides using a "thermal opener", the scientists have found another way of making the capsules more stable. They simply heat up the newly created microcapsules very slightly, so that the diameter of the hollow capsules becomes smaller. At the same time, the molecules in their shell are located closer to each other, thickening the capsule walls and better protecting their contents.

There is still, however, a major problem to solve before scientists can use this technology to create medicines which squeeze microcapsules into tumour cells. There is still no way to "steer" the microcapsules. Helmuth Möhwald says, "we have to add some kind of feature to the capsules so that they only recognise the target cells." Only these cells would then allow microcapsules through their membrane.

Chemical Signaling May Power Nanomachines

2008-11-30T20:38:00.000-08:00

In a finding that could provide controlled motion in futuristic nanomachines used for drug delivery, fuel cells, and other applications, researchers in Pennsylvania report that chemical signaling between synthetic microcapsules can trigger and direct movement of these capsules.
Researchers theorize that synthetic capsules can communicate with each other by physically shuffling chemical signals from capsule to capsule, much like passing water through a fireman's bucket brigade. Scientists recently suggested that this same signaling process also appears capable of sending cues to direct cell movement.

In the new study, Anna C. Balazs and colleagues used computer models to simulate the chemical signaling. They modeled a porous polymer microcapsule filled with nanonparticles to imitate a biological cell. When placed next to an empty capsule, nanoparticles from the filled capsule initiated the motion of the empty capsule, which in turn caused the movement of the filled "signaling" capsule. The same locomotion process could be engineered into futuristic nanomachines to help direct their movement through the body or through fuel cells, the researchers suggest.

Light-driven 'Molecular Brakes' Provide Stopping Power For Nanomachines

2008-11-30T20:36:00.001-08:00

Researchers in Taiwan report development of a new type of "molecular brake" that could provide on-demand stopping power for futuristic nanomachines. The brake, thousands of times smaller than the width of a human hair, is powered by light and is the first capable of working at room temperature, the researchers say.
Their study is scheduled for the June 5 issue of ACS' Organic Letters, a bi-weekly journal.

In the new study, Jye-Shane Yang and colleagues point out that the ability to control specific motions of small molecules or larger molecular structures is essential for the development of nanomachines. Some of these machines may find use in delivering drugs or performing surgery deep inside the human body.

Although scientists have already built molecular motors, wheels, and gears for powering nanomachines, the development of a practical braking system remains a challenge, the researchers say.

Yang’s group assembled a prototype molecular brake that resembles a tiny four-bladed wheel and contains light-sensitive molecules. The paddle-like structure spins freely when a nanomachine is in motion. In laboratory studies, the scientists showed that exposing the structure to light changes its shape so that "blades" stop spinning, putting on the brakes. The braking power can be turned off by altering the wavelength of light exposure, they add.

Remotely Controlled Nanomachines

2008-11-30T20:35:00.000-08:00

Physicists at the University of California at Berkeley have produced images that show how light can control some of the smallest possible machines.
By shining ultraviolet laser light on tiny molecules of azobenzene adhered on a layer of gold, they could force the molecules to change shape at will. Potentially, the molecules could be incorporated into nanomachines in the form of remotely controlled switches, pistons or other movable components.

Scientists have experimented with shape-shifting azobenzene in previous studies, but the molecules only responded properly when suspended in liquids or incorporated into plastics, neither of which makes a very good foundation for complex nanomachines.

In order to get the molecular machines to function while mounted on a gold surface, the physicists first had to add legs built of carbon and hydrogen atoms to hold the molecules slightly away from the metal. Although the legs anchoring the molecules to the surface only provided a fraction of a nanometer of clearance (less than a billionth of a meter), it was enough to allow the molecules to move in response to the UV illumination.

The team confirmed their achievement with a series of scanning tunneling microscope images showing that they could switch the molecules' shapes from one configuration and back again.

'The Photon Force Is With Us': Harnessing Light To Drive Nanomachines

2008-11-30T20:33:00.000-08:00

Science fiction writers have long envisioned sailing a spacecraft by the optical force of the sun's light. But, the forces of sunlight are too weak to fill even the oversized sails that have been tried. Now a team led by researchers at the Yale School of Engineering & Applied Science has shown that the force of light indeed can be harnessed to drive machines — when the process is scaled to nano-proportions.
Their work opens the door to a new class of semiconductor devices that are operated by the force of light. They envision a future where this process powers quantum information processing and sensing devices, as well as telecommunications that run at ultra-high speed and consume little power.

The research, appearing in the November 27 issue of Nature, demonstrates a marriage of two emerging fields of research — nanophotonics and nanomechanics. – which makes possible the extreme miniaturization of optics and mechanics on a silicon chip.

The energy of light has been harnessed and used in many ways. The "force" of light is different — it is a push or a pull action that causes something to move.

"While the force of light is far too weak for us to feel in everyday life, we have found that it can be harnessed and used at the nanoscale," said team leader Hong Tang, assistant professor at Yale. "Our work demonstrates the advantage of using nano-objects as "targets" for the force of light — using devices that are a billion-billion times smaller than a space sail, and that match the size of today's typical transistors."

Until now light has only been used to maneuver single tiny objects with a focused laser beam — a technique called "optical tweezers." Postdoctoral scientist and lead author, Mo Li noted, "Instead of moving particles with light, now we integrate everything on a chip and move a semiconductor device."

"When researchers talk about optical forces, they are generally referring to the radiation pressure light applies in the direction of the flow of light," said Tang. "The new force we have investigated actually kicks out to the side of that light flow."

While this new optical force was predicted by several theories, the proof required state-of-the-art nanophotonics to confine light with ultra-high intensity within nanoscale photonic wires. The researchers showed that when the concentrated light was guided through a nanoscale mechanical device, significant light force could be generated — enough, in fact, to operate nanoscale machinery on a silicon chip.

The light force was routed in much the same way electronic wires are laid out on today's large scale integrated circuits. Because light intensity is much higher when it is guided at the nanoscale, they were able to exploit the force. "We calculate that the illumination we harness is a million times stronger than direct sunlight," adds Wolfram Pernice, a Humboldt postdoctoral fellow with Tang.

"We create hundreds of devices on a single chip, and all of them work," says Tang, who attributes this success to a great optical I/O device design provided by their collaborators at the University of Washington.

It took more than 60 years to progress from the first transistors to the speed and power of today's computers. Creating devices that run solely on light rather than electronics will now begin a similar process of development, according to the authors.

"While this development has brought us a new device concept and a giant step forward in speed, the next developments will be in improving the mechanical aspects of the system. But," says Tang, "the photon force is with us."

Tang's team at Yale also included graduate student Chi Xiong. Collaborators at University of Washington were Thomas Baehr-Jones and Michael Hochberg. Funding in support of the project came from the National Science Foundation, the Air Force Office of Scientific Research and the Alexander von Humboldt post-doctoral fellowship program.

Toward Improving The Safety Of Lithium-ion Batteries

2008-11-30T20:32:00.000-08:00

After recalls and fires involving Lithium-ion batteries, battery manufacturers and scientists have launched an intensive effort to improve the safety of these rechargeable power packs found in dozens of consumer electronics products, according to an article scheduled for the Dec. 17 issue of Chemical & Engineering News.
In the article, C&EN Senior Editor Mitch Jacoby points out that fires and explosions involving Lithium-ion batteries are rare, occurring in anywhere from one in 1 million to one in 10 million batteries, according to the best estimates. Still, these widely-publicized incidents have worried consumers and forced costly recalls of millions of batteries.

Researchers in industry and academia do not fully understand why Lithium-ion batteries sometimes catch fire or explode, Jacoby notes. Possible explanations include impurities that short circuit the batteries and yet unidentified reactions that underlie the problem.

Nevertheless, researchers are exploring new battery materials, including components that generate less heat and reduce the risk of mishaps. Manufacturers are already selling or planning to sell safer Lithium-ion batteries for power tools and electric vehicles, with more improvements on the way, according to the article.

Title of article: "Lithium-Ion Battery Safety"

Improved Polymers For Lithium Ion Batteries Pave The Way For Next Generation Of Electric And Hybrid Cars

2008-11-30T20:30:00.000-08:00

The next generation of electric and hybrid cars may be a step closer thanks to new and improved polymer membranes that allow the development of bigger, safer, and more powerful lithium ion batteries, according to an article,"The Power of Pores" scheduled for the Feb. 18 issue of Chemical & Engineering News.
In the article, C&EN Senior Editor Alexander H. Tullo notes that polymer membranes are already an essential component of lithium ion batteries that power iPods, laptop computers, and other portable electronic devices. These porous, hair-thin separators control the flow of electrons through the battery. Their failure can result in overheating and even fires. Such problems have recently prompted the widespread recall of millions of lithium ion batteries.

Tullo points out that lithium ion batteries will need to be bigger, safer, and more powerful if they are to be used effectively in motor vehicles. For that purpose, improved polymer separators are needed.

Recently, battery manufacturers have stepped up to this challenge by developing new polymer separators with greater porosity for improved power flow and stronger insulation materials for improved safety. At least one manufacturer is already using a new type of polymer separator in a new line of electric vehicles, while other advanced polymers are making their way through the development pipeline, according to the article. "The reality of driving to work under electric power may only be a hair away," Tullo says.

New Electrodes May Provide Safer, More Powerful Lithium-ion (Li-ion) Batteries

2008-11-30T20:28:00.000-08:00

Researchers in Spain and the United Kingdom are reporting development of a new electrode material that could ease concerns about the safety of those unbiquitous lithium-ion (Li-ion) batteries, while giving Li-ion batteries a power boost, according to a new study
Li-ion batteries power an increasing number of laptop computers and portable electronic devices. They are now being eyed for motor vehicles of the future. However, recent recalls of millions of Li-ion batteries due to overheating have raised safety concerns, with researchers seeking new materials to make safer, more powerful batteries.

In the new study, M. Rosa Palacín and colleagues compared the performance of Li-ion batteries made with electrodes composed of lithium nickel nitride (LiNiN) to conventional Li-ion batteries containing carbon electrodes. The new materials are more efficient than the conventional electrodes and less likely to overheat, the researchers suggest. They note that "further improvements can be envisaged by changing the reaction conditions and the processing of the electrode."

The study,"Towards New Negative Electrode Materials for Li-Ion Batteries: Electrochemical Properties of LiNiN," is scheduled for the March 11 issue of ACS' Chemistry of Materials.

Sweet Nanotech Batteries: Nanotechnology Could Solve Lithium Battery Charging Problems

2008-11-30T20:26:00.000-08:00

Nanotechnology could improve the life of the lithium batteries used in portable devices, including laptop computers, mp3 players, and mobile phones. Research to be published in the Inderscience publication International Journal of Nanomanufacturing demonstrates that carbon nanotubes can prevent such batteries from losing their charge capacity over time.Researchers at the Shenyang National Laboratory for Materials Science, in China, have been investigating how to improve the kind of rechargeable batteries that are almost ubiquitous in today's portable devices. Mobile phones, mp3 players, personal digital assistants (PDAs), and laptop computers usually use lithium-ion batteries to give them portability. However, Li-ion batteries suffer from degradation especially when they get too hot or too cold and eventually lose the capacity to be fully recharged. This means a loss of talk time for mobile phone users and often no chance to use a laptop for the whole of a long haul flight.

The problem of the slow degradation of Li-ion batteries is usually due to the formation of a solid electrolyte interphase film that increase the batteries internal resistance and prevents a full recharge. Researchers have suggested using silicon in the composition of the negative electrode material in Li-ion batteries to improve charge capacity. However, this material leads to even faster capacity loss as it repeatedly alloys and then de-alloys during charge-discharge cycles.

Shengyang's Hui-Ming Cheng and colleagues have turned to carbon nanotubes (CNTs) to help them use silicon (Si) as the battery anode but avoid the problem of large volume change during alloying and de-alloying. Carbon nanotubes resemble rolled-up sheets of hexagonal chicken wire with a carbon atom at the crossover points of the wires and the wires themselves being the bonds between carbon atoms, and they can be up to a millimeter long but mere nanometers in diameter.

The researchers grew carbon nanotubes on the surface of tiny particles of silicon using a technique known as chemical vapor deposition in which a carbon-containing vapor decomposes and then condenses on the surface of the silicon particles forming the nanoscopic tubes. They then coated these particles with carbon released from sugar at a high temperature in a vacuum. A separate batch of silicon particles produced using sugar but without the CNTs was also prepared.

With the new Si-CNT anode material to hand, the team then investigated how well it functioned in a prototype Li-ion battery and compared the results with the material formed from sugar-coated silicon particles.

They found that after twenty cycles of the semi-cell experiments, the sugar-coated Si-CNT composite material achieved a discharge capacity of 727 milliamp hours per gram. In contrast the charge capacity of the simple sugar-coated particles had dropped to just 363 mAh per gram.

Highly Efficient Lithium Batteries Could Greatly Extend Battery Life Of Laptop Computers

2008-11-30T20:24:00.000-08:00

Rechargeable lithium ion batteries provide portable devices that require a lot of energy, such as mobile telephones, digital cameras, and notebook computers, with power. However, their capacity, and thus the running time of the devices, remain somewhat limited. A notebook computer thus usually runs only about two hours.
The reason for this is the relatively small capacity of the graphite anode in these batteries to absorb lithium ions. A team led by Jaephil Cho at Hanyang University in Korea has now developed a new material for anodes, which could clear a path for a new generation of rechargeable batteries. As reported in the journal Angewandte Chemie, their new material involves three-dimensional, highly porous silicon structures.

Lithium ion accumulator batteries produce current by moving lithium ions. The battery usually contains a cathode (positive electrode) made of a mixed metal oxide, such as lithium cobalt oxide, and an anode (negative electrode) made of graphite. While the battery is being charged, lithium ions migrate into the anode, where they are stored between the graphite layers. When the battery is being discharged, these ions migrate back to the cathode.

It would be nice to have an anodic material that could store more lithium ions than graphite. Silicon presents an interesting alternative. The problem: silicon expands a great deal while absorbing lithium ions (charging) and shrinks when giving them up (discharging). After several cycles the required thin silicon layers are pulverized and can no longer be charged.

Cho’s team has now developed a new method for the production of a porous silicon anode that can withstand this strain. They annealed silicon dioxide nanoparticles with silicon particles whose outermost silicon atoms have short hydrocarbon chains attached to them at 900 °C under an argon atmosphere. The silicon dioxide particles were removed from the resulting mass by etching. What remained were carbon-coated silicon crystals in a continuous, three-dimensional, highly porous structure.

Anodes made of this highly porous silicon have a high charge capacity for lithium ions. In addition, the lithium ions are rapidly transported and stored, making rapid charging and discharging possible. A high specific capacity is also attained with high current. The changes in volume that occur upon charging and discharging cause only a small degree of swelling and shrinking of the pore walls, which have a thickness of less than 70 nm.

In addition, the first charging cycle results in an amorphous (noncrystalline) silicon mass around residual nanocrystals in the pore walls. Consequently, even after 100 cycles, the stress in the pore wall is not noticeable in the material.

Toward A New Oral Delivery System For Insulin Using Nanoshell Shields

2008-11-19T22:31:00.000-08:00

Scientists in Taiwan are reporting development of a nanoparticle drug delivery system that shows promise as a potential way to administer insulin and perhaps other protein-based drugs by mouth rather than injection or nasal sprays.
Hsing-Wen Sung and colleagues at the National Tsing Hua University, the Chinese Naval Academy and the National Health Research Institute point out that stomach acid destroys protein-based drugs, making them ineffective.

That problem has led to broadly based efforts to find ways of encapsulating or otherwise protecting insulin from damage in the stomach so it could be given in a convenient oral form. Once the drug passes through the stomach, it can be absorbed in the small intestine.

In their new research, scheduled for the Jan. 8 issue of ACS' Biomacromolecules, a monthly journal, researchers describe loading insulin into nanospheres made from chitosan, a natural carbohydrate polymer material obtained commercially from shells of shrimp that is nontoxic and biocompatible.

When given to diabetic laboratory rats, the insulin-loaded nanoparticles successfully reduced blood sugar levels in the animals.

Nontoxic Nanoparticle Can Deliver And Track Drugs, According To New Research

2008-11-19T22:22:00.000-08:00

A nontoxic nanoparticle developed by Penn State researchers is proving to be an all-around effective delivery system for both therapeutic drugs and the fluorescent dyes that can track their delivery.
In a recent online issue of Nano Letters, an interdisciplinary group of materials scientists, chemists, bioengineers, physicists, and pharmacologists show that calcium phosphate particles ranging in size from 20 to 50 nanometers will successfully enter cells and dissolve harmlessly, releasing their cargo of drugs or dye.

Peter Butler, associate professor of bioengineering, and his students used high-speed lasers to measure the size of fluorescent dye-containing particles from their diffusion in solution.

"We use a technique called time correlated single photon counting," Butler says. "This uses pulses of laser light to read the time, on the order of nanoseconds, that molecules fluoresce."

With this method, his group was able to measure the size of the particles and their dispersion in solution, in this case a phosphate-buffered saline that is used as a simple model for blood.

"What we did in this study was to change the original neutral pH of the solution, which is similar to blood, to a more acidic environment, such as around solid tumors and in the parts of the cell that collect the nanoparticles-containing fluid immediately outside the cell membrane and bring it into the cell. When we lower the pH, the acidic environment dissolves the calcium phosphate particle," he adds.

"We can see that the size of the particles gets very small, essentially down to the size of the free dye that was inside the particles. That gives us evidence that this pH change can be used as a mechanism to release any drug that is encapsulated in the particle," Butler explains.

Although the primary use envisioned for these particles is for targeted cancer therapy, Butler's group is interested in their ability to deliver various drugs that have been shown to inhibit cell growth associated with vascular disease.

Several drugs have been shown in cultures to be promising for reducing hardening of the arteries and narrowing of blood vessels after balloon angioplasty. The problem has been in delivering any of these drugs to a target, Butler says.

Ceramide, a chemotherapeutic molecule that initiates cell death in cancer cells, has the ability to slow growth in healthy cells.

Mark Kester, professor of pharmacology, and Jong Yun, associate professor of pharmacology, both at Penn State College of Medicine, have optimized ceramide for both cancer and vascular disease.

Their groups found that by using human vascular smooth muscle cells in vitro, ceramide encapsulated in calcium phosphate nanoparticles reduced growth of muscle cells by up to 80 percent at a dose 25 times lower than ceramide administered freely, without damaging the cells.

The calcium phosphate nanoparticles were developed by James Adair, professor of materials science and engineering, and his students. The nanoparticles have several benefits other drug delivery systems do not, according to lead author Thomas Morgan, graduate student in chemistry.

Unlike quantum dots, which are composed of toxic metals, calcium phosphate is a safe, naturally occurring mineral that already is present in substantial amounts in the bloodstream.

"What distinguishes our method are smaller particles (for uptake into cells), no agglomeration (particles are dispersed evenly in solution), and that we put drugs or dyes inside the particle where they are protected, rather than on the surface," says Morgan. "For reasons we don't yet understand, fluorescent dyes encapsulated within our nanoparticles are four times brighter than free dyes.

"Drugs and dyes are expensive," he continues, "but an advantage of encapsulation is that you need much less of them. We can make high concentrations in the lab, and dilute them way down and still be effective. We even believe we can combine drug and dye delivery for simultaneous tracking and treatment. That's one of the things we are currently working on."

Other researchers on the project are graduate students Erhan Altinoglu and Amra Tabakovic, materials science and engineering, and former group member, Sara Rouse, Ph.D. in materials; graduate students Hari Muddana and Tristan Tabouillot, bioengineering; Timothy Russin, physics; Sriram Shanmugavelandy, pharmacology; and Peter Eklund, distinguished professor of physics and materials science and engineering.

New Nanotechnology Products Hitting The Market At The Rate Of 3-4 Per Week

2008-10-17T21:38:00.000-07:00

New nanotechnology consumer products are coming on the market at the rate of 3-4 per week, a finding based on the latest update to the nanotechnology consumer product inventory maintained by the Project on Emerging Nanotechnologies (PEN).

One of the new items among the more than 600 products now in the inventory is Swissdent Nanowhitening Toothpaste with "calcium peroxides, in the form of nano-particles." Today, in testimony before the Senate Commerce Committee, PEN Project Director David Rejeski cited Ace Silver Plus--another of the nine nano toothpastes in the inventory--as an example of the upsurge in nanotechnology consumer products in stores. The hearing marks the start of U.S. Senate debate on the future direction of the annual $1.5 billion federal investment in nanotechnology research and development (R&D).

The number of consumer products using nanotechnology has grown from 212 to 609 since PEN launched the world's first online inventory of manufacturer-identified nanotech goods in March 2006. Health and fitness items, which includes cosmetics and sunscreens, represent 60 percent of inventory products.

There are 35 automotive products in the PEN inventory, including the Hummer H2. General Motors Corporation bills the H2 as having a cargo bed that "uses about seven pounds of molded in color nanocomposite parts for its trim, center bridge, sail panel and box rail protector."

Nanoscale silver is the most cited nanomaterial used. It is found in 143 products or over 20 percent of the inventory. Carbon, including carbon nanotubes and fullerenes, is the second highest nanoscale material cited. Other nanoscale materials explicitly referenced in products are zinc (including zinc oxide) and titanium (including titanium dioxide), silica and gold.

While polls show most Americans know little or nothing about nanotechnology, in 2006 nanotechnology was incorporated into more than $50 billion in manufactured goods. By 2014, Lux Research estimates $2.6 trillion in manufactured goods will incorporate nanotechnology--or about 15 percent of total global output. Despite a 2006 worldwide investment of $12.4 billion in nanotech R&D, comparatively little was spent on examining nanotechnology's potential environmental, health and safety risks.

"Public trust is the 'dark horse' in nanotechnology's future," says Rejeski in his testimony. "If government and industry do not work to build public confidence in nanotechnology, consumers may reach for the 'No-Nano' label in the future and investors will put their money elsewhere."

According to Rejeski, "The use of nanotechnology in consumer products and industrial applications is growing rapidly, with the products listed in the PEN inventory showing just the tip of the iceberg. Public perceptions about risks--real and perceived--can have large economic consequences. How consumers respond to these early products--in food, electronics, health care, clothing and cars--is a litmus test for broader market acceptance of nanotechnologies in the future

Nanotechnology Surges Into Health And Fitness Products

2008-10-17T21:36:00.000-07:00

Say "nanotechnology," and geeks imagine iPhones, laptops and flash drives. But more than 60 percent of the 580 products in a newly updated inventory of nanotechnology consumer products are such "un-geeky" items as tennis racquets, clothing, and health products.An updated inventory includes Head® NanoTitanium Tennis Racquets, Eddie Bauer® Water Shorts with Nano-Dry® technology, Nano-In Foot Deodorant Powder/Spray, and Burt's Bees® sunscreen with "natural Titanium Dioxide mineral...micronized into a nano sized particle."

Since the Project on Emerging Nanotechnologies launched the world's first online inventory of manufacturer-identified nanotech goods in March 2006, the number of items has increased 175 percent--from 220 to 580 products. There are 356 products in the health and fitness category--the inventory's largest category--and 66 products in the food and beverage category. One of the largest subcategories is cosmetics with 89 products. All are available in shopping malls or over the Internet. The list includes merchandise from such well-known brands as Samsung, Chanel, Black & Decker, Wilson, L.L. Bean, Lancome and L'Oreal.

The nanomaterial of choice appears to be silver--which manufacturers claim is in 139 products or nearly 25 percent of inventory--far outstripping carbon, gold, or silica.

"The use of nanotechnology and nanomaterials in consumer products and industrial applications is growing rapidly, and the products listed in the inventory are just the tip of the iceberg," said Project on Emerging Nanotechnologies science advisor Andrew Maynard. "How consumers respond to these early products--in food, electronics, health care, clothing and cars--will be a bellwether for broader market acceptance of nanotechnologies in the future. This is especially true given that the Project's recent poll shows seventy percent of the public still knows little or nothing about the technology."

Nanotechnology

Nanotechnology is the ability to measure, see, manipulate and manufacture things usually between 1 and 100 nanometers (nm). A nanometer is one billionth of a meter. A human hair is roughly 100,000 nanometers wide. The limit of the human eye's capacity to see without a microscope is about 10,000 nm. By 2014, a projected $2.6 trillion in global manufactured goods will incorporate nanotech, or about 15 percent of total output.

Nanotechnology Now Used In Nearly 500 Everyday Products

2008-10-17T21:35:00.001-07:00

The number of consumer products using nanotechnology has more than doubled, from 212 to 475, in the 14 months since the Project on Emerging Nanotechnologies launched the world’s first online inventory of manufacturer-identified nanotech goods in March 2006. Clothing and cosmetics top the inventory at 77 and 75 products, respectively. A list of nanotechnology products that also includes bedding, jewelry, sporting goods, nutritional and personal care items is available free at http://www.nanotechproject.org/consumerproducts.
Nanotechnology Consumer Products Inventory Highlights:

* The food and beverages category, including containers and dietary supplements, doubled to 61 products since last year.
* Nanoscale silver is the most cited nanomaterial used. It is found in 95 products or 20 percent of the inventory. Carbon, including carbon nanotubes and fullerenes, is the second highest nanoscale material cited.
* Merchandise from 20 countries is now represented. The United States leads internationally with 52 percent or 247 consumer products that contain nanotechnology. East Asia now boasts 123 products, a 58 percent increase over last year.
* New products in the inventory include the Corsa Nanotech Ice Axe which uses an innovative Sandvik Nanoflex® steel alloy that’s 20 percent lighter than normal steel and up to 60 percent stronger. There’s also MaatShop™ Crystal Clear Nano Silver—a clear liquid dietary supplement which peddles protection against colds, flu and hundreds of diseases, even anthrax.

While polls show most Americans know little or nothing about nanotechnology, in 2005 nanotechnology was incorporated into more than $30 billion in manufactured goods. By 2014, Lux Research estimates $2.6 trillion in manufactured goods will incorporate nanotechnology—or about 15 percent of total global output.

“The use of nanotechnology in consumer products and industrial applications is growing rapidly, with the products listed in the inventory showing just the tip of the iceberg,” said Project on Emerging Nanotechnologies science advisor Andrew Maynard. “How consumers respond to these early products—in food, electronics, health care, clothing and cars—will be a litmus test for broader market acceptance of nanotechnologies in the future.”

Study Points Way To Communicating Nanotech

2008-10-17T21:33:00.000-07:00

If you could paint a gallon of paint one nanometer thick, how much area could you cover?

The surprising answer-about 930 acres, or slightly larger than New York's Central Park-certainly makes fun trivia fodder.

More importantly, however, it points nanotechnology researchers to strategies that help them more effectively communicate the scale, scope and "wow" of their work to non-technical audiences.

With consumer applications in everything from clothing, personal-care products and sporting goods to air purification systems, computers and home appliances, nanotechnology rapidly is becoming an integral part of everyday life. Yet survey results show that public audiences largely lack awareness and understanding of nanotechnology concepts, says Olivia Castellini, a former postdoctoral researcher with the University of Wisconsin-Madison Materials Research Science and Engineering Center (MRSEC) Interdisciplinary Education Group.

"In the very near future, the public will be asked to make a variety of decisions about nanotechnology, including whether or not to purchase nanotechnology products, how nanotechnology should be regulated-if at all-and whether public funding should be used to support nanotechnology research," she says. "The more knowledge and awareness the public has about nanotechnology, the better prepared they will be to make these kinds of decisions."

Now an exhibit developer in the Chicago Museum of Science and Industry Department of Science and Technology, Castellini led a study in which she and three undergraduate interns surveyed 495 people ages 7 to 91 to test their knowledge of atoms, nanotechnology and size scale, and to assess their attitudes toward nanotechnology. The group published its results, also available online, in Vol. 992 of the Journal of Nanoparticle Research.

"Our most significant finding is that public knowledge of fundamental science concepts related to nanotechnology varies a great deal based on age and educational experience," says Castellini.

Many survey respondents who had heard about nanotechnology said they learn about it from mass media like television, newspapers, movies or the Internet, yet less than 20 percent of all respondents could correctly define it as science and technology on a tiny scale (there are about 25 million nanometers in an inch).

In addition, survey responses relating to the size scale of such microscopic objects as an atom, cell, bacterium and water molecule showed that people find it difficult to grasp concepts they cannot visualize.

"The ideas that atoms are the building blocks of matter and a conceptual understanding of the tiny size of the nanoscale are central to understanding nanotechnology concepts," says Castellini. "Our study found that the majority of people educated at the middle-school level or higher could recall facts about atoms-but that fact-based knowledge did not necessarily guarantee their conceptual understanding of them."

The survey originated in fall 2004 when she and the students began developing museum exhibit prototypes about nanotechnology. At the time, they found very little published information about public knowledge of nanotechnology, says Wendy Crone, a UW-Madison associate professor of engineering physics. "The study was really crucial for our appreciation for what the public knows about nanotechnology and for our appreciation of the difficulties we would face in developing exhibits that involve a size scale that's smaller than you can see," says Crone, who directs the MRSEC Interdisciplinary Education Group.

Communication strategies that emerged from the study also enabled group members to deliver more meaningful nanotechnology information in face-to-face interactions with audiences like schoolchildren, K-12 teachers and the public, says Crone. "We learned some things that we had been doing wrong and adjusted how we were presenting information based on the research findings," she says.

Researchers commonly communicate nanotechnology concepts to general audiences via formal and informal public lectures, outreach events, and demonstrations. "One of the mistakes that's very common for researchers to make is to assume that, if I just blurt out everything I know, that people will get something from it," says Crone. "That one-way distribution of information isn't very effective."

Rather, says Castellini, researchers first should assess how much their audiences know about basic nanotechnology concepts such as atoms and size scale, and conduct a review, if necessary. "Highly visual presentations are particularly effective for this purpose," she says. "Additionally, we recommend limiting the number of nanotechnology concepts to two or three to prevent the audience from feeling overwhelmed with too much information."

As a result of the study, Crone has made her frequent nanotechnology talks more interactive and now includes nano "fun facts" and real-life examples and analogies that pique audience curiosity and encourage dialogue. One particularly successful example is the statement, "In the time it takes you to read this sentence, your fingernails will have grown one nanometer."

In the case of nanotechnology, the researchers learned that public audiences have a fairly neutral opinion of nanotechnology. "This is actually good news," says Castellini. "As public awareness and knowledge of nanotechnology grows, researchers may be able to avoid overcoming negative opinions or preconceived notions about the technology," she says.

In addition to Castellini and Crone, other paper authors include Gina K. Walejko, Carie E. Holladay, Terra J. Theim and Greta M. Zenner. The Materials Research Science and Engineering Center is funded via a National Science Foundation grant.

Nanotechnology? What's That?!

2008-10-17T21:24:00.000-07:00

Nanotechnology has already brought advances such as self-cleaning windows and energy-efficient LED lighting, and could soon deliver medical breakthroughs. To educate the public about nanotechnology's promise, the National Science Foundation has slated $20 million to fund a network of interactive exhibits at 100 museums around the country.MADISON, Wis.--Nanotechnology is the big buzz word in the world of science. It's going to impact just about everything we do, touch and see. And this next big thing is extraordinarily small.

You've heard the word, but do you know what nanotechnology is?

University of Wisconsin-Madison engineer Wendy Crone is on a mission. She and her interns are creating user-friendly exhibits to teach the public about the nanoworld.

"Nanotechnology is already starting to affect our lives, and it's anticipated that over the next 20 years it's going to have major impact on everything around us," Crone tells DBIS.

Nanotechnology means working at the scale of molecules. Crone's exhibits show just how small that scale is. "When you put nano in front of meter that means that's a billionth of a meter. So that means that you can fit 1 billion nanometers in one meter," she says. You'd have to slice one hair into 50,000 distinct strands to get a strand one-nanometer thick.

Nanotechnology is the secret behind how self-cleaning windows work and why LEDs are so energy-efficient.

"I think that nanotechnology, I mean, everyone continues to talk about it, is the next big thing," says intern Anne Vedder.

It might even save your life. Drug-coated nanoparticles will soon precisely deliver therapy to organs and tumors. Crone says it's going to be everywhere, and you probably won't even know that it's inside the products that you're using.

The National Science Foundation is giving $20 million to fund the national Nanoscale Informal Science Education Network (NISE Network), which will develop interactive exhibits to teach the public about nanotechnology. The network's goal is to have these exhibits in 100 museums across the United States in the next five years.

BACKGROUND: The engineering faculty, staff and students at the University of Wisconsin, Madison, are working with some of the nation's top science museums to create hands-on exhibits about nanotechnology. The effort is part of the $20 million Nanoscale Informal Science Education Network, which aims to develop innovative materials and vehicles to increase the public's knowledge and understanding of nanotechnology through exhibits.

ABOUT NANOTECHNOLOGY: Nanotechnology is science at the size of individual atoms and molecules: objects and devices measuring mere billionths of a meter, smaller than a red blood cell. At that size scale, materials have different chemical and physical properties than those of the same materials in bulk, because quantum mechanics is more important. For example, carbon atoms can conduct electricity and are stronger than steel when woven into hollow microscopic threads. Nanoparticles are already widely used in certain commercial consumer products, such as suntan lotions, "age-defying" make-up, and self-cleaning windows that shed dirt when it rains. One company manufactures a nanocrystal wound dressing with built-in antibiotic and anti-inflammatory properties. On the horizon is toothpaste that coats, protects and repairs damaged enamel, as well as self-cleaning shoes that never need polishing. Nanoparticles are also used as additives in building materials to strengthen the walls of any given structure, and to create tough, durable, yet lightweight fabrics.

SIZING THINGS UP: The tiny size scale makes it a challenge to translate nanotech research into something museum visitors can see, touch and comprehend, especially in an interactive format. UW-Madison already has the Nanoworld Discovery Center, which does just that. Among the exhibit's features is a segment about ferrofluids: tiny magnetic particles that flow like a liquid. They are used to damp vibrations and eliminate excess energy in expensive stereo systems. Visitors also learn about such applications as stain-resistant clothing, as well as compare incandescent bulbs to light-emitting diodes to learn how nanomaterials can help conserve energy.

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2008-10-13T10:15:00.000-07:00

Nanotechnology, sometimes shortened to nanotech, refers to a field of applied science whose theme is the control of matter on an atomic and molecular scale. Generally nanotechnology deals with structures 100 nanometers or smaller, and involves developing materials or devices within that size.

Nanotechnology is an extremely diverse and multidisciplinary field, ranging from novel extensions of conventional device physics, to completely new approaches based upon molecular self-assembly, to developing new materials with dimensions on the nanoscale, or the scale of nothing, even to speculation on whether we can directly control matter on the atomic scale.

There has been much debate on the future implications of nanotechnology. Nanotechnology has the potential to create many new materials and devices with wide-ranging applications, such as in medicine, electronics, and energy production. On the other hand, nanotechnology raises many of the same issues as with any introduction of new technology, including concerns about the toxicity and environmental impact of nanomaterials, and their potential effects on global economics, as well as speculation about various doomsday scenarios. These concerns have lead to a debate among advocacy groups and governments on whether special regulation of nanotechnology is warranted.