Japan nano-tech team creates palladium-like alloy: report

Japanese researchers have created an alloy with properties similar to palladium, a precious metal used in many high-tech goods, a news report said Thursday, dubbing the breakthrough"present-day alchemy".

Kyoto University professor Hiroshi Kitagawa and his team said they used nano-technology to combine rhodium and silver, elements which do not usually mix, to produce the new composite, the Yomiuri daily said.

The alloy has similar properties topalladium, which is used in cars' emission-reducing catalytic converters as well as in computers, mobile phones, flatscreen TVs and dentistry instruments.

Like other white metals, such as silver and platinum, palladium is expensive, with its deposits largely limited to South Africa and Russia.

Palladium also has applications in the production of fuel cells -- a clean andrenewable energy sourcethat produces electricity by combining hydrogen and oxygen, with water as the only byproduct.

To make the new alloy, the Kyoto team used nano-technology to"nebulise"the rhodium and silver and gradually mixed them with heated alcohol, with the two metals mixed stably at the atomic level, the report said.

Japan's industry ministry has listed 31 rare metals, including palladium and lithium, which are used in industrial products, such aselectronic devicesand batteries. Of these, 17 elements are called rare earth minerals.

Resource-poor Japan has tried to shift from its dependence on China, which controls the bulk of global rare earth production.

Kitagawa said he hopes to create morealloysusing nano-technology, without specifying which ones, the Yomiuri said.

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Researchers improve efficiency of low-cost solar cells

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(PhysOrg.com) -- As part of the recent progress in improving solar cells for widespread use, researchers from Purdue University have designed solar cells made of low-cost, abundant materials that are easily scalable and very stable. The researchers have increased the solar cells' total area efficiency to 7.2% and plan to make further improvements in the future.

The researchers, Qijie Guo, et al., have published their study on the improvedsolar cellsin a recent issue of theJournal of the American Chemical Society.They fabricated the solar cells from copper-zinc-tin-chalcogenide (CZTSSe), which is an Earth-abundant material, using a solution-based thin-film deposition method. Previous research has shown that these methods can provide high yields at lower manufacturing costs compared to other methods.

The solar cell design is based on the researchers' earlier study in which they demonstrated that solar cells fabricated using CZTS nanocrystals are potentially viable, although they had efficiencies of less than 1%. Here, the researchers made significant improvements to the design by tuning the composition of the nanocrystals as well as developing a more robust thin-film coating method.

After synthesizing the nanocrystals and applying them on asubstratefor a total film thickness of 1 micrometer, the researchers observed that the nanocrystal film featured large, densely packedgrains, which leads to improvedsolar cell efficiency. In testing, the solar cells could achieve a total area efficiency of 7.2%. As coauthor Hugh Hillhouse explained, the total area efficiency refers to the entire cell, rather than just the“active area.”

"It is the total area efficiency that matters most,"he toldPhysOrg.com.“Some people report an‘active area’ efficiency, which only includes areas that the light reaches. However, all thin film solar cells are made with metal contacts that block the light from reaching some areas. When you include this loss, we use the term‘total area’ efficiency. It is the most fair and important efficiency.”

The 7.2% efficiency was reached after“light soaking” for 15 minutes under one-sun illumination; when the light was turned off, the efficiency dropped to 6.89%.

“Light soaking simply means that we shine normal intensity simulated sunlight on the cell for a period of time before we make the measurement,” Hillhouse said.“Most likely, the light soaking allows photogenerated carriers to fill traps, shift the quasi-Fermi levels, and/or screen barriers created by band offsets. It doesn’t present a problem since real solar cells are naturally light soaked– they sit in the sun.”

Although currently there are no CZTS or CZTSSe solar cells on the market for comparison, the solar cells in this study are very competitive with other fabrication methods.

“The best cells formed by vacuum processes have only reached 6.7%,” Hillhouse said.“Typically, solar cells produced by vacuum-based processes have been more efficient, but also more expensive. For the case of CZTS, the solution phase approach (our nanocrystal route and IBM’s hydrazine route) is more efficient.”

One potential area for improvement for these solar cells lies in improving their low quantum efficiency for light of longer wavelengths (i.e., the near-infrared range). The researchers attempted to improve this efficiency by increasing the thickness of the absorber, although their initial experiments showed that thicker absorber layers also had increased resistance. In the future, they plan to optimize the fabrication for thicker films, which could further increase the overall efficiency.

“There is a lot of compositional freedom in the CZTSSe system, and it is likely that the optimum compositions, device structure, and processing conditions have not yet been found– but we are working on it,” Hillhouse said.

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New nanotube material stays rubbery over a more than 1,000 degree temperature range

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(PhysOrg.com) -- Silicone rubber is used in many applications in which a material is required to remain rubbery over a wide temperature range, since it retains its properties over the approximate range of -55°C to 300°C. Now a new material made of carbon nanotubes has been developed that retains its viscoelastic properties over a temperature range almost five times larger.

Scientists at the National Institute of Advanced Industrial Science and Technology (AIST) in Tsukuba, Japan created the nanotube material using chemical vapor deposition. The material has elastic properties of recoverable stretchiness, and viscoelastic properties that give it a thick-honey-like consistency, and allows it to stretch slowly and then spring back to its original shape. It retains these properties over the range of -196°C to 1000°C.

The research team, led by Dr. Ming Xu, has previously worked oncarbon nanotube“forests,” and development of the new material was the accidental product of an extension of this work. In the“forest” the long nanotubes grow upwards, but when the team modified the catalysts used in the process they found they could make the alignment of the nanotubes much less regular, and were able to create a random network of interconnected nanotubes, which Xu likened to a tangle of jungle vines.

They then investigated the properties of the new material and discovered it has similar viscoelastic properties to silicone rubber at roomtemperature, but unlikesiliconerubber, which becomes brittle when cold and breaks down at high temperatures, the newrubbermaterial remained flexible over a much larger temperature range and has excellent fatigue resistance properties. The researchers speculated the thermal stability could arise from energy dissipating as the carbon nanotubes zip and unzip at points of contact.

Until now, very little research has been done on the viscoelastic properties of carbon nanotubes, probably because they are difficult to make and because they oxidize readily at high temperatures. Xu said the research team is now looking for industrial applications for the new material, so they can further refine its properties to suit those applications. She also said she believed the temperature range could be extended much further, and the material could probably be made more elastic, stronger or softer, as required.

The material may find uses in space applications or rubbers for use in extremely hot environments, but the research is still at an early stage. The findings on the new material are published inScience.

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Israel's scientists think big with the very, very small

A material just one atom thick that is stronger than steel but flexes like rubber. A"mini-submarine"that can trick the immune system and deliver a payload of chemotherapy deep inside a tumour.

They sound like the fantasies of science fiction writers, but they are among the discoveries being presented at Nano Israel 2010, a nanotech conference in Tel Aviv that has attracted researchers from across the science world, united by their work with the very, very small.

The 1,500 participants at the two-day meeting which ends on Tuesday include chemists, physicists and medical researchers, all working withtiny structuresaround the thickness of a cell wall.

"We are all working to be able to manipulate molecules at anatomic level,"said Dan Peer, a professor at Tel Aviv University's Cell Research and Immunology Department.

Physicists are developing new materials by removing or adding to existing structures and nano-medical researchers are building new ways to deliver drugs.

Peer is trying to find out how to more effectively target cancer and the inflammation associated with diseases like multiple sclerosis by better directing toxic treatments like chemotherapy.

"Sometimes the drug is there, but it doesn't operate in a targeted manner,"he told AFP.

In such cases, scientists are trying to find ways to build"GPS systems"into the drugs so they travel directly tomalignant cellsor inflammation.

One way of doing that is to attach thecancer treatmentto a vitamin that tumours happily suck up, allowing the medication to penetrate the malignant cells with ease.

"You can potentially create new materials, new vehicles for drugs, like very small bubbles, like mini-submarines, which carry them into the body,"Peer told AFP.

Joseph Kost, a professor at Ben Gurion University of the Negev's chemical engineering department, is working on a technique that delivers chemotherapy drugCisplatininto tumours.

The drug is carried by a tiny vessel through gaps of between 100-1000 nanometres in size, giving scientists a"therapeutic warhead,"he said.

Once inside, researchers irradiate the drug vehicles with ultrasound, causing them to"explode"and disperse the treatment inside the tumour.

Others are looking at ways to trick the body's immune system to prevent it from identifying drug treatments as invading viruses and attacking them.

Elsewhere, physicists like Andre Geim, winner of this year's Nobel Prize for Physics, are usingnanotechnologyto develop new materials with a surprising range of applications.

Geim, a Russian scientist working in Britain, presented his work on graphene, a one-atom-thick slice of graphite that is stiffer than diamond.

"You can imagine you can make a thousand devices out of this graphene,"he told an audience of researchers from 35 countries, whose work could one day produce more efficient conductors and roll-up touchscreens for computers.

Graphene's structure could even allow it to be used for faster DNA sequencing, Geim said.

For Israel, hosting the gathering of nano-researchers is a way of showcasing a sector that the government is trying to foster.

"We see this as a major economic initiative for the future of Israel,"said Barry Breen, a spokesman for Israel's National Nanotechnology Initiative, a government advisory body."It should be a dominant economic engine."

INNI works to match Israel's nanotech researchers with private industry.

A recent project saw Jerusalem-based company 3G Solar work with scientists at Bar Ilan University to develop a solar cell that processes energy in a similar way to photosynthesis in plants.

Aharon Gedanken, a professor of chemistry at Bar Ilan University, is using nanotechnology to develop sterile hospital sheets and robes using a technique called sonochemistry.

The process uses a chemical reaction that produces"microjets,"which throw out nanoparticles of anti-bacterial metals like zinc oxide at"such a high speed that they are embedded in the surface."

The resulting fabric can be washed, even at the hospital standard of 92 degrees Celsius (197.6 degrees Fahrenheit), without losing its anti-bacterial properties.

"The vision of this project is that in the future all the fabrics in a hospital will be anti-bacterial,"he said.

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Gold and silver nano baubles

They might just be the smallest Christmas tree decorations ever. Tiny spherical particles of gold and silver that are more than 100 million times smaller than the gold and silver baubles used to decorate seasonal fir trees have been synthesized by researchers in Mexico and the US.

Writing in the December issue of theInternational Journal of Nanoparticles, materials engineer Xavier E. Guerrero-Dib, of the Universidad Autónoma de Nuevo León and colleagues there and at The University of Texas at Austin, describe the formation of gold,silverand alloyed, bimetallic nanoparticles just 25 nanometers in diameter. They used vitamin C, ascorbic acid, commonly found in tangerines, a favorite stocking filler in many parts of the world, and a soap-like, surfactant molecule known as cetyltrimethylammonium bromide, an antiseptic occasionally used in expensive cosmetics.

Reaction of silver nitrate and the gold compound chloroauric acid under these conditions led to successive reduction of the metals and the formation of different silver, gold and bimetallic nanoparticles. The precise structures of the nanoparticles were revealed using a high-resolution elemental mapping technique. The analysis shows the nanoparticles to have multiple layers, shells of gold within silver within gold, in the case of the bimetallic particles and some blending, or alloying, of the metals occurred.

Nanoparticles are of great interest to chemists and materials scientists for their potential as catalysts for speeding up chemical reactions, as novel drug-delivery agents, and as quantum dots for analytical applications. They may also be used in the fabrication of the components of future electronics devices beyond the silicon chip. Metal nanoparticles containing two or more different metals might have even more intriguing chemical, electronic and optical properties than single-metal nanoparticles because of the combination of the different chemistries of each metal as well as the size effects of the particles simply being, very, very small.

The researchers point out that the optical properties of nanoparticles depend very much on size and shape as well as the constituent metals. Gold and silver nanoparticles are particularly useful as their optical effects occur at visible wavelengths of light. The team adds that if it were possible to fine-tune the combination ofgoldand silver in the samenanoparticlesthen it might also be possible to tune theoptical propertiesof such particles.

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Researchers create new high-performance fiber

Researchers at Northwestern University have nanoengineered a new kind of fiber that could be tougher than Kevlar.

Working in a multidisciplinary team that includes groups from other universities and the MER Corporation, Horacio Espinosa, James N. and Nancy J. Farley Professor in Manufacturing&Entrepreneurship at the McCormick School of Engineering and Applied Science, and his group have created a high performance fiber from carbon nanotubes and a polymer that is remarkably tough, strong, and resistant to failure. Using state-of-the-art in-situ electron microscopy testing methods, the group was able to test and examine the fibers at many different scales— from the nano scale up to the macro scale— which helped them understand just exactly how tiny interactions affect the material's performance. Their results were recently published in the journalACS Nano.

"We want to create new-generation fibers that exhibit both superior strength and toughness,"said Espinosa said."A big issue in engineering fibers is that they are either strong or ductile— we want a fiber that is both. The fibers we fabricated show very high ductility and a very high toughness. They can absorb and dissipate large amounts of energy before failure. We also observed that the strength of the material stays very, very high, which has not been shown before. These fibers can be used for a wide variety of defense and aerospace applications."

The project is part of the Department of Defense's Multidisciplinary University Research Initiative (MURI) program, which supports research by teams of investigators that intersect more than one traditional science and engineering discipline. Espinosa and his collaborators received $7.5 million from the U.S. Army Research Office for the study of disruptive fibers, which could be used in bulletproof vests, parachutes, or compositematerialsused in vehicles, airplanes and satellites.

To create the new fiber, researchers began with carbon nanotubes—cylindrical-shaped carbon molecules, which individually have one of the highest strengths of any material in nature. When you bundle nanotubes together, however, they lose their strength— the tubes start to laterally slip between each other.

Working with the MER Corporation and using the corporation's CVD reactor, the team added a polymer to the nanotubes to bind them together, and then spun the resulting material into yarns. Then they tested the strength and failure rates of the material using in-situ SEM testing, which uses a powerful microscope to observe the deformation of materials under a scanning electron beam. This technology, which has only been available in the past few years, allows researchers to have extremely high resolution images of materials as they deform and fail and allows researchers to study materials on several different scales. They can examine individual bundles of nanotubes and the fiber as a whole.

"We learned on multiple scales how this material functions,"said Tobin Filleter, a postdoctoral researcher in Espinosa's group."We're going to need to understand how molecules function at these nanometer scales to engineer stronger and tougher fibers in the future."

The result is a material that is tougher than Kevlar— meaning it has a higher ability to absorb energy without breaking. But Kevlar is still stronger— meaning it has a higher resistance to failure. Next, researchers hope to continue to study how to engineer the interactions between carbon nanotube bundles and between the nanotubes within the bundle itself.

"Carbon nanotubes, the nanoscale building blocks of the developed yarns, are still 50 times stronger than the material we created,"said Mohammad Naraghi, a postdoctoral researcher in Espinosa's group."If we can better engineer the interactions between bundles, we can make the material stronger."

The group is currently looking at techniques— like covalently crosslinking tubes within bundles using high-energy electron radiation– to help better engineer those interactions.

Filleter and Naraghi said this work wouldn't have been possible without the interdisciplinary team that includes merging academia with industry.

"To work in an environment where we can trade information back and forth is a unique opportunity that will push the technology farther,"Naraghi said."MER has given us a unique raw material and a commercial perspective on the project. In turn, we provide the fundamental scientific understanding."

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Light touch brightens nanotubes (w/ Video)

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(PhysOrg.com) -- Rice University researchers have discovered a simple way to make carbon nanotubes shine brighter.

The Rice lab of researcher Bruce Weisman, a pioneer in nanotube spectroscopy, found that adding tiny amounts of ozone to batches of single-walled carbon nanotubes and exposing them tolightdecorates all the nanotubes withoxygen atomsand systematically changes their near-infrared fluorescence.

Chemical reactionson nanotube surfaces generally kill their limited natural fluorescence, Weisman said. But the new process actually enhances the intensity and shifts the wavelength.

He expects the breakthrough, reported online in the journalScience, to expand opportunities for biological and material uses of nanotubes, from the ability to track them in single cells to novel lasers.

Best of all, the process of making these bright nanotubes is incredibly easy --"simple enough for a physical chemist to do,"said Weisman, a physical chemist himself.

He and primary author Saunab Ghosh, a graduate student in his lab, discovered that a light touch was key."We're not the first people to study the effects of ozone reacting with nanotubes,"Weisman said."That's been done for a number of years.

"But all the prior researchers used a heavy hand, with a lot ofozone exposure. When you do that, you destroy the favorable optical characteristics of the nanotube. It basically turns off the fluorescence. In our work we only add about one oxygen atom for 2,000-3,000carbon atoms, a very tiny fraction."

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Ghosh and Weisman started with a suspension of nanotubes in water and added small amounts of gaseous or dissolved ozone. Then they exposed the sample to light. Even light from a plain desk lamp would do, they reported.

Most sections of the doped nanotubes remain pristine and absorbinfrared lightnormally, forming excitons, quasiparticles that tend to hop back and forth along the tube -- until they encounter oxygen.

"Anexcitoncan explore tens of thousands of carbon atoms during its lifetime,"Weisman said."The idea is that it can hop around enough to find one of these doping sites, and when it does, it tends to stay there, because it's energetically stable. It becomes trapped and emits light at a longer (red-shifted) wavelength.

"Essentially, most of the nanotube is turning into an antenna that absorbs light energy and funnels it to the doping site. We can make nanotubes in which 80 to 90 percent of the emission comes from doped sites,"he said.

Lab tests found the doped nanotubes' fluorescent properties to be stable for months.

Weisman said treated nanotubes could be detected without using visible light."Why does that matter? In biological detection, any time you excite at visible wavelengths, there's a little bit of background emission from the cells and from the tissues. By exciting instead in the infrared, we get rid of that problem,"he said.

The researchers tested their ability to view doped nanotubes in a biological environment by adding them to cultures of human uterine adenocarcinoma cells. Later, images of the cells excited in the near-infrared showed single nanotubes shining brightly, whereas the same sample excited with visible light displayed a background haze that made the tubes much more difficult to spot.

His lab is refining the process of doping nanotubes, and Weisman has no doubt about their research potential."There are many interesting scientific avenues to pursue,"he said."And if you want to see a single tube inside a cell, this is the best way to do it. The doped tubes can also be used for biodistribution studies.

"The nice thing is, this isn't an expensive or elaborate process,"Weisman said."Some reactions require days of work in the lab and transform only a small fraction of your starting material. But with this process, you can convert an entire nanotube sample very quickly."

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Radically simple technique developed to grow conducting polymer thin films

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(PhysOrg.com) -- Oil and water don't mix, but add in some nanofibers and all bets are off.

A team of UCLA chemists and engineers has developed a new method for coating large surfaces with nanofiber thin films that are both transparent and electrically conductive. Their method involves the vigorous agitation of water, dense oil and polymer nanofibers. After this solution is sufficiently agitated it spreads over virtually any surface, creating a film.

"The beauty of this method lies in its simplicity and versatility,"said CaliforniaNanoSystemsInstitute (CNSI) researcher Richard B. Kaner, a professor of chemistry and biochemistry and a professor of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science."The materials used are inexpensive and recyclable, the process works on virtually any substrate, it produces a uniform thin film which grows in seconds and the entire thing can be done at room temperature."

Conducting polymers combine the flexibility and toughness of plastics withelectrical properties. They have been proposed for applications ranging from printedelectronic circuitsto supercapacitors but have failed to gain widespread use because of difficulties processing them into films.

"Conducting polymers have enormous potential in electronics, and because this technique works with so many substrates, it can be used in a broad spectrum of applications, includingorganic solar cells, light-emitting diodes, smart glass and sensors,"said Yang Yang, a professor of materials science and engineering at the Samueli School of Engineering and Applied Science and faculty director of the Nano Renewable Energy Center at the CNSI.

One of the potential applications is smart, or switchable, glass that can change between states when an electric current is applied— for example, switching between see-through and opaque states to let light in or block it. The UCLA research group is applying the technique to other nanomaterials in addition to polymer nanofibers in the hopes of expanding the number of available applications.

The team's solution-based technique, published in the peer-reviewed journalProceedings of National Academy of Sciences, was discovered serendipitously when a transparent film of polymer spread up the walls of a container while nanofibers in water were being purified with chloroform.

"What drew me in immediately was the eerie phenomenon of what appeared to be self-propelled fluid flow,"said Julio M. D'Arcy, lead author on thePNASpaper and a senior graduate student in the Kaner's UCLA lab.

"Now I can tell people that I make films in L.A.,"he joked.

When water and oil are mixed, a blend of droplets is formed, creating a water–oil interface that serves as an entry point for trapping polymer nanofibers at liquid–liquid interfaces. As droplets unite, a change in the concentration of blended solids at the water–oil interface leads to a difference in surface tension. Spreading up a glass wall occurs as result of an attempt to reduce the surface-tension difference. Directional fluid flow leads to a continuously conductive thin film comprised of a single monolayer of polymer nanofibers. The uniformity of the film surface is due to the particles being drawn out of the water–oil interface, sandwiched between two fluids of opposing surface tensions.

Development of the technology is occurring in collaboration with Fibron Technologies Inc., with support from the National Science Foundation through a Small Business Technology Transfer grant. Fibron is a small company that has licensed the technology from UCLA. It was founded by Kaner, who serves as chief scientific adviser, and two of his former Ph.D. students— Christina Baker and Henry Tran, who have gone on to take leadership roles in the company.

Fibron's CEO, Christian Behrenbruch, said"working with UCLA to develop this technology has been a win-win. It enables us to access incredibly innovative people, but also, the NSF has helped enable the establishment of a formal and transparent IP releationship with the university. The good news is that this technology is moving rapidly into commercial development."

Other techniques exist for creating thin films of conducting polymers, but each technique tends to work only a limited number of applications, or they are not feasible for scaling up. A method has long been sought which would overcome the limitations of each of the previous methods. The water and oil technique, with a bit of nanotechnology thrown in, might provide just that— a scalable universal method for creating largethin filmsof conducting polymers.

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Measuring the temperature of nanoparticles

One of the holy grails of nanotechnology in medicine is to control individual structures and processes inside a cell. Nanoparticles are well suited for this purpose because of their small size; they can also be engineered for specific intracellular tasks. When nanoparticles are excited by radio-frequency (RF) electromagnetic fields, interesting effects may occur. For example, the cell nucleus could get damaged inducing cell death; DNA might melt; or protein aggregates might get dispersed.

Some of these effects may be due to the localized heating produced by each tiny nanoparticle. Yet, such local heating, which could mean a difference of a few degrees Celsius across a few molecules, cannot be explained easily by heat-transfer theories. However, the existence of local heating cannot be dismissed either, because it's difficult to measure thetemperaturenear these tinyheatsources.

Scientists at Rensselaer Polytechnic Institute have developed a new technique for probing the temperature rise in the vicinity of RF-actuated nanoparticles using fluorescentquantum dotsas temperature sensors. The results are published in theJournal of Applied Physics.

Amit Gupta and colleagues found that when the nanoparticles were excited by an RF field the measured temperature rise was the same regardless of whether the sensors were simply mixed with the nanoparticles or covalently bonded to them."This proximity measurement is important because it shows us the limitations of RF heating, at least for the frequencies investigated in this study,"says project leader Diana Borca-Tasciuc."The ability to measure the local temperature advances our understanding of these nanoparticle-mediated processes."

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Researchers create iridescent glass that can reflect UV or infrared light

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(PhysOrg.com) -- Using nanocrystals of cellulose, the main component of pulp and paper, chemistry researchers at the University of British Columbia have created glass films that have applications for energy conservation in building design because of their ability to reflect specific wavelengths of light, such as ultra violet, visible or infrared.

These nanoporous films, described in a paper published in today’s issue ofNature, may also be used in optical filters, sensors, or for molecule separation in the pharmaceutical industry.

“This is the first time that the unique, helical structure of cellulose has been replicated in a mineral,” says Mark MacLachlan, associate professor in the chemistry department at UBC and co-authour of the paper.“The films have many applications and we created them from an exciting new product derived from our wood processing industry right here in British Columbia.”

At the molecular level, the films have the helical structure of nanocrystalline cellulose, a building block of wood pulp, explains MacLachlan.

MacLachlan and PhD student Kevin Shopsowitz, post-doctoral fellow Hao Qi and Wadood Hamad of FPInnovations, stumbled upon this discovery while trying to create a hydrogen storage material.

The UBC researchers mixed the cellulose from the wood pulp with a silica, or glass, precursor and then burned away the cellulose. The resulting glass films are composed of pores, or holes, arranged in a helical structure that resembles a spiral staircase. Each hole is less than 1/10,000th of the diameter of a human hair.

“When Kevin showed me the films and they were red, blue, yellow and green, I knew we’d been able to maintain the helical structure found in thecellulose.”

“The helical organization we produced synthetically mimics the structure of the exoskeletons of some iridescent beetles,” says Shopsowitz.

The pores in the helix give the films a wide range of applications. When certain liquids are added to the film, the liquid gets trapped in the pores and changes the optical properties of the films.

“By functionalizing the pores to make them more selective to particular chemicals, we may be able to develop new sensors that are very sensitive for detecting substances in the environment,” says Shopsowitz.

To reduce the energy needed to cool buildings, windows could be treated with the transparent films that reflect infrared light– the light that heats up a building. Right now, metal particles are often used to do this but they tint the windows brown.

This research was done in partnership with FPInnovations, an organization dedicated to developing new products from the forest sector, and with funding from the Natural Sciences and Engineering Research Council of Canada.

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New high performance insulating plaster developed at Empa

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Empa scientists have developed a high performance plaster which boasts a thermal insulation value three-times better than convention plaster thanks to so-called aerogels. The new material offers an elegant method of renovating historic buildings to save energy without altering their appearances.

Those undertaking the renovation of historical buildings are frequently faced with the challenge of how to improve the thermalinsulationlevels of old structures effectively yet elegantly. To date there has been no method available which offers a technically satisfactory solution to this problem without noticeably changing the appearance of the historic building.

Now, however, researchers from Empa’s Building Technologies Laboratory, working in cooperation with a leading manufacturer of building materials, have developed an aerogel-based high performance insulatingplasterwhich will undergo field trials next year and is expected to be commercially available by 2013. Thanks to its mineral basis, the new plaster is both optically and in application very similar to the original historical building materials, and this makes it ideal for use on old buildings– on internal as well as external surfaces.

The"secret"behind the novel insulating plaster is a so-called aerogel. This substance possesses nanometer-sized pores and consists of 90 to 98 per cent air. These minute pores make aerogels an excellent material for use in the new insulating plaster, lending it a thermal conductivity value of less than 30 mW/m•K which is some two to three times better than that of conventional plaster.

A further advantage of the new plaster is its property of being simultaneously water repellent and permeable to water vapor. The new product is significantly more breathable than conventional plasters, and yet its surface does not become wet. Co-developer Thomas Stahl explains.”The porous structure of the aerogel makes the plaster permeable to water molecules, but for macroscopic water droplets the nano-pores are much to fine.”

The first buildings will be plastered with the new high performance material on a trial basis beginning in mid-2012. The additional cost of this innovative new plaster compared to conventional materials is expected to be between CHF 50 and 100 per square meter, depending on how thickly it is applied.

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UH professor taking next step with graphene research

The 2010 Nobel Prize in Physics went to the two scientists who first isolated graphene, one-atom-thick crystals of graphite. Now, a researcher with the University of Houston Cullen College of Engineering is trying to develop a method to mass-produce this revolutionary material.

Graphene has several properties that make it different from literally everything else on Earth: it is the first two-dimensional material ever developed; the world's thinnest and strongest material; the best conductor of heat ever found; a far better conductor of electricity than copper; it is virtually transparent; and is so dense that no gas can pass through it. These properties makegraphenea game changer for everything from energy storage devices to flat device displays.

Most importantly, perhaps, is graphene's potential as a replacement for silicon in computer chips. The properties of graphene would enable the historical growth in computing power to continue for decades to come.

To realize these benefits, though, a way to create plentiful, defect-free graphene must be developed. Qingkai Yu, an assistant research professor with the college's department of electrical and computer engineering and the university's Center for Advanced Materials, is developing methods to mass-produce such high-quality graphene.

Yu is using a technology known as chemical vapor deposition. During this process, he heats methane to around 1000 degrees Celsius, breaking the gas down into its building blocks of carbon andhydrogen atoms. Thecarbon atomsthen attach to a metallic surface to form graphene.

"This approach could produce cheap, high-quality graphene on a large scale,"Yu said.

Yu first demonstrated the viability of chemical vapor deposition for graphene creation two years ago in a paper in the journalApplied Physics Letters. He has since continued working to perfect this method.

Yu's initial research would often result in several layers of graphene stacked together on a nickel surface. He subsequently discovered the effectiveness of copper for graphene creation. Copper has since been adopted by graphene researchers worldwide.

Yu's work is not finished. The single layers of graphene he is now able to create are formed out of multiple graphene crystals that join together as they grow. The places where these crystals combine, known as the grain boundaries, are defects that limit the usefulness of graphene, particularly as a replacement for silicon-basedcomputer chips.

Yu is attempting to create large layers of graphene that form out of a single crystal.

"You can imagine how important this sort of graphene is,"said Yu."Semiconductors became a multibillion-dollar industry based on single-crystal silicon and graphene is called the post-silicon-era material. So single-crystal graphene is the Holy Grail for the next age of semiconductors."

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Revealing the secrets of chemical bath deposition

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X-ray absorption near-edge structure (XANES) spectroscopy is well known as a versatile and powerful technique for examining the microstructure of everything from crystalline solids to amorphous materials, even liquids. Its extreme sensitivity also makes it an ideal tool for probing the kinetics of various chemical reactions<i>in situ</i>.

Experimenters utilizing the U.S. Department of Energy Office of Science’s Advanced Photon Source at Argonne recently demonstrated a new wrinkle for XANES that has opened a window on a poorly-understood technique for deposition of materials. These insights will encourage the development of better-controlled and more precise chemical synthesis techniques for semiconductor and other nanomaterial applications, and are valuable as a demonstration of the extension of XANES spectroscopy into other realms of experimentation.

While chemical bath deposition (CBD) is widely used in the laboratory and industry for the creation of thin films and nanostructures for semiconductors and photovoltaics, its actual molecular workings have remained something of a mystery. This has somewhat limited its utility, because precise tailoring of CBD products is not possible without a clear understanding and thus control of CBD mechanics. Scientists from Drexel University and the University of Notre Dame have obtained the first detailed look at how CBD operates at the molecular level, using XANES spectroscopy to witness in situ the formation of zinc oxide nanowires. The work was published in October 2010 inChemistry of Materials.

CBD begins with a water solution with chemical precursors containing the components from which the desired film structure will be formed. But because the precursor chemical species tend to be very dilute within the solution, identifying and isolating them to monitor their activity during the deposition process has been a daunting challenge.“It’s very difficult to find experimental techniques that will allow you to assess the different things that you need to measure,” said principal investigator Jason Baxter of Drexel University.“This has led to some criticism of CBD for being too recipe-based, where it can be difficult to take one set of conditions and say what might happen elsewhere.” XANES proved to be the ideal window into the CBD process.“It gives you very high sensitivity so you can measure species that are very dilute,” Baxter said.“So we were able to look at CBD with a degree of accuracy that people could not achieve before.”

The researchers subjected a solution of zinc nitrate and HMTA (hexamethylenetetramine) to different temperatures and pressures inside a custom-built microreactor device to induce ZnO nanowire growth, observing the reactions with XANES spectroscopy at the Materials Research Collaborative Access Team (MR-CAT) beamline 10-ID at the Advanced Photon Source. Baxter points out a particular advantage of XANES for the current work:“It also has good enough time resolution that we could actually watch the reaction proceeding in time. Every minute we could take a new set of data and look at thekineticsof the reaction.”

One open question the researchers sought to address was the specific role of HMTA in the ZnO CBD process. Previous work had suggested that HMTA might break down into intermediate forms that provided the raw materials for the ZnO film, perhaps even binding to zinc ions in the solution, or that it might act simply as a pH buffer to facilitate the reactions.

This firstin situview afforded by the XANES technique demonstrated that HMTA decomposes slowly under heating, releasing hydroxide ions that react with zinc ions in the formation of ZnO. This slow release of hydroxides also has the effect of minimizing ZnO saturation and thus controlling the solution pH.

“HMTA releases the hydroxide at the appropriate rate, just at the borderline where you’re primarily growing zinc oxide on the substrate with minimal precipitation,” says Baxter.

The team observed the growth of ZnO nanowires from zinc nitrate and HMTA precursors at 90° C after two hours, with typical hexagonal cross-sections and diameters of 300-500 nm.

They also employed principal component analysis (PCA) techniques to obtain quantitative data on the observed species during the CBD process. This showed that the ZnO nanowire growth occurred through direct crystallization from the precursor materials without any long-lived intermediates. The pH buffering provided by the HMTA helps to avoid overabundant precipitation of ZnO in the solution, allowing the controlled growth of the nanowire structures.

These new insights into the mechanisms of CBD will encourage the development of better-controlled and more precise chemical synthesis techniques for semiconductor and other nanomaterial applications.

The work is also valuable as a demonstration of the extension of XANES spectroscopy into other realms.

“I think the more widely useful part of this paper is actually in the application of XANESspectroscopyto a new type of system,” said Baxter.

He and his team plan to extend their work to study other CBD chemistries and processes.“You can actually see what’s happening as it is growing,” he said.“It gives one a lot of information about the process. I think that’s the exciting part.”

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Microreactor speeds nanotech particle production by 500 times

Engineers at Oregon State University have discovered a new method to speed the production rate of nanoparticles by 500 times, an advance that could play an important role in making nanotechnology products more commercially practical.

The approach uses an arrayed microchannel reactor and a"laminated architecture"in which many sheets, each with thousands of microchannels in them, are stacked in parallel to provide a high volume of production and excellent control of the processes involved.

Applications could be possible in improved sensors, medical imaging, electronics, and evensolar energyor biomedical uses when the same strategy is applied to abundant materials such as copper, zinc or tin.

A patent has been applied for, university officials say. The work, just published in the journalNanotechnology, was done in the research group of Brian Paul, a professor in the OSU School of Mechanical, Industrial and Manufacturing Engineering.

"A number of new and important types ofnanoparticleshave been developed with microtechnology approaches, which often use very small microfluidic devices,"said Chih-hung Chang, a professor in the OSU School of Chemical, Biological and Environmental Engineering, and principal investigator on the study.

"It had been thought that commercial production might be as simple as just grouping hundreds of these small devices together,"Chang said."But with all the supporting equipment you need, things like pumps and temperature controls, it really wasn't that easy. Scaling things up to commercial volumes can be quite challenging."

The new approach created by a research team of five engineers at OSU used amicroreactorwith the new architecture that produced"undecagold nanoclusters"hundreds of times faster than conventional"batch synthesis"processes that might have been used.

"In part because it's faster and more efficient, this process is also more environmentally sensitive, using fewer solvents and less energy,"Chang said."This could be very significant in helping to commercialize nanotech products, where you need high volumes, high quality and low costs."

This research, Chang said, created nanoparticles based on gold, but the same concept should be applicable to other materials as well. By lowering the cost of production, even the gold nanoclusters may find applications, he said, because the cost of the gold needed to make them is actually just a tiny fraction of the overall cost of the finished product.

Nanoparticles are extraordinarily tiny groups of atoms and compounds that, because of their extremely small size and large surface areas, can have unusual characteristics that make them valuable for many industrial, electronic, medical or energy applications.

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A wide range of nano-coatings in a few spray applications

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Easy-to-use nano-coating sprays with optical, electronic, biological properties, etc to cover surfaces. French teams from the Institut Charles Sadron and the Laboratoire de Biomateriaux et Ingenierie Tissulaire, have managed to improve and extend their technique of"layer by layer"deposition. This scientific synergy has led to the development of a very wide range of nano-coatings with new and varied applications that will doubtless be of great interest to industry. Their work was published online on 23 November 2010 on the site of the journal<i>Angewandte Chemie International Edition</i>.

Contact lenses, cars, non-stick saucepans or stickers: numerous objects in our daily lives have coatings with specific functions. Over fifteen years ago, Gero Decher invented a novel method of depositing nano-materials in the form ofthin films. The principle of this technique simply consists in“stacking”, with nanometric precision, layers whose structure and chemical functionalities are controlled by the sequence and nature of the constituents incorporated in the film (polymers, pigments, proteins, particles, etc.). This“layer-by-layer” method makes it possible to produce materials with extremely varied properties. Neither costly nor polluting, this process ranks among the ten most important results in chemistry over the last decade.

Recently, teams of chemists and physical chemistry specialists, headed by Gero Decher and Pierre Schaaf of the Institut Charles Sadron, have succeeded in making this deposition method even more powerful and easy to apply. Initially, the technique required successive dippings in different liquids and long deposition times. Now, using two bottles, the scientists can simultaneously spray two liquids on a surface to be coated. Time saving and logistical advantages are considerable.

Better still, this original method applies to a whole range of nano-coatings, including completely new classes of materials, such as purely inorganic films. The already wide range of applications of these thin films has therefore been further extended. The nano-coatings obtained by these various deposition methods have many applications in materials science: light emitting diodes, fuel cells, photovoltaic cells, anti-corrosion coatings, flexible screens, separation membranes, etc.

Furthermore, the introduction of biologically active molecules (peptides, enzymes, medicines, proteins, DNA, cells, etc.) within these films makes it possible to obtain nano-coatings that have numerous applications in life sciences: biocompatibility of implants, preparation of dressings, tissue engineering, gene transfection, pharmaceutical vectors, bio-sensors, etc. This host of applications is likely to meet industry's objectives to cut production costs, invest in sustainable product development and extend product ranges. In short, this innovative nano-assembly method makes it possible to envisage the elaboration of a large number of (bio)-materials or products that do not yet exist.

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All sprayed at once: Ultrathin coatings made through simultaneous spraying of interacting substances

(PhysOrg.com) -- Coatings functionalize surfaces or protect them from processes such as corrosion, abrasion, and weathering, and may provide an aesthetic appearance—automotive coatings and non-stick frying pans are good examples. Contact lenses, implants, LEDs, or photovoltaic cells require extremely thin coatings.

In the journalAngewandte Chemie, the teams led by Gero Decher at the Institut Charles Sadron in Strasbourg (France) have now introduced a new process for the production of ultrathin coatings that is especially simple, versatile, and suitable for large-scale processes.

A simple yet powerful method for the assembly of nanoscale films is the already well-known layer-by-layer technique. Two mutually interacting species, for example positively and negatively charged polymers, are consecutively adsorbed from solution, forming hybrid thin films through a self-organization process. One major improvement to this method was introduced with the technique of spray-assisted deposition, in which atomized mists of solutions containing each of the two substances are sprayed on asurfacein an alternating fashion. This accelerates the process and facilitates scaling up to industrial levels.

The French–German researchers led by Decher and Pierre Schaaf at the Centre National de la Recherche Scientifique and Jean-Claude Voegel at the Institut National de la Santé et de la Recherche Médicale have now been able to make another substantial improvement to this technique: In“simultaneous spraycoatingof interacting species” (SSCIS), the two complementary components are not applied consecutively, but are simultaneously sprayed against a receiving surface. Depending on the process conditions, the partner substances rapidly form a continuous layer. The thickness of the film is controlled by changing the spraying time and can range from a few nanometers to a few micrometers. This results in highly homogenous coatings that can even possess optical quality.

The one-step process is cheap, robust, user-friendly, and unbelievably versatile. In principle, all pairs of substances that interact with each other, such as inorganic ions of opposite charge, are suitable for use with the simultaneous spray process. It is thus possible to produce films of calcium fluoride (for optical components) or deposits of calcium phosphate (for use in biomaterials).

Interestingly, the new technique also works with pairs that do not produce intact layers when the conventional layer-by-layer process is used. Thus the presented results open up a wealth of new possibilities to produce surfaces with tailored specific functionalities, for example for catalysis, to make implants more biocompatible or for tissue engineering.

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Risk review suggests that carbon nanotubes be treated, for now, 'as if' hazardous

(PhysOrg.com) -- In a new paper published by the Society for Risk Analysis, a UC Berkeley researcher argues for caution when dealing with carbon nanotubes. Because environmental and health information on carbon nanotubes is incomplete and sometimes conflicting, an"anticipatory governance"approach to the technology is needed, says post-doc researcher Mark Philbrick.

While offering great promise in a host of new applications, carbon nanotubes (CNTs) could be harmful to humans and a new risk review suggests that product designers and others should provisionally treat CNTs"as if"they are hazardous.

Carbon nanotubes are extremely small, with a diameter measured in nanometers. A nanometer is one-billionth of a meter, or about one eighty-thousandth the thickness of a human hair. CNTs are very versatile and come in several forms, conferring great strength while also being very light.

Because environmental andhealth informationon CNTs is incomplete and sometimes conflicting, an“anticipatory governance” approach to the technology is needed, according to Mark Philbrick, post-doctoral researcher at the Center of Integrated Nanomechanical Systems at the University of California, Berkeley. Anticipatory governance is an approach designed to support decision makers where there is uncertainty about safety, a common situation when managing emerging technologies.

The research was funded by the National Science Foundation and the conclusions are detailed in Philbrick's article“An Anticipatory Governance Approach to Carbon Nanotubes,” in the November issue of the journalRisk Analysispublished by the Society for Risk Analysis. The entire November issue is devoted to risk analysis articles related to nanotechnology.

An anticipatory approach is particularly important until the toxicity and behavior of CNTs in the environment are better understood, especially as they can remain airborne for extended periods, and share some characteristics with asbestos. While a few rodent studies have found similarities between the health effects of inhaling both substances, there is not enough data to draw firm conclusions.

The article notes the promise held out by CNTs is immense: some types conduct electricity and heat better than copper, others are stronger than steel while weighing less than aluminum, and yet others could be used in targeted drug delivery. These properties could find uses in aircraft frames, sensors, and electrical transmission. Nevertheless, treating them“as if” they are hazardous is a prudent course of action given uncertainty about their potential health consequences, the author said.

Given the“conflicted character of the data,” how“relevant actors” should respond is the central question Philbrick asks in developing strategies for utilizing CNTs. He asserts that treating carbon nanotubes“as if” they are hazardous implies limiting exposure throughout product life-cycles. This means implementing strong engineering controls for CNT research and manufacturing, avoiding applications where the CNTs would be routinely released to the environment, and planning for recycling at the end of a product’s useful life. The article also argues that“the anticipatory governance approach is particularly important as innovation rates in nanotechnologies exceed our capacity to assess human and environmental consequences of these innovations, especially when deployed at commercial scales… it helps identify uncertainties in our knowledge and focuses future research to address those gaps."

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Scientists imitate nature to engineer nanofilms

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In nature, water striders can walk on water, butterflies can shed water from their wings, and plants can trap insects and pollen. Scientists at the Naval Research Laboratory are part of a research team working to engineer surfaces that imitate some of these water repellency features found in nature.

This technology offers the possibility of significant advances for producing new generations of coatings that will be of great value for military, medical, and energy applications. The research is published in the December 2010 issue ofNature Materials.

Dr. Walter Dressick from NRL, working with Professor Melik Demirel of Penn State and Dr. Matthew Hancock of MIT, have collaborated to create an engineered water-repellant thin film. What sets this development apart from earlier technologies is that this newest film has the ability to control the directionality of liquid transport.

In this system, parylene nanorods are deposited on the surface by a simple, straightforwardvapor depositionmethod. The single step usually takes less than 60 minutes, compared with the more complex, multi-step lithography processes often used in previous systems. This is the first time this kind of surface has been engineered at the nanoscale.

In the newly created surface, the nanorods that form the film are smooth on a micron scale. This size and smoothness in the posts means that when droplets are placed on the surface, they move without being distorted in any way. Also, they can be moved without pumps or optical waves. Previous systems caused thewater dropletsto be distorted, which could rupture, spill, or destroy the cargo in the droplet when used in medical or microassembly applications. As they continue the research, the team will focus on optimizing the droplet transport mechanism and tuning the preparation method.

Looking to the future, researchers are hopeful that this film could be used as a coating on the hull of ships where it would reduce the drag and slow the fouling. In industry applications, the film might have uses in directional syringes and fluid diodes, pump-free digital fluidic devices, increased efficiency of thermal cooling for microchips, and tire coatings.

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Doctoral candidate publishes on graphene's potential

Since graphene was first isolated in 2004 with the help of Scotch tape, researchers have excitedly turned to the material to discover its potential applications. A single layer of carbon atoms whose applications range from ultrafast electronics to biosensors to flexible displays, graphene is strong, light, transparent, and a conductor of heat and electricity. But what can we do with this new material? As researchers across the globe peel away layer after layer of potential application, Milan Begliarbekov, a doctoral candidate at Stevens Institute of Technology, has found some unique applications for this distinctive material.

Graphene is charged with possibilities for Milan. With the help of a world-class Stevens faculty, support from the National Science Foundation (NSF) Graduate Teaching Fellows in K-12 Education (GK-12) program through the New Jersey Alliance for Engineering Education (NJAEE), and an award from the Air Force Office of Scientific Research (AFOSR), Milan is conducting groundbreaking research of the material. He has already published two papers ongrapheneinApplied Physics Lettersin pursuit of his Ph.D. and has a third paper in the pipeline. Both published articles have also been selected for theVirtual Journal of Nanoscale Science and Technology.

His first published article,"Determination of edge purity in bilayer graphene usingµ-Raman spectroscopy,"confirms a technique for differentiating between monolayer and bilayer graphene, and introduces a new method to quantify the composition of graphenes chiral edges throughµ-Raman spectroscopy.

Milan's second article,"Aperiodic conductivity oscillations in quasiballistic graphene heterojunctions,"establishes a new signature of Klein tunneling in graphene heterojunctions. The research has applications in nanolectronics such as graphene field effect transistors (GFET), which have been shown to be capable of ultra-high frequency (300 GHz) operation.

Milan's next article, yet to be published, is"Quantum Inductance and High Frequency Oscillators in Graphene Nanoribbons."The paper proposes a novel technique for measuring the speed of ultra-high frequency transistors. Currently it is very difficult to measure ultra-high-frequency signals above 40 GHz by purely electronic means. However, Milan's research indicates that graphene nanoribbons can serve as all-electronic ultra-high frequency oscillators and filters, which would extend the possibilities of high-frequency electronics into new realms.

Since graphene planes were first isolated, much research has focused on the material's applications in nanoelectronics, due to its high electrical conductivity. But researchers at Stevens have taken a different approach, pioneering applications of this unique material in optics. Milan's research represents a fine example of this innovative thinking.

As he works with a material whose greatest applications may still be unrealized, Milan says he enjoys the level of creativity he is afforded in exploring graphene's possibilities."I like working with Professor Strauf, because of the freedom he gives me to choose my own research projects,"Milan says."He allows me to explore things I find interesting, rather than asking me to work on a pre-defined research objective."

"Given that the our team just started two years ago to work with graphene in a collaboration with Professor Yang's group from the Mechanical Engineering Department, Milan's research success is quite remarkable,"says Dr. Stefan Strauf, Assistant Professor of Physics and Engineering Physics (PEP) and Director of the Nanophotonics lab."Milan is one of these unique graduate students you would like to clone into a dozen in your lab in order to implement all of his ideas."

The exploration of ideas has also led to the creation of a system that utilizes graphene's unique reaction to light. Working with Stevens faculty Dr. Stefan Strauf and Dr. Chris Search, who is also an Assistant Professor of PEP, Milan is determined to convert new ideas into patentable technology."We are pleased to announce that with the help of the Office of Academic Entrepreneurship, Milan is in the process of applying for a patent with a novel application of graphene that exploits its near-perfect efficiency as aconductor,"says Dr. Christos Christodoulatos, Professor and Associate Provost of Academic Entrepreneurship.

In addition to the AFOSR grant, Milan was also supported by the NSF GK-12 program through NJAEE. As an NJAEE fellow from 2008 to 2010, Milan worked alongside teacher mentors in local high school classrooms to expose younger students to cutting edge science and engineering research. The GK-12 program was established to support the NSF's goal of enhancing science, technology, engineering, and mathematics (STEM) curriculums for K-12 teachers and students."The NJAEE program provides a unique opportunity for graduate students to enhance their teaching and communication skills, instills in them the spirit of innovation and entrepreneurship, and at the same time provides them a forum to share their passion and enthusiasm for science and engineering with younger students,"says Dr. Frank Fisher, Associate Professor of Mechanical Engineering and co-Director of the Stevens Nanotechnology Graduate Program who is a co-PI on the NJAEE project."Milan was just fantastic as a NJAEE Fellow, and has recently been able to apply these skills as an instructor in the Physics department here at Stevens as well as Queensborough Community College of CUNY."

The patent and papers are the most recent examples of Milan's success at Stevens. As an undergraduate at Stevens, Begliarbekov took advantage of both the Charles V. Schaeffer, Jr. School of Engineering and Sciences and what would become the College of Arts and Letters to graduate with two degrees, a B.S. in Physics and a B.A. in Literature. Having taken graduate-level courses in nanotechnology as an undergraduate,"I was already ahead of the curve,"he says, when it came to searching for a graduate program.

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What changes will nanoelectronics bring to our lives?

We are surrounded by nanoelectronics through products such as computers, mobile phones, sensors and electric cars. Nanoelectronics may also grow much stronger in the energy efficiency area in the near future. However, the sustainable growth faces several challenges.

Innanoelectronics, miniaturisedelectronic circuitsare integrated on semiconductor chips where the basic element is the transistor. The size of the transistors produced is under 100 nm. Andreas Wild is Executive Director of the ENIAC JU. The task of this public-private partnership is to coordinate European research in nanoelectronics. He sees many interesting changes coming with the evolution of nanoelectronics.

“We have little electronics in the buildings, but the buildings are huge energy consumers. There will be an influx of nanoelectronics that will completely change the ways we are living in and using buildings, making them energy self-consistent, extremely comfortable and adaptable to the needs of the people. The buildings will be able to read how many people are inside, what are they doing, then adjust everything and also give the people a human interface to express their wishes. Rather than pilot projects this will be the norm. Europe has already issued regulations. I believe in the next five to ten years nobody will construct a building that haven’t got these features.”

Laurent Malier, CEO of the research center CEA-Leti in France, highlights another area where nanoelectronics may be prominent.“What we are going to explore more are nanoelectronic devices for biology and healthcare. It could be easy and low cost diagnostics. This is an area of growth in a large perspective,” he said.

The sustainable growth of nanoelectronics faces several challenges.“You see technological challenges, materials, processes and so forth. You see design challenges, how to put together billions of components quickly, reliably and predictably. Then there are systemic challenges, what are the functions that all these billions oftransistorsare supposed to achieve on every chip and how do they relate to the everyday life of the people using the devices,” Wild said.

Malier sees additional challenges.“One is the compromise between low electrical power consumption and very fast processing capability. The other one is lithography, the capability to reduce the size of features. The third one is to increase complexity with either 3D integration, stacking chips on each other, or integration of new functions.”
We are dependent on nanoelectronic devices and soon we might see a drastic reduction in our energy consumption thanks to the advances in this area.

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Secrets of nanohair adhesion un-peeled by UA polymer scientists

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Not long after Dr. Ali Dhinojwala, chairman of The University of Akron Department of Polymer Science, unpeeled the secret (fine, clingy hairs) behind the remarkable adhesion of gecko feet, he and fellow researchers came up with a synthetic replica: carbon nanotubes. Now, five years after that initial discovery, the basis of the success of these nanotubes is published in the Oct. 12, 2010, issue of the American Chemical Society’s<i><a href="http://pubs.acs.org/doi/pdf/10.1021/nl102398w">Nano Letters</a></i>.

While the story of nanotubes is one of success, not all carbon nanotubes are equal, nor is the individual adhesion performance of each strand, according to Dhinojwala. Although Dhinojwala and UApolymerscience graduate student Liehui Ge determined that these 8-nanometer-diameter carbon hairs— each 2,000 times smaller than the diameter of a human hair— adhere powerfully to glass and similar substrates, they furthered their research to learn why some strands have a firmer grip than others.

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Getting a grip on adhesion

Findings by the UA scientists, in collaboration with Lijie Ci and Anubha Goyal, researchers with the Department of Mechanical Engineering and Materials Science at Rice University; Rachel Shi, UA Research Experience for Undergraduates (REU) intern; and L. Mahadevan, professor of applied mathematics and professor of organismic and evolutionary biology at Harvard University, reveal that the softer the nanotube, the greater its adhesion.

Using a combination of mechanics, electrical resistance and scanning electron microscopy (SEM) to study the contact between hairs of a large number of vertically aligned carbon nanotubes with glass or silicon substrates, the researchers found that soft nanotubes clasp and curve when pressure is applied, contributing to their adhesive strength.

“We found out that the diameter of the tubes is an important parameter for adhesion because we have to balance the adhesion and bending rigidity of the tubes,” Ge says.“Also, if you apply a high pressure, the tubes bend and buckle and make a larger contact area with the surface, which is the reason for higheradhesion.”

The dry adhesive, unlike liquid glue counterparts, promises successful use in extreme atmospheric and temperature conditions and in other applications that present challenges.

“The carbon nanotube-based gecko adhesives are going to open up opportunities to using these materials on robots, to climb vertical walls, and could actually be used in outer space (vacuum condition) because these materials stick without any liquid glue,” Dhinojwala says.

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DNA can act like Velcro for nanoparticles

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DNA can do more than direct how bodies our made -- it can also direct the composition of many kinds of materials, according to a new study from the U.S. Department of Energy’s Argonne National Laboratory.

Argonne researcher Byeongdu Lee and his colleagues at Northwestern University discovered that strands of DNA can act as a kind of nanoscopic"Velcro"that binds differentnanoparticlestogether."It’s generally difficult to precisely control the assembly of these types of nanostructures,"Lee said."By using DNA, we’re borrowing nature's power."

The"Velcro"effect of the DNA is caused by the molecule’s"sticky ends,"which are regions of unpaired nucleotides— the building blocks of DNA— that are apt to bond chemically to their base-pair partners, just like in our genes. When sufficiently similar regions contact each other, chemical bonds form a rigid lattice. Scientists and engineers believe these complex nanostructures have the potential to form the basis of new plastics, electronics and fuels.

In 2008, Lee and his colleagues attached DNA to spherical nanoparticles made of gold, hoping to control the way the particles arrange themselves into compact, ordered crystals. This process is called nanoparticle"packing,"and Lee believed that by affixing DNA to the nanoparticles, he could control how they packed together."Materials that are packed differently— even if they are made from the same substance— have been shown to exhibit dramatically different physical and chemical properties,"Lee said.

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While the 2008 experiment showed that DNA appeared to control that instance of nanosphere packing, it was not known whether the effect would occur with different nanoparticle geometries. The more recent experiment looked at different shapes of nanoparticles to determine whether their contours affected how they packed.

According to Lee, the spherical nanoparticles in the earlier experiment tended to arrange themselves into one of two separate types of cubic crystals: a face-centered cube (a simple cube with nanospheres at each vertex and additional ones located in the middle of each face) or a body-centered cube (a simple cube with an additional nanosphere located in the middle of the cube itself). The type of lattice that the nanoparticles formed was determined by how the"sticky ends"attached to the nanoparticles paired together.

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In the more recent experiment, the particles' shape did change the material's final structure, but only insofar as it altered how the DNA"sticky ends"attached to each other. In fact, the study showed that dodecahedral (12-sided) nanoparticles arranged into a face-centered cubic configuration while octahedral (8-sided) nanoparticles formed body-centered cubes— even when the nanoparticles were attached to identical strands of DNA."We may be able to make all different types of nanoparticle packing structures, but the structure that will result will always be the one that maximizes the amount of binding,"he said.

"The face-centered cubic structure is the most compact way for the nanoparticles to arrange themselves, while the body-centered cubic is slightly less compact. TheDNAbinding is really the true force controlling the construction of the lattice,"he added.

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A new twist for nanopillar light collectors

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Sunlight represents the cleanest, greenest and far and away most abundant of all energy sources, and yet its potential remains woefully under-utilized. High costs have been a major deterrant to the large-scale applications of silicon-based solar cells. Nanopillars– densely packed nanoscale arrays of optically active semiconductors– have shown potential for providing a next generation of relatively cheap and scalable solar cells, but have been hampered by efficiency issues. The nanopillar story, however, has taken a new twist and the future for these materials now looks brighter than ever.

“By tuning the shape and geometry of highly ordered  nanopillar arrays of germanium or cadmium sulfide, we have been able to drastically enhance the optical absorption properties of our nanopillars,” says Ali Javey, a chemist who holds joint appointments with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

Javey, a faculty scientist with Berkeley Lab’s Materials Sciences Division and a UC Berkeley professor of electrical engineering and computer science, has been at the forefront of nanopillar research. He and his group were the first to demonstrate a technique by which cadmium sulfide nanopillars can be mass-produced in large-scale flexible modules. In this latest work, they were able to produce nanopillars that absorb light as well or even better than commercial thin-film solar cells, using far less semiconductor material and without the need for anti-reflective coating.

“To enhance the broad-band optical absorption efficiency of our nanopillars we used a novel dual-diameter structure that features a small (60 nanometers) diameter tip with minimal reflectance to allow more light in, and a large (130 nanometers) diameter base for maximal absorbtion to enable more light to be converted into electricity,” Javey says.“This dual-diameter structure absorbed 99-percent of incident visible light, compared to the 85 percent absorbtion by our earlier nanopillars, which had the same diameter along their entire length.”

Theoretical and experimental works have shown that 3-D arrays of semiconductor nanopillars– with well-defined diameter, length and pitch– excel at trapping light while using less than half the semiconductor material required for thin-film solar cells made of compound semiconductors, such as cadmium telluride, and about one-percent of the material used in solar cells made from bulk silicon. But until the work of Javey and his research group, fabricating such nanopillars was a complex and cumbersome procedure.

Javey and his colleagues fashioned their dual diameter nanopillars from molds they made in 2.5 millimeter-thick alumina foil. A two-step anodization process was used to create an array of one micrometer deep pores in the mold with dual diameters– narrow at the top and broad at the bottom. Gold particles were then deposited into the pores to catalyze the growth of the semiconductor nanopillars.

“This process enables fine control over geometry and shape of the single-crystalline nanopillar arrays, without the use of complex epitaxial and/or lithographic processes,” Javey says.“At a height of only two microns, our nanopillar arrays were able to absorb 99-percent of all photons ranging in wavelengths between 300 to 900 nanometers, without having to rely on any anti-reflective coatings.”

The germanium nanopillars can be tuned to absorb infrared photons for highly sensitive detectors, and the cadmium sulfide/telluride nanopillars are ideal forsolar cells. The fabrication technique is so highly generic, Javey says, it could be used with numerous other semiconductor materials as well for specific applications. Recently, he and his group demonstrated that the cross-sectional portion of the nanopillar arrays can also be tuned to assume specific shapes– square, rectangle or circle– simply by changing the shape of the template.

“This presents yet another degree of control in the optical absorption properties of nanopillars,” Javey says.

Javey’s dual-diameter nanopillar research was partially funded through the National Science Foundation’s Center of Integrated Nanomechanical Systems (COINS) and through Berkeley Lab LDRD funds.

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New possibilities for solar energy with molecular 'stencils'

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Scientists at the U.S. Department of Energy’s Argonne National Laboratory have begun to use molecular"stencils"to pave the way to new materials that could potentially find their way into future generations of solar cells, catalysts and photonic crystals.

Researchers at Argonne’s Center for Nanoscale Materials and Energy Systems Division have developed a technique known as sequential infiltration synthesis (SIS), which relies on the creation of self-assembled nanoscale chemical domains into which other materials can be grown. In this technique, a film composed of large molecules called block copolymers acts as a template for the creation of a highly-tunable patterned material.

This new method represents an extension of atomic layer deposition (ALD), a popular technique for materials synthesis that is routinely used by Argonne scientists. Instead of just layering two-dimensional films of differentnanomaterialson top of one another, however, SIS allows scientists to construct materials that have much more complex geometries.

“This new technique allows us to create materials that just weren’t possible with ALD or block copolymers alone,” said Seth Darling, an Argonne nanoscientist who helped to develop SIS in collaboration with Argonne chemist Jeff Elam.“Having the ability to control the geometry of the material we’re making as well as its chemical composition opens the door to a whole universe of new materials.”

According to Darling, the success of the technique relies on the unique chemistry of block copolymers. Every block copolymer is composed of two chemically distinct subunits; for instance, one subunit might have an affinity for water while the other might repel water. In such a case, like would seek out like, creating a heterogeneous matrix of interspersed homogenous regions.

“You can think of a block copolymer as like a pair of molecular Siamese twins where one likes to talk and one likes to read quietly,” Darling said.“If you put a bunch of these twins together in a room, the talkative ones are going to try to be near the talkative ones and the readers are going to try to be near the readers, but they can’t simply all separate themselves to either side of the room, and it’s this action that gives us the geometries we’re looking for.”

Depending on the initial substrate, the block copolymers, and the processing that materials scientists use, regions can form that have many different shapes, from spherical to cylindrical to planar. While there are many types of block copolymers, in general they cannot serve as wide an array of purposes as inorganic materials. The challenge, according to Darling, is to bring the self-assembly of block copolymers together with the functionality of inorganic materials.

The physical and chemical properties of a material generated using SIS depend on how block copolymer chemistry and morphology interact with the chemistry of ALD techniques.“We can tailor our materials synthesis efforts in a much more precise way than we ever could before,” Darling said.

Darling and Elam have spent most of their careers at Argonne focused on the development of new types of materials, including the development of solar cells that combine organic and inorganic components. They believe that the types of materials that SIS can generate will drive fundamental solar energy technologies to greater efficiencies and lower cost.

“Oursolar energyfuture does not have a one-size-fits-all solution,” Elam said.“We need to investigate the problem from many different angles with many differentmaterials, and SIS will give researchers like us many new routes of attack.”

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