With unique properties and potential applications in areas from electronics to biodevices, graphene, which consists of a single sheet of carbon atoms, has been hailed as a rising star in the materials world.

Now, an ORNL study published in Nature Nanotechnology suggests that point defects, composed of silicon atoms that replace individual carbon atoms in graphene, could aid attempts to transfer data on an atomic scale by coupling light with electrons.

"In this proof of concept experiment, we have shown that a tiny wire made up of a pair of single silicon atoms in graphene can be used to convert light into an electronic signal, transmit the signal and then convert the signal back into light," said coauthor Juan-Carlos Idrobo, who holds a joint appointment at ORNL and Vanderbilt University.

An ORNL-led team discovered this novel behavior by using aberration-corrected scanning transmission electron microscopy to image the plasmon response, or optical-like signals, of the point defects.

The team's analysis found that the silicon atoms act like atomic-sized antennae, enhancing the local surface plasmon response of graphene, and creating a prototypical plasmonic device.

"The idea with plasmonic devices is that they can convert optical signals into electronic signals," Idrobo said.

"So you could make really tiny wires, put light in one side of the wire, and that signal will be transformed into collective electron excitations known as plasmons. The plasmons will transmit the signal through the wire, come out the other side and be converted back to light."

Although other plasmonic devices have been demonstrated, previous research in surface plasmons has been focused primarily on metals, which has limited the scale at which the signal transfer occurs.

"When researchers use metal for plasmonic devices, they can usually only get down to 5 - 7 nanometers," said coauthor Wu Zhou. "But when you want to make things smaller, you always want to know the limit. Nobody thought we could get down to a single atom level."

In-depth analysis at the level of a single atom was made possible through the team's access to an electron microscope that is part of ORNL's Shared Research Equipment (ShaRE) User Facility.

"It is the one of only a few electron microscopes in the world that we can use to look at and study materials and obtain crystallography, chemistry, bonding, optical and plasmon properties at the atomic scale with single atom sensitivity and at low voltages," Idrobo said.

"This is an ideal microscope for people who want to research carbon-based materials, such as graphene."

In addition to its microscopic observations, the ORNL team employed theoretical first-principles calculations to confirm the stability of the observed point defects.

]]> Wed, 08 FEB 2012 08:47:15 AEST Austin TX (SPX) Jan 13, 2012 - A new form of graphene created by researchers at The University of Texas at Austin could prevent laptops and other electronics from overheating, ultimately, overcoming one of the largest hurdles to building smaller and more powerful electronic devices.

The research team, which includes colleagues at The University of Texas at Dallas, the University of California-Riverside and Xiamen University in China, published its findings online in the Advance Online Publication of Nature Materials. The study will also appear in the print journal of Nature Materials.

Led by Professor Rodney S. Ruoff in the Cockrell School's Department of Mechanical Engineering and the Materials Science and Engineering Program, the research demonstrates for the first time that a type of graphene created by the University of Texas researchers is 60 percent more effective at managing and transferring heat than normal graphene.

"This demonstration brings graphene a step closer to being used as a conductor for managing heat in a variety of devices. The potential of this material, and its promise for the electronic industry, is very exciting," said Ruoff, a physical chemist and Cockrell Regents Family Chair, who has pioneered research on graphene-based materials for more than 12 years.

The findings could have a significant impact on the future development of semiconductor electronics. As silicon transistors - foundations of modern-day electronics - are built smaller and faster, more effective heat removal techniques are needed to remove heat dissipated by the transistors as they operate.

The latter has become a crucial issue for the electronics industry - one that has spurred a scientific race to develop and find materials more efficient at conducting heat than the materials currently used.

Graphene, an atom-thick layer of carbon, has shown great promise at doing so, and the research findings demonstrate for the first time that not only graphene - but the type of graphene used - can play a significant role in how effectively heat is transferred.

Using a laser to both heat and take measurements of a single-layer of graphene, the researchers found that a type of graphene created by Ruoff and other University of Texas researchers is better than any other material tested to date at dissipating heat.

Whereas naturally occurring carbon is found at concentrations of 98.9 percent 12C (carbon) and 1.1 percent 13C, the graphene created at The University of Texas at Austin was made of isotopically pure carbon, 99.99 percent 12C.

"Because self-heating of fast and densely packed devices deteriorates their performance, graphene's ability to conduct heat well will be very helpful in improving them," said Alexander Balandin, a professor of Electrical Engineering, chair of Materials Science and Engineering at the University of California Riverside and a corresponding author of the research paper.

"Initially, graphene would likely be used in some niche applications, such as thermal interface materials for chip packaging or transparent electrodes in photovoltaic solar cells or flexible displays. But, in a few years, the uses of graphene will be diverse, broad and far-reaching because the excellent heat conduction properties of this material are beneficial for all its proposed electronic applications."

]]> Wed, 08 FEB 2012 08:47:15 AEST Detroit, Michigan (AFP) Jan 8, 2012 - Germany's Volkswagen sold more than eight million vehicles worldwide in 2011, possibly enough to grab the top spot among global automakers for the first time, chairman Martin Winterkorn said Sunday.

VW boosted sales by more than one million vehicles, or 14 percent, to 8.16 million last year, Winterkorn said on the eve of the annual North American International Auto Show in Detroit.

That was likely enough to put it past the champion of the previous three years, Japan's Toyota, which found production last year hobbled by the March 11 earthquake-tsunami disaster.

But total world sales for General Motors, which held the crown for 77 year until it was snatched by Toyota in 2008, have yet to be reported.

VW sales include Volkswagens as well as the group's Audi, Seat, Skoda, Bentley, Bugatti, and Lamborghini brands.

The group has aimed at capturing the title of the world's leading vehicle maker by sales and profitability by 2018.

VW recently bought the heavy truck builder MAN -- sales of which are not included in the 2011 figures -- and is in the process of taking over Porsche.

It also owns a 19.9 percent share of Suzuki of Japan.

Winterkorn said he did not expect a recession this year to dampen auto sales.

Even if the prospects for Europe are not bright, he said, "We continue to build on the growth of North America and China."

]]> Wed, 08 FEB 2012 08:47:15 AEST Champaign IL (SPX) Nov 01, 2011 - New observations could improve industrial production of high-quality graphene, hastening the era of graphene-based consumer electronics, thanks to University of Illinois engineers.

By combining data from several imaging techniques, the team found that the quality of graphene depends on the crystal structure of the copper substrate it grows on. Led by electrical and computer engineering professors Joseph Lyding and Eric Pop, the researchers published their findings in the journal Nano Letters.

"Graphene is a very important material," Lyding said. "The future of electronics may depend on it. The quality of its production is one of the key unsolved problems in nanotechnology. This is a step in the direction of solving that problem."

To produce large sheets of graphene, methane gas is piped into a furnace containing a sheet of copper foil. When the methane strikes the copper, the carbon-hydrogen bonds crack. Hydrogen escapes as gas, while the carbon sticks to the copper surface.

The carbon atoms move around until they find each other and bond to make graphene. Copper is an appealing substrate because it is relatively cheap and promotes single-layer graphene growth, which is important for electronics applications.

"It's a very cost-effective, straightforward way to make graphene on a large scale," said Joshua Wood, a graduate student and the lead author of the paper.

"However, this does not take into consideration the subtleties of growing graphene," he said. "Understanding these subtleties is important for making high-quality, high-performance electronics."

While graphene grown on copper tends to be better than graphene grown on other substrates, it remains riddled with defects and multi-layer sections, precluding high-performance applications.

Researchers have speculated that the roughness of the copper surface may affect graphene growth, but the Illinois group found that the copper's crystal structure is more important.

Copper foils are a patchwork of different crystal structures. As the methane falls onto the foil surface, the shapes of the copper crystals it encounters affect how well the carbon atoms form graphene.

Different crystal shapes are assigned index numbers. Using several advanced imaging techniques, the Illinois team found that patches of copper with higher index numbers tend to have lower-quality graphene growth.

They also found that two common crystal structures, numbered (100) and (111), have the worst and the best growth, respectively. The (100) crystals have a cubic shape, with wide gaps between atoms. Meanwhile, (111) has a densely packed hexagonal structure.

"In the (100) configuration the carbon atoms are more likely to stick in the holes in the copper on the atomic level, and then they stack vertically rather than diffusing out and growing laterally," Wood said. "The (111) surface is hexagonal, and graphene is also hexagonal. It's not to say there's a perfect match, but that there's a preferred match between the surfaces."

Researchers now are faced with balancing the cost of all (111) copper and the value of high-quality, defect-free graphene. It is possible to produce single-crystal copper, but it is difficult and prohibitively expensive.

The U. of I. team speculates that it may be possible to improve copper foil manufacturing so that it has a higher percentage of (111) crystals. Graphene grown on such foil would not be ideal, but may be "good enough" for most applications.

"The question is, how do you optimize it while still maintaining cost effectiveness for technological applications?" said Pop, a co-author of the paper. "As a community, we're still writing the cookbook for graphene. We're constantly refining our techniques, trying out new recipes. As with any technology in its infancy, we are still exploring what works and what doesn't."

Next, the researchers hope to use their methodology to study the growth of other two-dimensional materials, including insulators to improve graphene device performance. They also plan to follow up on their observations by growing graphene on single-crystal copper.

"There's a lot of confusion in the graphene business right now," Lyding said. "The fact that there is a clear observational difference between these different growth indices helps steer the research and will probably lead to more quantitative experiments as well as better modeling. This paper is funneling things in that direction."

Lyding and Pop are affiliated with the Beckman Institute for Advanced Science and Technology at the U. of I. The Office of Naval Research, the Air Force Office of Scientific Research, and the Army Research Office supported this research.

]]> Wed, 08 FEB 2012 08:47:15 AEST Santa Barbara CA (SPX) Oct 26, 2011 - Making waves as the material that will revolutionize electronics, graphene - composed of a single layer of Carbon atoms - has nonetheless been challenging to produce in a way that will be practical for innovative electronics applications. Researchers at UC Santa Barbara have discovered a method to synthesize high quality graphene in a controlled manner that may pave the way for next-generation electronics application.

Kaustav Banerjee, a professor with the Electrical and Computer Engineering department and Director of the Nanoelectronics Research Lab at UCSB that has been studying carbon nanomaterials for more than seven years, led the research team to perfect methods of growing sheets of graphene, as detailed in a study to be published in the November 2011 issue of the journal Carbon.

"Our process has certain unique advantages that give rise to high quality graphene," says Banerjee. "For the electronics industry to effectively use graphene, it must first be grown selectively and in larger sheets. We have developed a synthesis technique that yields high- quality and high-uniformity graphene that can be translated into a scalable process for industry applications."

Using adhesive tape to lift flakes of graphene from graphite, University of Manchester researchers Geim and Novoselov were awarded the 2010 Nobel Prize in Physics for their pioneering isolation and characterization of the material. To launch graphene into futuristic applications, however, researchers have been seeking a controlled and efficient way to grow a higher quality of this single-atom-thick material in larger areas.

The discovery by UCSB researchers turns graphene production into an industry-friendly process by improving the quality and uniformity of graphene using efficient and reproducible methods. They were able to control the number of graphene layers produced - from mono-layer to bi-layer graphene - an important distinction for future applications in electronics and other technology.

"Intel has a keen interest in graphene due to many possibilities it holds for the next generation of energy- efficient computing, but there are many roadblocks along the way," added Intel Fellow, Shekhar Borkar. "The scalable synthesis technique developed by Professor Banerjee's group at UCSB is an important step forward."

As a material, graphene is the thinnest and strongest in the world - more than 100 times stronger than diamond - and is capable of acting as an ultimate conductor at room temperature. If it can be produced effectively, graphene's properties make it ideal for advancements in green electronics, super strong materials, and medical technology.

Graphene could be used to make flexible screens and electronic devices, computers with 1,000 GHz processors that run on virtually no energy, and ultra-efficient solar power cells.

Key to the UCSB team's discovery is their understanding of graphene growth kinetics under the influence of the substrate. Their approach uses a method called low pressure chemical vapor deposition (LPCVD) and involves disintegrating the hydrocarbon gas methane at a specific high temperature to build uniform layers of carbon (as graphene) on a pretreated copper substrate.

Banerjee's research group established a set of techniques that optimized the uniformity and quality of graphene, while controlling the number of graphene layers they grew on their substrate.

According to Dr. Wei Liu, a post-doctoral researcher and co-author of the study, "Graphene growth is strongly affected by imperfection sites on the copper substrate. By proper treatment of the copper surface and precise selection of the growth parameters, the quality and uniformity of graphene are significantly improved and the number of graphene layers can be controlled."

Professor Banerjee and credited authors Wei Liu, Hong Li, Chuan Xu and Yasin Khatami are not the first research team to make graphene using the CVD method, but they are the first to successfully refine critical methods to grow a high quality of graphene. In the past, a key challenge for the CVD method has been that it yields a lower quality of graphene in terms of carrier mobility - or how well it conducts electrons.

"Our graphene exhibits the highest reported field-effect mobility to date for CVD graphene, having an average value of 4000 cm2/V.s with the highest peak value at 5500 cm2/V.s.

This is an extremely high value compared with the mobility of silicon." added Hong Li, a Ph.D. candidate in Banerjee's research group.

"Kaustav Banerjee's group is leading graphene nanoelectronics research efforts at UCSB, from material synthesis to device design and circuit exploration. His work has provided our campus with unique and very powerful capabilities," added David Awschalom, Professor of Physics, Electrical and Computer Engineering, and Director of the California NanoSystems Institute (CNSI) at UCSB where Banerjee's laboratory is located.

"This new facility has also boosted our opportunities for collaborations across various science and engineering disciplines."

"There is no doubt graphene is a superior material. Intrinsically it is amazing," says Banerjee. "It is up to us, the scientists and engineers, to show how we can use graphene and harness its capabilities. There are challenges in how to grow it, how to transfer or not to transfer and pattern it, and how to tailor its properties for specific applications. But these challenges are fertile grounds for exciting research in the future."

]]> Wed, 08 FEB 2012 08:47:15 AEST Houston TX (SPX) Oct 24, 2011 - Giant flakes of graphene oxide in water aggregate like a stack of pancakes, but infinitely thinner, and in the process gain characteristics that materials scientists may find delicious.

A new paper by scientists at Rice University and the University of Colorado details how slices of graphene, the single-atom form of carbon, in a solution arrange themselves to form a nematic liquid crystal in which particles are free-floating but aligned.

That much was already known. The new twist is that if the flakes - in this case, graphene oxide - are big enough and concentrated enough, they retain their alignment as they form a gel. That gel is a handy precursor for manufacturing metamaterials or fibers with unique mechanical and electronic properties.

"Graphene materials and fluid phases are a great research area," Pasquali said. "From the fundamental point of view, fluid phases comprising flakes are relatively unexplored, and certainly so when the flakes have important electronic properties.

"From the application standpoint, graphene and graphene oxide can be important building blocks in such areas as flexible electronics and conductive and high-strength materials, and can serve as templates for ordering plasmonic structures," he said.

By "giant," the researchers referred to irregular flakes of graphene oxide up to 10,000 times as wide as they are high. (That's still impossibly small: on average, roughly 12 microns wide and less than a nanometer high.)

Previous studies showed smaller bits of pristine graphene suspended in acid would form a liquid crystal and that graphene oxide would do likewise in other solutions, including water.

This time the team discovered that if the flakes are big enough and concentrated enough, the solution becomes semisolid. When they constrained the gel to a thin pipette and evaporated some of the water, the graphene oxide flakes got closer to each other and stacked up spontaneously, although imperfectly.

"The exciting part for me is the spontaneous ordering of graphene oxide into a liquid crystal, which nobody had observed before," said Behabtu, a member of Pasquali's lab. "It's still a liquid, but it's ordered. That's useful to make fibers, but it could also induce order on other particles like nanorods."

He said it would be a simple matter to heat the concentrated gel and extrude it into something like carbon fiber, with enhanced properties provided by "mix-ins."

Testing the possibilities, the researchers mixed gold microtriangles and glass microrods into the solution, and found both were effectively forced to line up with the pancaking flakes. Their inclusion also helped the team get visual confirmation of the flakes' orientation.

The process offers the possibility of the large-scale ordering and alignment of such plasmonic particles as gold, silver and palladium nanorods, important components in optoelectronic devices and metamaterials, they reported.

Behabtu added that heating the gel "crosslinks the flakes, and that's good for mechanical strength. You can even heat graphene oxide enough to reduce it, stripping out the oxygen and turning it back into graphite."

Co-authors of the paper are Angel Martinez and Julian Evans, graduate students of Smalyukh at the University of Colorado at Boulder.

The team reported its discovery online this week in the Royal Society of Chemistry journal Soft Matter. Rice authors include Matteo Pasquali, a professor of chemical and biomolecular engineering and of chemistry; James Tour, the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science; postdoctoral research associate Dmitry Kosynkin; and graduate students Budhadipta Dan and Natnael Behabtu. Ivan Smalyukh, an assistant professor of physics at the University of Colorado at Boulder, led research for his group, in which Dan served as a visiting scientist.

]]> Wed, 08 FEB 2012 08:47:15 AEST Stanford CA (SPX) Oct 20, 2011 - An amorphous diamond - one that lacks the crystalline structure of diamond, but is every bit as hard - has been created by a Stanford-led team of researchers. But what good is an amorphous diamond? "Sometimes amorphous forms of a material can have advantages over crystalline forms," said Yu Lin, a Stanford graduate student involved in the research.

The biggest drawback with using diamond for purposes other than jewelry is that even though it is the hardest material known, its crystalline structure contains planes of weakness. Those planes are what allow diamond cutters to cleave all the facets that help give a diamond its dazzle - they are actually breaking the gem along weak planes, not cutting it.

"With diamond, the strength depends on the direction a lot. It's not a bad property, necessarily, but it is limiting," said Wendy Mao, the Stanford mineral physicist who led the research. "But if diamond is amorphous, it may have the same strength in all directions."

That uniform super-hardness, combined with the light weight that is characteristic of all forms of carbon - including diamond - could open up exciting areas of application, such as cutting tools and wear-resistant parts for all kinds of transportation.

Other researchers have tried to create diamond-like amorphous carbon, but have only been able to make extremely thin films that contain impurities such as hydrogen and do not have completely diamond-like atomic bonds. The amorphous diamond created by Mao and Lin can be made in thicker bulk forms, opening up more potential applications.

Lin is the lead author of a paper describing the research that will be published in Physical Review Letters. Mao, Lin's adviser, is a coauthor. Colleagues at the Carnegie Institution of Washington contributed to the research and are also coauthors.

The researchers created the new, super-hard form of carbon using a high-pressure device called a diamond anvil cell. They did a series of experiments with tiny spheres of glassy carbon, an amorphous form of carbon which they compressed between the two diamond anvils. The spheres were a few tens of micrometers (millionths of a meter) in diameter.

They slowly cranked up the pressure on the spheres. When the pressure exceeded 40 gigapascals - 400,000 times atmospheric pressure - the arrangement of the bonds between the carbon atoms in the glassy spheres had completely shifted to a form that endowed the spheres with diamond-like strength.

The researchers detected the shift in internal bonding by probing the spheres with X-rays.

They also did experiments in which a glassy sphere was simultaneously subjected to different pressures from different directions, to further assess the strength of the new form of carbon. While the diamonds in the anvil pressed in on the sides of the sphere with a pressure of 60 gigapascals - about 600,000 times atmospheric pressure - the pressure on the tip of the sphere reached 130 gigapascals.

"The amorphous diamond survived a pressure difference of 70 gigapascals - 700,000 atmospheres - which only diamond has been able to do," Mao said. "Nothing else can withstand that sort of stress difference."

Although the bonds between atoms in the glassy spheres were altered by the extreme pressure, the amorphous, or disordered, structure of the spheres was unchanged.

"The material doesn't get any more ordered as we compress it. It maintains its disorder," Mao said. The outer form of the original material was also retained - if the researchers started with a sphere, then even at the highest pressures, the sphere was still a sphere. The only change was in the type of bonds between the carbon atoms.

One characteristic of the new amorphous diamond is that it is not always hard or always soft. The hardness of the amorphous carbon is tunable; it is soft at low pressure, but the greater the pressure, the harder it gets. Once the pressure of the anvil was released, it returned to its original form as simple glassy carbon, with strength no greater than it had to begin with.

For the amorphous diamond to find widespread application, Mao said, someone will have to find a way to either make the material at low pressure or figure out how to preserve it once the super-hard form is created under high pressure.

Even though the amorphous diamond returned to plain old glassy carbon when the pressure was released, there are still potential applications. The material could be used as a gasket in high-pressure devices where having a gasket that hardens with pressure would be beneficial. Or it could be used in further high-pressure experiments.

"We use a diamond anvil cell to compress samples for high-pressure research, but because this amorphous diamond phase hardens with pressure, it could be a second stage anvil inside the diamond anvil," Lin said.

"Having another anvil in sequence would let us create even higher pressures at the very tip."

Since the focus of Mao's research group is to answer questions about the extreme environments in the deep Earth and other planetary interiors, a "double diamond" anvil could prove extremely useful. One can only speculate as to what exotic materials might be discovered with such an amped-up anvil.

Mao is an assistant professor with a joint appointment in Geological and Environmental Sciences at Stanford University and of Photon Science at the Department of Energy's SLAC National Accelerator Laboratory. Lin is a graduate student in Geological and Environmental Sciences.

]]> Wed, 08 FEB 2012 08:47:15 AEST Washington DC (SPX) Oct 12, 2011 - Carbon is the fourth-most-abundant element in the universe and takes on a wide variety of forms, called allotropes, including diamond and graphite. Scientists at Carnegie's Geophysical Laboratory are part of a team that has discovered a new form of carbon, which is capable of withstanding extreme pressure stresses that were previously observed only in diamond. This breakthrough discovery will be published in Physical Review Letters.

The team was led by Stanford's Wendy L. Mao and her graduate student Yu Lin and includes Carnegie's Ho-kwang (Dave) Mao, Li Zhang, Paul Chow, Yuming Xiao, Maria Baldini, and Jinfu Shu.

The experiment started with a form of carbon called glassy carbon, which was first synthesized in the 1950s, and was found to combine desirable properties of glasses and ceramics with those of graphite.

The team created the new carbon allotrope by compressing glassy carbon to above 400,000 times normal atmospheric pressure.

This new carbon form was capable of withstanding 1.3 million times normal atmospheric pressure in one direction while confined under a pressure of 600,000 times atmospheric levels in other directions.

No substance other than diamond has been observed to withstand this type of pressure stress, indicating that the new carbon allotrope must indeed be very strong.

However, unlike diamond and other crystalline forms of carbon, the structure of this new material is not organized in repeating atomic units. It is an amorphous material, meaning that its structure lacks the long-range order of crystals.

This amorphous, superhard carbon allotrope would have a potential advantage over diamond if its hardness turns out to be isotropic-that is, having hardness that is equally strong in all directions.

In contrast, diamond's hardness is highly dependent upon the direction in which the crystal is oriented.

"These findings open up possibilities for potential applications, including super hard anvils for high-pressure research and could lead to new classes of ultradense and strong materials," said Russell Hemley, director of Carnegie's Geophysical Laboratory.

This research was funded, in part, by the Department of Energy's Office of Basic Energy Sciences Division of Materials Sciences and Engineering, EFree, HPCAT, where some of the experiments were performed, is funded by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. APS, where some of the experiments were performed, is supported by DOE-BES.

]]> Wed, 08 FEB 2012 08:47:15 AEST University Park PA (SPX) Oct 12, 2011 - A team of scientists led by a Penn State University chemist has demonstrated the strengths and weaknesses of an alternative method of molecular depth profiling - a technique used to analyze the surface of ultra-thin materials such as human tissue, nanoparticles, and other substances.

In the new study, the researchers used computer simulations and modeling to show the effectiveness and limitations of the alternative method, which is being used by a research group in Taiwan.

The new computer-simulation findings may help future researchers to choose when to use the new method of analyzing how and where particular molecules are distributed throughout the surface layers of ultra-thin materials. The research will be published in the Journal of Physical Chemistry Letters.

Team leader Barbara Garrison, the Shapiro Professor of Chemistry and the head of the Department of Chemistry at Penn State University, explained that bombarding a material with buckyballs - hollow molecules composed of 60 carbon atoms that are formed into a spherical shape resembling a soccer ball - is an effective means of molecular depth profiling.

The name, "buckyball," is an homage to an early twentieth-century American engineer, Buckminster Fuller, whose design of a geodesic dome very closely resembles the soccer-ball-shaped 60-carbon molecule.

"Researchers figured out a few years ago that buckyballs could be used to profile molecular-scale depths very effectively," Garrison explained.

"Buckyballs are much bigger and chunkier than the spacing between the molecules at the surface of the material being studied, so when the buckyballs hit the surface, they tend to break it up in a way that allows us to peer inside the solid and to actually see which molecules are arranged where.

"We can see, for example, that one layer is composed of one kind of molecule and the next layer is composed of another kind of molecule, similar to the way a meteor creates a crater that exposes sub-surface layers of rock."

Garrison and her colleagues decided to use computer modeling to test the effectiveness of an alternative approach that another research group had been using. The other group had used not only large, high-energy buckyballs to bombard a surface, but also another smaller, low-energy chemical element - argon - in the process.

"In our computer simulations, we modeled the bombardment of surfaces first with high-energy buckyballs and then later, with low-energy argon atoms," Garrison said.

Garrison's group found that, with buckyball bombardment alone at grazing angles, the end result is a very rough surface with many troughs and ridges in one direction.

"In many instances, this approach works out well for depth profiling. However, in other instances, using buckyballs alone makes for a bumpy surface on which to perform molecular depth profiling because the molecules can be distributed unevenly throughout the peaks and valleys," Garrison explained.

"In these instances, when low-energy argon bombardment is added to the process, the result is a much more even, smoother surface, which, in turn, makes for a better area on which to do analyses of molecular arrangement.

In these cases, researchers can get a clearer picture of the many layers of molecules and exactly which molecules make up each layer."

However, Garrison's team also concluded that the argon must be low enough in energy in order to avoid further damage of the molecules that are being profiled.

"According to our simulations, the bottom line is that the buckyball conditions that the other research group used are not the best for depth profiling; thus, co-bombardment with low-energy argon assisted the process," Garrison said.

"That is, the co-bombardment method works only in some very specific instances. We do not think low-energy argon will help in instances where the buckyballs are at sufficiently high energies."

Garrison added that previous researchers had tried using smaller, simpler atomic projectiles at high, rather than low energies, but these projectiles tended to simply penetrate deeply into the surface, without giving scientists a clear view into the arrangement and identity of the molecules beneath.

Garrison said that molecular depth profiling is a crucial aspect of many chemical experiments and its applications are far-reaching.

For example, molecular depth profiling is one way to get around the challenges of working with something so small and intricate as a biological cell. A cell is composed of thin layers of distinct materials, but it is difficult to slice into something so tiny to analyze the composition of those super-fine layers.

In addition, molecular depth profiling can be used to analyze other kinds of human tissue, such as brain tissue - a process that could help researchers to understand neurological disease and injury.

In the future, molecular depth profiling also could be used to study nanoparticles - extremely small objects with dimensions of between 1 and 10 nanometers, visible only with an electron microscope.

Because nanoparticles already are being used experimentally as drug-delivery systems, a detailed analysis of their properties using molecular depth profiling could help researchers to test the effectiveness of the drug-delivery systems.

In addition to Garrison, other members of the research team include Zachary J. Schiffer, a high-school student at the State College Area High School near the Penn State University Park campus, Paul E. Kennedy of Penn State's Department of Chemistry, and Zbigniew Postawa of the Smoluchowski Institute of Physics at Jagiellonian University in Poland. Funding for this research was provided by the National Science Foundation and the Polish Ministry of Science and Higher Education.

]]> Wed, 08 FEB 2012 08:47:15 AEST Hong Kong (AFP) Oct 6, 2011 - One of the world's largest diamonds, a pear-shaped 110.3-carat yellow rock, will go under the hammer in Geneva in November expecting to fetch about $15 million, an auction house said Thursday.

The Sun-Drop diamond, discovered in South Africa last year, is billed by Sotheby's as the "world's largest known pear-shaped fancy vivid yellow diamond".

"This stone has immense presence and is truly stunning. It is also one of the largest diamonds ever to have appeared at auction," Sotheby's Switzerland co-chairman David Bennett told a news conference in Hong Kong.

The Chinese city, which has emerged as the world's third-largest auction centre after New York and London, was the first stop of an international tour on which the precious stone is being showcased before the November 15 auction.

]]> Wed, 08 FEB 2012 08:47:15 AEST Subscribe to our daily selection of space, military, environment and energy newsletters responseText http://visitor.constantcontact.com/manage/optin/ea?v=0016gbbKsaiGSpQFojVO8ZoHw%3D%3D