Graphene grows better on certain copper crystals

ScienceDaily (Oct. 27, 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.

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The above story is reprinted from materials provided by University of Illinois at Urbana-Champaign.

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Journal Reference:

Joshua D. Wood, Scott W. Schmucker, Austin S. Lyons, Eric Pop, Joseph W. Lyding. Effects of Polycrystalline Cu Substrate on Graphene Growth by Chemical Vapor Deposition. Nano Letters, 2011; : 111004083339002 DOI: 10.1021/nl201566c

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Better lithium-ion batteries are on the way

ScienceDaily (Sep. 26, 2011) — Lithium-ion batteries are everywhere, in smart phones, laptops, an array of other consumer electronics, and the newest electric cars. Good as they are, they could be much better, especially when it comes to lowering the cost and extending the range of electric cars. To do that, batteries need to store a lot more energy.

The anode is a critical component for storing energy in lithium-ion batteries. A team of scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles.

The secret is a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge. The new anodes are made from low-cost materials, compatible with standard lithium-battery manufacturing technologies. The research team reports its findings in Advanced Materials, now available online.

High-capacity expansion

"High-capacity lithium-ion anode materials have always confronted the challenge of volume change -- swelling -- when electrodes absorb lithium," says Gao Liu of Berkeley Lab's Environmental Energy Technologies Division (EETD), a member of the BATT program (Batteries for Advanced Transportation Technologies) managed by the Lab and supported by DOE's Office of Vehicle Technologies.

Says Liu, "Most of today's lithium-ion batteries have anodes made of graphite, which is electrically conducting and expands only modestly when housing the ions between its graphene layers. Silicon can store 10 times more -- it has by far the highest capacity among lithium-ion storage materials -- but it swells to more than three times its volume when fully charged."

This kind of swelling quickly breaks the electrical contacts in the anode, so researchers have concentrated on finding other ways to use silicon while maintaining anode conductivity. Many approaches have been proposed; some are prohibitively costly.

One less-expensive approach has been to mix silicon particles in a flexible polymer binder, with carbon black added to the mix to conduct electricity. Unfortunately, the repeated swelling and shrinking of the silicon particles as they acquire and release lithium ions eventually push away the added carbon particles. What's needed is a flexible binder that can conduct electricity by itself, without the added carbon.

"Conducting polymers aren't a new idea," says Liu, "but previous efforts haven't worked well, because they haven't taken into account the severe reducing environment on the anode side of a lithium-ion battery, which renders most conducting polymers insulators."

One such experimental polymer, called PAN (polyaniline), has positive charges; it starts out as a conductor but quickly loses conductivity. An ideal conducting polymer should readily acquire electrons, rendering it conducting in the anode's reducing environment.

The signature of a promising polymer would be one with a low value of the state called the "lowest unoccupied molecular orbital," where electrons can easily reside and move freely. Ideally, electrons would be acquired from the lithium atoms during the initial charging process. Liu and his postdoctoral fellow Shidi Xun in EETD designed a series of such polyfluorene-based conducting polymers -- PFs for short.

When Liu discussed the excellent performance of the PFs with Wanli Yang of Berkeley Lab's Advanced Light Source (ALS), a scientific collaboration emerged to understand the new materials. Yang suggested conducting soft x-ray absorption spectroscopy on Liu and Xun's candidate polymers using ALS beamline 8.0.1 to determine their key electronic properties.

Says Yang, "Gao wanted to know where the ions and electrons are and where they move. Soft x-ray spectroscopy has the power to deliver exactly this kind of crucial information."

Compared with the electronic structure of PAN, the absorption spectra Yang obtained for the PFs stood out immediately. The differences were greatest in PFs incorporating a carbon-oxygen functional group (carbonyl).

"We had the experimental evidence," says Yang, "but to understand what we were seeing, and its relevance to the conductivity of the polymer, we needed a theoretical explanation, starting from first principles." He asked Lin-Wang Wang of Berkeley Lab's Materials Sciences Division (MSD) to join the research collaboration.

Wang and his postdoctoral fellow, Nenad Vukmirovic, conducted ab initio calculations of the promising polymers at the Lab's National Energy Research Scientific Computing Center (NERSC). Wang says, "The calculation tells you what's really going on -- including precisely how the lithium ions attach to the polymer, and why the added carbonyl functional group improves the process. It was quite impressive that the calculations matched the experiments so beautifully."

The simulation did indeed reveal "what's really going on" with the type of PF that includes the carbonyl functional group, and showed why the system works so well. The lithium ions interact with the polymer first, and afterward bind to the silicon particles. When a lithium atom binds to the polymer through the carbonyl group, it gives its electron to the polymer -- a doping process that significantly improves the polymer's electrical conductivity, facilitating electron and ion transport to the silicon particles.

Cycling for success

Having gone through one cycle of material synthesis at EETD, experimental analysis at the ALS, and theoretical simulation at MSD, the positive results triggered a new cycle of improvements. Almost as important as its electrical properties are the polymer's physical properties, to which Liu now added another functional group, producing a polymer that can adhere tightly to the silicon particles as they acquire or lose lithium ions and undergo repeated changes in volume.

Scanning electron microscopy and transmission electron microscopy at the National Center for Electron Microscopy (NCEM), showing the anodes after 32 charge-discharge cycles, confirmed that the modified polymer adhered strongly throughout the battery operation even as the silicon particles repeatedly expanded and contracted. Tests at the ALS and simulations confirmed that the added mechanical properties did not affect the polymer's superior electrical properties.

"Without the input from our partners at the ALS and in MSD, what can be modified and what should not be modified in the next generation of polymers would not have been obvious," says Vince Battaglia, Program Manager of EETD's Advanced Energy Technologies Department.

"This achievement provides a rare scientific showcase, combining advanced tools of synthesis, characterization, and simulation in a novel approach to materials development," says Zahid Hussain, the ALS Division Deputy for Scientific Support and Scientific Support Group Leader. "The cyclic approach can lead to the discovery of new practical materials with a fundamental understanding of their properties."

The icing on the anode cake is that the new PF-based anode is not only superior but economical. "Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far," says Gao Liu. "The whole manufacturing process is low cost and compatible with established manufacturing technologies. The commercial value of the polymer has already been recognized by major companies, and its possible applications extend beyond silicon anodes."

Anodes are a key component of lithium-ion battery technology, but far from the only challenge. Already the research collaboration is pushing to the next step, studying other battery components including cathodes.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Gao Liu, Shidi Xun, Nenad Vukmirovic, Xiangyun Song, Paul Olalde-Velasco, Honghe Zheng, Vince S. Battaglia, Lin-Wang Wang, and Wanli Yang. Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes. Advanced Materials, 2011 DOI: 10.1002/adma.201102421

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Building better catalysts

ScienceDaily (Sep. 30, 2011) — University of Utah chemists developed a method to design and test new catalysts, which are substances that speed chemical reactions and are crucial for producing energy, chemicals and industrial products. By using the new method, the chemists also made a discovery that will make it easier to design future catalysts.

The discovery: the sizes and electronic properties of catalysts interact to affect how well a catalyst performs, and are not independent factors as was thought previously. Chemistry Professor Matt Sigman and doctoral student Kaid Harper, report their findings in the Sept. 30, 2011, issue of the journal Science.

"It opens our eyes to how to design new catalysts that we wouldn't necessarily think about designing, for a broad range of reactions," Sigman says. "We're pretty excited."

Sigman believes the new technique for designing and testing catalysts "is going to be picked up pretty fast," first by academic and then by industrial chemists, who "will see it's a simple way to rapidly design better catalysts."

'Catalysts Make the World Go 'Round'

Catalysts speed chemical reactions without being consumed by those reactions. Their importance to society and the economy is tough to overstate. Products made with catalysts include medicines, fuels, foods and fertilizers.

Ninety percent of U.S. chemical manufacturing processes involve catalysts, which also are used to make more than one-fifth of all industrial products. Those processes consume much energy, so making catalytic reactions more efficient would both save energy and reduce emissions of climate-warming carbon dioxide gas.

"Catalysts make the world go 'round," says Sigman. "Catalysts are how we make molecules more efficiently and, more important, make molecules that can't be made using any other method."

The Utah researchers developed a new method for rapidly identifying and designing what are known as "asymmetric catalysts," which are catalyst molecules that are considered either left-handed or right-handed because they are physically asymmetrical. In chemistry, this property of handedness is known as chirality.

Chemists want new asymmetric catalysts because they impart handedness or chirality to the molecules they are used to make. For example, when a left-handed or right-handed catalyst is used to speed a chemical reaction, the chemical that results from that reaction can be either left-handed or right-handed.

"Handedness is an essential component of a drug's effectiveness," Sigman says.

Drugs generally work by latching onto proteins involved in a disease-causing process. The drug is like a key that fits into a protein lock, and chirality "is the direction the key goes" to fit properly and open the lock, says Sigman.

"However, developing asymmetric catalysts [to produce asymmetric drug molecules] can be a time-consuming and sometimes unsuccessful undertaking" because it usually is done by trial and error, he adds.

Sigman says the new study "is a step toward developing faster methods to identify optimal catalysts and insight into how to design them."

A Mathematical Approach to Catalyst Design

Harper and Sigman combined principles of data analysis with principles of catalyst design to create a "library" of nine related catalysts that they hypothesized would effectively catalyze a given reaction -- one that could be useful for making new pharmaceuticals. Essentially, they used math to find the optimal size and electronic properties of the candidate catalysts.

Then the chemists tested the nine catalysts -- known as "quinoline proline ligands" -- to determine how well their degree of handedness would be passed on to the chemical reaction products the catalysts were used to produce.

Sigman and Harper depicted results of the reactions using the different catalysts as a three-dimensional mathematical surface that bulges upward. The highest part of the bulge represents those among the nine catalysts that had the greatest degree of handedness.

This technique was used -- and can be used in the future -- to identify the optimal catalysts among a number of candidates. But it also revealed the unexpected link between the size and electronic properties of catalysts in determining their effectiveness in speeding reactions.

"This study shows quantitatively that the two factors are related," and knowing that will make it easier to design many future catalysts, Sigman says.

The new study was funded by the National Science Foundation.

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Utah.

Journal Reference:

Matt Sigman and Kaid Harper. A Well-Behaved Catalyst. Science, 30 September 2011: 1797 DOI: 10.1126/science.333.6051.1797-f

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Better lithium-ion batteries are on the way

ScienceDaily (Sep. 26, 2011) — Lithium-ion batteries are everywhere, in smart phones, laptops, an array of other consumer electronics, and the newest electric cars. Good as they are, they could be much better, especially when it comes to lowering the cost and extending the range of electric cars. To do that, batteries need to store a lot more energy.

The anode is a critical component for storing energy in lithium-ion batteries. A team of scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has designed a new kind of anode that can absorb eight times the lithium of current designs, and has maintained its greatly increased energy capacity after over a year of testing and many hundreds of charge-discharge cycles.

The secret is a tailored polymer that conducts electricity and binds closely to lithium-storing silicon particles, even as they expand to more than three times their volume during charging and then shrink again during discharge. The new anodes are made from low-cost materials, compatible with standard lithium-battery manufacturing technologies. The research team reports its findings in Advanced Materials, now available online.

High-capacity expansion

"High-capacity lithium-ion anode materials have always confronted the challenge of volume change -- swelling -- when electrodes absorb lithium," says Gao Liu of Berkeley Lab's Environmental Energy Technologies Division (EETD), a member of the BATT program (Batteries for Advanced Transportation Technologies) managed by the Lab and supported by DOE's Office of Vehicle Technologies.

Says Liu, "Most of today's lithium-ion batteries have anodes made of graphite, which is electrically conducting and expands only modestly when housing the ions between its graphene layers. Silicon can store 10 times more -- it has by far the highest capacity among lithium-ion storage materials -- but it swells to more than three times its volume when fully charged."

This kind of swelling quickly breaks the electrical contacts in the anode, so researchers have concentrated on finding other ways to use silicon while maintaining anode conductivity. Many approaches have been proposed; some are prohibitively costly.

One less-expensive approach has been to mix silicon particles in a flexible polymer binder, with carbon black added to the mix to conduct electricity. Unfortunately, the repeated swelling and shrinking of the silicon particles as they acquire and release lithium ions eventually push away the added carbon particles. What's needed is a flexible binder that can conduct electricity by itself, without the added carbon.

"Conducting polymers aren't a new idea," says Liu, "but previous efforts haven't worked well, because they haven't taken into account the severe reducing environment on the anode side of a lithium-ion battery, which renders most conducting polymers insulators."

One such experimental polymer, called PAN (polyaniline), has positive charges; it starts out as a conductor but quickly loses conductivity. An ideal conducting polymer should readily acquire electrons, rendering it conducting in the anode's reducing environment.

The signature of a promising polymer would be one with a low value of the state called the "lowest unoccupied molecular orbital," where electrons can easily reside and move freely. Ideally, electrons would be acquired from the lithium atoms during the initial charging process. Liu and his postdoctoral fellow Shidi Xun in EETD designed a series of such polyfluorene-based conducting polymers -- PFs for short.

When Liu discussed the excellent performance of the PFs with Wanli Yang of Berkeley Lab's Advanced Light Source (ALS), a scientific collaboration emerged to understand the new materials. Yang suggested conducting soft x-ray absorption spectroscopy on Liu and Xun's candidate polymers using ALS beamline 8.0.1 to determine their key electronic properties.

Says Yang, "Gao wanted to know where the ions and electrons are and where they move. Soft x-ray spectroscopy has the power to deliver exactly this kind of crucial information."

Compared with the electronic structure of PAN, the absorption spectra Yang obtained for the PFs stood out immediately. The differences were greatest in PFs incorporating a carbon-oxygen functional group (carbonyl).

"We had the experimental evidence," says Yang, "but to understand what we were seeing, and its relevance to the conductivity of the polymer, we needed a theoretical explanation, starting from first principles." He asked Lin-Wang Wang of Berkeley Lab's Materials Sciences Division (MSD) to join the research collaboration.

Wang and his postdoctoral fellow, Nenad Vukmirovic, conducted ab initio calculations of the promising polymers at the Lab's National Energy Research Scientific Computing Center (NERSC). Wang says, "The calculation tells you what's really going on -- including precisely how the lithium ions attach to the polymer, and why the added carbonyl functional group improves the process. It was quite impressive that the calculations matched the experiments so beautifully."

The simulation did indeed reveal "what's really going on" with the type of PF that includes the carbonyl functional group, and showed why the system works so well. The lithium ions interact with the polymer first, and afterward bind to the silicon particles. When a lithium atom binds to the polymer through the carbonyl group, it gives its electron to the polymer -- a doping process that significantly improves the polymer's electrical conductivity, facilitating electron and ion transport to the silicon particles.

Cycling for success

Having gone through one cycle of material synthesis at EETD, experimental analysis at the ALS, and theoretical simulation at MSD, the positive results triggered a new cycle of improvements. Almost as important as its electrical properties are the polymer's physical properties, to which Liu now added another functional group, producing a polymer that can adhere tightly to the silicon particles as they acquire or lose lithium ions and undergo repeated changes in volume.

Scanning electron microscopy and transmission electron microscopy at the National Center for Electron Microscopy (NCEM), showing the anodes after 32 charge-discharge cycles, confirmed that the modified polymer adhered strongly throughout the battery operation even as the silicon particles repeatedly expanded and contracted. Tests at the ALS and simulations confirmed that the added mechanical properties did not affect the polymer's superior electrical properties.

"Without the input from our partners at the ALS and in MSD, what can be modified and what should not be modified in the next generation of polymers would not have been obvious," says Vince Battaglia, Program Manager of EETD's Advanced Energy Technologies Department.

"This achievement provides a rare scientific showcase, combining advanced tools of synthesis, characterization, and simulation in a novel approach to materials development," says Zahid Hussain, the ALS Division Deputy for Scientific Support and Scientific Support Group Leader. "The cyclic approach can lead to the discovery of new practical materials with a fundamental understanding of their properties."

The icing on the anode cake is that the new PF-based anode is not only superior but economical. "Using commercial silicon particles and without any conductive additive, our composite anode exhibits the best performance so far," says Gao Liu. "The whole manufacturing process is low cost and compatible with established manufacturing technologies. The commercial value of the polymer has already been recognized by major companies, and its possible applications extend beyond silicon anodes."

Anodes are a key component of lithium-ion battery technology, but far from the only challenge. Already the research collaboration is pushing to the next step, studying other battery components including cathodes.

Recommend this story on Facebook, Twitter,
and Google +1:

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Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Gao Liu, Shidi Xun, Nenad Vukmirovic, Xiangyun Song, Paul Olalde-Velasco, Honghe Zheng, Vince S. Battaglia, Lin-Wang Wang, and Wanli Yang. Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes. Advanced Materials, 2011 DOI: 10.1002/adma.201102421

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Building better catalysts

ScienceDaily (Sep. 30, 2011) — University of Utah chemists developed a method to design and test new catalysts, which are substances that speed chemical reactions and are crucial for producing energy, chemicals and industrial products. By using the new method, the chemists also made a discovery that will make it easier to design future catalysts.

The discovery: the sizes and electronic properties of catalysts interact to affect how well a catalyst performs, and are not independent factors as was thought previously. Chemistry Professor Matt Sigman and doctoral student Kaid Harper, report their findings in the Sept. 30, 2011, issue of the journal Science.

"It opens our eyes to how to design new catalysts that we wouldn't necessarily think about designing, for a broad range of reactions," Sigman says. "We're pretty excited."

Sigman believes the new technique for designing and testing catalysts "is going to be picked up pretty fast," first by academic and then by industrial chemists, who "will see it's a simple way to rapidly design better catalysts."

'Catalysts Make the World Go 'Round'

Catalysts speed chemical reactions without being consumed by those reactions. Their importance to society and the economy is tough to overstate. Products made with catalysts include medicines, fuels, foods and fertilizers.

Ninety percent of U.S. chemical manufacturing processes involve catalysts, which also are used to make more than one-fifth of all industrial products. Those processes consume much energy, so making catalytic reactions more efficient would both save energy and reduce emissions of climate-warming carbon dioxide gas.

"Catalysts make the world go 'round," says Sigman. "Catalysts are how we make molecules more efficiently and, more important, make molecules that can't be made using any other method."

The Utah researchers developed a new method for rapidly identifying and designing what are known as "asymmetric catalysts," which are catalyst molecules that are considered either left-handed or right-handed because they are physically asymmetrical. In chemistry, this property of handedness is known as chirality.

Chemists want new asymmetric catalysts because they impart handedness or chirality to the molecules they are used to make. For example, when a left-handed or right-handed catalyst is used to speed a chemical reaction, the chemical that results from that reaction can be either left-handed or right-handed.

"Handedness is an essential component of a drug's effectiveness," Sigman says.

Drugs generally work by latching onto proteins involved in a disease-causing process. The drug is like a key that fits into a protein lock, and chirality "is the direction the key goes" to fit properly and open the lock, says Sigman.

"However, developing asymmetric catalysts [to produce asymmetric drug molecules] can be a time-consuming and sometimes unsuccessful undertaking" because it usually is done by trial and error, he adds.

Sigman says the new study "is a step toward developing faster methods to identify optimal catalysts and insight into how to design them."

A Mathematical Approach to Catalyst Design

Harper and Sigman combined principles of data analysis with principles of catalyst design to create a "library" of nine related catalysts that they hypothesized would effectively catalyze a given reaction -- one that could be useful for making new pharmaceuticals. Essentially, they used math to find the optimal size and electronic properties of the candidate catalysts.

Then the chemists tested the nine catalysts -- known as "quinoline proline ligands" -- to determine how well their degree of handedness would be passed on to the chemical reaction products the catalysts were used to produce.

Sigman and Harper depicted results of the reactions using the different catalysts as a three-dimensional mathematical surface that bulges upward. The highest part of the bulge represents those among the nine catalysts that had the greatest degree of handedness.

This technique was used -- and can be used in the future -- to identify the optimal catalysts among a number of candidates. But it also revealed the unexpected link between the size and electronic properties of catalysts in determining their effectiveness in speeding reactions.

"This study shows quantitatively that the two factors are related," and knowing that will make it easier to design many future catalysts, Sigman says.

The new study was funded by the National Science Foundation.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Utah.

Journal Reference:

Matt Sigman and Kaid Harper. A Well-Behaved Catalyst. Science, 30 September 2011: 1797 DOI: 10.1126/science.333.6051.1797-f

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New insights on an old material will enable design of better polymer batteries, water purification

ScienceDaily (June 19, 2011) — Designing new materials depends upon understanding the properties of today's materials. One such material, Nafion ©, is a polymer that efficiently conducts ions (a polymer electrolyte) and water through its nanostructure, making it important for many energy-related industrial applications, including in fuel cells, organic batteries, and reverse-osmosis water purification. But since Nafion was invented 50 years ago, scientists have only been able to speculate about how to build new materials because they have not been able to see details on how the molecules come together and work within Nafion.

Now, two Virginia Tech research groups have combined forces to devise a way to measure Nafion's internal structure and, in the process, have discovered how to manipulate this structure to enhance the material's applications.

The research is published in the June 19 issue of Nature Materials in the Letters article, "Linear coupling of alignment with transport in a polymer electrolyte membrane," by Jing Li, Jong Keun Park, Robert B. Moore, and Louis A. Madsen, all with the chemistry department in the College of Science and the Macromolecules and Interfaces Institute at Virginia Tech.

Nafion is made up of molecules that combine the non-stick and tough nature of Teflon with the conductive properties of an acid, such as battery acid. A network of tiny channels, nanometers in size, carries water or ions quickly through the polymer. "But, due to the irregular structure of Nafion, scientists have not been able to get reliable information about its properties using most standard analysis tools, such as transmission electron microscopy," said Madsen, assistant professor of physical, polymer, and materials chemistry.

Madsen and Moore, professor of physical and polymer chemistry; Madsen's post-doctoral associate Jing Li; and Moore's Ph.D. student Jong Keun Park, of Korea, were able to use nuclear magnetic resonance (NMR)to measure molecular motion, and a combination of NMR and X-ray scattering to measure molecular alignment within Nafion. "We were looking at water molecules inside Nafion as internal reporters of structure and efficiency of conduction," said Madsen. "The new feature we discovered is the locally aligned aggregates of polymer molecules in the material. The molecules align like strands of dry spaghetti lined up in a box. We can measure the speed (diffusion) of the water molecules and the direction they travel within those structures, which relates strongly to the alignment of the polymer molecule strands."

The researchers observed that the alignment of the channels influenced the speed and preferential direction of water motion. And a startlingly clear picture presented itself when the scientists stretched the Nafion and measured its structure and water motion.

"Stretching drastically influences the degree of alignment," said Madsen. "So the molecules move faster along the direction of the stretch, and in a very predictable way. These materials actually share some properties with liquid crystals -- molecules that line up with each other and are used in every LCD television, projector, and screen."

These relationships have not been previously recognized in a polymer electrolyte, Madsen said.

The ability to observe motion and direction, and understand what is happening within Nafion, has implications for using the material in new ways, and for designing new materials, the researchers write in the Nature Materials article. Ion-based applications could include actuator devices such as artificial muscles, organic batteries, and more energy efficient fuel cells. A water-based application would be improved reverse osmosis membranes for water purification.

Madsen and Moore started this collaborative project shortly after they arrived at Virginia Tech (Madsen in 2006, Moore in 2007), and they are furthering their work together by investigating new polymeric materials using their unique combination of analysis techniques.

"Alignment provides for a better flow of the molecules through the polymer," Madsen said.

The research is supported by Madsen's National Science Foundation Faculty Early Career Development (CAREER) Award. His research focuses on improving advanced polymers for fuel cells and reverse-osmosis water purification by combining detailed analysis of these materials with theoretical understanding. The research is also supported by the US Army Research Office under Ionic Liquids in Electro-Active Devices (ILEAD) Multidisciplinary University Research Initiative (MURI) grant.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Virginia Tech, via EurekAlert!, a service of AAAS.

Journal Reference:

Jing Li, Jong Keun Park, Robert B. Moore and Louis A. Madsen. Linear coupling of alignment with transport in a polymer electrolyte membrane. Nature Materials, June 19 2011 DOI: 10.1038/NMAT3048

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Want better math teachers? Then train them better

ScienceDaily (June 9, 2011) — It's time for the United States to consider establishing higher standards for math teachers if the nation is going to break its "vicious cycle" of mediocrity, a Michigan State University education scholar argues in Science magazine.

As American students continue to be outpaced in mathematics by pupils in countries such as Russia and Taiwan, William Schmidt recommends adopting more rigorous, demanding and internationally benchmarked teacher-preparation standards for math teachers.

"Our research shows that current teacher-preparation programs for middle-school math instructors in the United States do not produce teachers with an internationally competitive level of mathematics knowledge," said Schmidt, a University Distinguished Professor and co-director of MSU's Education Policy Center.

Schmidt makes his argument in an "education forum" paper in the June 10 edition of Science. MSU researchers Richard Houang and Leland Cogan co-authored the paper.

Current standards for math teachers are established on a state-by-state level. Schmidt suggests the states could come together to establish more rigorous and uniform standards, similar to the Common Core State Standards Initiative for K-12 students.

That initiative, which establishes more rigorous math and English-Language Arts standards for students, is led by the National Governors Association and the Council of Chief State School Officers. Thus far, 42 states have adopted the common standards.

But even with higher pupil standards, U.S. students can't get better at math if their instructors aren't fully prepared to teach them, Schmidt noted.

"Weak K-12 math curricula taught by teachers with an inadequate mathematics background produce high school graduates who are similarly weak," Schmidt said. "A long-term and better solution is to break the vicious cycle of mediocrity in which we find ourselves."

Schmidt led the U.S. portion of the Teacher Education Study in Mathematics, or TEDS-M, by far the largest study of its kind, surveying more than 3,300 future teachers in the United States and 23,244 future teachers across 16 countries.

The U.S. study was sponsored by Boeing Co., Carnegie Corp. of New York, the Bill & Melinda Gates Foundation and the GE Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Michigan State University.

Journal Reference:

William H. Schmidt, Richard Houang, Leland S. Cogan. Preparing Future Math Teachers. Science, 10 June 2011: Vol. 332 no. 6035 pp. 1266-1267 DOI: 10.1126/science.1193855

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Want better math teachers? Then train them better

ScienceDaily (June 9, 2011) — It's time for the United States to consider establishing higher standards for math teachers if the nation is going to break its "vicious cycle" of mediocrity, a Michigan State University education scholar argues in Science magazine.

As American students continue to be outpaced in mathematics by pupils in countries such as Russia and Taiwan, William Schmidt recommends adopting more rigorous, demanding and internationally benchmarked teacher-preparation standards for math teachers.

"Our research shows that current teacher-preparation programs for middle-school math instructors in the United States do not produce teachers with an internationally competitive level of mathematics knowledge," said Schmidt, a University Distinguished Professor and co-director of MSU's Education Policy Center.

Schmidt makes his argument in an "education forum" paper in the June 10 edition of Science. MSU researchers Richard Houang and Leland Cogan co-authored the paper.

Current standards for math teachers are established on a state-by-state level. Schmidt suggests the states could come together to establish more rigorous and uniform standards, similar to the Common Core State Standards Initiative for K-12 students.

That initiative, which establishes more rigorous math and English-Language Arts standards for students, is led by the National Governors Association and the Council of Chief State School Officers. Thus far, 42 states have adopted the common standards.

But even with higher pupil standards, U.S. students can't get better at math if their instructors aren't fully prepared to teach them, Schmidt noted.

"Weak K-12 math curricula taught by teachers with an inadequate mathematics background produce high school graduates who are similarly weak," Schmidt said. "A long-term and better solution is to break the vicious cycle of mediocrity in which we find ourselves."

Schmidt led the U.S. portion of the Teacher Education Study in Mathematics, or TEDS-M, by far the largest study of its kind, surveying more than 3,300 future teachers in the United States and 23,244 future teachers across 16 countries.

The U.S. study was sponsored by Boeing Co., Carnegie Corp. of New York, the Bill & Melinda Gates Foundation and the GE Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Michigan State University.

Journal Reference:

William H. Schmidt, Richard Houang, Leland S. Cogan. Preparing Future Math Teachers. Science, 10 June 2011: Vol. 332 no. 6035 pp. 1266-1267 DOI: 10.1126/science.1193855

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Chemists devise better way to prepare workhorse molecules

ScienceDaily (June 9, 2011) — In chemistry, so-called aromatic molecules compose a large and versatile family of chemical compounds that are the stuff of pharmaceuticals, electronic materials and consumer products ranging from sunscreen to plastic soda bottles.

Writing in the current online issue (June 9) of the journal Science, a team led by University of Wisconsin-Madison chemistry Professor Shannon Stahl reports a new, environmentally friendly way to make substituted aromatic molecules that can be customized for different industrial needs.

As college chemistry students know, aromatic molecules have a special stability conferred by a ring of six carbon atoms with alternating single and double bonds. "The ultimate utility of these molecules depends on the chemical groups attached at the corners of this hexagonal platform," explains Stahl. "Interest in preparing substituted aromatic molecules traces back to the dawn of organic chemistry."

In fact, the 2010 Nobel Prize in Chemistry was awarded for catalytic chemical reactions that allow the introduction of specific groups to the periphery of aromatic molecules. These methods, and older traditional methods, rely on modifying an existing aromatic molecule, Stahl explains. But the stability of aromatic molecules can make such approaches difficult, and existing methods also have many limitations in the types and patterns of chemical groups that can be installed.

The method devised by Stahl and Wisconsin colleagues Yusuke Izawa and Doris Pun owes its success to the discovery of a new palladium catalyst. The catalyst gives chemists a way to peel off hydrogen from cyclic molecules to form aromatic products with the desired substitution patterns already in place. The hydrogen removed by the palladium catalyst is combined with oxygen, and water is formed as the only byproduct.

The Wisconsin team demonstrated the utility and efficiency of the new process on phenols, aromatic compounds that are produced on a large scale as precursors to many kinds of industrial materials and pharmaceutical agents. While the new catalytic method can be used to make a broad spectrum of aromatic molecules of interest to science and industry, the new work will be of most immediate practical use to drug companies, according to Stahl. For example, an anticancer agent that was difficult to make using previously known methods was efficiently produced using the strategy devised by the team.

Stahl notes that the work published June 9 in Science will require more development before it is suitable for large-scale industrial production, but he emphasizes that concepts introduced by the new work will have broad utility. "Many new catalysts, reaction conditions and target molecules can be envisioned. Overall, this route to substituted aromatic molecules has a lot of potential," he says.

The new study was supported by grants from the U.S. National Institutes of Health, the Mitsubishi Chemical Corp. and the U.S. National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Wisconsin-Madison.

Journal Reference:

Yusuke Izawa, Doris Pun and Shannon S. Stahl. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science, 9 June 2011 DOI: 10.1126/science.1204183

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

New method to make sodium ion-based battery cells could lead to better, cheaper batteries for the electrical grid

ScienceDaily (June 8, 2011) — By adding the right amount of heat, researchers have developed a method that improves the electrical capacity and recharging lifetime of sodium ion rechargeable batteries, which could be a cheaper alternative for large-scale uses such as storing energy on the electrical grid.

To connect solar and wind energy sources to the electrical grid, grid managers require batteries that can store large amounts of energy created at the source. Lithium ion rechargeable batteries -- common in consumer electronics and electric vehicles -- perform well, but are too expensive for widespread use on the grid because many batteries will be needed, and they will likely need to be large. Sodium is the next best choice, but the sodium-sulfur batteries currently in use run at temperatures above 300 degrees Celsius, or three times the temperature of boiling water, making them less energy efficient and safe than batteries that run at ambient temperatures.

Battery developers want the best of both worlds -- to use both inexpensive sodium and use the type of electrodes found in lithium rechargeables. A team of scientists at the Department of Energy's Pacific Northwest National Laboratory and visiting researchers from Wuhan University in Wuhan, China used nanomaterials to make electrodes that can work with sodium, they reported June 3 online in the journal Advanced Materials.

"The sodium-ion battery works at room temperature and uses sodium ions, an ingredient in cooking salt. So it will be much cheaper and safer," said PNNL chemist Jun Liu, who co-led the study with Wuhan University chemist Yuliang Cao.

The electrodes in lithium rechargeables that interest researchers are made of manganese oxide. The atoms in this metal oxide form many holes and tunnels that lithium ions travel through when batteries are being charged or are in use. The free movement of lithium ions allows the battery to hold electricity or release it in a current. But simply replacing the lithium ions with sodium ions is problematic -- sodium ions are 70 percent bigger than lithium ions and don't fit in the crevices as well.

To find a way to make bigger holes in the manganese oxide, PNNL researchers went much much smaller. They turned to nanomaterials -- materials made on the nanometer-sized scale, or about a million times thinner than a dime -- that have surprising properties due to their smallness. For example, the short distances that sodium ions have to travel in nanowires might make the manganese oxide a better electrode in ways unrelated to the size of the tunnels.

To explore, the team mixed two different kinds of manganese oxide atomic building blocks -- one whose atoms arrange themselves in pyramids, and another one whose atoms form an octahedron, a diamond-like structure from two pyramids stuck together at their bases. They expected the final material to have large S-shaped tunnels and smaller five-sided tunnels through which the ions could flow.

After mixing, the team treated the materials with temperatures ranging from 450 to 900 degrees Celsius, then examined the materials and tested which treatment worked best. Using a scanning electron microscope, the team found that different temperatures created material of different quality. Treating the manganese oxide at 750 degrees Celsius created the best crystals: too low and the crystals appeared flakey, too high and the crystals turned into larger flat plates.

Zooming in even more using a transmission electron microscope at EMSL, DOE's Environmental Molecular Sciences Laboratory on PNNL's campus, the team saw that manganese oxide heated to 600 degrees had pockmarks in the nanowires that could impede the sodium ions, but the 750 degree-treated wires looked uniform and very crystalline.

But even the best-looking material is just window-dressing if it doesn't perform well. To find out if it lived up to its good looks, the PNNL-Wuhan team dipped the electrode material in electrolyte, the liquid containing sodium ions that will help the manganese oxide electrodes form a current. Then they charged and discharged the experimental battery cells repeatedly.

The team measured peak capacity at 128 milliAmp hours per gram of electrode material as the experimental battery cell discharged. This result surpassed earlier ones taken by other researchers, one of which achieved peak capacity of 80 milliAmp hours per gram for electrodes made from manganese oxide but with a different production method. The researchers think the lower capacity is due to sodium ions causing structural changes in that manganese oxide that do not occur or occur less frequently in the heat-treated nano-sized material.

In addition to high capacity, the material held up well to cycles of charging and discharging, as would occur in consumer use. Again, the material treated at 750 Celsius performed the best: after 100 cycles of charging-discharging, it lost only 7 percent of its capacity. Material treated at 600 Celsius or 900 Celsius lost about 37 percent and 25 percent, respectively.

Even after 1,000 cycles, the capacity of the 750 Celsius-treated electrodes only dropped about 23 percent. The researchers thought the material performed very well, retaining 77 percent of its initial capacity.

Last, the team charged the experimental cell at different speeds to determine how quickly it could take up electricity. The team found that the faster they charged it, the less electricity it could hold. This suggested to the team that the speed with which sodium ions could diffuse into the manganese oxide limited the battery cell's capacity -- when charged fast, the sodium ions couldn't enter the tunnels fast enough to fill them up.

To compensate for the slow sodium ions, the researchers suggest in the future they make even smaller nanowires to speed up charging and discharging. Grid batteries need fast charging so they can collect as much newly made energy coming from renewable sources as possible. And they need to discharge fast when demands shoots up as consumers turn on their air conditioners and television sets, and plug in their electric vehicles at home.

Such high performing batteries could take the heat off an already taxed electrical power grid.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by DOE/Pacific Northwest National Laboratory.

Journal Reference:

Yuliang Cao, Lifen Xiao, Wei Wang, Daiwon Choi, Zimin Nie, Jianguo Yu, Laxmikant V. Saraf, Zhenguo Yang, Jun Liu. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life. Advanced Materials, 2011; DOI: 10.1002/adma.201100904

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Chemists devise better way to prepare workhorse molecules

ScienceDaily (June 9, 2011) — In chemistry, so-called aromatic molecules compose a large and versatile family of chemical compounds that are the stuff of pharmaceuticals, electronic materials and consumer products ranging from sunscreen to plastic soda bottles.

Writing in the current online issue (June 9) of the journal Science, a team led by University of Wisconsin-Madison chemistry Professor Shannon Stahl reports a new, environmentally friendly way to make substituted aromatic molecules that can be customized for different industrial needs.

As college chemistry students know, aromatic molecules have a special stability conferred by a ring of six carbon atoms with alternating single and double bonds. "The ultimate utility of these molecules depends on the chemical groups attached at the corners of this hexagonal platform," explains Stahl. "Interest in preparing substituted aromatic molecules traces back to the dawn of organic chemistry."

In fact, the 2010 Nobel Prize in Chemistry was awarded for catalytic chemical reactions that allow the introduction of specific groups to the periphery of aromatic molecules. These methods, and older traditional methods, rely on modifying an existing aromatic molecule, Stahl explains. But the stability of aromatic molecules can make such approaches difficult, and existing methods also have many limitations in the types and patterns of chemical groups that can be installed.

The method devised by Stahl and Wisconsin colleagues Yusuke Izawa and Doris Pun owes its success to the discovery of a new palladium catalyst. The catalyst gives chemists a way to peel off hydrogen from cyclic molecules to form aromatic products with the desired substitution patterns already in place. The hydrogen removed by the palladium catalyst is combined with oxygen, and water is formed as the only byproduct.

The Wisconsin team demonstrated the utility and efficiency of the new process on phenols, aromatic compounds that are produced on a large scale as precursors to many kinds of industrial materials and pharmaceutical agents. While the new catalytic method can be used to make a broad spectrum of aromatic molecules of interest to science and industry, the new work will be of most immediate practical use to drug companies, according to Stahl. For example, an anticancer agent that was difficult to make using previously known methods was efficiently produced using the strategy devised by the team.

Stahl notes that the work published June 9 in Science will require more development before it is suitable for large-scale industrial production, but he emphasizes that concepts introduced by the new work will have broad utility. "Many new catalysts, reaction conditions and target molecules can be envisioned. Overall, this route to substituted aromatic molecules has a lot of potential," he says.

The new study was supported by grants from the U.S. National Institutes of Health, the Mitsubishi Chemical Corp. and the U.S. National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Wisconsin-Madison.

Journal Reference:

Yusuke Izawa, Doris Pun and Shannon S. Stahl. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science, 9 June 2011 DOI: 10.1126/science.1204183

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Better glasses-free 3-D: Mew approach to make 3-D illusions more realistic

ScienceDaily (May 5, 2011) — Nintendo's 3DS portable gaming system, the first commercial device with a glasses-free 3-D screen, has been available in the United States for barely a month, and it's already sold more than a million units. Its three-hour battery life, however, is less than half that of its predecessor, the 2-D DS device.

Researchers at MIT's Media Lab have developed a fundamentally new approach to glasses-free 3-D, called HR3D, which they say could double the battery life of devices like the 3DS without compromising screen brightness or resolution. Among other advantages, the technique could also expand the viewing angle of a 3-D screen, making it practical for larger devices with multiple users, and it would maintain the 3-D effect even when the screen is rotated -- something that happens routinely with handheld devices.

According to Doug Lanman, a postdoc in Associate Professor Ramesh Raskar's Camera Culture Group at the Media Lab, the 3DS relies on a century-old technology known as a parallax barrier. Like most 3-D technologies, this one requires two versions of the same image, one tailored to the left eye and one to the right. The two images are sliced into vertical segments and interleaved on a single surface.

By itself, the composite image looks like an incoherent jumble. But if you place a screen with vertical slits in it -- the parallax barrier -- just in front of the image and stand the right distance away, a 3-D image pops out. The opaque sections of the screen shield the parts of the image intended for the right eye from the left eye, and vice versa, but the slits allow each eye to see the segments intended for it.

The 3DS screen consists of two parallel liquid-crystal displays (LCDs) a small distance apart. When the device is operating in 3-D mode, the front display serves as the parallax barrier, depicting a series of opaque vertical stripes. Since the stripes block half the light coming from the screen, the device's backlight has to be twice as bright, which drains the battery twice as quickly. Moreover, because the spacing of the stripes is calibrated to the horizontal separation of human eyes, if the screen is tilted, the 3-D illusion disappears.

All the angles

Raskar and Lanman, along with postdoc Yun Hee Kim and graduate student Matthew Hirsch, decided to rethink glasses-free 3-D from the ground up. In the real world, as a viewer moves around an object, his or her perspective on it changes constantly. A convincing simulation of 3-D visual experience, Lanman argues, might require a display that offers a dozen different perspectives as the viewer moves from right to left.

But with parallax-barrier 3-D, each new perspective further restricts light emission. Adding multiple perspectives in the vertical direction as well as the horizontal would require a parallax barrier with horizontal as well as vertical bands. For a display with enough different views, the parallax barrier ends up looking like an opaque sheet with pinholes poked in it.

Like the 3DS, the MIT researchers' HR3D system uses two layers of liquid-crystal displays. But instead of displaying vertical bands, as the 3DS does, or pinholes, as a multiperspective parallax-barrier system would, the top LCD displays a pattern customized to the image beneath it.

Going into the project, the researchers had no idea what the customized pattern would look like. But once they'd done the math, they found that the ideal pattern ends up looking a lot like the source image. Instead of consisting of a few big, vertical slits, the parallax barrier consists of thousands of tiny slits, whose orientations follow the contours of the objects in the image.

Number crunching

Because the slits are oriented in so many different directions, the 3-D illusion is consistent no matter whether the image is upright or rotated 90 degrees. Adding more perspectives changes the pattern of the slits, but they allow just as much light to pass.

If a device like the 3DS used HR3D, Lanman says, its battery life would be longer, because the parallax barrier would block less light. The 3-D effect would also be consistent no matter the device's orientation: applications could actually take advantage of screen rotation, particularly in devices that have built-in motion sensors. "But the real win," Lanman says, "comes with full parallax motion" -- that is, a display that shows multiple perspectives in both the horizontal and vertical directions.

"The great thing about Ramesh's group is that they think of things that no one else has thought of and then demonstrate that they can actually be done," says Neil Dodgson, professor of graphics and imaging at the University of Cambridge in England, who was one of the reviewers of the paper when it was accepted last year to the SIGGRAPH Asia graphics conference. "It's quite a clever idea they've got here."

Dodgson points out, however, that HR3D is very computationally intensive. "If you're saving battery power because you've got this extra brightness, but you're actually using all that battery power to do the computation, then you're not saving anything," he says.

While Lanman acknowledges that the algorithm for calculating the barrier pattern that he and his colleagues described in the SIGGRAPH Asia paper is computationally complex, he believes that it can be refined so that "it requires far less computation." He also points out that special-purpose chips designed specifically to run a refined version of the algorithm would consume much less power than a general-purpose processor performing the same computations.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Massachusetts Institute of Technology. The original article was written by Larry Hardesty, MIT News Office.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Better glasses-free 3-D: Mew approach to make 3-D illusions more realistic

ScienceDaily (May 5, 2011) — Nintendo's 3DS portable gaming system, the first commercial device with a glasses-free 3-D screen, has been available in the United States for barely a month, and it's already sold more than a million units. Its three-hour battery life, however, is less than half that of its predecessor, the 2-D DS device.

Researchers at MIT's Media Lab have developed a fundamentally new approach to glasses-free 3-D, called HR3D, which they say could double the battery life of devices like the 3DS without compromising screen brightness or resolution. Among other advantages, the technique could also expand the viewing angle of a 3-D screen, making it practical for larger devices with multiple users, and it would maintain the 3-D effect even when the screen is rotated -- something that happens routinely with handheld devices.

According to Doug Lanman, a postdoc in Associate Professor Ramesh Raskar's Camera Culture Group at the Media Lab, the 3DS relies on a century-old technology known as a parallax barrier. Like most 3-D technologies, this one requires two versions of the same image, one tailored to the left eye and one to the right. The two images are sliced into vertical segments and interleaved on a single surface.

By itself, the composite image looks like an incoherent jumble. But if you place a screen with vertical slits in it -- the parallax barrier -- just in front of the image and stand the right distance away, a 3-D image pops out. The opaque sections of the screen shield the parts of the image intended for the right eye from the left eye, and vice versa, but the slits allow each eye to see the segments intended for it.

The 3DS screen consists of two parallel liquid-crystal displays (LCDs) a small distance apart. When the device is operating in 3-D mode, the front display serves as the parallax barrier, depicting a series of opaque vertical stripes. Since the stripes block half the light coming from the screen, the device's backlight has to be twice as bright, which drains the battery twice as quickly. Moreover, because the spacing of the stripes is calibrated to the horizontal separation of human eyes, if the screen is tilted, the 3-D illusion disappears.

All the angles

Raskar and Lanman, along with postdoc Yun Hee Kim and graduate student Matthew Hirsch, decided to rethink glasses-free 3-D from the ground up. In the real world, as a viewer moves around an object, his or her perspective on it changes constantly. A convincing simulation of 3-D visual experience, Lanman argues, might require a display that offers a dozen different perspectives as the viewer moves from right to left.

But with parallax-barrier 3-D, each new perspective further restricts light emission. Adding multiple perspectives in the vertical direction as well as the horizontal would require a parallax barrier with horizontal as well as vertical bands. For a display with enough different views, the parallax barrier ends up looking like an opaque sheet with pinholes poked in it.

Like the 3DS, the MIT researchers' HR3D system uses two layers of liquid-crystal displays. But instead of displaying vertical bands, as the 3DS does, or pinholes, as a multiperspective parallax-barrier system would, the top LCD displays a pattern customized to the image beneath it.

Going into the project, the researchers had no idea what the customized pattern would look like. But once they'd done the math, they found that the ideal pattern ends up looking a lot like the source image. Instead of consisting of a few big, vertical slits, the parallax barrier consists of thousands of tiny slits, whose orientations follow the contours of the objects in the image.

Number crunching

Because the slits are oriented in so many different directions, the 3-D illusion is consistent no matter whether the image is upright or rotated 90 degrees. Adding more perspectives changes the pattern of the slits, but they allow just as much light to pass.

If a device like the 3DS used HR3D, Lanman says, its battery life would be longer, because the parallax barrier would block less light. The 3-D effect would also be consistent no matter the device's orientation: applications could actually take advantage of screen rotation, particularly in devices that have built-in motion sensors. "But the real win," Lanman says, "comes with full parallax motion" -- that is, a display that shows multiple perspectives in both the horizontal and vertical directions.

"The great thing about Ramesh's group is that they think of things that no one else has thought of and then demonstrate that they can actually be done," says Neil Dodgson, professor of graphics and imaging at the University of Cambridge in England, who was one of the reviewers of the paper when it was accepted last year to the SIGGRAPH Asia graphics conference. "It's quite a clever idea they've got here."

Dodgson points out, however, that HR3D is very computationally intensive. "If you're saving battery power because you've got this extra brightness, but you're actually using all that battery power to do the computation, then you're not saving anything," he says.

While Lanman acknowledges that the algorithm for calculating the barrier pattern that he and his colleagues described in the SIGGRAPH Asia paper is computationally complex, he believes that it can be refined so that "it requires far less computation." He also points out that special-purpose chips designed specifically to run a refined version of the algorithm would consume much less power than a general-purpose processor performing the same computations.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Massachusetts Institute of Technology. The original article was written by Larry Hardesty, MIT News Office.

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here