Solar power could get boost from new light absorption design

ScienceDaily (Nov. 2, 2011) — Solar power may be on the rise, but solar cells are only as efficient as the amount of sunlight they collect. Under the direction of a new McCormick professor, researchers have developed a new material that absorbs a wide range of wavelengths and could lead to more efficient and less expensive solar technology.

A paper describing the findings, "Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers," was published November 1 in the journal Nature Communications.

"The solar spectrum is not like a laser -- it's very broadband, starting with UV and going up to near-infrared," said Koray Aydin, assistant professor of electrical engineering and computer science and the paper's lead author. "To capture this light most efficiently, a solar cell needs to have a broadband response. This design allows us to achieve that."

The researchers used two unconventional materials -- metal and silicon oxide -- to create thin but complex, trapezoid-shaped metal gratings on the nanoscale that can trap a wider range of visible light. The use of these materials is unusual because on their own, they do not absorb light; however, they worked together on the nanoscale to achieve very high absorption rates, Aydin said.

The uniquely shaped grating captured a wide range of wavelengths due to the local optical resonances, causing light to spend more time inside the material until it gets absorbed. This composite metamaterial was also able to collect light from many different angles -- a useful quality when dealing with sunlight, which hits solar cells at different angles as sun moves from east to west throughout the day.

This research is not directly applicable to solar cell technology because metal and silicon oxide cannot convert light to electricity; in fact, the photons are converted to heat and might allow novel ways to control the heat flow at the nanoscale. However, the innovative trapezoid shape could be replicated in semiconducting materials that could be used in solar cells, Aydin said.

If applied to semiconducting materials, the technology could lead to thinner, lower-cost, and more efficient solar cells, he said.

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The above story is reprinted from materials provided by Northwestern University. The original article was written by Sarah Ostman.

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Journal Reference:

Koray Aydin, Vivian E. Ferry, Ryan M. Briggs, Harry A. Atwater. Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers. Nature Communications, 2011; 2: 517 DOI: 10.1038/ncomms1528

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Quantum Scheme Could Allow Submarines to Communicate Securely

Quantum Scheme Could Allow Submarines to Communicate Securely | Popular Science@import "/files/css/a1c433465f8fe485195cb11d70c36108.css";@import "/files/css/33f6b7ecb4513ed2fe6c670880a27187.css"; home Login/Register Newsletter Subscribe RSS GadgetsComputersCamerasSmartphonesVideo GamesCarsConceptsHybridsElectric CarsScienceFuture of the EnvironmentEnergyHealthPopSci Eco TourTechnologyMilitaryAviationSpaceRobotsEngineeringDIYProjectsHacksToolsAuto DIYMore From Our Partner: Toolmonger GalleriesVideosColumnsThe GrouseSex FilesGreen Dream Innovation ChallengesHow It WorksFeatures Tweet Digg Quantum Scheme Could Allow Submarines to Communicate Securely By Clay Dillow Posted 11.01.2011 at 2:41 pm 5 Comments
A Virginia Class Attack Sub Concept Artist's rendering. U.S. Navy via Wikimedia

Submarines are excellent at avoiding detection. When submerged they are so far off the grid, in fact, that it’s difficult for them to stay in contact with the naval bases that supply them with orders and information, or for them to beam information back to base. But a new quantum communications solution could change all this, allowing submerged submarines to communicate via laser pulses by exchanging encryption keys and messages over satellites.

Currently, submarines use randomized codes or “keys” to encrypt messages. These are established ahead of time between a sub and its communications base, and each code is only used one time so that an enemy cannot crack a code and use it to decipher future communications.

Related ArticlesNASA Puts Its Money on Quantum Communications, Plasma Propulsion, and Other Future TechWith New Quantum Encryption Scheme, Messages Can Only Be Read in Designated Geographical LocationScientists Reproduce Quantum Entanglement, Einstein's “Spooky Action” TagsTechnology, Clay Dillow, military, quantum communication, quantum entanglement, quantum mechanics, spooky action, submarinesBut this is problematic. For one, it is logistically cumbersome. And a submarine that’s going on a long-duration mission has to pack lots and lots of keys, which could fall into enemy hands if the sub is overtaken. Moreover, even with plenty of secure keys, the communications between sub and base are extremely slow. In order to penetrate water, transmitters have to use very low frequency radio waves. These only allow for a few characters to be transmitted each second. While the rest of the world (and the battle space) communicates at high speed, subs are stuck with dial-up. In order to send or receive information in bulk or at speed subs have to surface, and that leaves them visible and vulnerable.

But researchers at defense firm ITT have an idea. Using quantum key distribution, subs could encode a key into photons (using the photons’ polarization to represent ones and zeros) making for a virtually un-hackable key--any attempt to intercept the photons would disturb the quantum system in a measurable way, alerting the sender and receiver that a third party is listening in (this is generally achieved via quantum entanglement).

With a secure key established, submarines could then--theoretically at least--stay a few hundred feet below the surface and transmit photons via lasers to satellites, where they could be bounced back to a base on the ground. The researchers’ simulations apparently demonstrate a system that could send and receive data at rates of 170 megabytes per second while a submarine is below the water line. That’s video-worthy data streaming.

Of course, first you would have to figure out just how well photons will hold their quantum states as they travel through water, as any deviation that disrupts the quantum system would render the system insecure (and pointless). And then you need a satellite that can receive and relay quantum-encrypted signaling--again, without disrupting the quantum states of the photons. In other words, this technology is far from battle-ready. But it could someday take high-speed, secure data transfer to depths where it currently doesn’t exist.

[New Scientist]

Previous Article: Chinese Officials Deny Hacking U.S. Environment-Monitoring Satellites 5 Comments Link to this comment Grunt 11/01/11 at 3:25 pm

First, it is easily possible to float to the surface UHF or VHF antenna and communicate with a satellite, while the submarine is several hundred feet below water.

Now add to this line of underwater conduit a floating laser and the problem is solved. Radio waves to guide the laser towards the satellite and laser communication to make it harder to listen in too.

Link to this comment scientific anomaly 11/01/11 at 3:39 pm

i think they should make a drone that can be launched from the sub while it is still hundreds of feet underwater that goes to the surface, communicates whatever it is the people are trying to convey, then self destructs so the enemies cant get it and hack it or something.

-Knock knock
-Who's there?
-The Doctor.
-Doctor Who?
-Yes

Link to this comment Vector13 11/01/11 at 7:16 pm

@scientific anomaly

Well, the problem is with someone intercepting the transmission itself, not necessarily at the transmission point. Just as well, there would need to be a drone for every time someone wanted to transmit or receive a message, and that would be pretty cumbersome :p

Link to this comment TheZomb 11/02/11 at 1:14 am

This article is incorrect in several points. First, the codes submarines use to communicate aka one time pad ciphers are impossible to "hack" or break individually, no matter of time or computing power will ever break one. The only way to break a one time pad cipher is to use two encrypted with the same key to break each other. This is the real reason the codes can be used once. The sentence "These are established ahead of time between a sub and its communications base, and each code is only used one time so that an enemy cannot crack a code and use it to decipher future communications." is incorrect in that respect.

Second, Quantum encryption has nothing to do with entanglement and bits are not encoded by polarity. Its called quantum encryption because it relies on a superposition of states in the light particles being sent (like schrodingers cat) and the Heisenberg uncertainty principle.

Each particle has a polarity, determined by the sender and unknown by the receiver. The receiver has to guess what polarity to use to decode a particle. If you guess wrong the data may not be encoded to bits correctly. You only get on chance to read a particle since reading it permanently changes its polarity. The sender and receiver then pick some at random and send them unencrypted, if they are the wrong polarity someone has tried to eavesdrop. The receiver then tells the sender all of his polarity guesses and then they use the bits from the correctly guessed polarities to form a one time pad cipher just like before.

Link to this comment gizmowiz 11/02/11 at 2:35 am

Wouldn't that in theory allow for an enemy to use detection systems to identify Photon signals being sent to a submerged sub and thereby LOCATE the sub EXCACTLY and blast it out of the water?

It seems plausible this could nullify the subs ability to play hide and seek.

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November 2011: Data Is Power

This month, we examine all the ways information is driving our future, from dating to crime to how we see the world.

Plus: turning your smartphone into a wallet, BMW's electric cars, and a space heater with no fan.

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Highly efficient oxygen catalyst found: Rechargeable batteries and hydrogen-fuel production could benefit

ScienceDaily (Oct. 28, 2011) — A team of researchers at MIT has found one of the most effective catalysts ever discovered for splitting oxygen atoms from water molecules -- a key reaction for advanced energy-storage systems, including electrolyzers, to produce hydrogen fuel and rechargeable batteries. This new catalyst liberates oxygen at more than 10 times the rate of the best previously known catalyst of its type.

The new compound, composed of cobalt, iron and oxygen with other metals, splits oxygen from water (called the Oxygen Evolution Reaction, or OER) at a rate at least an order of magnitude higher than the compound currently considered the gold standard for such reactions, the team says. The compound's high level of activity was predicted from a systematic experimental study that looked at the catalytic activity of 10 known compounds.

The team, which includes materials science and engineering graduate student Jin Suntivich, mechanical engineering graduate student Kevin J. May and professor Yang Shao-Horn, published their results in Science on Oct. 28.

The scientists found that reactivity depended on a specific characteristic: the configuration of the outermost electron of transition metal ions. They were able to use this information to predict the high reactivity of the new compound -- which they then confirmed in lab tests.

"We not only identified a fundamental principle" that governs the OER activity of different compounds, "but also we actually found this new compound" based on that principle, says Shao-Horn, the Gail E. Kendall (1978) Associate Professor of Mechanical Engineering and Materials Science and Engineering.

Many other groups have been searching for more efficient catalysts to speed the splitting of water into hydrogen and oxygen. This reaction is key to the production of hydrogen as a fuel to be used in cars; the operation of some rechargeable batteries, including zinc-air batteries; and to generate electricity in devices called fuel cells. Two catalysts are needed for such a reaction -- one that liberates the hydrogen atoms, and another for the oxygen atoms -- but the oxygen reaction has been the limiting factor in such systems.

Other groups, including one led by MIT's Daniel Nocera, have focused on similar catalysts that can operate -- in a so-called "artificial leaf" -- at low cost in ordinary water. But such reactions can occur with higher efficiency in alkaline solutions, which are required for the best previously known catalyst, iridium oxide, as well as for this new compound.

Shao-Horn and her collaborators are now working with Nocera, integrating their catalyst with his artificial leaf to produce a self-contained system to generate hydrogen and oxygen when placed in an alkaline solution. They will also be exploring different configurations of the catalyst material to better understand the mechanisms involved. Their initial tests used a powder form of the catalyst; now they plan to try thin films to better understand the reactions.

In addition, even though they have already found the highest rate of activity yet seen, they plan to continue searching for even more efficient catalyst materials. "It's our belief that there may be others with even higher activity," Shao-Horn says.

Jens Norskov, a professor of chemical engineering at Stanford University and director of the Suncat Center for Interface Science and Catalysis there, who was not involved in this work, says, "I find this an extremely interesting 'rational design' approach to finding new catalysts for a very important and demanding problem."

The research, which was done in collaboration with visiting professor Hubert A. Gasteiger (currently a professor at the Technische Universität München in Germany) and professor John B. Goodenough from the University of Texas at Austin, was supported by the U.S. Department of Energy's Hydrogen Initiative, the National Science Foundation, the Toyota Motor Corporation and the Chesonis Foundation.

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The above story is reprinted from materials provided by Massachusetts Institute of Technology. The original article was written by David L. Chandler, MIT News Office.

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Journal Reference:

J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, Y. Shao-Horn. A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science, 2011; DOI: 10.1126/science.1212858

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Printed protection: Low-cost paper-based wireless sensor could help detect explosive devices

ScienceDaily (Oct. 27, 2011) — Researchers at the Georgia Institute of Technology have developed a prototype wireless sensor capable of detecting trace amounts of a key ingredient found in many explosives.

The device, which employs carbon nanotubes and is printed on paper or paper-like material using standard inkjet technology, could be deployed in large numbers to alert authorities to the presence of explosives, such as improvised explosive devices (IEDs).

"This prototype represents a significant step toward producing an integrated wireless system for explosives detection," said Krishna Naishadham, a principal research scientist who is leading the work at the Georgia Tech Research Institute (GTRI). "It incorporates a sensor and a communications device in a small, low-cost package that could operate almost anywhere."

Other types of hazardous gas sensors are based on expensive semiconductor fabrication and gas chromatography, Naishadham said, and they consume more power, require human intervention, and typically do not operate at ambient temperatures. Furthermore, those sensors have not been integrated with communication devices such as antennas.

The wireless component for communicating the sensor information -- a resonant lightweight antenna -- was printed on photographic paper using inkjet techniques devised by Professor Manos Tentzeris of Georgia Tech's School of Electrical and Computer Engineering. Tentzeris is collaborating with Naishadham on development of the sensing device.

The sensing component, based on functionalized carbon nanotubes (CNTs), has been fabricated and tested for detection sensitivity by Xiaojuan (Judy) Song, a GTRI research scientist. The device relies on carbon-nanotube materials optimized by Song.

A presentation on this sensing technology was given in July at the IEEE Antennas and Propagation Symposium (IEEE APS) in Spokane, Wash., by Hoseon Lee, a Ph.D. student in ECE co-advised by Tentzeris and Naishadham. The paper received the Honorable Mention Award in the Best Student Paper competition at the symposium.

This is not the first inkjet-printed ammonia sensor that has been integrated with an antenna on paper, said Tentzeris. His group produced a similar integrated sensor last year in collaboration with the research group of C.P. Wong, who is Regents professor and Smithgall Institute Endowed Chair in the School of Materials Science and Engineering at Georgia Tech.

"The fundamental difference is that this newest CNT sensor possesses dramatically improved sensitivity to miniscule ammonia concentrations," Tentzeris said. "That should enable the first practical applications to detect trace amounts of hazardous gases in challenging operational environments using inkjet-printed devices."

Tentzeris explained that the key to printing components, circuits and antennas lies in novel "inks" that contain silver nanoparticles in an emulsion that can be deposited by the printer at low temperatures -- around 100 degrees Celsius. A process called sonication helps to achieve optimal ink viscosity and homogeneity, enabling uniform material deposition and permitting maximum operating effectiveness for paper-based components.

"Ink-jet printing is low-cost and convenient compared to other technologies such as wet etching," Tentzeris said. "Using the proper inks, a printer can be used almost anywhere to produce custom circuits and components, replacing traditional clean-room approaches."

Low-cost materials -- such as heavy photographic paper or plastics like polyethylene terephthalate -- can be made water resistant to ensure greater reliability, he added. Inkjet component printing can also use flexible organic materials, such as liquid crystal polymer (LCP), which are known for their robustness and weather resistance. The resulting components are similar in size to conventional components but can conform and adhere to almost any surface.

Naishadham explained that the same inkjet techniques used to produce RF components, circuits and antennas can also be used to deposit the functionalized carbon nanotubes used for sensing. These nanoscale cylindrical structures -- about one-billionth of a meter in diameter, or 1/50,000th the width of a human hair -- are functionalized by coating them with a conductive polymer that attracts ammonia, a major ingredient found in many IEDs.

Sonication of the functionalized carbon nanotubes produces a uniform water-based ink that can be printed side-by-side with RF components and antennas to produce a compact wireless sensor node.

"The optimized carbon nanotubes are applied as a sensing film, with specific functionalization designed for a particular gas or analyte," Song said. "The GTRI sensor detects trace amounts of ammonia usually found near explosive devices, and it can also be designed to detect similar gases in household, healthcare and industrial environments at very low concentration levels."

The sensor has been designed to detect ammonia in trace amounts -- as low as five parts per million, Naishadham said.

The resulting integrated sensing package can potentially detect the presence of trace explosive materials at a distance, without endangering human lives. This approach, called standoff detection, involves the use of RF technology to identify explosive materials at a relatively safe distance. The GTRI team has designed the device to send an alert to nearby personnel when it detects ammonia.

The wireless sensor nodes require relatively low power, which could come from a number of technologies including thin-film batteries, solar cells or power-scavenging and energy-harvesting techniques. In collaboration with Tentzeris's and Wong's groups, GTRI is investigating ways to make the sensor operate passively, without any power consumption.

"We are focusing on providing standoff detection for those engaged in military or humanitarian missions and other hazardous situations," Naishadham said. "We believe that it will be possible, and cost-effective, to deploy large numbers of these detectors on vehicles or robots throughout a military engagement zone."

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The above story is reprinted from materials provided by Georgia Institute of Technology Research News. The original article was written by Rick Robinson.

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New hybrid technology could bring 'quantum information systems'

ScienceDaily (Oct. 28, 2011) — The merging of two technologies under development -- plasmonics and nanophotonics -- is promising the emergence of new "quantum information systems" far more powerful than today's computers.

The technology hinges on using single photons -- the tiny particles that make up light -- for switching and routing in future computers that might harness the exotic principles of quantum mechanics.

The quantum information processing technology would use structures called "metamaterials," artificial nanostructured media with exotic properties.

The metamaterials, when combined with tiny "optical emitters," could make possible a new hybrid technology that uses "quantum light" in future computers, said Vladimir Shalaev, scientific director of nanophotonics at Purdue University's Birck Nanotechnology Center and a distinguished professor of electrical and computer engineering.

The concept is described in an article published on October 28 in the journal Science. The article appeared in the magazine's Perspectives section and was written by Shalaev and Zubin Jacob, an assistant professor of electrical and computer engineering at the University of Alberta, Canada.

"A seamless interface between plasmonics and nanophotonics could guarantee the use of light to overcome limitations in the operational speed of conventional integrated circuits," Shalaev said.

Researchers are proposing the use of "plasmon-mediated interactions," or devices that manipulate individual photons and quasiparticles called plasmons that combine electrons and photons.

One of the approaches, pioneered at Harvard University, is a tiny nanowire that couples individual photons and plasmons. Another approach is to use hyperbolic metamaterials, suggested by Jacob; Igor Smolyaninov, a visiting research scientist at the University of Maryland; and Evgenii Narimanov, an associate professor of electrical and computer engineering at Purdue. Quantum-device applications using building blocks for such hyperbolic metamaterials have been demonstrated in Shalaev's group.

"We would like to record and read information with single photons, but we need a very efficient source of single photons," Shalaev said. "The challenge here is to increase the efficiency of generation of single photons in a broad spectrum, and that is where plasmonics and metamaterials come in."

Today's computers work by representing information as a series of ones and zeros, or binary digits called "bits."

Computers based on quantum physics would have quantum bits, or "qubits," that exist in both the on and off states simultaneously, dramatically increasing the computer's power and memory. Quantum computers would take advantage of a strange phenomenon described by quantum theory called "entanglement." Instead of only the states of one and zero, there are many possible "entangled quantum states" in between one and zero.

An obstacle in developing quantum information systems is finding a way to preserve the quantum information long enough to read and record it. One possible solution might be to use diamond with "nitrogen vacancies," defects that often occur naturally in the crystal lattice of diamonds but can also be produced by exposure to high-energy particles and heat.

"The nitrogen vacancy in diamond operates in a very broad spectral range and at room temperature, which is very important," Shalaev said.

The work is part of a new research field, called diamond photonics. Hyperbolic metamaterials integrated with nitrogen vacancies in diamond are expected to work as efficient "guns" of single photons generated in a broad spectral range, which could bring quantum information systems, he said.

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Journal Reference:

Z. Jacob, V. M. Shalaev. Plasmonics Goes Quantum. Science, 2011; 334 (6055): 463 DOI: 10.1126/science.1211736

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Giant flakes make graphene oxide gel: Discovery could boost metamaterials, high-strength fibers

ScienceDaily (Oct. 20, 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.

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.

"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 Institute for Complex Adaptive Matter, the Colorado Renewable and Sustainable Energy Initiative, the National Science Foundation, the Air Force Research Lab, the Air Force Office of Scientific Research, the Welch Foundation, the U.S. Army Corps of Engineers Environmental Quality and Installation Program and M-I Swaco supported the research.

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Journal Reference:

Budhadipta Dan, Natnael Behabtu, Angel Martinez, Julian S. Evans, Dmitry V. Kosynkin, James M. Tour, Matteo Pasquali, Ivan I. Smalyukh. Liquid crystals of aqueous, giant graphene oxide flakes. Soft Matter, 2011; DOI: 10.1039/C1SM06418E

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Chiral metal surfaces may help to manufacture pharmaceuticals; Novel approach could be used in pharmaceutical drug synthesis

ScienceDaily (Oct. 26, 2011) — New research shows how metal surfaces that lack mirror symmetry could provide a novel approach towards manufacturing pharmaceuticals.

These 'intrinsically chiral' metal surfaces offer potential new ways to control chiral chemistry, pointing to the intriguing possibility of using heterogeneous catalysis in drug synthesis. Such surfaces could also become the basis of new biosensor technologies.

A chiral object, such as your hand, is one that cannot be superposed on its mirror image. Chirality is fundamental in biochemistry. The building blocks of life -- amino acids and sugars -- are chiral molecules: their molecular structures can exist in either "left-handed" or "right-handed" forms (or "enantiomers").

A living organism may respond differently to the two enantiomers of a chiral substance. This is crucially important in the case of pharmaceutical drugs, where the therapeutic effect is often tied strongly to just one enantiomer of the drug molecule. Controlling chirality is therefore vital in pharmaceutical synthesis.

Research into controlling chiral synthesis focuses mainly on using homogeneous catalysts, where the catalyst is in the same phase as the reactants and products, such as a liquid added to a liquid-phase reaction. However, this poses significant practical challenges in recovering the valuable catalyst material from the mixture. To avoid this problem, an attractive alternative would be heterogeneous catalysis over a solid surface -- the type of catalysis used in catalytic converters in car exhaust systems, as well as in industrial Haber-Bosch synthesis of ammonia and Fischer-Tropsch synthesis of synthetic fuel, for example. The question then is how to achieve enantiomer-specific effects at a surface.

To help answer this question, scientists at the University of Cambridge have been probing the spontaneous self-organization of a simple chiral amino acid, alanine, into regular molecular arrays on copper single-crystal surfaces. Thanks to a powerful scanning tunnelling microscope, capable of resolving individual atoms and molecules, their work is revealing the various manifestations of chirality that occur, giving important clues to how they arise, and how they might be controlled and exploited.

Dr Stephen Driver, of the Department of Chemistry at the University of Cambridge, who led the experimental work, said: "We set out to investigate two distinct scenarios. In one scenario, the surface is non-chiral, so any chirality that we see can only arise from the chirality of the alanine molecule. In the other scenario, we move to a surface that is intrinsically chiral. Now the question becomes: do the two enantiomers of alanine behave differently on this chiral surface?"

On the non-chiral surface, the researchers found that alanine can self-organise into either of two patterns. In one of these, the self-organisation is driven by hydrogen bonding between the molecules, while the chiral centre has no discernable impact on the regular array. In the other structure, a network of long-range chiral boundaries punctuates the array, and the boundary chirality switches with molecular chirality.

Driver explained: "The implication is that the chiral centre is having a direct influence on the packing of two alanine neighbours at the boundary, and that the chirality of this pair propagates to the next pair and the next and so on, so that the chiral boundary is built up over a long range."

The chiral surface is created simply by choosing a surface orientation that lies away from any of the bulk mirror symmetry planes of the metal crystal. When the researchers added alanine, they found that the surface changes its local orientation, forming nanometre-scale facets. The two enantiomers of alanine self-organise into different chiral patterns: a strong, enantiomer-specific structural effect. This "proof of principle" could potentially be exploited in chiral recognition, in chiral synthesis (forming a chiral product from non-chiral reactants), and in chiral separations.

Driver added: "It looks like alanine can shape a comfortable, chiral bonding site for itself. The copper surface has the flexibility to adapt itself to the shape of the alanine molecule, and this shape is different for the two different molecular enantiomers."

The results imply that certain surface orientations will form stable, ordered structures with one molecular enantiomer but not the other: exactly the right conditions to promote chiral chemical effects.

Professor Sir David King, former Chief Scientific Advisor to the UK Government and current Director of the Smith School of Enterprise and the Environment at Oxford, brought together the team carrying out this research. "These results are very exciting," said King. "Tailoring the right surface to the right molecule should lead to strong enantiospecific effects. We see a real basis here for a breakthrough technology in the pharmaceuticals sector. It's something that pharma companies should be taking a close interest in."

The Cambridge team's findings are published in Topics in Catalysis.

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Journal Reference:

Marian L. Clegg, Leonardo Morales de la Garza, Sofia Karakatsani, David A. King, Stephen M. Driver. Chirality in Amino Acid Overlayers on Cu Surfaces. Topics in Catalysis, 2011; DOI: 10.1007/s11244-011-9758-y

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.

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High-quality white light produced by four-color laser source; Diode lasers could challenge LEDs for home and industrial lighting supremacy

ScienceDaily (Oct. 26, 2011) — The human eye is as comfortable with white light generated by diode lasers as with that produced by increasingly popular light-emitting diodes (LEDs), according to tests conceived at Sandia National Laboratories.

Both technologies pass electrical current through material to generate light, but the simpler LED emits lights only through spontaneous emission. Diode lasers bounce light back and forth internally before releasing it.

The finding is important because LEDs -- widely accepted as more efficient and hardier replacements for century-old tungsten incandescent bulb technology -- lose efficiency at electrical currents above 0.5 amps. However, the efficiency of a sister technology -- the diode laser -- improves at higher currents, providing even more light than LEDs at higher amperages.

"What we showed is that diode lasers are a worthy path to pursue for lighting," said Sandia researcher Jeff Tsao, who proposed the comparative experiment. "Before these tests, our research in this direction was stopped before it could get started. The typical response was, 'Are you kidding? The color rendering quality of white light produced by diode lasers would be terrible.' So finally it seemed like, in order to go further, one really had to answer this very basic question first."

Little research had been done on diode lasers for lighting because of a widespread assumption that human eyes would find laser-based white light unpleasant. It would comprise four extremely narrow-band wavelengths -- blue, red, green, and yellow -- and would be very different from sunlight, for example, which blends a wide spectrum of wavelengths with no gaps in between. Diode laser light is also ten times narrower than that emitted by LEDs.

The tests -- a kind of high-tech market research -- took place at the University of New Mexico's Center for High Technology Materials. Forty volunteers were seated, one by one, before two near-identical scenes of fruit in bowls, housed in adjacent chambers. Each bowl was randomly illuminated by warm, cool, or neutral white LEDs, by a tungsten-filament incandescent light bulb, or by a combination of four lasers (blue, red, green, yellow) tuned so their combination produced a white light.

The experiment proceeded like an optometrist's exam: the subjects were asked: Do you prefer the left picture, or the right? All right, how about now?

The viewers were not told which source provided the illumination. They were instructed merely to choose the lit scene with which they felt most comfortable. The pairs were presented in random order to ensure that neither sequence nor tester preconceptions played roles in subject choices, but only the lighting itself. The computer program was written, and the set created, by Alexander Neumann, a UNM doctoral student of CHTM director Steve Brueck.

Each participant, selected from a variety of age groups, was asked to choose 80 times between the two changing alternatives, a procedure that took ten to twenty minutes, said Sandia scientist Jonathan Wierer, who helped plan, calibrate and execute the experiments. Five results were excluded when the participants proved to be color-blind. The result was that there was a statistically significant preference for the diode-laser-based white light over the warm and cool LED-based white light, Wierer said, but no statistically significant preference between the diode-laser-based and either the neutral LED-based or incandescent white light.

The results probably won't start a California gold rush of lighting fabricators into diode lasers, said Tsao, but they may open a formerly ignored line of research. Diode lasers are slightly more expensive to fabricate than LEDs because their substrates must have fewer defects than those used for LEDs. Still, he said, such substrates are likely to become more available in the future because they improve LED performance as well.

Also, while blue diode lasers have good enough performance that the automaker BMW is planning their use in its vehicles' next-generation white headlights, performance of red diode lasers is not as good, and yellow and green have a ways to go before they are efficient enough for commercial lighting opportunities.

Still, says Tsao, a competition wouldn't have to be all or nothing. Instead, he said, a cooperative approach might use blue and red diode lasers with yellow and green LEDs. Or blue diode lasers could be used to illuminate phosphors -- the technique currently used by fluorescent lights and the current generation of LED-based white light -- to create desirable shades of light.

The result makes possible still further efficiencies for the multibillion dollar lighting industry. The so-called ''smart beams'' can be adjusted on site for personalized color renderings for health reasons and, because they are directional, also can provide illumination precisely where it's wanted.

Colorimetric and experimental guidance was provided by the National Institute of Standards and Technology.

The research was published in the July 1 issue of Optics Express.

This work was conducted as part of the Solid-State Lighting Science Energy Frontier Research Center, funded by the U.S. DOE Office of Science.

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Journal Reference:

A. Neumann, J. J. Wierer, W. Davis, Y. Ohno, S. R. J. Brueck, J.Y. Tsao. Four-color laser white illuminant demonstrating high color-rendering quality. Optics Express, 2011; 19 (S4): A982 DOI: 10.1364/OE.19.00A982

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'Microring' device could aid in future optical technologies

ScienceDaily (Oct. 20, 2011) — Researchers at Purdue University and the National Institute of Standards and Technology (NIST) have created a device small enough to fit on a computer chip that converts continuous laser light into numerous ultrashort pulses, a technology that might have applications in more advanced sensors, communications systems and laboratory instruments.

"These pulses repeat at very high rates, corresponding to hundreds of billions of pulses per second," said Andrew Weiner, the Scifres Family Distinguished Professor of Electrical and Computer Engineering.

The tiny "microring resonator" is about 80 micrometers, or the width of a human hair, and is fabricated from silicon nitride, which is compatible with silicon material widely used for electronics. Infrared light from a laser enters the chip through a single optical fiber and is directed by a structure called a waveguide into the microring.

The pulses have many segments corresponding to different frequencies, which are called "comb lines" because they resemble teeth on a comb when represented on a graph.

By precisely controlling the frequency combs, researchers hope to create advanced optical sensors that detect and measure hazardous materials or pollutants, ultrasensitive spectroscopy for laboratory research, and optics-based communications systems that transmit greater volumes of information with better quality while increasing bandwidth. The comb technology also has potential for a generation of high-bandwidth electrical signals with possible applications in wireless communications and radar.

The light originates from a continuous-wave laser, also called a single-frequency laser.

"This is a very common type of laser," Weiner said. "The intensity of this type of laser is constant, not pulsed. But in the microring the light is converted into a comb consisting of many frequencies with very nice equal spacing. The microring comb generator may serve as a competing technology to a special type of laser called a mode-locked laser, which generates many frequencies and short pulses. One advantage of the microrings is that they can be very small."

The laser light undergoes "nonlinear interaction" while inside the microring, generating acomb of new frequencies that is emitted out of the device through another optical fiber.

"The nonlinearity is critical to the generation of the comb," said doctoral student Fahmida Ferdous. "With the nonlinearity we obtain a comb of many frequencies, including the original one, and the rest are new ones generated in the microring."

Findings are detailed in a research paper appearing online this month in the journal Nature Photonics. The paper is scheduled for publication in the Dec. 11 issue.

Although other researchers previously have demonstrated the comb-generation technique, the team is the first to process the frequencies using "optical arbitrary waveform technology," pioneered by Purdue researchers led by Weiner. The researchers were able to control the amplitude and phase of each spectral line, learning that there are two types of combs -- "highly coherent" and "partially coherent" -- opening up new avenues to study the physics of the process.

"In future investigations, the ability to extract the phase of individual comb lines may furnish clues into the physics of the comb-generation process," Ferdous said. "Future work will include efforts to create devices that have the proper frequency for commercial applications."

The silicon-nitride device was fabricated by a team led by Houxun Miao, a researcher at NIST's Center for Nanoscale Science and Technology and the Maryland Nanocenter at the University of Maryland. Some of the work was performed at the Birck Nanotechnology Center in Purdue's Discovery Park, and experiments demonstrating short-pulse generation were performed in Purdue's School of Electrical and Computer Engineering.

The effort at Purdue is funded in part by the National Science Foundation and the Naval Postgraduate School.

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The above story is reprinted from materials provided by Purdue University. The original article was written by Emil Venere.

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Journal Reference:

Fahmida Ferdous, Houxun Miao, Daniel E. Leaird, Kartik Srinivasan, Jian Wang, Lei Chen, Leo Tom Varghese, Andrew M. Weiner. Spectral line-by-line pulse shaping of on-chip microresonator frequency combs. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.255

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

'Microring' device could aid in future optical technologies

ScienceDaily (Oct. 20, 2011) — Researchers at Purdue University and the National Institute of Standards and Technology (NIST) have created a device small enough to fit on a computer chip that converts continuous laser light into numerous ultrashort pulses, a technology that might have applications in more advanced sensors, communications systems and laboratory instruments.

"These pulses repeat at very high rates, corresponding to hundreds of billions of pulses per second," said Andrew Weiner, the Scifres Family Distinguished Professor of Electrical and Computer Engineering.

The tiny "microring resonator" is about 80 micrometers, or the width of a human hair, and is fabricated from silicon nitride, which is compatible with silicon material widely used for electronics. Infrared light from a laser enters the chip through a single optical fiber and is directed by a structure called a waveguide into the microring.

The pulses have many segments corresponding to different frequencies, which are called "comb lines" because they resemble teeth on a comb when represented on a graph.

By precisely controlling the frequency combs, researchers hope to create advanced optical sensors that detect and measure hazardous materials or pollutants, ultrasensitive spectroscopy for laboratory research, and optics-based communications systems that transmit greater volumes of information with better quality while increasing bandwidth. The comb technology also has potential for a generation of high-bandwidth electrical signals with possible applications in wireless communications and radar.

The light originates from a continuous-wave laser, also called a single-frequency laser.

"This is a very common type of laser," Weiner said. "The intensity of this type of laser is constant, not pulsed. But in the microring the light is converted into a comb consisting of many frequencies with very nice equal spacing. The microring comb generator may serve as a competing technology to a special type of laser called a mode-locked laser, which generates many frequencies and short pulses. One advantage of the microrings is that they can be very small."

The laser light undergoes "nonlinear interaction" while inside the microring, generating acomb of new frequencies that is emitted out of the device through another optical fiber.

"The nonlinearity is critical to the generation of the comb," said doctoral student Fahmida Ferdous. "With the nonlinearity we obtain a comb of many frequencies, including the original one, and the rest are new ones generated in the microring."

Findings are detailed in a research paper appearing online this month in the journal Nature Photonics. The paper is scheduled for publication in the Dec. 11 issue.

Although other researchers previously have demonstrated the comb-generation technique, the team is the first to process the frequencies using "optical arbitrary waveform technology," pioneered by Purdue researchers led by Weiner. The researchers were able to control the amplitude and phase of each spectral line, learning that there are two types of combs -- "highly coherent" and "partially coherent" -- opening up new avenues to study the physics of the process.

"In future investigations, the ability to extract the phase of individual comb lines may furnish clues into the physics of the comb-generation process," Ferdous said. "Future work will include efforts to create devices that have the proper frequency for commercial applications."

The silicon-nitride device was fabricated by a team led by Houxun Miao, a researcher at NIST's Center for Nanoscale Science and Technology and the Maryland Nanocenter at the University of Maryland. Some of the work was performed at the Birck Nanotechnology Center in Purdue's Discovery Park, and experiments demonstrating short-pulse generation were performed in Purdue's School of Electrical and Computer Engineering.

The effort at Purdue is funded in part by the National Science Foundation and the Naval Postgraduate School.

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

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Story Source:

The above story is reprinted from materials provided by Purdue University. The original article was written by Emil Venere.

Note: ScienceDaily reserves the right to edit materials for content and length. For further information, please contact the source cited above.

Journal Reference:

Fahmida Ferdous, Houxun Miao, Daniel E. Leaird, Kartik Srinivasan, Jian Wang, Lei Chen, Leo Tom Varghese, Andrew M. Weiner. Spectral line-by-line pulse shaping of on-chip microresonator frequency combs. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.255

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

Smartphone Accelerometers Could Be Used To Eavesdrop On Nearby Devices

Smartphone Accelerometers Could Be Used To Eavesdrop On Nearby Devices | Popular Science@import "/files/css/1857af3413d9ad8bd2f9d3926af8ec39.css";@import "/files/css/33f6b7ecb4513ed2fe6c670880a27187.css"; home Login/Register Newsletter Subscribe RSS GadgetsComputersCamerasSmartphonesVideo GamesCarsConceptsHybridsElectric CarsScienceFuture of the EnvironmentEnergyHealthPopSci Eco TourTechnologyMilitaryAviationSpaceRobotsEngineeringDIYProjectsHacksToolsAuto DIYMore From Our Partner: Toolmonger GalleriesVideosColumnsThe GrouseSex FilesGreen Dream Innovation ChallengesHow It WorksFeatures Tweet Digg Smartphone Accelerometers Could Be Used To Eavesdrop On Nearby Devices By Rebecca Boyle Posted 10.19.2011 at 11:07 am 3 Comments
SpyPhone Patrick Traynor shows off the "SpiPhone" app he created to tap keystrokes with phone accelerometers. Georgia Tech

As you logged in to write a comment this morning, think about where your smartphone was sitting. Was it next to your keyboard, where you could ensure you didn’t miss any notifications? If so, your phone could track everything you wrote. It could use the accelerometer to detect keyboard vibrations, deciphering every word of your insightful anonymous commentary. A hacker could conceivably use it to find out everything you write, with up to 80 percent accuracy, researchers say.

Here’s how it would work: An accelerometer samples a phone’s vibration about 100 times per second, so it would be able to detect pairs of keystrokes, according to a Georgia Tech news release about this research. It would model “keyboard events” and determine where the pairs of keys are located on the keyboard, and how far apart they are. Then it would compare the results against a dictionary the researchers developed for this demonstration. The dictionary defines words based on their locations on a typical QWERTY keyboard, like left/right or near/far. So in Georgia Tech’s example, the word “canoe” would translate to c-a, a-n, n-o, o-e possibilities. That works out to left-left-near, and so on. The location code is checked against the dictionary, and it turns up “canoe” as the most likely word.

Related ArticlesA DIY UAV That Hacks Wi-Fi Networks, Cracks Passwords, and Poses as a Cell Phone TowerYour iPhone Keeps a Secret Log of Everywhere You Go, Security Experts FindLast Shuttle Mission Will Carry iPhones to the Space StationTagsTechnology, Rebecca Boyle, accelerometer, iphone, keystrokes, malware, smartphones, spying, spyware, typingUsing a dictionary of about 58,000 words, the researchers were able to decipher typing with about 80 percent accuracy.

Researchers have studied smartphone as spy-phone before, using the phones’ microphones to sample vibrations and decipher keystrokes. But they are very sensitive and so a much more obvious security risk — many smartphones now will ask users to give a new app permission to access sensors like microphones. Not accelerometers, however. So how would an app with this capability get onto your smartphone? The authors of this study say it would probably be included as malware on an innocent-seeming app. Then when the phone is placed next to a keyboard, the malware turns on and starts listening, sending data to a hacker who wants to know what you have to say.

Granted, this all works only if your phone is pretty proximate to your keyboard, admits Patrick Traynor, an assistant professor in Georgia Tech’s School of Computer Science who was involved in the study. So just keep it elsewhere on your desk or in your bag. Plus it’s unlikely that anyone has to worry about this right now, he added.

“This was really hard to do. But could people do it if they really wanted to? We think yes.”

The work is being presented Thursday at the ACM Conference on Computer and Communications Security in Chicago.

Previous Article: Wearable Projector and Kinect-Like Camera Turns Any Object Into a TouchscreenNext Article: Germany's ROSAT Satellite Could Come Crashing Down Somewhere On Earth As Soon As Friday 3 Comments Link to this comment Midoman 10/19/11 at 11:39 am

SuperPhones take Phreaking to a whole new level.

Link to this comment Q 10/19/11 at 12:42 pm

The CIA, FBI, others and other countries have been doing this for years, but with big large electronics. I suppose what is novel today it's now an App.

Besides Governmental offices locking down what type of cell phones can be brought into their areas, this also applies to civilian companies.

This will open the door to gaining access to logins and passwords, everywhere.

Just listen and record the clicks several days in a row. Will an average 80% copy quality; it should only take a few days of listening to find the login and password.

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October 2011: The Search for Alien Life

This month, we examine all the ways we're looking for extraterrestrial life, within our solar system and beyond.

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