Site of the day: http://www.wired.com/
Paper.
Authors: Li, Mo ; Pernice, W H P ; Tang, H X
The optical binding forces between guided lightwaves in dielectric waveguides can be either repulsive or attractive. So far only attractive force has been observed. Here we experimentally demonstrate a bipolar optical force between coupled nanomechanical waveguides. Both attractive and repulsive optical forces are obtained. The sign of the force can be switched reversibly by tuning the relative phase of the interacting lightwaves. This tunable, bipolar interaction forms the foundation for the operation of a new class of light force devices and circuits.
Links:
http://www.nature.com/nphoton/journal/v3/n8/abs/nphoton.2009.116.html
http://arxiv.org/ftp/arxiv/papers/0903/0903.5117.pdf
Saturday, March 27, 2010
Light twists rigid structures in unexpected nanotech finding
After 72 hours of exposure to ambient light, strands of nanoparticles twisted and bunched together. Credit: Nicholas Kotov
Site of the day: http://www.wired.com/
ANN ARBOR, Mich.—In findings that took the experimenters three years to believe, University of Michigan engineers and their collaborators have demonstrated that light itself can twist ribbons of nanoparticles.
The results are published in the current edition of Science.
Matter readily bends and twists light. That's the mechanism behind optical lenses and polarizing 3-D movie glasses. But the opposite interaction has rarely been observed, said Nicholas Kotov, principal investigator on the project. Kotov is a professor in the departments of Chemical Engineering, Biomedical Engineering and Materials Science and Engineering.
While light has been known to affect matter on the molecular scale—bending or twisting molecules a few nanometers in size—it has not been observed causing such drastic mechanical twisting to larger particles. The nanoparticle ribbons in this study were between one and four micrometers long. A micrometer is one-millionth of a meter.
"I didn't believe it at the beginning," Kotov said. "To be honest, it took us three and a half years to really figure out how photons of light can lead to such a remarkable change in rigid structures a thousand times bigger than molecules."
Kotov and his colleagues had set out in this study to create "superchiral" particles—spirals of nano-scale mixed metals that could theoretically focus visible light to specks smaller than its wavelength. Materials with this unique "negative refractive index" could be capable of producing Klingon-like invisibility cloaks, said Sharon Glotzer, a professor in the departments of Chemical Engineering and Materials Science and Engineering who was also involved in the experiments. The twisted nanoparticle ribbons are likely to lead to the superchiral materials, the professors say.
To begin the experiment, the researchers dispersed nanoparticles of cadmium telluride in a water-based solution. They checked on them intermittently with powerful microscopes. After about 24 hours under light, the nanoparticles had assembled themselves into flat ribbons. After 72 hours, they had twisted and bunched together in the process.
But when the nanoparticles were left in the dark, distinct, long, straight ribbons formed.
"We discovered that if we make flat ribbons in the dark and then illuminate them, we see a gradual twisting, twisting that increases as we shine more light," Kotov said. "This is very unusual in many ways."
The light twists the ribbons by causing a stronger repulsion between nanoparticles in them.
The twisted ribbon is a new shape in nanotechnology, Kotov said. Besides superchiral materials, he envisions clever applications for the shape and the technique used to create I it. Sudhanshu Srivastava, a postdoctoral researcher in his lab, is trying to make the spirals rotate.
"He's making very small propellers to move through fluid—nanoscale submarines, if you will," Kotov said. "You often see this motif of twisted structures in mobility organs of bacteria and cells."
The nanoscale submarines could conceivably be used for drug-delivery and in microfluidic systems that mimic the body for experiments.
This newly-discovered twisting effect could also lead to microelectromechanical systems that are controlled by light. And it could be utilized in lithography, or microchip production.
Glotzer and Aaron Santos, a postdoctoral researcher in her lab, performed computer simulations that helped Kotov and his team better understand how the ribbons form. The simulations showed that under certain circumstances, the complex combination of forces between the tetrahedrally-shaped nanoparticles could conspire to produce ribbons of just the width observed in the experiments. A tetrahedron is a pyramid-shaped, three-dimensional polyhedron.
"The precise balance of forces leading to the self-assembly of ribbons is very revealing," Glotzer said. "It could be used to stabilize other nanostructures made of non-spherical particles. It's all about how the particles want to pack themselves."
Other collaborators include researchers from the University of Leeds in the UK, Chungju National University in Korea, Argonne National Laboratory, Pusan National University in Korea and Jiangnan University in China.
The paper is titled Light-Controlled Self-Assembly of Semiconductor Nanoparticles into Twisted Ribbons. The research is funded by the Air Force Office of Scientific Research, the Korea Science and Engineering Foundation and the U.S. Department of Energy.
(http://www.ns.umich.edu/htdocs/releases/story.php?id=7573)
Friday, March 5, 2010
Diamonds And Quantum Science
A diamond-based nanowire device. Researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely. Illustrated by Jay Penni.
Site of the day: http://nanotechweb.org/
Digging Deep Into Diamonds, Physicists Advance Quantum Science And Technology
By creating diamond-based nanowire devices, a team at Harvard has taken another step towards making applications based on quantum science and technology possible.
The new device offers a bright, stable source of single photons at room temperature, an essential element in making fast and secure computing with light practical.
The finding could lead to a new class of nanostructured diamond devices suitable for quantum communication and computing, as well as advance areas ranging from biological and chemical sensing to scientific imaging.
Published in the February 14th issue of Nature Nanotechnology, researchers led by Marko Loncar, Assistant Professor of Electrical Engineering at the Harvard School of Engineering and Applied Sciences (SEAS), found that the performance of a single photon source based on a light emitting defect (color center) in diamond could be improved by nanostructuring the diamond and embedding the defect within a diamond nanowire.
Scientists, in fact, first began exploiting the properties of natural diamonds after learning how to manipulate the electron spin, or intrinsic angular momentum, associated with the nitrogen vacancy (NV) color center of the gem. The quantum (qubit) state can be initialized and measured using light.
The color center "communicates" by emitting and absorbing photons. The flow of photons emitted from the color center provides a means to carry the resulting information, making the control, capture, and storage of photons essential for any kind of practical communication or computation. Gathering photons efficiently, however, is difficult since color-centers are embedded deep inside the diamond.
"This presents a major problem if you want to interface a color center and integrate it into real-world applications," explains Loncar. "What was missing was an interface that connects the nano-world of a color center with macro-world of optical fibers and lenses."
The diamond nanowire device offers a solution, providing a natural and efficient interface to probe an individual color center, making it brighter and increasing its sensitivity. The resulting enhanced optical properties increases photon collection by nearly a factor of ten relative to natural diamond devices.
"Our nanowire device can channel the photons that are emitted and direct them in a convenient way," says lead-author Tom Babinec, a graduate student at SEAS.
Further, the diamond nanowire is designed to overcome hurdles that have challenged other state-of-the-art systems—such as those based on fluorescent dye molecules, quantum dots, and carbon nanotubes—as the device can be readily replicated and integrated with a variety of nano-machined structures.
The researchers used a top-down nanofabrication technique to embed color centers into a variety of machined structures. By creating large device arrays rather than just "one-of-a-kind" designs, the realization of quantum networks and systems, which require the integration and manipulation of many devices in parallel, is more likely.
"We consider this an important step and enabling technology towards more practical optical systems based on this exciting material platform," says Loncar. "Starting with these synthetic, nanostructured diamond samples, we can start dreaming about the diamond-based devices and systems that could one day lead to applications in quantum science and technology as well as in sensing and imaging."
(http://www.physorg.com/news185372725.html)
Other articles:
http://www.popularmechanics.co.za/content/news/singlepage.asp?key=926
http://www.nature.com/nnano/journal/v5/n3/abs/nnano.2010.6.html
Thursday, March 4, 2010
Junctionless transistor makes its debut
Site of the day: http://fooledbyrandomness.com/
Researchers in Ireland have succeeded in making the first junctionless transistor ever. The device, which resembles a structure first proposed way back in 1925 but not realized until now, has nearly "ideal" electrical properties, according to the team. It could potentially operate faster and use less power than any conventional transistor on the market today.
Transistors are the fundamental building blocks of modern electronic devices – and all existing transistors contain semiconductor junctions. The most common type of junction is the p–n junction, which is formed by the contact between a p-type piece of silicon – doped with impurities to create an excess of holes – and an n-type piece of silicon, doped to create an excess of electrons. Other junctions include the heterojunction, which is simply a p–n junction containing two different semiconductors, and the Schottky junction between metal and semiconductor.
The number of transistors on a single silicon microchip has been increasing exponentially since the early 1970s, and has gone up from a few hundred to over several billion today. As a result, transistors are becoming so tiny that it is becoming increasingly difficult to create high-quality junctions. In particular, it is very difficult to change the doping concentration of a material over distances shorter than about 10 nm. Junctionless transistors could therefore help chipmakers continue to make smaller and smaller devices.
Patented in 1925
Now, Jean-Pierre Colinge and colleagues at the Tyndall National Institute of University College Cork have dispensed with the very idea of a junction and instead have turned to a concept first proposed in 1925 by Austrian-Hungarian physicist Julius Edgar Lilienfield. Patented under the title "Device for controlling electric current", it is a simple resistor and contains a gate that controls the density of electrons and holes, and thus current flow.
The team's version of the device consists of a silicon nanowire in which current flow is perfectly controlled by a silicon gate that is separated from the nanowire by a thin insulating layer. The structure itself is very simple, looking a bit like a telephone cable that is fixed to a surface by a plastic clip (see figure). Crucially, there is no need to alter the doping over very short distances. Instead, the entire silicon nanowire is heavily n-doped, making it an excellent conductor. However, the gate is p-doped and its presence has the effect of depleting the number of electrons in the region of the nanowire under the gate.
If a voltage is simply applied along the nanowire, current cannot flow through this depleted region. According to Colinge, this region "squeezes" the current in the nanowire in the same way as the flow of water in a hose is stopped by squeezing it. However, if a voltage is applied to the gate, the squeezing effect is reduced and current can flow. The team also made a similar device with a p-type nanowire and n-type gate.
The most perfect of transistors
The structure is simple to build, even at the nanoscale, which means reduced costs compared with conventional junction fabrication technologies, which are becoming more and more complex. The device also has near-ideal electrical properties, adds Colinge, and behaves like the most perfect of transistors. This means that it hardly suffers at all from current leakage – the bane of conventional devices – and so could potentially operate faster and using less energy.
The Tyndall team says that it is now talking to some of the world's leading semiconductor companies to further develop and possibly license its technology.
"Although the idea of a transistor without junctions may seem quite unorthodox, the word "transistor" does not imply the presence of junctions, per se," write the researchers in Nature Nanotechnology, where the work was published. "A transistor is a solid-state device that controls current flow and the word transistor is a contraction of 'trans- resistor'."
(http://physicsworld.com/cws/article/news/41881)
Bloom Energy unveils fuel cell of the future
Site of the day: http://fooledbyrandomness.com/
A man stands next to a Bloom Energy server called a "Bloom Box" during a product launch at the eBay headquarters in San Jose, California. Bloom Energy, a Silicon Valley start up, introduced the "Bloom Box", a solid oxide fuel cell server that can generate electricity at a cost of 8 to 10 cents per kilowatt hour using natural gas.
Stealth start-up Bloom Energy on Wednesday publicly unveiled an innovative fuel cell that promises to deliver affordable, clean energy to even remote corners of the world.
Compact Bloom Servers built with energy cells made from silicon -- a plentiful element found in sand -- made their formal debut in an eBay building here partially powered by the energy source.
"Bloom fuel cell technology has the potential to revolutionize the energy industry," California governor Arnold Schwarzenegger said while introducing Bloom founder K.R. Sridhar.
"He is someone shaping the future of energy not just for California but for the world," Schwarzenegger said.
A high-powered audience gathered for the invitation-only event included Google co-founder Larry Page, eBay chief executive John Donahoe, and former US secretaries of state George Shultz and Colin Powell.
"The core of our technology simply is sand," Sridhar said pulling a black cloth off a clear glass container of sand and then holding up a greeting-card sized cell made from the material.
"It is available in plenty... and it has the scientific property that enabled us to make a fuel cell," he said.
Fuel cell technology dates back to the mid 1800s, but Bloom found a way to eliminate the need for expensive metals such as platinum and to generate electricity by pushing around oxygen molecules.
Bloom servers work with a variety of fuels, meaning users can freely switch to whatever is locally available or most affordable, according to Sridhar.
The servers, referred to by some as "Bloom boxes" despite Sridhar cringing at the nickname, have been secretly tested in California by a group of major corporations including eBay, Wal-Mart, and Coca Cola.
Google was Bloom's first customer, buying four servers that it installed at its campus in Mountain View, California.
"I'm a big supporter of this," Page said during an on-stage chat with renowned Silicon Valley venture capitalist John Doerr of Kleiner Perkins Caulfield & Byers, a major backer of Bloom.
"I'd love to see us have a whole data center running on this at some point when they are ready," Page said.
Bloom servers capable of pumping out 100 kilowatts of electricity each cost 700,000 to 800,000 dollars but the price is expected to plummet as production ramps up and efficiencies of scale are achieved.
Sridhar predicted it will take about a decade for the technology to get to the point where it can be used in homes.
Bloom servers are 60 percent cleaner than coal-fired power plants and produce reliable energy on-site instead of having electricity routed through wires from far-off generation plants, Schwarzenegger said.
The inspiration for the fuel cell is rooted in Sridhar's decade as a university professor working on ways to sustain a human colony on Mars.
"I was trying to make Mars our second home," Sridhar said. "The technology was robust but, unfortunately, I couldn't say the same thing about the funding and the rockets."
Sridhar focused his inventive energy on Earth's need to curb pollution and sate growing energy demands. "If we continued the way we were going we would be handing our children a broken planet," he said.
The cells are described as being twice as efficient as the US electricity grid, meaning it takes half the fuel to produce the same amount of energy.
Sridhar hefted a brick-sized fuel cell in one hand, saying it could power a standard light bulb but will soon be able to satisfy the electricity needs of a typical US home.
"In a few years we will use it to make a home energy server of the future," Sridhar said.
Sridhar pulled back a curtain to reveal a set of Bloom Servers -- refrigerator-sized metal boxes housing stacks of fuel cells.
"That's my baby," he said. "Isn't she beautiful."
Electricity generated by Bloom servers costs about nine cents per kilowatt/hour as opposed to the 14 or 15 cents typically charged here by utilities.
The cost of the servers is recovered in three to five years by energy savings, according to Sridhar. The servers are guaranteed for 10 years. Sridhar would not disclose the lifespans of the fuel cells.
"We sent our chief financial officer to make sure this thing penciled out," Donahoe said of eBay's decision to try Bloom technology. "It is something that makes good green sense making good business sense."
Former secretary of state Colin Powell, a Bloom board member and retired general, said the servers could be a boon to the military, which has grown increasingly energy-dependent as technology infuses the tools of war.
"This is a breakthrough," Powell said. "Sooner or later it is going to be in homes all across America. Think what it will ultimately do for humankind."
(http://www.physorg.com/news186246027.html)
Other articles:
http://www.physorg.com/news186123245.html
http://www.technologyreview.com/energy/24650/
A man stands next to a Bloom Energy server called a "Bloom Box" during a product launch at the eBay headquarters in San Jose, California. Bloom Energy, a Silicon Valley start up, introduced the "Bloom Box", a solid oxide fuel cell server that can generate electricity at a cost of 8 to 10 cents per kilowatt hour using natural gas.
Stealth start-up Bloom Energy on Wednesday publicly unveiled an innovative fuel cell that promises to deliver affordable, clean energy to even remote corners of the world.
Compact Bloom Servers built with energy cells made from silicon -- a plentiful element found in sand -- made their formal debut in an eBay building here partially powered by the energy source.
"Bloom fuel cell technology has the potential to revolutionize the energy industry," California governor Arnold Schwarzenegger said while introducing Bloom founder K.R. Sridhar.
"He is someone shaping the future of energy not just for California but for the world," Schwarzenegger said.
A high-powered audience gathered for the invitation-only event included Google co-founder Larry Page, eBay chief executive John Donahoe, and former US secretaries of state George Shultz and Colin Powell.
"The core of our technology simply is sand," Sridhar said pulling a black cloth off a clear glass container of sand and then holding up a greeting-card sized cell made from the material.
"It is available in plenty... and it has the scientific property that enabled us to make a fuel cell," he said.
Fuel cell technology dates back to the mid 1800s, but Bloom found a way to eliminate the need for expensive metals such as platinum and to generate electricity by pushing around oxygen molecules.
Bloom servers work with a variety of fuels, meaning users can freely switch to whatever is locally available or most affordable, according to Sridhar.
The servers, referred to by some as "Bloom boxes" despite Sridhar cringing at the nickname, have been secretly tested in California by a group of major corporations including eBay, Wal-Mart, and Coca Cola.
Google was Bloom's first customer, buying four servers that it installed at its campus in Mountain View, California.
"I'm a big supporter of this," Page said during an on-stage chat with renowned Silicon Valley venture capitalist John Doerr of Kleiner Perkins Caulfield & Byers, a major backer of Bloom.
"I'd love to see us have a whole data center running on this at some point when they are ready," Page said.
Bloom servers capable of pumping out 100 kilowatts of electricity each cost 700,000 to 800,000 dollars but the price is expected to plummet as production ramps up and efficiencies of scale are achieved.
Sridhar predicted it will take about a decade for the technology to get to the point where it can be used in homes.
Bloom servers are 60 percent cleaner than coal-fired power plants and produce reliable energy on-site instead of having electricity routed through wires from far-off generation plants, Schwarzenegger said.
The inspiration for the fuel cell is rooted in Sridhar's decade as a university professor working on ways to sustain a human colony on Mars.
"I was trying to make Mars our second home," Sridhar said. "The technology was robust but, unfortunately, I couldn't say the same thing about the funding and the rockets."
Sridhar focused his inventive energy on Earth's need to curb pollution and sate growing energy demands. "If we continued the way we were going we would be handing our children a broken planet," he said.
The cells are described as being twice as efficient as the US electricity grid, meaning it takes half the fuel to produce the same amount of energy.
Sridhar hefted a brick-sized fuel cell in one hand, saying it could power a standard light bulb but will soon be able to satisfy the electricity needs of a typical US home.
"In a few years we will use it to make a home energy server of the future," Sridhar said.
Sridhar pulled back a curtain to reveal a set of Bloom Servers -- refrigerator-sized metal boxes housing stacks of fuel cells.
"That's my baby," he said. "Isn't she beautiful."
Electricity generated by Bloom servers costs about nine cents per kilowatt/hour as opposed to the 14 or 15 cents typically charged here by utilities.
The cost of the servers is recovered in three to five years by energy savings, according to Sridhar. The servers are guaranteed for 10 years. Sridhar would not disclose the lifespans of the fuel cells.
"We sent our chief financial officer to make sure this thing penciled out," Donahoe said of eBay's decision to try Bloom technology. "It is something that makes good green sense making good business sense."
Former secretary of state Colin Powell, a Bloom board member and retired general, said the servers could be a boon to the military, which has grown increasingly energy-dependent as technology infuses the tools of war.
"This is a breakthrough," Powell said. "Sooner or later it is going to be in homes all across America. Think what it will ultimately do for humankind."
(http://www.physorg.com/news186246027.html)
Other articles:
http://www.physorg.com/news186123245.html
http://www.technologyreview.com/energy/24650/
Energy-Efficient Lighting Made Without Mercury
Site of the day: http://fooledbyrandomness.com/
ScienceDaily (Feb. 15, 2010) — RTI International has developed a revolutionary lighting technology that is more energy efficient than the common incandescent light bulb and does not contain mercury, making it environmentally safer than the compact fluorescent light (CFL) bulb.
At the core of RTI's breakthrough is an advanced nanofiber structure that provides exceptional lighting management. Nanofibers are materials with diameters and surface features much smaller than the human hair but with comparable lengths.
RTI's technology, which was funded in part by the Department of Energy's Solid-State Lighting program, centers around advancements in the nanoscale properties of materials to create high-performance, nanofiber-based reflectors and photoluminescent nanofibers (PLN). When the two nanoscale technologies are combined, a high-efficiency lighting device is produced that is capable of generating in excess of 55 lumens of light output per electrical watt consumed. This efficiency is more than five times greater than that of traditional incandescent bulbs.
"By using flexible photoluminescent nanofiber technologies for light management, RTI has opened the door to the creation of new designs for solid-state lighting applications," says Lynn Davis, Ph.D., director of RTI's Nanoscale Materials Program. "This new class of materials can provide cost-effective, safe and efficient lighting solutions."
Additionally, RTI's technology produces an aesthetically pleasing light with better color rendering properties than is typically found in CFLs. The technology has demonstrated color rendering indices in excess of 90 for warm white, neutral white, and cool white illumination sources.
"Because lighting consumes almost one-fourth of all electricity generated in the United States, our technology could have a significant impact in reducing energy consumption and carbon dioxide emissions," Davis said. "The technology also does not contain mercury, which makes it more environmentally friendly and safer to handle than CFLs and other fluorescent lamps."
RTI is continuing development of this technology and is actively pursuing commercialization opportunities in the marketplace. It is anticipated that commercial products containing this breakthrough will be available in three to five years.
(http://www.sciencedaily.com/releases/2010/02/100211140629.htm)
ScienceDaily (Feb. 15, 2010) — RTI International has developed a revolutionary lighting technology that is more energy efficient than the common incandescent light bulb and does not contain mercury, making it environmentally safer than the compact fluorescent light (CFL) bulb.
At the core of RTI's breakthrough is an advanced nanofiber structure that provides exceptional lighting management. Nanofibers are materials with diameters and surface features much smaller than the human hair but with comparable lengths.
RTI's technology, which was funded in part by the Department of Energy's Solid-State Lighting program, centers around advancements in the nanoscale properties of materials to create high-performance, nanofiber-based reflectors and photoluminescent nanofibers (PLN). When the two nanoscale technologies are combined, a high-efficiency lighting device is produced that is capable of generating in excess of 55 lumens of light output per electrical watt consumed. This efficiency is more than five times greater than that of traditional incandescent bulbs.
"By using flexible photoluminescent nanofiber technologies for light management, RTI has opened the door to the creation of new designs for solid-state lighting applications," says Lynn Davis, Ph.D., director of RTI's Nanoscale Materials Program. "This new class of materials can provide cost-effective, safe and efficient lighting solutions."
Additionally, RTI's technology produces an aesthetically pleasing light with better color rendering properties than is typically found in CFLs. The technology has demonstrated color rendering indices in excess of 90 for warm white, neutral white, and cool white illumination sources.
"Because lighting consumes almost one-fourth of all electricity generated in the United States, our technology could have a significant impact in reducing energy consumption and carbon dioxide emissions," Davis said. "The technology also does not contain mercury, which makes it more environmentally friendly and safer to handle than CFLs and other fluorescent lamps."
RTI is continuing development of this technology and is actively pursuing commercialization opportunities in the marketplace. It is anticipated that commercial products containing this breakthrough will be available in three to five years.
(http://www.sciencedaily.com/releases/2010/02/100211140629.htm)
New Energy Source from the Common Pea: Scientists Create a Solar Energy Device from a Plant Protein Structure
Site of the day: http://fooledbyrandomness.com/
ScienceDaily (Mar. 4, 2010) — If harnessing the unlimited solar power of the sun were easy, we wouldn't still have the greenhouse gas problem that results from the use of fossil fuel. And while solar energy systems work moderately well in hot desert climates, they are still inefficient and contribute only a small percentage of the general energy demand. A new solution may be coming from an unexpected source -- a source that may be on your dinner plate tonight.
"Looking at the most complicated membrane structure found in a plant, we deciphered a complex membrane protein structure which is the core of our new proposed model for developing 'green' energy," says structural biologist Prof. Nathan Nelson of Tel Aviv University's Department of Biochemistry. Isolating the minute crystals of the PSI super complex from the pea plant, Prof. Nelson suggests these crystals can be illuminated and used as small battery chargers or form the core of more efficient artificial solar cells.
Nanoscience is the science of small particles of materials and is one of the most important research frontiers in modern technology. In nature, positioning of molecules with sub-nanometer precision is routine, and crucial to the operation of biological complexes such as photosynthetic complexes. Prof. Nelson's research concentrates on this aspect.
The mighty PSI
To generate useful energy, plants have evolved very sophisticated "nano-machinery" which operates with light as its energy source and gives a perfect quantum yield of 100%. Called the Photosystem I (PSI) complex, this complex was isolated from pea leaves, crystalized and its crystal structure determined by Prof. Nelson to high resolution, which enabled him to describe in detail its intricate structure.
"My research aims to come close to achieving the energy production that plants can obtain when converting sun to sugars in their green leaves," explains Prof. Nelson.
Described in 1905 by Albert Einstein, quantum physics and photons explained the basic principles of how light energy works. Once light is absorbed in plant leaves, it energizes an electron which is subsequently used to support a biochemical reaction, like sugar production.
"If we could come even close to how plants are manufacturing their sugar energy, we'd have a breakthrough. It's therefore important to solve the structure of this nano-machine to understand its function," says Prof. Nelson, whose lab is laying the foundations for this possibility.
Since the PSI reaction center is a pigment-protein complex responsible for the photosynthetic conversion of light energy to another form of energy like chemical energy, these reaction centers, thousands of which are precisely packed in the crystals, may be used to convert light energy to electricity and serve as electronic components in a variety of different devices.
"One can imagine our amazement and joy when, upon illumination of those crystals placed on gold covered plates, we were able to generate a voltage of 10 volts. This won't solve our world's energy problem, but this could be assembled in power switches for low-power solar needs, for example," he concludes.
(http://www.sciencedaily.com/releases/2010/03/100304112237.htm)
ScienceDaily (Mar. 4, 2010) — If harnessing the unlimited solar power of the sun were easy, we wouldn't still have the greenhouse gas problem that results from the use of fossil fuel. And while solar energy systems work moderately well in hot desert climates, they are still inefficient and contribute only a small percentage of the general energy demand. A new solution may be coming from an unexpected source -- a source that may be on your dinner plate tonight.
"Looking at the most complicated membrane structure found in a plant, we deciphered a complex membrane protein structure which is the core of our new proposed model for developing 'green' energy," says structural biologist Prof. Nathan Nelson of Tel Aviv University's Department of Biochemistry. Isolating the minute crystals of the PSI super complex from the pea plant, Prof. Nelson suggests these crystals can be illuminated and used as small battery chargers or form the core of more efficient artificial solar cells.
Nanoscience is the science of small particles of materials and is one of the most important research frontiers in modern technology. In nature, positioning of molecules with sub-nanometer precision is routine, and crucial to the operation of biological complexes such as photosynthetic complexes. Prof. Nelson's research concentrates on this aspect.
The mighty PSI
To generate useful energy, plants have evolved very sophisticated "nano-machinery" which operates with light as its energy source and gives a perfect quantum yield of 100%. Called the Photosystem I (PSI) complex, this complex was isolated from pea leaves, crystalized and its crystal structure determined by Prof. Nelson to high resolution, which enabled him to describe in detail its intricate structure.
"My research aims to come close to achieving the energy production that plants can obtain when converting sun to sugars in their green leaves," explains Prof. Nelson.
Described in 1905 by Albert Einstein, quantum physics and photons explained the basic principles of how light energy works. Once light is absorbed in plant leaves, it energizes an electron which is subsequently used to support a biochemical reaction, like sugar production.
"If we could come even close to how plants are manufacturing their sugar energy, we'd have a breakthrough. It's therefore important to solve the structure of this nano-machine to understand its function," says Prof. Nelson, whose lab is laying the foundations for this possibility.
Since the PSI reaction center is a pigment-protein complex responsible for the photosynthetic conversion of light energy to another form of energy like chemical energy, these reaction centers, thousands of which are precisely packed in the crystals, may be used to convert light energy to electricity and serve as electronic components in a variety of different devices.
"One can imagine our amazement and joy when, upon illumination of those crystals placed on gold covered plates, we were able to generate a voltage of 10 volts. This won't solve our world's energy problem, but this could be assembled in power switches for low-power solar needs, for example," he concludes.
(http://www.sciencedaily.com/releases/2010/03/100304112237.htm)
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