(NanoRealm) - Will we soon be plugging our mobile phone into our t-shirt instead of putting in a battery? This vision is not totally out of reach: the first steps in this direction have already been taken.

Now a team led by Zhong Lin Wang at the Georgia Institute of Technology (Atlanta, USA) and Jong Min Kim of Samsung Electronics in South Korea is introducing a prototype for a flexible energy storage device that can be worked into textiles. As the scientists report in the journal Angewandte Chemie, this supercapacitor is made of a very special arrangement of zinc oxide nanowires grown on conventional fibers.

Although smaller, lighter components are constantly being developed, most devices for energy generation and storage are much too bulky and heavy for increasingly miniaturized electronic devices of the future. Supercapacitors are an interesting alternative to batteries and rechargeable batteries for energy storage. They can be recharged almost endlessly and extremely fast; however, previous examples have not been flexible or light enough.

The research team has now developed a prototype for a high-efficiency fiber-based electrochemical micro-supercapacitor that uses zinc oxide nanowires as electrodes. The substrate for one of the electrode is a flexible, fine plastic wire; for the other electrode it is a fiber made of Kevlar. Kevlar is the material used to make bulletproof vests. The researchers were able to grow zinc oxide nanowires on each of these substrates. Additional coatings with materials like gold and manganese oxide could further improve the charge capacitance. Using tweezers, the researchers then wrapped each of the plastic wires with a Kevlar fiber. This assembly was then embedded in a solid gel electrolyte that separates the two electrodes and allows for the necessary charge transport. A bundle of these fibers could be processed to form a thread.


Zinc oxide has special advantages over conventional supercapacitor materials,: it can be grown on any desired substrate in any form at low temperature (below 100 °C) and it is both biocompatible and environmentally friendly.

A particularly intriguing application would be the use of these new charge-storage media in combination with flexible fiber nanogenerators, which Wang and his team have previously developed. The wearer’s heartbeat and steps, or even a light wind, would be enough to move the piezoelectric zinc oxide nanowires in the fibers, generating electrical current.

In the form of a "power shirt" such a system could deliver enough current for small electronic devices, such as mobile phones or small sensors like those used to warn firemen of toxins.

For More information: Zhong Lin Wang, Fiber Supercapacitors Made of Nanowire-Fiber Hybrid Structures for Wearable/Flexible Energy Storage, Angewandte Chemie International Edition,
http://dx.doi.org/10.1002/anie.201006062

(NanoRealm) - In a revolutionary leap that could transform solar power from a marginal, boutique alternative into a mainstream energy source, MIT researchers have overcome a major barrier to large-scale solar power: storing energy for use when the sun doesn't shine.

Inspired by the photosynthesis performed by plants, Nocera and Matthew Kanan, a postdoctoral fellow in Nocera's lab, have developed an unprecedented process that will allow the sun's energy to be used to split water into hydrogen and oxygen gases. Later, the oxygen and hydrogen may be recombined inside a fuel cell, creating carbon-free electricity to power your house or your electric car, day or night.

The key component in Nocera and Kanan's new process is a new catalyst that produces oxygen gas from water; another catalyst produces valuable hydrogen gas. The new catalyst consists of cobalt metal, phosphate and an electrode, placed in water. When electricity — whether from a photovoltaic cell, a wind turbine or any other source — runs through the electrode, the cobalt and phosphate form a thin film on the electrode, and oxygen gas is produced.





Combined with another catalyst, such as platinum, that can produce hydrogen gas from water, the system can duplicate the water splitting reaction that occurs during photosynthesis.

The new catalyst works at room temperature, in neutral pH water, and it's easy to set up, Nocera said. "That's why I know this is going to work. It's so easy to implement," he said.

'Just the beginning'

Currently available electrolyzers, which split water with electricity and are often used industrially, are not suited for artificial photosynthesis because they are very expensive and require a highly basic (non-benign) environment that has little to do with the conditions under which photosynthesis operates.

More engineering work needs to be done to integrate the new scientific discovery into existing photovoltaic systems, but Nocera said he is confident that such systems will become a reality.

"This is just the beginning," said Nocera, principal investigator for the Solar Revolution Project funded by the Chesonis Family Foundation and co-Director of the Eni-MIT Solar Frontiers Center. "The scientific community is really going to run with this."

Nocera hopes that within 10 years, homeowners will be able to power their homes in daylight through photovoltaic cells, while using excess solar energy to produce hydrogen and oxygen to power their own household fuel cell. Electricity-by-wire from a central source could be a thing of the past.

The project is part of the MIT Energy Initiative, a program designed to help transform the global energy system to meet the needs of the future and to help build a bridge to that future by improving today's energy systems. MITEI Director Ernest Moniz, Cecil and Ida Green Professor of Physics and Engineering Systems, noted that "this discovery in the Nocera lab demonstrates that moving up the transformation of our energy supply system to one based on renewables will depend heavily on frontier basic science."

The success of the Nocera lab shows the impact of a mixture of funding sources — governments, philanthropy, and industry. This project was funded by the National Science Foundation and by the Chesonis Family Foundation, which gave MIT $10 million this spring to launch the Solar Revolution Project, with a goal to make the large scale deployment of solar energy within 10 years.

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Source: MIT News - http://web.mit.edu/newsoffice/2008/oxygen-0731.html

(NanoRealm) - The Shimizu Corporation, a Japanese construction firm, has recently proposed a plan to harness solar energy on a larger scale than almost any previously proposed concept. Their ambitious plan involves building a belt of solar cells around the Moon’s 6,800-mile (11,000-kilometer) equator, converting the electricity to powerful microwaves and lasers to be beamed at Earth, and finally converting the beams back to electricity at terrestrial power stations. The Luna Ring concept, the company says, could meet the entire world's energy needs.

Shimizu envisions that robots would play a vital role in building the Luna Ring. Teleoperated 24 hours a day from the Earth, the robots would perform tasks such as ground leveling and assembling machines and equipment, which would be done in space before landing them on the Moon. A team of astronauts would support the robots on-site.



Due to the massive amount of solar panels and other materials needed for the project, Shimizu proposes that lunar resources should be used to the fullest extent possible. The company’s plans call for producing water by reducing lunar soil with hydrogen imported from Earth. Lunar resources could also be used to make cementing material and concrete, while solar-heat treatments could help produce bricks, glass fibers, and other structural materials needed for the project.

The Luna Ring itself would initially have a width of a few kilometers, but could be extended up to 400 kilometers wide. The electric power generated by the solar cells would be transmitted by electric cables to transmission facilities on the near side of the Moon, which is constantly facing Earth. After the electricity is converted into microwave beams and laser beams, 20-kilometer-diameter antennas would beam the power to receivers on Earth. A guidance radio beacon would ensure accurate transmission to the receivers. The energy would then be converted back to electricity and supplied to grids, or possibly converted to hydrogen for fuel or storage.



Shimizu points out that one of the biggest advantages of the Luna Ring is that, since the Moon has virtually no atmosphere, there is no bad weather or clouds that could inhibit the efficiency of the solar panels. As such, the Luna Ring achieves 24/7 continuous clean energy generation, potentially ending our reliance on limited natural resources.

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Source: Shimuzu Corperation

(NanoRealm) - Could you imagine a laptop battery that lasted for 500 hours? How about an electric car that boasts a range many times that of a gasoline vehicle? For that matter, think about environmental sensors that could be scattered into the air like dust and collect data. While the last thing might not exactly be what you want for Christmas, a breakthrough in energy production made by MIT researchers could make such technology a reality during the next few years.

The process, dubbed “thermopower waves” by its discoverer, MIT’s Dr. Michael Strano, does nothing less than open up “a new area of energy research, which is rare,” says the scientist. MSNBC’s Michelle Bryner describes the phenomenon and its applications in brief, writing:

Researchers have found a way to produce large amounts of electricity from tiny cylinders made from carbon atoms.

The achievement could replace decades-old methods of generating electricity, such as combustion engines and turbines, the researchers say.

The cylinders are known as “carbon nanotubes,” which are, writes The Energy Collective, “submicroscopic hollow tubes made of a ‘chicken-wire-like’ lattice of carbon atoms.”

To describe the process in more detail, the MIT researchers took the nanotubes, applied a layer of fuel, and then ignited them at one end, creating a “fast-moving thermal [heat] wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse,” explains the Environment News Service (ENS). This process is facilitated by the fact that nanotubes conduct heat far better than metals — up to 100 times faster. Then, getting more technical still, ENS writes, “As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins [sic] (2,726 degrees Celsius or 4,940 degrees Fahrenheit) this ring of heat speads [sic] along the tube 10,000 times faster than the normal spread of this chemical reaction.”

This is where Dr. Strano and his team experienced their Ivory Soap moment. While Strano claims to be the first scientist to predict that thermal waves coursing through a nanotube could create electric current, the great amount of it yielded was not predicted by thermoelectric calculations. “Lo and behold,” said the scientist, “we were really surprised by the size of the resulting voltage peak.” Strano and his team have called this unexpected phenomenon “electron entrainment,” “since part of the current appears to scale with wave velocity,” said Strano.

Because this energy source is so new, it’s hard to predict what the practical applications will be. However, the thermopower-wave process produces 100 times the energy per unit of weight of the average lithium-ion battery. Additionally, Strano says that such a power source would be composed of non-toxic substances, eliminating the disposal problems posed by current-generation energy cells.

The technology could also be used to help create sensors the size of a grain of rice that could be injected into the body and used to monitor health (e.g., heart function), administer medical treatment or, well, use your imagination. There are some ominous implications as well.

One obvious use of the technology, however, would be to create practical electric fuel cells for automobiles. One common drawback of electric cars is that they typically have a very limited range relative to combustion engine vehicles, owing to the fact that gasoline contains far more energy per unit of weight than today’s electric fuel cells. But thermopower-wave generation could change that, providing light, long-range batteries and relatively inexpensive electricity. This could finally allow us to break our dependence on foreign oil.

Whatever the particulars, Dr. Strano’s discovery is just the latest frontier in the staggering field of nanotechnology. The science of manipulating matter on the molecular and even atomic levels, it is quickly making science fiction, science fact.

For more on the subject, see Selwyn Duke's “The New Nanotech World” in the March 31, 2008 issue of The New American.

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Provided by MIT
Source: http://www.thenewamerican.com/index.php/tech-mainmenu-30/energy/3133-nanotech-energy-source-discovered

(NanoRealm) - 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.

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Adapted from American Friends of Tel Aviv University (http://www.aftau.org/)
Source: Science Daily - http://www.sciencedaily.com/releases/2010/03/100304112237.htm

(NanoRealm) - Consider this T-shirt: It can monitor your heart rate and breathing, analyze your sweat and even cool you off on a hot summer's day. What about a pillow that monitors your brain waves, or a solar-powered dress that can charge your ipod or MP4 player? This is not science fiction - this is cotton in 2010.

Now, the laboratory of Juan Hinestroza, assistant professor of Fiber Science and Apparel Design, has developed cotton threads that can conduct electric current as well as a metal wire can, yet remain light and comfortable enough to give a whole new meaning to multi-use garments. This technology works so well that simple knots in such specially treated thread can complete a circuit - and solar-powered dress with this technology literally woven into its fabric will be featured at the annual Cornell Design League Fashion Show on Saturday, March 13 at Cornell University's Barton Hall.

Using multidisciplinary nanotechnology developed at Cornell in collaboration with the universities at Bologna and Cagliari, Italy, Hinestroza and his colleagues developed a technique to permanently coat cotton fibers with electrically conductive nanoparticles. "We can definitively have sections of a traditional cotton fabric becoming conductive, hence a great myriad of applications can be achieved," Hinestroza said.
"The technology developed by us and our collaborators allows cotton to remain flexible, light and comfortable while being electronically conductive," Hinestroza said. "Previous technologies have achieved conductivity but the resulting fiber becomes rigid and heavy. Our new techniques make our yarns friendly to further processing such as weaving, sewing and knitting."
This technology is beyond the theory stage. Hinestroza's student, Abbey Liebman, was inspired by the technology enough to design a dress that actually uses flexible solar cells to power small electronics from a USB charger located in the waist. The charger can power a smartphone or an MP3 player.

"Instead of conventional wires, we are using our conductive cotton to transmit the electricity -- so our conductive yarns become part of the dress," Hinestroza said. "Cotton used to be called the 'fabric of our lives' but based on these results, we can now call it 'The fabric of our lights.'"

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Provided by Cornell University (http://www.cornell.edu/)
Source: http://www.physorg.com/news187372919.html

(NanoRealm) - A team of scientists at MIT have discovered a previously unknown phenomenon that can cause powerful waves of energy to shoot through minuscule wires known as carbon nanotubes. The discovery could lead to a new way of producing electricity, the researchers say.

The phenomenon, described as thermopower waves, “opens up a new area of energy research, which is rare,” says Michael Strano, MIT’s Charles and Hilda Roddey Associate Professor of Chemical Engineering, who was the senior author of a paper describing the new findings that appeared in Nature Materials on March 7. The lead author was Wonjoon Choi, a doctoral student in mechanical engineering.

Like a collection of flotsam propelled along the surface by waves traveling across the ocean, it turns out that a thermal wave — a moving pulse of heat — traveling along a microscopic wire can drive electrons along, creating an electrical current.

The key ingredient in the recipe is carbon nanotubes — submicroscopic hollow tubes made of a chicken-wire-like lattice of carbon atoms. These tubes, just a few billionths of a meter (nanometers) in diameter, are part of a family of novel carbon molecules, including buckyballs and graphene sheets, that have been the subject of intensive worldwide research over the last two decades.

A previously unknown phenomenon

In the new experiments, each of these electrically and thermally conductive nanotubes was coated with a layer of a reactive fuel that can produce heat by decomposing. This fuel was then ignited at one end of the nanotube using either a laser beam or a high-voltage spark, and the result was a fast-moving thermal wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse. Heat from the fuel goes into the nanotube, where it travels thousands of times faster than in the fuel itself. As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins, this ring of heat speeds along the tube 10,000 times faster than the normal spread of this chemical reaction. The heating produced by that combustion, it turns out, also pushes electrons along the tube, creating a substantial electrical current.

Combustion waves — like this pulse of heat hurtling along a wire — “have been studied mathematically for more than 100 years,” Strano says, but he was the first to predict that such waves could be guided by a nanotube or nanowire and that this wave of heat could push an electrical current along that wire.

In the group’s initial experiments, Strano says, when they wired up the carbon nanotubes with their fuel coating in order to study the reaction, “lo and behold, we were really surprised by the size of the resulting voltage peak” that propagated along the wire.

After further development, the system now puts out energy, in proportion to its weight, about 100 times greater than an equivalent weight of lithium-ion battery.

The amount of power released, he says, is much greater than that predicted by thermoelectric calculations. While many semiconductor materials can produce an electric potential when heated, through something called the Seebeck effect, that effect is very weak in carbon. “There’s something else happening here,” he says. “We call it electron entrainment, since part of the current appears to scale with wave velocity.”
The thermal wave, he explains, appears to be entraining the electrical charge carriers (either electrons or electron holes) just as an ocean wave can pick up and carry a collection of debris along the surface. This important property is responsible for the high power produced by the system, Strano says.

Exploring possible applications

Because this is such a new discovery, he says, it’s hard to predict exactly what the practical applications will be. But he suggests that one possible application would be in enabling new kinds of ultra-small electronic devices — for example, devices the size of grains of rice, perhaps with sensors or treatment devices that could be injected into the body. Or it could lead to “environmental sensors that could be scattered like dust in the air,” he says.

In theory, he says, such devices could maintain their power indefinitely until used, unlike batteries whose charges leak away gradually as they sit unused. And while the individual nanowires are tiny, Strano suggests that they could be made in large arrays to supply significant amounts of power for larger devices.

The researchers also plan to pursue another aspect of their theory: that by using different kinds of reactive materials for the coating, the wave front could oscillate, thus producing an alternating current. That would open up a variety of possibilities, Strano says, because alternating current is the basis for radio waves such as cell phone transmissions, but present energy-storage systems all produce direct current. “Our theory predicted these oscillations before we began to observe them in our data,” he says.

Also, the present versions of the system have low efficiency, because a great deal of power is being given off as heat and light. The team plans to work on improving that.

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Provided by Massachusetts Institute of Technology (http://web.mit.edu/)
Source: http://www.physorg.com/news187186888.html

(NanoRealm) - A study published in the American Chemical Society's journal Nano Letters reveals that thermocells based on carbon nanotube electrodes might eventually be used for generating electrical energy from heat discarded by chemical plants, automobiles and solar cell farms.

The research was a joint collaboration between Baratunde Cola, assistant professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, and an international team of researchers from the U.S., Australia, China, India and the Philippines.
Cola, director of Georgia Tech’s NanoEngineered Systems and Transport Research Group (NEST), described the study as a breakthrough in efficiently harvesting electrical energy from various sources of exhaust or wasted heat.

"Our NEST Lab was fortunate to team with Dr. Ray Baughman's NanoTech Institute at UT Dallas and Dr. Gordon Wallace's Intelligent Polymer Research Institute in Wollongong, Australia, in the final year of a long collaboration that solved key technical problems,” he said. “We brought fresh eyes, as well as our knowledge and experience with heat transfer engineering from the nanoscale to the scale of practical devices to the problem, which provided a key missing link. The team will together work to enable additional breakthroughs that are required for this technology to reach its full commercial potential."

Efficiently harvesting the thermal energy currently wasted in industrial plants or along pipelines could also create local sources of clean energy that in turn could be used to lower costs and shrink an organization’s energy footprint.

The new thermocells use nanotube electrodes that provide a threefold increase in energy conversion efficiency over conventional electrodes.

One of the demonstrated thermocells looks just like the button cell batteries used in watches, calculators and other small electronics. One key difference, however, is that these new thermocells can continuously generate electricity, instead of running down like a battery. The research netted other thermocells, as well, including electrolyte-filled, textile-separated nanotube sheets that can be wrapped around pipes carrying hot waste streams from manufacturing or electrical power plants. The temperature difference between the pipe and its surroundings produces an electrochemical potential difference between the carbon nanotube sheets, which thermocells utilize to generate electricity.

The research team estimates that multi-walled carbon nanotubes in large thermocells could eventually produce power at a cost of about $2.76 per watt from freely available waste energy, compared with a cost of $4.31 per watt for solar cells, which can only be used when the sun is shining. On a smaller scale, button cell-sized thermocells could be used to power sensors or electronic circuits.

The new thermocells take advantage of the exceptional electronic, mechanical, thermal and chemical properties of carbon nanotubes. The nanotubes’ giant surface area and unique electronic structure afforded by their small diameter and nearly one-dimensional structure offer high current densities, which enhance the output of electrical power and the efficiency of energy harvesting.

"Georgians have worked with state support, and in partnership with initiatives such as the Strategic Energy Institute at Georgia Tech, to realize significant gains in renewable energy production,” Cola said. “But to become a leading energy state, we must increasingly explore new ways to extract and utilize all forms of energy. Harvesting waste heat as electricity is one direction our NEST Lab takes with international partners to help provide increased renewable energy options for Georgia and the world."

This research was sponsored by the Office of Naval Research, the National Science Foundation, The Welch Foundation and the Australian Research Council.

Cola recently received the 2009 Defense Advanced Research Projects Agency (DARPA) Young Faculty Award for his work on solar energy conversion. As director of the NEST Lab, his research focuses on realizing the benefits of nanoscience in applications related to waste thermal energy harvesting, solar energy conversion, and thermal management of electronics and energy systems.

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Provided by Georgia Institute of Technology
Source: http://www.physorg.com/news186769267.html

(NanoRealm) - Berkeley Lab researchers have found a better way to trap light in photovoltaic cells through the use of vertical arrays of silicon nanowires. This could substantially cut the costs of solar electric power by reducing the quantity and quality of silicon needed for efficient solar panels.

Solar cells made from silicon are projected to be a prominent factor in future renewable green energy equations, but so far the promise has far exceeded the reality. While there are now silicon photovoltaics that can convert sunlight into electricity at impressive 20 percent efficiencies, the cost of this solar power is prohibitive for large-scale use. Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab), however, are developing a new approach that could substantially reduce these costs. The key to their success is a better way of trapping sunlight.



“Through the fabrication of thin films from ordered arrays of vertical silicon nanowires we’ve been able to increase the light-trapping in our solar cells by a factor of 73,” says chemist Peidong Yang, who led this research. “Since the fabrication technique behind this extraordinary light-trapping enhancement is a relatively simple and scalable aqueous chemistry process, we believe our approach represents an economically viable path toward high-efficiency, low-cost thin-film solar cells.”

Yang holds joint appointments with Berkeley Lab’s Materials Sciences Division, and the University of California Berkeley’s Chemistry Department. He is a leading authority on semiconductor nanowires - one-dimensional strips of materials whose width measures only one-thousandth that of a human hair but whose length may stretch several microns.

“Typical solar cells are made from very expensive ultrapure single crystal silicon wafers that require about 100 micrometers of thickness to absorb most of the solar light, whereas our radial geometry enables us to effectively trap light with nanowire arrays fabricated from silicon films that are only about eight micrometers thick,” he says. “Furthermore, our approach should in principle allow us to use metallurgical grade or “dirty” silicon rather than the ultrapure silicon crystals now required, which should cut costs even further.”

Yang has described this research in a paper published in the journal Nano Letters, which he co-authored with Erik Garnett, a chemist who was then a member of Yang’s research group. The paper is titled “Light Trapping in Silicon Nanowire Solar Cells.”

Generating Electricity from Sunlight

At the heart of all solar cells are two separate layers of material, one with an abundance of electrons that functions as a negative pole, and one with an abundance of electron holes (positively-charged energy spaces) that functions as a positive pole. When photons from the sun are absorbed, their energy is used to create electron-hole pairs, which are then separated at the interface between the two layers and collected as electricity.



Because of its superior photo-electronic properties, silicon remains the photovoltaic semiconductor of choice but rising demand has inflated the price of the raw material.

Furthermore, because of the high-level of crystal purification required, even the fabrication of the simplest silicon-based solar cell is a complex, energy-intensive and costly process.

Yang and his group are able to reduce both the quantity and the quality requirements for silicon by using vertical arrays of nanostructured radial p-n junctions rather than conventional planar p-n junctions. In a radial p-n junction, a layer of n-type silicon forms a shell around a p-type silicon nanowire core. As a result, photo-excited electrons and holes travel much shorter distances to electrodes, eliminating a charge-carrier bottleneck that often arises in a typical silicon solar cell. The radial geometry array also, as photocurrent and optical transmission measurements by Yang and Garrett revealed, greatly improves light trapping.

“Since each individual nanowire in the array has a p-n junction, each acts as an individual solar cell,” Yang says. “By adjusting the length of the nanowires in our arrays, we can increase their light-trapping path length.”

While the conversion efficiency of these solar nanowires was only about five to six percent, Yang says this efficiency was achieved with little effort put into surface passivation, antireflection, and other efficiency-increasing modifications.

“With further improvements, most importantly in surface passivation, we think it is possible to push the efficiency to above 10 percent,” Yang says.

Combining a 10 percent or better conversion efficiency with the greatly reduced quantities of starting silicon material and the ability to use metallurgical grade silicon, should make the use of silicon nanowires an attractive candidate for large-scale development.

As an added plus Yang says, “Our technique can be used in existing solar panel manufacturing processes.”

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Provided by: Provided by Lawrence Berkeley National Laboratory (http://www.lbl.gov/)
Source: http://www.physorg.com/news186850199.html

(NanoRealm) - Researchers at Tyndall National Institute in Cork, Ireland led by professor Jean-Pierre Colinge have reported in Nature Nanotechnology how they have designed and fabricated what is claimed to be the first junctionless transistor, which could significantly reduce power consumption and simplify the fabrication process for silicon chips, it is reckoned.

Existing transistors are based on junctions formed by adjacent layers of semiconductor material with different dopant-atom-induced polarities. Since controlling the junction allows current in the device to be turned on and off, it is the precise fabrication of this junction that determines the characteristics and quality of the transistor and is a major factor in production costs. However, as the distance between junctions drops below 10nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions require increasingly complex and costly fabrication processes.

Tyndall’s new transistor consists of a silicon nanowire (about 30nm across just 10nm thick), and it has no junctions and no doping concentration gradients, since current flow is controlled by a ‘wedding ring’ gate structure around the wire. “These structures are easy to fabricate even on a miniature scale, which leads to the major breakthrough in potential cost reduction,” claims Colinge.

Another key challenge for the semiconductor industry is reducing the power consumption of complex transistors, with minimizing current leakage one of the main challenges. The new transistors — which can be made to have full CMOS functionality — have near-ideal subthreshold slope, extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors, Tyndall claims. “They have the potential of operating faster and using less energy than the conventional transistors used in today’s microprocessors,” says Colinge.

The junctionless transistor resembles the first ideal transistor structure, proposed in 1925, but to-date no-one had been able to fabricate it, continues Colinge. He attributes Tyndall’s junctionless transistor to the ability to fabricate a silicon nanowire with a diameter of just a few dozen atoms using electron-beam writing techniques and commercial silicon-on-insulator (SOI) wafers.

“We are beginning to talk about these results with some of the world’s leading semiconductor companies, and are receiving a lot of interest in further development and possible licensing of the technology,” says Tyndall’s CEO, professor Roger Whatmore.

The work was funded by Science Foundation Ireland, and is also underpinned by substantial investments in Tyndall by the Department of Enterprise Trade and Employment and the Higher Education Authority, comments Whatmore.

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Source: Semiconductor today - http://www.semiconductor-today.com/news_items/2010/MARCH/TYNDALL_010310.htm

Visit: www.nature.com

Visit: www.tyndall.ie/control

Stanford researcher Yi Cui and his team are re-conceptualizing batteries using nanotechnology

(NanoRealm) - By dipping ordinary paper or fabric in a special ink infused with nanoparticles, Stanford engineer Yi Cui has found a way to cheaply and efficiently manufacture lightweight paper batteries and supercapacitors (which, like batteries, store energy, but by electrostatic rather than chemical means), as well as stretchable, conductive textiles known as "eTextiles" – capable of storing energy while retaining the mechanical properties of ordinary paper or fabric.

While the technology is still new, Cui's team has envisioned numerous functional uses for their inventions. Homes of the future could one day be lined with energy-storing wallpaper. Gadget lovers would be able to charge their portable appliances on the go, simply plugging them into an outlet woven into their T-shirts. Energy textiles might also be used to create moving-display apparel, reactive high-performance sportswear and wearable power for a soldier's battle gear.

The key ingredients in developing these high-tech products are not visible to the human eye. Nanostructures, which can be assembled in patterns that allow them to transport electricity, may provide the solutions to a number of problems encountered with electrical storage devices currently available on the market.

The type of nanoparticle used in the Cui group's experimental devices varies according to the intended function of the product – lithium cobalt oxide is a common compound used for batteries, while single-walled carbon nanotubes, or SWNTs, are used for supercapacitors.

Cui, an assistant professor of materials science and engineering at Stanford, leads a research group that investigates new applications of nanoscale materials. The objective, said Cui, is not only to supply answers to theoretical inquiries but also to pursue projects with practical value. Recently, his team has focused on ways to integrate nanotechnology into the realm of energy development.

"Energy storage is a pretty old research field," said Cui. "Supercapacitors, batteries – those things are old. How do you really make a revolutionary impact in this field? It requires quite a dramatic difference of thinking."

While electrical energy storage devices have come a long way since Alessandro Volta debuted the world's first electrical cell in 1800, the technology is facing yet another revolution. Current methods of manufacturing energy storage devices can be capital intensive and environmentally hazardous, and the end products have noticeable performance constraints – conventional lithium ion batteries have a limited storage capacity and are costly to manufacture, while traditional capacitors provide high power but at the expense of energy storage capacity.


With a little help from new science, the batteries of the future may not look anything like the bulky metal units we've grown accustomed to. Nanotechnology is favored as a remedy both for its economic appeal and its capability to improve energy performance in devices that integrate it. Replacing the carbon (graphite) anodes found in lithium ion batteries with anodes of silicon nanowires, for example, has the potential to increase their storage capacity by 10 times, according to experiments conducted by Cui's team.

Silicon had previously been recognized as a favorable anode material because it can hold a larger amount of lithium than carbon. But applications of silicon were limited by its inability to sustain physical stress – namely, the fourfold volume increase that silicon undergoes when lithium ions attach themselves to a silicon anode in the process of charging a battery, as well as the shrinkage that occurs when lithium ions are drawn out as it discharges. The result was that silicon structures would disintegrate, causing anodes of this material to lose much if not all of their storage capacity.

Cui and collaborators demonstrated in previous publications in Nature, Nanotechnology and Nano Letters that the use of silicon nanowire battery electrodes, mechanically capable of withstanding the absorption and discharge of lithium ions, was one way to sidestep the problem.

The findings hold promise for the development of rechargeable lithium batteries offering a longer life cycle and higher energy capacity than their contemporaries. Silicon nanowire technology may one day find a home in electric cars, portable electronic devices and implantable medical appliances.

Cui now hopes to direct his research toward studying both the "hard science" behind the electrical properties of nanomaterials and designing real-world applications.

"This is the right time to really see what we learn from nanoscience and do practical applications that are extremely promising," said Cui. "The beauty of this is, it combines the lowest cost technology that you can find to the highest tech nanotechnology to produce something great. I think this is a very exciting idea … a huge impact for society."

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The Cui group's latest research on energy storage devices was detailed in papers published in the online editions of the Proceedings of the National Academy of Sciences in December 2009 ("Highly Conductive Paper for Energy-Storage Devices") and Nano Letters in January 2010 ("Stretchable, Porous and Conductive Energy Textiles").

Cui's talk at the symposium "Nanotechnology: Will Nanomaterials Revolutionize Energy Applications?" is scheduled for 9:50 a.m. Feb. 20 in Room 1B of the San Diego Convention Center.

Video/photos:
Conductive eTextiles: Stanford finds a new use for cloth
http://news.stanford.edu/news/2010/february1/batteries-from-cloth-020510.html

At Stanford, nanotubes + ink + paper = instant battery
http://news.stanford.edu/news/2009/december7/nanotubes-ink-paper-120709.html

Source: http://www.eurekalert.org/pub_releases/2010-02/su-nse021910.php

(NanoRealm) - A tiny scaffold-like titanium structure of Nanonets coated with silicon particles could pave the way for faster, lighter and longer-lasting Lithium-ion batteries, according to a team of Boston College chemists who developed the new anode material using nanotechnology.

The web-like Nanonets developed in the lab of Assistant Professor of Chemistry Dunwei Wang offer a unique structural strength, more surface area and greater conductivity, which produced a charge/re-charge rate five to 10 times greater than typical Lithium-ion anode material, a common component in batteries for a range of consumer electronics, according to findings published in the current online edition of the American Chemical Society journal Nano Letters.

In addition, the Nanonets proved exceptionally durable, showing a negligible drop-off in capacity during charge and re-charge cycles. The researchers observed an average of 0.1% capacity fade per cycle between the 20th and the 100th cycles.

"As researchers pursue the next generation of re-chargeable Lithium-ion battery technology, a premium has been placed on increased power and a greater battery life span," said Wang. "In that context, the Nanonet device makes a giant leap toward those two goals and gives us a superior anode material."

Lithium-ion batteries are commonly used in consumer electronics devices. This type of rechargeable battery allows Lithium ions to move from the anode electrode to the cathode when in use. When charged, the ions move from cathode back to the anode.

The structure and conductivity of the Nanonets improved the ability to insert and extract Lithium ions from the particulate silicon coating, the team reported. Running at a charge/discharge rate of 8,400 milliamps per gram (mA/g) - which is approximately five to 10 times greater than similar devices - the specific capacity of the material was greater than 1,000 milliamps-hour per gram (mA-h/g). Typically, laptop Lithium-ion batteries are rated anywhere between 4,000 and 12,000 mA/h, meaning it would only take between four and 12 grams of the Nanonet anode material to achieve similar capacity.

Wang said the capability to preserve the crystalline titanium silicon core during the charge/discharge process was the key to achieving the high performance of the Nanonet anode material. Additional research in his lab will examine the performance of the Nanonet as a cathode material.

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News adapted from PhyOrg.com

More information: View the Nano Letters paper at http://pubs.acs.org/doi/abs/10.1021/nl903345f

Provided by Boston College (web)

(NanoRealm)- The world's first "power suit" seems closer to reality now. Scientists have come up with new fiber nanogenerators which may help design the very first one.

Researchers at University of California, Berkeley, developed the energy-scavenging nanofibers that can convert energy created through mechanical stress, stretches and twists into electricity, furthering hope of creating clothing that can power small electronics.

Liwei Lin, UC Berkeley professor of mechanical engineering and head of the international research team that developed the fiber nanogenerators, said: "This technology could eventually lead to wearable 'smart clothes' that can power hand-held electronics through ordinary body movements."

Lin, also co-director of the Berkeley Sensor and Actuator Center at UC Berkeley, added: "And because the nanofibers are so small, we could weave them right into clothes with no perceptible change in comfort for the user."

Chieh Chang, the study's lead author, who conducted the experiments while he was a graduate student in mechanical engineering at UC Berkeley, explained: "Surprisingly, the energy efficiency ratings of the nanofibers are much greater than the 0.5 to 4 percent achieved in typical power generators made from experimental piezoelectric PVDF thin films, and the 6.8 percent in nanogenerators made from zinc oxide fine wires."

Lin continued: "We think the efficiency likely could be raised further. For our preliminary results, we see a trend that the smaller the fiber we have, the better the energy efficiency. We don't know what the limit is."

Other co-authors of the study were Yiin-Kuen Fuh, a UC Berkeley graduate student in mechanical engineering; Van H. Tran, a graduate student at the Technische Universitat Munchen (Technical University of Munich) in Germany; and Junbo Wang, a researcher at the Institute of Electronics at the Chinese Academy of Sciences in Beijing, China.

The fiber nanogenerators were described in the Nano Letters, a peer-reviewed journal published by the American Chemical Society.

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Source-ANI

News from: MedIndia - (web)

Material scientists at the Nano/Bio Interface Center of theUniversity of Pennsylvania have demonstrated the transduction of optical radiation to electrical current in a molecular circuit. The system, an array of nano-sized molecules of gold, respond to electromagnetic waves by creating surface plasmons that induce and project electrical current across molecules, similar to that of photovoltaic solar cells.

The results may provide a technological approach for higher efficiency energy harvesting with a nano-sized circuit that can power itself, potentially through sunlight. Recently, surface plasmons have been engineered into a variety of light-activated devices such as biosensors.

It is also possible that the system could be used for computer data storage. While the traditional computer processor represents data in binary form, either on or off, a computer that used such photovoltaic circuits could store data corresponding to wavelengths of light.

Because molecular compounds exhibit a wide range of optical and electrical properties, the strategies for fabrication, testing and analysis elucidated in this study can form the basis of a new set of devices in which plasmon-controlled electrical properties of single molecules could be designed with wide implications to plasmonic circuits and optoelectronic and energy-harvesting devices.

Dawn Bonnell, a professor of materials science and the director of the Nano/Bio Interface Center at Penn, and colleagues fabricated an array of light sensitive, gold nanoparticles, linking them on a glass substrate. Minimizing the space between the nanoparticles to an optimal distance, researchers used optical radiation to excite conductive electrons, called plasmons, to ride the surface of the gold nanoparticles and focus light to the junction where the molecules are connected. The plasmon effect increases the efficiency of current production in the molecule by a factor of 400 to 2000 percent, which can then be transported through the network to the outside world.


In the case where the optical radiation excites a surface plasmon and the nanoparticles are optimally coupled, a large electromagnetic field is established between the particles and captured by gold nanoparticles. The particles then couple to one another, forming a percolative path across opposing electrodes. The size, shape and separation can be tailored to engineer the region of focused light. When the size, shape and separation of the particles are optimized to produce a “resonant” optical antennae, enhancement factors of thousands
might result.

Furthermore, the team demonstrated that the magnitude of the photoconductivity of the plasmon-coupled nanoparticles can be tuned independently of the optical characteristics of the molecule, a result that has significant implications for future nanoscale optoelectronic devices.

“If the efficiency of the system could be scaled up without any additional, unforeseen limitations, we could conceivably manufacture a one-amp, one-volt sample the diameter of a human hair and an inch long," Bonnell said.

The study, published in the current issue of the journal ACS Nano, was conducted by Bonnell, David Conklin and Sanjini Nanayakkara of the Department of Materials Science and Engineering in the School of Engineering and Applied Science at Penn; Tae-Hong Park of the Department of Chemistry in the School of Arts and Sceicnes at Penn; Parag Banerjee of the Department of Materials Science and Engineering at the University of Maryland; and Michael J. Therien of the Department of Chemistry at Duke University.

This work was supported by the Nano/Bio Interface Center, National Science Foundation, the John and Maureen Hendricks Energy Fellowship and the U.S. Department of Energy.

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Source: University of Pennsylvania(web)

   Power-generating rubber films developed by Princeton University engineers could harness natural body movements such as breathing and walking to power pacemakers, mobile phones and other electronic devices.