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Bio Computer Chip 053015 uploaded_1076

Portable electronics — typically made of non-renewable, non-biodegradable and potentially toxic materials — are discarded at an alarming rate in consumers’ pursuit of the next best electronic gadget.

In an effort to alleviate the environmental burden of electronic devices, a team of University of Wisconsin-Madison researchers has collaborated with researchers in the Madison-based U.S. Department of Agriculture Forest Products Laboratory (FPL) to develop a surprising solution: a semiconductor chip made almost entirely of wood.
The research team, led by UW-Madison electrical and computer engineering professor Zhenqiang “Jack” Ma, described the new device in a paper published today (May 26, 2015) by the journal Nature Communications. The paper demonstrates the feasibility of replacing the substrate, or support layer, of a computer chip, with cellulose nanofibril (CNF), a flexible, biodegradable material made from wood.
“The majority of material in a chip is support. We only use less than a couple of micrometers for everything else,” Ma says. “Now the chips are so safe you can put them in the forest and fungus will degrade it. They become as safe as fertilizer.”
Zhiyong Cai, project leader for an engineering composite science research group at FPL, has been developing sustainable nanomaterials since 2009.
“If you take a big tree and cut it down to the individual fiber, the most common product is paper. The dimension of the fiber is in the micron stage,” Cai says. “But what if we could break it down further to the nano scale? At that scale you can make this material, very strong and transparent CNF paper.”
“You don’t want it to expand or shrink too much. Wood is a natural hydroscopic material and could attract moisture from the air and expand,” Cai says. “With an epoxy coating on the surface of the CNF, we solved both the surface smoothness and the moisture barrier.”Working with Shaoqin “Sarah” Gong, a UW-Madison professor of biomedical engineering, Cai’s group addressed two key barriers to using wood-derived materials in an electronics setting: surface smoothness and thermal expansion.
Gong and her students also have been studying bio-based polymers for more than a decade. CNF offers many benefits over current chip substrates, she says.
“The advantage of CNF over other polymers is that it’s a bio-based material and most other polymers are petroleum-based polymers. Bio-based materials are sustainable, bio-compatible and biodegradable,” Gong says. “And, compared to other polymers, CNF actually has a relatively low thermal expansion coefficient.”
The group’s work also demonstrates a more environmentally friendly process that showed performance similar to existing chips.
The majority of today’s wireless devices use gallium arsenide-based microwave chips due to their superior high-frequency operation and power handling capabilities. However, gallium arsenide can be environmentally toxic, particularly in the massive quantities of discarded wireless electronics.
Yei Hwan Jung, a graduate student in electrical and computer engineering and a co-author of the paper, says the new process greatly reduces the use of such expensive and potentially toxic material.
“I’ve made 1,500 gallium arsenide transistors in a 5-by-6 millimeter chip. Typically for a microwave chip that size, there are only eight to 40 transistors. The rest of the area is just wasted,” he says. “We take our design and put it on CNF using deterministic assembly technique, then we can put it wherever we want and make a completely functional circuit with performance comparable to existing chips.”
While the biodegradability of these materials will have a positive impact on the environment, Ma says the flexibility of the technology can lead to widespread adoption of these electronic chips.
“Mass-producing current semiconductor chips is so cheap, and it may take time for the industry to adapt to our design,” he says. “But flexible electronics are the future, and we think we’re going to be well ahead of the curve.”
Source: http://www.news.wisc.edu/23805

Diodes 053015 diodes-are-fundamental-building-blocks-of-integrated-circuits-they-allow-current-to-flow-in-only-one-directionResearchers created a single-molecule diode, which has been sought after since the 1970s.

Scientists have designed a new way to create a single-molecule diode that performs 50 times better than past models.

These single-molecule diodes are the first that could be used for real-world applications in nanoscale devices, Columbia University School of Engineering and Applied Sciencereported. The idea of creating a single-molecule diode was first proposed in the 1970s by Arieh Aviram and Mark Ratner, who theorized that a molecule could act as a “rectifier” to conduct one-way currents.

Molecular electronics ever since its inception with Aviram and Ratner’s 1974 seminal paper, represents the ultimate in functional miniaturization that can be achieved for an electronic device,” said Latha Venkataraman, associate professor of applied physics at Columbia Engineering.

Since the 1974 paper, scientists have determined single-molecules attached themselves to metal electrodes, and act as a number of circuit elements such as switches, resistors, and diodes. A diode works as an “electricity valve,” and requires an asymmetrical structure in order to create different environments for electricity flowing in each direction.

Diodes 053015 diodes-are-fundamental-building-blocks-of-integrated-circuits-they-allow-current-to-flow-in-only-one-direction

“While such asymmetric molecules do indeed display some diode-like properties, they are not effective,” said Brian Capozzi, a PhD student working with Venkataraman and lead author of the paper. “A well-designed diode should only allow current to flow in one direction-the ‘on’ direction-and it should allow a lot of current to flow in that direction. Asymmetric molecular designs have typically suffered from very low current flow in both ‘on’ and ‘off’ directions, and the ratio of current flow in the two has typically been low. Ideally, the ratio of ‘on’ current to ‘off’ current, the rectification ratio, should be very high.”

To remedy this, the researchers worked to develop asymmetry in the environment around the molecular junction. They accomplished this by surrounding the active molecule with an ionic solution and employed the use of gold metal electrodes that differed in size to contact the molecule. The method led to rectification ratios as high as 250, which is 50 times higher than earlier designs.

“It’s amazing to be able to design a molecular circuit, using concepts from chemistry and physics, and have it do something functional,” Venkataraman said. “The length scale is so small that quantum mechanical effects are absolutely a crucial aspect of the device. So it is truly a triumph to be able to create something that you will never be able to physically see and that behaves as intended.”

The findings were published in a recent edition of the journal Nature Nanotechnology.

http://engineering.columbia.edu/news-archive

QDOT imagesCA1L02JV 5 Just as alchemists always dreamed of turning common metal into gold, their 19th century physicist counterparts dreamed of efficiently turning heat into electricity, a field called thermoelectrics. Such scientists had long known that, in conducting materials, the flow of energy in the form of heat is accompanied by a flow of electrons. What they did not know at the time is that it takes nanometric-scale systems for the flow of charge and heat to reach a level of efficiency that cannot be achieved with larger scale systems. Now, in a paper published in EPJ B Barbara Szukiewicz and Karol Wysokiński from Marie Curie-Skłodowska University, in Lublin, Poland have demonstrated the importance of thermoelectric effects, which are not easily modelled, in nanostructures.

Since the 1990s, scientists have looked into developing efficient energy generation from nanostructures such as quantum dots. Their advantage: they display a greater energy conversion efficiency leading to the emergence of nanoscale thermoelectrics. The authors evaluate the thermoelectric performance of models made of two quantum dots—which are coupled electrostatically—connected to two electrodes kept at a different temperature and a single quantum dot with two levels. First, they using the theoretical approach based on approximations to calculate the so-called thermoelectric figure of merit, expected to be high for systems with high energy conversion efficiency. Then, they calculated the charge and heat fluxes as a means to define the efficiency of the system.

They found that the outcomes of the direct calculations giving the actual—as opposed to theoretical—performance of the system were less optimistic. For most parameters with an excellent performance, calculated predictions turned out to be surprisingly poor. These findings reveal that effects that are not easily formalized using equations are important at the nanoscale. This, in turn, calls for new ways to optimize the structures before they can be used for nanoscale energy harvesting.

KAIST-emissive-graphene-quantum-dots-img_assist-400x257 From Scopii News

Ground-breaking research has successfully created the world’s first truly electronic textile, using the wonder material Graphene. An international team of scientists, including Professor Monica Craciun from the University of Exeter, have pioneered a new technique to embed transparent, flexible graphene electrodes into fibers commonly associated with the textile industry.

The discovery could revolutionize the creation of wearable electronic devices, such as clothing containing computers, phones and MP3 players, which are lightweight, durable and easily transportable.
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The international collaborative research, which includes experts from the Centre for Graphene Science at the University of Exeter, the Institute for Systems Engineering and Computers, Microsystems and Nanotechnology (INESC-MN) in Lisbon, the Universities of Lisbon and Aveiro in Portugal and the Belgian Textile Research Centre (CenTexBel), is published in the leading scientific journal Scientific Reports.
Professor Craciun, co-author of the research said: “This is a pivotal point in the future of wearable electronic devices. The potential has been there for a number of years, and transparent and flexible electrodes are already widely used in plastics and glass, for example. But this is the first example of a textile electrode being truly embedded in a yarn. The possibilities for its use are endless, including textile GPS systems, to biomedical monitoring, personal security or even communication tools for those who are sensory impaired.  The only limits are really within our own imagination.”

At just one atom thick, graphene is the thinnest substance capable of conducting electricity. It is very flexible and is one of the strongest known materials. The race has been on for scientists and engineers to adapt graphene for the use in wearable electronic devices in recent years.
This new research has identified that ‘monolayer graphene’, which has exceptional electrical, mechanical and optical properties, make it a highly attractive proposition as a transparent electrode for applications in wearable electronics. In this work graphene was created by a growth method called chemical vapor deposition (CVD) onto copper foil, using a state-of-the-art nanoCVD system recently developed by Moorfield.

The collaborative team established a technique to transfer graphene from the copper foils to a polypropylene fibre already commonly used in the textile industry.
Dr Helena Alves who led the research team from INESC-MN and the University of Aveiro said: “The concept of wearable technology is emerging, but so far having fully textile-embedded transparent and flexible technology is currently non-existing. Therefore, the development of processes and engineering for the integration of graphene in textiles would give rise to a new universe of commercial applications. “
Dr Ana Neves, Associate Research Fellow in Prof Craciun’s team from Exeter’s Engineering Department and former postdoctoral researcher at INESC added: “We are surrounded by fabrics, the carpet floors in our homes or offices, the seats in our cars, and obviously all our garments and clothing accessories. The incorporation of electronic devices on fabrics would certainly be a game-changer in modern technology.

“All electronic devices need wiring, so the first issue to be address in this strategy is the development of conducting textile fibers while keeping the same aspect, comfort and lightness. The methodology that we have developed to prepare transparent and conductive textile fibers by coating them with graphene will now open way to the integration of electronic devices on these textile fibers.”

Dr Isabel De Schrijver,an expert of smart textiles fromCenTexBel said: “Successful manufacturing of wearable electronics has the potential for a disruptive technology with a wide array of potential new applications. We are very excited about the potential of this breakthrough and look forward to seeing where it can take the electronics industry in the future.”

Professor Saverio Russo, co-author and also from the University of Exeter, added: “This breakthrough will also nurture the birth of novel and transformative research directions benefitting a wide range of sectors ranging from defense to health care. “
In 2012 Professor Craciun and Professor Russo, from the University of Exeter’s Centre for Graphene Science, discovered GraphExeter – sandwiched molecules of ferric chloride between two graphene layers which makes a whole new system that is the best known transparent material able to conduct electricity.  The same team recently discovered that GraphExeter is also more stable than many transparent conductors commonly used by, for example, the display industry.

Source: University of Exeter

Silicon Photonics id39403 Researchers at the University of Rochester have shown that defects on an atomically thin semiconductor can produce light-emitting quantum dots. The quantum dots serve as a source of single photons and could be useful for the integration of quantum photonics with solid-state electronics — a combination known as integrated photonics.

Scientists have become interested in integrated solid-state devices for quantum information processing uses. Quantum dots in atomically thin semiconductors could not only provide a framework to explore the fundamental physics of how they interact, but also enable nanophotonics applications, the researchers say.

Quantum dots are often referred to as artificial atoms. They are artificially engineered or naturally occurring defects in solids that are being studied for a wide range of applications. Nick Vamivakas, assistant professor of optics at the University of Rochester and senior author on the paper, adds that atomically thin, 2D materials, such as graphene, have also generated interest among scientists who want to explore their potential for optoelectronics. However, until now, optically active quantum dots have not been observed in 2D materials.

In a paper published in Nature Nanotechnology this week, the Rochester researchers show how tungsten diselenide (WSe2) can be fashioned into an atomically thin semiconductor that serves as a platform for solid-state quantum dots. Perhaps most importantly the defects that create the dots do not inhibit the electrical or optical performance of the semiconductor and they can be controlled by applying electric and magnetic fields.

Vamivakas explains that the brightness of the quantum dot emission can be controlled by applying the voltage. He adds that the next step is to use voltage to “tune the color” of the emitted photons, which can make it possible to integrate these quantum dots with nanophotonic devices.

A key advantage is how much easier it is to create quantum dots in atomically thin tungsten diselenide compared to producing quantum dots in more traditional materials like indium arsenide.

“We start with a black crystal and then we peel layers of it off until we have an extremely thin later left, an atomically thin sheet of tungsten diselenide,” said Vamivakas.1-nano devices howtomakemob

The researchers take two of these atomically thin sheets and lay one over the other one. At the point where they overlap, a quantum dot is created. The overlap creates a defect in the otherwise smooth 2D sheet of semiconductor material. The extremely thin semiconductors are much easier to integrate with other electronics.

The quantum dots in tungsten diselenide also possess an intrinsic quantum degree of freedom — the electron spin. This is a desirable property as the spin can both act as a store of quantum information as well as provide a probe of the local quantum dot environment.

COMING ~ JUNE 2015 ~ WATCH OUR NEW VIDEO ~ Genesis Nanotechnology ~ “Great Things from Small Things”

“What makes tungsten diselenide extremely versatile is that the color of the single photons emitted by the quantum dots is correlated with the quantum dot spin,” said first author Chitraleema Chakraborty. Chakraborty added that the ease with which the spins and photons interact with one another should make these systems ideal for quantum information applications as well as nanoscale metrology.


Story Source:

The above story is based on materials provided by University of Rochester. Note: Materials may be edited for content and length.

Difference engine

Graphene’s lightbulb moment

Can the “wonder material” live up to all the hype?

PHYSICISTS Andre Geim and Kostya Novoselev have been rightly feted for their isolation, in 2003, of graphene—sheets of pure carbon a single atom thick—whose existence had been pondered for decades, but which theory suggested was too unstable to survive. The two Soviet-born researchers won the Nobel physics prize in 2010 for their groundbreaking work, carried out at Manchester University, which involved peeling layers of graphene from blocks of graphite. Both men, now British citizens, were knighted in 2012 for their contribution to science. Their work has won generous support from the British government and the European Union—in particular, the construction, at a cost of £61m ($92m), of the National Graphene Institute, which was opened by George Osborne, Chancellor of the Exchequer, in March.

The researchers now have another distinction to their credit: their discovery is about to become a commercial product. A graphene-based lightbulb, said to be longer-lasting, more efficient and cheaper to make than today’s domestic LED lamps, will go on sale in a few months’ time. Though graphene flakes have already been incorporated into tennis racquets, skis and conductive ink, the new lightbulb is claimed by its manufacturer—Graphene Lighting Plc, a spin-out from the National Graphene Institute and Manchester University—to be the first commercially viable consumer product based on the material.

That may be splitting hairs. Even so, going from discovery to commercialisation in little more than a decade is quick. Many entrepreneurial companies find turning an invention into a successful innovation can take 20 years or more.

Graphene is composed of a single layer of carbon atoms arranged in the form of a hexagonal lattice. This means there is a world of difference between it and a three-dimensional crystalline structure like graphite. The electrons associated with carbon atoms in graphite can interact with other carbon atoms in the layers above and below them. In a sheet, this electron-coupling effect disappears, and the electrons are free to behave in entirely different ways.

The most striking consequence of this is that those electrons are thus able to move great distances at close to the speed of light, resulting in a material that has exceptionally low resistance. Because graphene can transport electricity 200 times faster than silicon, it seems a good candidate to replace that element as the semiconductor material used in computer chips.

Hype aside, graphene has not been called a “wonder material” for nothing. Apart from its remarkable electrical properties (and also, thermal and acoustical properties), it is the thinnest and lightest substance known, as well as being the strongest (more than 100 times stronger than high-strength steel). As if all that were not enough, graphene is also extremely flexible and almost totally transparent, absorbing only a minuscule amount of the light falling on it.

As such, potential applications of graphene appear myriad. Some of the more obvious ones include rapid-charging lithium-ion batteries, better solar cells, compact supercapacitors, printable electronics, foldable LED touchscreens, tunable sensors, ultrafast molecular sieves, improved DNA sequencers, corrosion-resistant coatings, a replacement for Kevlar, terahertz wave generators for extremely fast wireless communication, and, of course, more efficient lightbulbs. The list of proposals for future graphene products goes on and on, as researchers cozy up to potential sponsors.

There is little, save lack of money and consumer interest, to stop a good number of these suggestions reaching the market in the not-too-distant future. But the one graphene application that could turn the whole of electronics on its head—a replacement for silicon-based semiconductors—remains tantalisingly over the horizon.

Big computer, wireless and electronics firms—including such research powerhouses as IBM, Intel and Samsung—have been racing to create a field-effect transistor that uses graphene instead of silicon. They have a big incentive to do so. After 50 years of success, Moore’s Law (that the processing power of semiconductor devices doubles every 18 months or so) appears to be coming to an end, at least as far as silicon is concerned. Another material is needed to take its place.

Despite the billions poured into finding an alternative, attempts to make graphene work as a semiconductor have been disappointing. The problem is that the material has no “band gap”—the property that makes a solid an insulator (large band gap), a conductor (tiny or no band gap) or something in between—ie, a semiconductor (small band gap). Having no band gap at all is why graphene is such an excellent conductor. Making it into a semiconductor is tricky.

That is not all. A transistor works by flipping between two states—one insulating and the other conductive—in the presence of an electric field. These two states (off and on) represent the digital zeros and ones of computerspeak. By its nature, a graphene gate (switch) is on all the time. Getting it to turn off, let alone flip on and off billions of times a second, is the stumbling block.

There have been various attempts to open a band gap in graphene. One approach has been to dope it with compounds like silicon carbide or boron nitride that have matching crystalline lattice structures. Unfortunately, creating a band gap big enough to turn graphene into a usable semiconductor destroys the very properties—especially the high electron mobility—that made the material so attractive in the first place.

Older and wiser, researchers have turned to building hybrid chips that are fabricated, layer by layer, using conventional silicon epitaxy for everything except the final graphene transistor channels on the top of the device. These delicate structures are added at the end, so as not to get damaged during fabrication. So far, only analogue chips have been built this way. Even IBM has failed to create a band gap in graphene that would result in a digital device capable of challenging silicon’s preeminence. Transistors made entirely from graphene appear to be decades away.

So, where does that leave graphene’s prospects? While a replacement for silicon may be a long shot, many applications that do not rely on a band gap have a better chance of success. That said, not all graphene proposals being hyped at present can expect to survive the inevitable shake-out.

Had Gartner, an information-technology consultancy in Connecticut, included graphene-based processes as a stand-alone entry in its latest Emerging Technologies Hype Cycle, such processes would be over two-thirds the way up the slope to its “peak of inflated expectations”,which comes before the tip-over into the “trough of disillusionment” (see “Divining reality from hype”, August 27th 2014). Experience suggests that only those innovations which show genuine commercial value manage to crawl out of the trough and up the subsequent slope of enlightenment towards the plateau of productivity and market acceptance. Venture capitalists reckon no more than one in seven, at this stage of development, manages such a feat. It is too early to say whether graphene lightbulbs will be among them.

Readers with long memories may have noticed how the trajectory graphene is following resembles the one blazed by carbon fibre back in the 1960s. Then, as now, the new material was seen as a wonder product that would have numerous applications. Then, as now also, the British government felt it had a sacred duty to protect and promote what it perceived to be a home-grown invention—with the promise of jobs and exports.

If truth be told, the first hank of pyrolysed nylon (a carbon-fibre precursor) was snaffled from a Japanese textile factory and flown back to Britain in a diplomatic bag. At the time, British officials involved considered the super-strength material ideal for making gas centrifuges for enriching uranium. But samples that landed up at the Royal Aircraft Establishment in Farnborough led to the first carbon-fibre composite (Hyfil) being made available to select industrial partners, including the aeroengine manufacturer Rolls-Royce.

Of the many applications touted for carbon fibre, its promise to revolutionise air travel captured the most attention. With stronger, lighter fan blades, made from Hyfil instead of aluminium alloy or titanium, in a fan-jet’s first compressor stage, Rolls-Royce’s latest aircraft engine at the time, the RB211, would have had a significant weight-saving advantage—and thus better fuel economy—over rivals from General Electric and Pratt & Whitney.

The outcome was rather different. While turbine blades made from Hyfil had all the tensile strength, and more, to withstand the centrifugal forces of a big fan engine at full power, their shear strength left much to be desired. The story of how compressor blades shattered when a frozen chicken was fired at them to simulate bird impact contributed to carbon fibre’s fall from grace.

Meanwhile, the cost and delay involved in replacing the RB211’s Hyfil blades with titanium ones plunged Rolls-Royce into bankruptcy. Britain’s proudest engineering firm then had to be rescued at taxpayer expense. So much for governments picking winners. Hopefully, graphene is spared a similar fate.

1-california-drought-farmsNano-Filtration and the Water Crisis

Abstract: Adam Alonzi
The approaching water crisis will be solved by devices made possible by nanotechnology.

Since its conception concerns have been raised about nanotechnology’s potentially deleterious impact on the environment, but at this point it looks as though it will do more good than harm. From water remediation to solar cells to pollutant monitoring, nanotechnology, as I wrote in a recent blog entry, presents humanity with a “bevy of Black Swans.” The world’s fresh water supply is dwindling. Nanotech devices can empower governments and individuals around the world to use otherwise untapped sources through desalination and reclamation.

Zhang calls the scale of groundwater pollution “enormous” and the complexity “seemingly intractable.” Of the hundreds of thousands of sites in the United States identified by environmental agencies over the last three decades less than one third have been restored. Old mining areas, factories, landfills and dumping grounds continue to increase. As well as obvious undesirables like pathogens and heavy metals, more modern toxins, like endocrine disruptors and pharmaceuticals, must also be removed. While infrastructure improvements are necessary and inevitable in many places, nanotech research will accelerate, and be expedited by, the decentralization of water treatment.

 

Lockheed simulated-nanoporous-graphene-filtering-salt-ions

Nanofiltration involves using membranes with tiny pores (1-10 NM across) to remove specific molecules from a solution. Among other applications they are used to separate whey from the other constituents of milk and antibiotics from salty waste products. The major advantage they have over their competitors is the amount of pressure needed to pass liquid through them. Carbon nanotube membranes can remove an assortment of contaminants and aluminum based nanostructures are good at dismantling negatively charged baddies like viruses and bacteria, as well as some organic and inorganic compounds. Biomagnetite removes chlorinated organic molecules, silver slays bacteria and titanium dioxide, which is already used in a variety of consumer and industrial products, can break down organic compounds.

Dr. Sujoy Das assembled a silica-silver nanocomposite via biosynthesis. In other words, its production is cheap and green. The proteins covering the nanoparticles prevent them from leaching into the water. They also function as both reducing and protective agents for the silver nanoparticles. The nanocomposite removes dyes and microorganisms quickly. Moreover, the material can be reused several times.The LifeSaver bottle, invented shortly after hurricane Katrina, removes objects larger than 15 nanometers and works well for up to 1,500 gallons. It does not take out salt or some metals, however. This is unfortunate as in many regions the ocean is the only option.

Yet desalination is costly. It requires approximately 12 times the electricity needed to prepare fresh water for consumption. There is also the large initial investment of 200 million dollars or more to build a plant. Although for a glass of water 3 kilowatt hours is not bad at all, desalination is unfeasible on a large scale. Perforene, a graphene nanomembrane developed by Lockheed-Martin, was originally touted as being 100 times more efficient than other methods, but this estimate was later lowered to 20%. Thus, the enthusiasm was massively excessive and woefully premature. Yet this should not discourage. Every boom, or potential boom industry, has its share of exaggerated but stock boosting announcements, and does not mitigate the promise held by the technology in question.

Graphene, a hydrophobic material almost synonymous with nanotech, creates ultrafine capillaries through which water can pass. The pores can be extremely selective and the water can pass through them as easily as through a coffee filter, thus eliminating the need for energy-intensive high pressure systems. However, as Dr. Cohen cautions, a membrane that is five hundred times more permeable than its predecessor will not translate into proportional savings. Dr. Nair, one of the researchers working with this material says it “is as fast and as precise as one could possibly hope for such narrow capillaries. Now we want to control the graphene mesh size and reduce it below nine Angstroms to filter out even the smallest salts like in seawater. Our work shows that it is possible.”

Baines, Lawrence. “The Fight for Water.” Project-Based Writing in Science. SensePublishers, 2014. 81-89.

Cohen-Tanugi, David, and Jeffrey C. Grossman. “Water desalination across nanoporous graphene.” Nano letters 12.7 (2012): 3602-3608.

Inderscience Publishers. “Nanotechnology for water purification.” ScienceDaily. ScienceDaily, 28 July 2010. .

R. K. Joshi, P. Carbone, F. C. Wang, V. G. Kravets, Y. Su, I. V. Grigorieva, H. A. Wu, A. K. “Precise and Ultrafast Molecular Sieving through Graphene Oxide Membranes” Geim and R. R. Nair, Science, 2014.

Qu, Xiaolei, Pedro JJ Alvarez, and Qilin Li. “Applications of nanotechnology in water and wastewater treatment.” water research 47.12 (2013): 3931-3946.

Fuel Cells 0426 116806119How can nanotechnology improve fuel cells?

 *** From UnderstandingNano.com ***

Catalysts are used with fuels such as hydrogen or methanol to produce hydrogen ions. Platinum, which is very expensive, is the catalyst typically used in this process. Companies are using nanoparticles of platinum to reduce the amount of platinum needed, or using nanoparticles of other materials to replace platinum entirely and thereby lower costs.

Fuel cells contain membranes that allow hydrogen ions to pass through the cell but do not allow other atoms or ions, such as oxygen, to pass through. Companies are using nanotechnology to create more efficient membranes; this will allow them to build lighter weight and longer lasting fuel cells.

Small fuel cells are being developed that can be used to replace batteries in handheld devices such as PDAs or laptop computers. Most companies working on this type of fuel cell are using methanol as a fuel and are calling them DMFC’s, which stands for direct methanol fuel cell. DMFC’s are designed to last longer than conventional batteries. In addition, rather than plugging your device into an electrical outlet and waiting for the battery to recharge, with a DMFC you simply insert a new cartridge of methanol into the device and you’re ready to go.

Fuel cells that can replace batteries in electric cars are also under development. Hydrogen is the fuel most researchers propose for use in fuel cell powered cars. In addition to the improvements to catalysts and membranes discussed above, it is necessary to develop a lightweight and safe hydrogen fuel tank to hold the fuel and build a network of refueling stations. To build these tanks, researchers are trying to develop lightweight nanomaterials that will absorb the hydrogen and only release it when needed. The Department of Energy is estimating that widespread usage of hydrogen powered cars will not occur until approximately 2020.

Fuel Cells: Nanotechnology Applications

Researchers at the University of Copenhagen have demonstrated the ability to significantly reduce the amount of platinum needed as a catalyst in fuel cells.  The researchers found that the spacing between platinum nanoparticles affected the catalytic behavior, and that by controlling the packing density of the platinum nanoparticles they could reduce the amount of platinum needed.

Researchers at Brown University are developing a catalyst that uses no platinum. The catalyst is made from a sheet of graphene coated with cobalt nanoparticles. If this catalyst works out for production use with fuel cells it should be much less expensive than platinum based catalysts.

Researchers at Ulsan National Institute of Science and Technology have demonstrated how to produce edge-halogenated graphene nanoplatelets that have good catalytic properties. The researchers prepared the nanoplatelets by ball-milling graphene flakes in the presence of chlorine, bromine or iodine. They believe these halogenated nanoplatelets could be used as a replacement for expensive platinum catalystic material in fuel cells.

Researchers at Cornell University have developed a catalyst using platinum-cobalt nanoparticles that produces 12 times more catalytic activity than pure platinum. In order to achieve this performance the researchers annealed the nanoparticles so they formed a crystalline lattice which reduced the spacing between platinum atoms on the surface, increasing their reactivity.

Researchers at the University of Illinois have developed a proton exchange membrane using a silicon layer with pores of about 5 nanometers in diameter capped by a layer of porous silica. The silica layer is designed to insure that water stays in the nanopores. The water combines with the acid molecules along the wall of the nanopores to form an acidic solution, providing an easy pathway for hydrogen ions through the membrane. Evaluation of this membrane showed it to have much better conductivity of hydrogen ions (100 times better conductivity was reported) in low humidity conditions than the membrane normally used in fuel cells.

Researchers at Rensselaer Polytechnic Institute have investigated the storage of hydrogen in graphene (single atom thick carbon sheets). Hydrogen has a high bonding energy to carbon, and the researchers used annealing and plasma treatment to increase this bonding energy. Because graphene is only one atom thick it has the highest surface area exposure of carbon per weight of any material. High hydrogen to carbon bonding energy and high surface area exposure of carbon gives graphene has a good chance of storing hydrogen. The researchers found that they could store14% by weight of hydrogen in graphene.

Researchers at Stony Brook University have demonstrated that gold nanoparticles can be very effective at using solar energy to generate hydrogen from water. The key is making the nanoparticles very small. They found that  nanoparticles containing less than a dozen gold atoms are very effective photocatalysts for the generation of hydrogen.goldstand

Researchers at the SLAC National Accelerator Laboratory have developed a way to use less platinum for the cathode in a fuel cell, which could significantly reduce the cost of fuel cells. They alloyed platinum with copper and then removed the copper from the surface of the film, which caused the platinum atoms to move closer to each other (reducing the lattice space). It turns out that platinum with reduced lattice spacing is more a more effective catalyst for breaking up oxygen molecules into oxygen ion. The difference is that the reduced spacing changes the electronic structure of the platinum atoms so that the separated oxygen ions more easily released, and allowed to react with the hydrogen ions passing through the proton exchange membrane.

Another way to reduce the use of platinum for catalyst in fuel cell cathodes is being developed by researchers at Brown University. They deposited a one nanometer thick layer of platinum and iron on spherical nanoparticles of palladium. In laboratory scale testing they found that an catalyst made with these nanoparticles generated 12 times more current than a catalyst using pure platinum, and lasted ten times longer. The researchers believe that the improvement is due to a more efficient transfer of electrons than in standard catalysts.

Increasing catalyst surface area and efficiency by depositing platinum on porous alumina

Allowing the use of lower purity, and therefore less expensive, hydrogen with an anode made made of platinum nanoparticles deposited on titanium oxide.

Replacing platinum catalysts with less expensive nanomaterials

Using hydrogen fuel cells to power cars

Using nanostructured vanadium oxide in the anode of solid oxide fuel cells. The structure forms a battery, as well a fuel cell, therefore the cell can continue to provide electric current after the hydrogen fuel runs out.

 

Fuel Cells: Nanotechnology Company Directory

Company Product Advantage
QuantumSphere Non-platinum catalyst Reduces cost
MTI Micro DMFC’s Minimizes moving parts, reduces cost, size and weight
UltraCell DMFC’s that uses an extra catalyst to convert methanol to hydrogen before reaching the core of the fuel cell Increases power density and cell voltage
EDC Ovonics Hydrogen fuel tanks using metal hydrides as the storage media Reduce size, weight and pressure for storing hydrogen
Unidym Carbon nanotube based electrodes Improve efficiency of fuel cells by reducing resistive and mass transfer losses
GridShift Hydrogen generation using nanoparticle coated electrodes Improve efficiency of hydrogen generation by electrolysis
Aerogel Composite Catalyst with platinum nanoparticles embedded in a carbon aerogel Reduces platinum usage

Fuel Cell Resources

Hydrogen, Fuel Cells & Infrastructure Technologies Program at DOE

National Hydrogen Energy Roadmap

National Fuel Cell Research Center

California Fuel Cell Partnership

Department of Energy Hydrogen Permitting Web site

Listing of Hydrogen Fueling Station Location Worldwide

 

Given that less than 1 percent of the water on the planet is drinkable, a process to remove minerals, like salt, from water could help to alleviate many problems for the global community.
In the U.S., a research group based at the Department of Energy’s Oak Ridge National Laboratory have been working on a low-energy efficient desalination process. The newly devised method deploys a porous membrane made of graphene.

Graphene is a very strong, low weight material. It is 100 times stronger than steel and it conducts heat and electricity with great efficiency. The material is being investigated for many potential applications, including water purification.

The graphene membrane is, according to the researchers, more effective and uses less energy compared with current polymeric membranes, which work on the basis of reverse osmosis. With reverse osmosis an applied pressure is used to overcome osmotic pressure; this allows water to pass through a membrane whilst at the same time particles are retained.

With the new method the most important aspect is making the pores in the graphene. The size here is important: large enough to allow water molecules to pass through but sufficiently small to stop salt molecules from traversing the mesh.

The reason that the graphene process is more energy efficient comes down to the size of the mesh. Graphene is considerably thinner (just one atom in thickness) than the plastic polymers and the result of this is that less energy is required to push the fluid through.

The graphene structure was manufactured by passing methane gas through a tube furnace at 1,000 degrees C over a copper foil. This decomposed the methane into carbon and hydrogen. The carbon then assembled into a hexagonal configuration of one atom thick molecules. The graphene was then mounted onto a silicon nitride support. Small pores in the graphene are created using a plasma (an ionized gas.) Pores were created at the rate of one pore for every 100 square nanometers of graphene.

In experimental runs the graphene filter was used to remove salt from sea water in order to create water of drinking water quality. The test runs were effective with almost 100 percent of the salt removed.

The research has been published in the journal Nature Nanotechnology. The title of the paper is “Water Desalination Using Nanoporous Single-Layer Graphene.”

Read more: http://www.digitaljournal.com/science/graphene-technology-used-to-desalinate-water/article/429594#ixzz3Y4AR4wTh


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