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  • richardmitnick 3:48 pm on April 16, 2015 Permalink | Reply
    Tags: , , , Nanotechnology   

    From LBL: “News Center Major Advance in Artificial Photosynthesis Poses Win/Win for the Environment” 

    Berkeley Logo

    Berkeley Lab

    April 16, 2015
    Lynn Yarris (510) 486-5375

    1
    A major advance in artificial photosynthesis poses win/win for the environment – using sequestered CO2 for green chemistry, including renewable fuel production. (Photo by Caitlin Givens)

    A potentially game-changing breakthrough in artificial photosynthesis has been achieved with the development of a system that can capture carbon dioxide emissions before they are vented into the atmosphere and then, powered by solar energy, convert that carbon dioxide into valuable chemical products, including biodegradable plastics, pharmaceutical drugs and even liquid fuels.

    Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have created a hybrid system of semiconducting nanowires and bacteria that mimics the natural photosynthetic process by which plants use the energy in sunlight to synthesize carbohydrates from carbon dioxide and water. However, this new artificial photosynthetic system synthesizes the combination of carbon dioxide and water into acetate, the most common building block today for biosynthesis.

    “We believe our system is a revolutionary leap forward in the field of artificial photosynthesis,” says Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division and one of the leaders of this study. “Our system has the potential to fundamentally change the chemical and oil industry in that we can produce chemicals and fuels in a totally renewable way, rather than extracting them from deep below the ground.”

    2
    This break-through artificial photosynthesis system has four general components: (1) harvesting solar energy, (2) generating reducing equivalents, (3) reducing CO2 to biosynthetic intermediates, and (4) producing value-added chemicals.

    Yang, who also holds appointments with UC Berkeley and the Kavli Energy NanoSciences Institute (Kavli-ENSI) at Berkeley, is one of three corresponding authors of a paper describing this research in the journal Nano Letters. The paper is titled Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals. The other corresponding authors and leaders of this research are chemists Christopher Chang and Michelle Chang. Both also hold joint appointments with Berkeley Lab and UC Berkeley. In addition, Chris Chang is a Howard Hughes Medical Institute (HHMI) investigator. (See below for a full list of the paper’s authors.)

    The more carbon dioxide that is released into the atmosphere the warmer the atmosphere becomes. Atmospheric carbon dioxide is now at its highest level in at least three million years, primarily as a result of the burning of fossil fuels. Yet fossil fuels, especially coal, will remain a significant source of energy to meet human needs for the foreseeable future. Technologies for sequestering carbon before it escapes into the atmosphere are being pursued but all require the captured carbon to be stored, a requirement that comes with its own environmental challenges.

    3
    (From left) Peidong Yang, Christopher Chang and Michelle Chang led the development of an artificial photosynthesis system that can convert CO2 into valuable chemical products using only water and sunlight. (Photo by Roy Kaltschmidt)

    The artificial photosynthetic technique developed by the Berkeley researchers solves the storage problem by putting the captured carbon dioxide to good use.

    “In natural photosynthesis, leaves harvest solar energy and carbon dioxide is reduced and combined with water for the synthesis of molecular products that form biomass,” says Chris Chang, an expert in catalysts for carbon-neutral energy conversions. “In our system, nanowires harvest solar energy and deliver electrons to bacteria, where carbon dioxide is reduced and combined with water for the synthesis of a variety of targeted, value-added chemical products.”

    By combining biocompatible light-capturing nanowire arrays with select bacterial populations, the new artificial photosynthesis system offers a win/win situation for the environment: solar-powered green chemistry using sequestered carbon dioxide.

    “Our system represents an emerging alliance between the fields of materials sciences and biology, where opportunities to make new functional devices can mix and match components of each discipline,” says Michelle Chang, an expert in biosynthesis. “For example, the morphology of the nanowire array protects the bacteria like Easter eggs buried in tall grass so that these usually-oxygen sensitive organisms can survive in environmental carbon-dioxide sources such as flue gases.”

    The system starts with an “artificial forest” of nanowire heterostructures, consisting of silicon and titanium oxide nanowires, developed earlier by Yang and his research group.

    “Our artificial forest is similar to the chloroplasts in green plants,” Yang says. “When sunlight is absorbed, photo-excited electron−hole pairs are generated in the silicon and titanium oxide nanowires, which absorb different regions of the solar spectrum. The photo-generated electrons in the silicon will be passed onto bacteria for the CO2 reduction while the photo-generated holes in the titanium oxide split water molecules to make oxygen.”

    3
    Cross-sectional SEM image of the nanowire/bacteria hybrid array used in a revolutionary new artificial photosynthesis system.

    Once the forest of nanowire arrays is established, it is populated with microbial populations that produce enzymes known to selectively catalyze the reduction of carbon dioxide. For this study, the Berkeley team used Sporomusa ovata, an anaerobic bacterium that readily accepts electrons directly from the surrounding environment and uses them to reduce carbon dioxide.

    “S. ovata is a great carbon dioxide catalyst as it makes acetate, a versatile chemical intermediate that can be used to manufacture a diverse array of useful chemicals,” says Michelle Chang. “We were able to uniformly populate our nanowire array with S. ovata using buffered brackish water with trace vitamins as the only organic component.”

    Once the carbon dioxide has been reduced by S. ovata to acetate (or some other biosynthetic intermediate), genetically engineered E.coli are used to synthesize targeted chemical products. To improve the yields of targeted chemical products, the S. ovata and E.coli were kept separate for this study. In the future, these two activities – catalyzing and synthesizing – could be combined into a single step process.

    A key to the success of their artificial photosynthesis system is the separation of the demanding requirements for light-capture efficiency and catalytic activity that is made possible by the nanowire/bacteria hybrid technology. With this approach, the Berkeley team achieved a solar energy conversion efficiency of up to 0.38-percent for about 200 hours under simulated sunlight, which is about the same as that of a leaf.

    The yields of target chemical molecules produced from the acetate were also encouraging – as high as 26-percent for butanol, a fuel comparable to gasoline, 25-percent for amorphadiene, a precursor to the antimaleria drug artemisinin, and 52-percent for the renewable and biodegradable plastic PHB. Improved performances are anticipated with further refinements of the technology.

    “We are currently working on our second generation system which has a solar-to-chemical conversion efficiency of three-percent,” Yang says. “Once we can reach a conversion efficiency of 10-percent in a cost effective manner, the technology should be commercially viable.”

    In addition to the corresponding authors, other co-authors of the Nano Letters paper describing this research were Chong Liu, Joseph Gallagher, Kelsey Sakimoto and Eva Nichols.

    This research was primarily funded by the DOE Office of Science.

    See the full article here.

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  • richardmitnick 7:51 am on April 6, 2015 Permalink | Reply
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    From NOVA: “Silver Nanoparticles Could Give Millions Microbe-free Drinking Water” 

    PBS NOVA

    NOVA

    24 Mar 2015
    Cara Giaimo

    1
    Microbe-free drinking water is hard to come by in many areas of India.

    Chemists at the Indian Institute of Technology Madras have developed a portable, inexpensive water filtration system that is twice as efficient as existing filters. The filter doubles the well-known and oft-exploited antimicrobial effects of silver by employing nanotechnology. The team, led by Professor Thalappil Pradeep, plans to use it to bring clean water to underserved populations in India and beyond.

    Left alone, most water is teeming with scary things. A recent study showed that your average glass of West Bengali drinking water might contain E. coli, rotavirus, cryptosporidium, and arsenic. According to the World Health Organization, nearly a billion people worldwide lack access to clean water, and about 80% of illnesses in the developing world are water-related. India in particular has 16% of the world’s population and less than 3% of its fresh water supply. Ten percent of India’s population lacks water access, and every day about 1,600 people die of diarrhea, which is caused by waterborne microbes.

    Pradeep has spent over a decade using nanomaterials to chemically sift these pollutants out. He started by tackling endosulfan, a pesticide that was hugely popular until scientists determined that it destroyed ozone and brain cells in addition to its intended insect targets. Endosulfan is now banned in most places, but leftovers persist in dangerous amounts. After a bout of endosulfan poisoning in the southwest region of Kerala, Pradeep and his colleagues developed a drinking water filter that breaks the toxin down into harmless components. They licensed the design to a filtration company, who took it to market in 2007. It was “the first nano-chemistry based water product in the world,” he says.

    But Pradeep wanted to go bigger. “If pesticides can be removed by nanomaterials,” he remembers thinking, “can you also remove microbes without causing additional toxicity?” For this, Pradeep’s team put a new twist on a tried-and-true element: silver.

    Silver’s microbe-killing properties aren’t news—in fact, people have known about them for centuries, says Dr. David Barillo, a trauma surgeon and the editor of a recent silver-themed supplement of the journal Burns.

    “Alexander the Great stored and drank water in silver vessels when going on campaigns” in 335 BC, he says, and 19th century frontier-storming Americans dropped silver coins into their water barrels to suppress algae growth. During the space race, America and the Soviet Union both developed silver-based water purification techniques (NASA’s was “basically a silver wire sticking in the middle of a pipe that they were passing electricity through,” Barillo says). And new applications keep popping up: Barillo himself pioneered the use of silver-infused dressings to treat wounded soldiers in Afghanistan. “We’ve really run the gamut—we’ve gone from 300 BC to present day, and we’re still using it for the same stuff,” he says.

    No one knows exactly how small amounts of silver are able to kill huge swaths of microbes. According to Barillo, it’s probably a combination of attacks on the microbe’s enzymes, cell wall, and DNA, along with the buildup of silver free radicals, which are studded with unpaired electrons that gum up cellular systems. These microbe-mutilating strategies are so effective that they obscure our ability to study them, because we have nothing to compare them to. “It’s difficult to make something silver-resistant, even in the lab where you’re doing it intentionally,” Barillo says.

    But unlike equal-opportunity killers like endosulfan, silver knocks out the monsters and leaves the good guys alone. In low concentrations, it’s virtually harmless to humans. “It’s not a carcinogen, it’s not a mutagen, it’s not an allergen,” Barillo says. “It seems to have no purpose in human physiology—it’s not a metal that we need to have in our bodies like copper or magnesium. But it doesn’t seem to do anything bad either.”

    Though silver’s mysterious germ-killing properties are old news, Pradeep is taking advantage of them in new ways. The particles his team works with are less than 50 nanometers long on any one side—about four times smaller than the smallest bacteria. Working at this level allows him greater control over desired chemical reactions, and the ability to fine-tune his filters to improve efficiency or add specific effects. Two years ago, his team developed their biggest hit yet—a combination filter that kills microbes with silver and breaks down chemical toxins with other nanoparticles. It’s portable, works at room temperature, and doesn’t require electricity. Pradeep is working with the government to make these filters available to underserved communities. Currently 100,000 households have them; “by next year’s end,” he hopes, “it will reach 600,000 people.”

    The latest filter goes one better: it “tunes” the silver with carbonate, a negatively-charged ion that strips protective proteins from microbe cell membranes. This leaves the microbes even more vulnerable to silver’s attack. “In the presence of carbonate, silver is even more effective,” he explains, so he can use less of it: “Fifty parts per billion can be brought down to [25].” Unlike the earlier filter, this one kills viruses, too—good news, since according to the National Institute of Virology, most do not.

    Going from 50 parts per billion of silver to 25 may not seem like a huge leap. But for Pradeep—who aims to help a lot of people for a long time—every little bit counts. Filters that contain less silver are less expensive to produce. This is vital if you want to keep costs low enough for those who need them most to buy them, or to entice the government into giving them away. He estimates that one of his new filter units will cost about $2 per year, proportionately less than what the average American pays for water.

    Using less silver also improves sustainability. “Globally, silver is the most heavily used nanomaterial,” Pradeep says, and it’s not renewable: anything we use “is lost for the world.” If all filters used his carbonate trick, he points out, we could make twice as many of them before we run out of raw materials—and even more if, as he hopes, his future tunings bring the necessary amount down further. This will become especially important if his filters catch on in other places with no infrastructure and needy populations. “Ultimately, I want to use the very minimum quantity of silver,” he says.

    “Pradeep’s work shows enormous potential,” says Dr. Theresa Dankovich, a water filtration expert at the University of Virginia’s Center for Global Health. But, she points out, “carbonate anions are naturally occurring in groundwater and surface waters,” so “it warrants further study to determine how they are already enhancing the effect of silver ions and silver nanoparticles,” even without purposeful manipulation by chemists. Others see potential shortcomings. James Smith, a professor of environmental engineering at the University of Virginia and the inventor of a nanoparticle-coated clay filtering pot, worries that the nanotech-heavy production process “would not allow for manufacturing in a developing world setting,” especially if Pradeep’s continuous tweaking of the model deters large-scale companies from actually producing it.

    Nevertheless, Pradeep plans to continue scaling up. “If you can provide clean water, you have provided a solution for almost everything,” he says. When you have the lessons of history and the technology of the future, why settle for anything less?

    See the full article here.

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  • richardmitnick 7:29 am on April 6, 2015 Permalink | Reply
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    From AAAS: “U.S. takes possible first step toward regulating nanochemicals” 

    AAAS

    AAAS

    2 April 2015
    Puneet Kollipara

    1
    Nanocubes, which researchers have explored as a possible way to store hydrogen for energy. BASF/Flickr

    The U.S. Environmental Protection Agency (EPA) is ratcheting up its scrutiny of nanoscale chemicals amid concerns that they could pose unique environmental and health risks. Late last month, the agency proposed requiring companies to submit data on industrial nanomaterials that they already make and sell. Observers say EPA’s move could be a prelude to tighter federal regulation of nanomaterials, which have begun to show up in consumer products.

    For years, EPA has grappled with whether and how to use the Toxic Substances Control Act (TSCA), the nation’s leading chemical regulation law, to handle nanomaterials. TSCA is silent on nanoproducts, generally defined as materials composed of structures between 1 and 100 billionths of a meter. But many environmental groups worry that they potentially carry unknown risks by virtue of their size. Other observers, however, have argued that size alone shouldn’t trigger new regulation and that existing rules are adequate to deal with the new products.

    EPA’s 25 March proposal actually walks back an earlier version—now scrapped—that would have let the agency more easily clamp down on any new uses of nanomaterials. Still, the weaker version being proposed now represents the first time EPA would use its powers under TSCA to request information specifically on nanomaterials. (The proposal comes as Congress is debating revamping TSCA, which has drawn extensive criticism.)

    Under the rule, manufacturers would have to submit a range of data regarding the nanoscale substances they now make and that fall under TSCA’s scope—such as substances used in industrial applications. EPA wants to know how much the company is producing, for example, as well as potential public exposures, and manufacturing and processing methods. It also wants see any existing health and safety data. In addition, the agency would require manufacturers of proposed new nanomaterials to submit existing data before they want to start making and selling those substances.

    The rule wouldn’t force companies to generate any new health and safety data. And by itself, the rule wouldn’t restrict any nanomaterials’ use, EPA notes in its draft proposal. The agency’s actions “do not conclude and are not intended to conclude that nanoscale materials as a class, or specific uses of nanoscale materials, necessarily give rise to or are likely to cause harm,” the notice states. Rather, EPA says the information would let it better assess nanomaterials’ risks.

    And the agency states that its approach would help protect human health and the environment “without prejudging new technologies or creating unnecessary barriers to trade or hampering innovation.” EPA argues that case-by-case approach would jibe with a set of nanotech regulation principles released in 2011 by the White House Office of Science and Technology Policy. Those principles advise agencies against making one-size-fits-all judgments.

    The American Chemistry Council (ACC), the largest chemical industry trade group, is still evaluating the proposal, it said in a statement. But it “is particularly interested in how EPA defines the materials to be covered by the proposed rule,” says Jay West, manager of ACC’s Nanotechnology Panel, says in the statement.

    The proposal is “logical” and “creatively written,” says Lynn Bergeson, a managing partner with the law firm Bergeson & Campbell, P.C. in Washington, D.C., which advises companies on EPA regulatory compliance. Some companies may argue the rule is too broad or burdensome, she says, or worry that EPA’s move could stigmatize their products. But the government effort to collect information could potentially help the industry by reassuring a skeptical public, she adds. “If there are no data on which EPA is able to rely to conclude that there is no risk, then the agency really is not doing its job,” she says.

    The proposal is a good first step for EPA, says Jaydee Hanson, policy director at the International Center for Technology Assessment, a group in Washington, D.C., that has raised concerns about nanotechnology’s potential risks. But he worries that many companies might simply not respond and that the cash-strapped EPA would struggle to crack down on violators. And he worries that the proposal would let companies keep too much information secret, by claiming it as confidential business information. (TSCA reforms that Congress is debating would limit the types of information that companies could claim as confidential, he notes.) But Hanson is looking on the bright side. “We wish [EPA was] doing more, but we’re excited that they are doing it,” he says.

    Still, even with all the new information in hand, it’s unclear how much action EPA could take to restrict nanomaterials under current law. In general, EPA has moved slowly to regulate new chemicals, and struggled to meet the burden that TSCA sets on it for removing, restricting, or preventing the sale of chemicals found to be unsafe. Congress says it wants to make that process easier, but it is unclear how any new rules would apply to nanotechnologies.

    See the full article here.

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  • richardmitnick 11:47 am on March 25, 2015 Permalink | Reply
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    From UW: “UW scientists build a nanolaser using a single atomic sheet” 

    U Washington

    University of Washington

    March 23, 2015
    Jennifer Langston

    1
    The ultra-thin semiconductor, which is about 100,000 times thinner than a human hair, stretches across the top of the photonic cavity.U of Washington

    University of Washington scientists have built a new nanometer-sized laser — using the thinnest semiconductor available today — that is energy efficient, easy to build and compatible with existing electronics.

    Lasers play essential roles in countless technologies, from medical therapies to metal cutters to electronic gadgets. But to meet modern needs in computation, communications, imaging and sensing, scientists are striving to create ever-smaller laser systems that also consume less energy.

    The UW nanolaser, developed in collaboration with Stanford University, uses a tungsten-based semiconductor only three atoms thick as the “gain material” that emits light. The technology is described in a paper published in the March 16 online edition of Nature.

    “This is a recently discovered, new type of semiconductor which is very thin and emits light efficiently,” said Sanfeng Wu, lead author and a UW doctoral candidate in physics. “Researchers are making transistors, light-emitting diodes, and solar cells based on this material because of its properties. And now, nanolasers.”

    Nanolasers — which are so small they can’t be seen with the eye — have the potential to be used in a wide range of applications from next-generation computing to implantable microchips that monitor health problems. But nanolasers so far haven’t strayed far from the research lab.

    Other nanolaser designs use gain materials that are either much thicker or that are embedded in the structure of the cavity that captures light. That makes them difficult to build and to integrate with modern electrical circuits and computing technologies.

    The UW version, instead, uses a flat sheet that can be placed directly on top of a commonly used optical cavity, a tiny cave that confines and intensifies light. The ultrathin nature of the semiconductor — made from a single layer of a tungsten-based molecule — yields efficient coordination between the two key components of the laser.

    The UW nanolaser requires only 27 nanowatts to kickstart its beam, which means it is very energy efficient.

    Other advantages of the UW team’s nanolaser are that it can be easily fabricated, and it can potentially work with silicon components common in modern electronics. Using a separate atomic sheet as the gain material offers versatility and the opportunity to more easily manipulate its properties.

    “You can think of it as the difference between a cell phone where the SIM card is embedded into the phone versus one that’s removable,” said co-author Arka Majumdar, UW assistant professor of electrical engineering and of physics.

    “When you’re working with other materials, your gain medium is embedded and you can’t change it. In our nanolasers, you can take the monolayer out or put it back, and it’s much easier to change around,” he said.

    2
    This emission map of the nano-device shows the light is confined by and emitted from the photonic cavity.U of Washington

    The researchers hope this and other recent innovations will enable them to produce an electrically-driven nanolaser that could open the door to using light, rather than electrons, to transfer information between computer chips and boards.

    The current process can cause systems to overheat and wastes power, so companies such as Facebook, Oracle, HP, Google and Intel with massive data centers are keenly interested in more energy-efficient solutions.

    Using photons rather than electrons to transfer that information would consume less energy and could enable next-generation computing that breaks current bandwidth and power limitations. The recently proven UW nanolaser technology is one step toward making optical computing and short distance optical communication a reality.

    “We all want to make devices run faster with less energy consumption, so we need new technologies,” said co-author Xiaodong Xu, UW associate professor of materials science and engineering and of physics. “The real innovation in this new approach of ours, compared to the old nanolasers, is that we’re able to have scalability and more controls.”

    Still, there’s more work to be done in the near future, Xu said. Next steps include investigating photon statistics to establish the coherent properties of the laser’s light.

    Co-authors are John Schaibley of the UW, Liefeng Feng of the UW and Tianjin University in China, Sonia Buckley and Jelena Vuckovic of Stanford University, Jiaqiang Yan and David G. Mandrus of Oak Ridge National Laboratory and the University of Tennessee, Fariba Hatami of Humboldt University in Berlin and Wang Yao of the University of Hong Kong.

    Primary funding came from the Air Force Office of Scientific Research. Other funders include the National Science Foundation, the state of Washington through the Clean Energy Institute, the Presidential Early Award for Scientists and Engineers administered through the Office of Naval Research, the U.S. Department of Energy, and the European Commission.

    For more information, contact Xu at xuxd@uw.edu and Majumdar at arka@uw.edu.

    See the full article here.

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  • richardmitnick 8:41 am on March 19, 2015 Permalink | Reply
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    From SLAC: “Scientists Watch Quantum Dots ‘Breathe’ in Response to Stress” 


    SLAC Lab

    March 18, 2015

    Nanocrystal Study at SLAC’s X-ray Laser Could Aid in the Design of New Materials

    1
    In this illustration, intense X-rays produced at SLAC’s Linac Coherent Light Source strike nanocrystals of a semiconductor material. Scientists used the X-rays to study an ultrafast “breathing” response in the crystals induced quadrillionths of a second earlier by laser light. (SLAC National Accelerator Laboratory)

    Researchers at the Department of Energy’s SLAC National Accelerator Laboratory watched nanoscale semiconductor crystals expand and shrink in response to powerful pulses of laser light. This ultrafast “breathing” provides new insight about how such tiny structures change shape as they start to melt – information that can help guide researchers in tailoring their use for a range of applications.

    In the experiment using SLAC’s Linac Coherent Light Source (LCLS) X-ray laser, a DOE Office of Science User Facility, researchers first exposed the nanocrystals to a burst of laser light, followed closely by an ultrabright X-ray pulse that recorded the resulting structural changes in atomic-scale detail at the onset of melting.

    SLAC LCLS Inside
    LCLS

    “This is the first time we could measure the details of how these ultrasmall materials react when strained to their limits,” said Aaron Lindenberg, an assistant professor at SLAC and Stanford who led the experiment. The results were published March 12 in Nature Communications.

    Getting to Know Quantum Dots

    The crystals studied at SLAC are known as “quantum dots” because they display unique traits at the nanoscale that defy the classical physics governing their properties at larger scales. The crystals can be tuned by changing their size and shape to emit specific colors of light, for example.

    So scientists have worked to incorporate them in solar panels to make them more efficient and in computer displays to improve resolution while consuming less battery power. These materials have also been studied for potential use in batteries and fuel cells and for targeted drug delivery.

    Scientists have also discovered that these and other nanomaterials, which may contain just tens or hundreds of atoms, can be far more damage-resistant than larger bits of the same materials because they exhibit a more perfect crystal structure at the tiniest scales. This property could prove useful in battery components, for example, as smaller particles may be able to withstand more charging cycles than larger ones before degrading.

    A Surprise in the ‘Breathing’ of Tiny Spheres and Nanowires

    In the LCLS experiment, researchers studied spheres and nanowires made of cadmium sulfide and cadmium selenide that were just 3 to 5 nanometers, or billionths of a meter, across. The nanowires were up to 25 nanometers long. By comparison, amino acids – the building blocks of proteins – are about 1 nanometer in length, and individual atoms are measured in tenths of nanometers.

    By examining the nanocrystals from many different angles with X-ray pulses, researchers reconstructed how they change shape when hit with an optical laser pulse. They were surprised to see the spheres and nanowires expand in width by about 1 percent and then quickly contract within femtoseconds, or quadrillionths of a second. They also found that the nanowires don’t expand in length, and showed that the way the crystals respond to strain was coupled to how their structure melts.

    In an earlier, separate study, another team of researchers had used LCLS to explore the response of larger gold particles on longer timescales.

    “In the future, we want to extend these experiments to more complex and technologically relevant nanostructures, and also to enable X-ray exploration of nanoscale devices while they are operating,” Lindenberg said. “Knowing how materials change under strain can be used together with simulations to design new materials with novel properties.”

    Participating researchers were from SLAC, Stanford and two of their joint institutes, the Stanford Institute for Materials and Energy Sciences (SIMES) and Stanford PULSE Institute; University of California, Berkeley; University of Duisburg-Essen in Germany; and Argonne National Laboratory. The work was supported by the DOE Office of Science and the German Research Council.

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  • richardmitnick 9:04 am on February 19, 2015 Permalink | Reply
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    From MIT: “New nanogel for drug delivery” 


    MIT News

    February 19, 2015
    Anne Trafton | MIT News Office

    1

    Self-healing gel can be injected into the body and act as a long-term drug depot.

    Scientists are interested in using gels to deliver drugs because they can be molded into specific shapes and designed to release their payload over a specified time period. However, current versions aren’t always practical because must be implanted surgically.

    To help overcome that obstacle, MIT chemical engineers have designed a new type of self-healing hydrogel that could be injected through a syringe. Such gels, which can carry one or two drugs at a time, could be useful for treating cancer, macular degeneration, or heart disease, among other diseases, the researchers say.

    The new gel consists of a mesh network made of two components: nanoparticles made of polymers entwined within strands of another polymer, such as cellulose.

    “Now you have a gel that can change shape when you apply stress to it, and then, importantly, it can re-heal when you relax those forces. That allows you to squeeze it through a syringe or a needle and get it into the body without surgery,” says Mark Tibbitt, a postdoc at MIT’s Koch Institute for Integrative Cancer Research and one of the lead authors of a paper describing the gel in Nature Communications on Feb. 19.

    Koch Institute postdoc Eric Appel is also a lead author of the paper, and the paper’s senior author is Robert Langer, the David H. Koch Institute Professor at MIT. Other authors are postdoc Matthew Webber, undergraduate Bradley Mattix, and postdoc Omid Veiseh.

    Heal thyself

    Scientists have previously constructed hydrogels for biomedical uses by forming irreversible chemical linkages between polymers. These gels, used to make soft contact lenses, among other applications, are tough and sturdy, but once they are formed their shape cannot easily be altered.

    The MIT team set out to create a gel that could survive strong mechanical forces, known as shear forces, and then reform itself. Other researchers have created such gels by engineering proteins that self-assemble into hydrogels, but this approach requires complex biochemical processes. The MIT team wanted to design something simpler.

    “We’re working with really simple materials,” Tibbitt says. “They don’t require any advanced chemical functionalization.”

    The MIT approach relies on a combination of two readily available components. One is a type of nanoparticle formed of PEG-PLA copolymers, first developed in Langer’s lab decades ago and now commonly used to package and deliver drugs. To form a hydrogel, the researchers mixed these particles with a polymer — in this case, cellulose.

    Each polymer chain forms weak bonds with many nanoparticles, producing a loosely woven lattice of polymers and nanoparticles. Because each attachment point is fairly weak, the bonds break apart under mechanical stress, such as when injected through a syringe. When the shear forces are over, the polymers and nanoparticles form new attachments with different partners, healing the gel.

    Using two components to form the gel also gives the researchers the opportunity to deliver two different drugs at the same time. PEG-PLA nanoparticles have an inner core that is ideally suited to carry hydrophobic small-molecule drugs, which include many chemotherapy drugs. Meanwhile, the polymers, which exist in a watery solution, can carry hydrophilic molecules such as proteins, including antibodies and growth factors.

    Long-term drug delivery

    In this study, the researchers showed that the gels survived injection under the skin of mice and successfully released two drugs, one hydrophobic and one hydrophilic, over several days.

    This type of gel offers an important advantage over injecting a liquid solution of drug-delivery nanoparticles: While a solution will immediately disperse throughout the body, the gel stays in place after injection, allowing the drug to be targeted to a specific tissue. Furthermore, the properties of each gel component can be tuned so the drugs they carry are released at different rates, allowing them to be tailored for different uses.

    The researchers are now looking into using the gel to deliver anti-angiogenesis drugs to treat macular degeneration. Currently, patients receive these drugs, which cut off the growth of blood vessels that interfere with sight, as an injection into the eye once a month. The MIT team envisions that the new gel could be programmed to deliver these drugs over several months, reducing the frequency of injections.

    Another potential application for the gels is delivering drugs, such as growth factors, that could help repair damaged heart tissue after a heart attack. The researchers are also pursuing the possibility of using this gel to deliver cancer drugs to kill tumor cells that get left behind after surgery. In that case, the gel would be loaded with a chemical that lures cancer cells toward the gel, as well as a chemotherapy drug that would kill them. This could help eliminate the residual cancer cells that often form new tumors following surgery.

    “Removing the tumor leaves behind a cavity that you could fill with our material, which would provide some therapeutic benefit over the long term in recruiting and killing those cells,” Appel says. “We can tailor the materials to provide us with the drug-release profile that makes it the most effective at actually recruiting the cells.”

    The research was funded by the Wellcome Trust, the Misrock Foundation, the Department of Defense, and the National Institutes of Health.

    See the full article here.

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  • richardmitnick 2:38 am on February 14, 2015 Permalink | Reply
    Tags: , Nanotechnology,   

    From phys.org: “Getting two for one: ‘Bonus’ electrons in germanium nanocrystals can lead to better solar cells” 

    physdotorg
    phys.org

    February 14, 2015
    Ans Hekkenberg

    1
    The material is illuminated with photons. In some of the germanium nanocrystals, the photons cause electrons to be excited, and thus form an electron-hole (e-h) pair. There are two possibilities. (1) The incoming photon has an energy in the range between once and twice the bandgap energy. One e-h pair is formed. (2) The incoming photon has an energy of more than two times the bandgap energy. The excess energy of the electron – the ‘kinetic’ energy of the electron which is excited high up in the conduction band – is sufficient to create a second e-h pair in the same nanocrystal. In that way, carrier multiplication is achieved. Credit: Fundamental Research on Matter (FOM)

    Researchers from FOM, the University of Amsterdam, the Delft University of Technology and the University of the Algarve have discovered that when light hits germanium nanocrystals, the crystals produce ‘bonus electrons’. These additional electrons could increase the yield of solar cells and improve the sensitivity of photodetectors. The researchers will publish their work in Light: Science & Applications today.

    In nanocrystals, the absorption of a single photon can lead to the excitation of multiple electrons: two for one! This phenomenon, known as carrier multiplication, was already well known in silicon nanocrystals. Silicon is the most commonly used material in solar cells. However, the researchers found that carrier multiplication also occurs in germanium nanocrystals, which are more suitable for optimizing the efficiency than silicon nanocrystals. Their discovery could lead to better solar cells.

    Semiconductor physics

    Germanium and silicon are examples of semiconductors: materials that have an energy bandgap. When these materials absorb light, electrons from the band below this energy gap (valence band) leap to the band above the gap (conduction band). These excited ‘hot’ electrons and the holes they leave behind can be harvested to form an electrical current. They form the basic fuel for a solar cell.

    Nanocrystals and carrier multiplication

    If an absorbed photon contains more energy than an electron requires to leap over the bandgap, the excess energy can be used to excite a second electron. Earlier research has shown that a bandgap energy from 0.6 to 1.0 electronvolts is ideal to achieve this carrier multiplication.

    Nanocrystals are extremely small, about a thousand times smaller than the width of a human hair. Due to their size, the energy structure of the crystals is dramatically different from that of bulk material. In fact, the bandgap energy depends on the nanocrystal size. Bulk germanium has an energy bandgap of 0.67 electronvolts. By tuning the germanium nanocrystals’ size, the researchers can change the bandgap energy to values between 0.6 and 1.4 electronvolts. This is within the ideal range for optimizing carrier multiplication, or the amount of ‘bonus electrons’.

    Performing the experiment

    To investigate carrier multiplication in nanocrystals, the researchers used an optical technique called pump-probe spectroscopy. An initial laser pulse, called the pump, emits photons that excite the nanocrystal by creating one free electron in the conduction band. A second pulse of photons, called the probe, can then be absorbed by this electron.

    The researchers found that if the energy of the pump photon is twice the bandgap energy of the germanium nanocrystals, the probe light is absorbed by two electrons instead of one. This effect is the well-known fingerprint of carrier multiplication. In other words, if the pump photon carries sufficient energy, the hot electron contains enough excess energy to excite a second electron in the same nanocrystal. Using this carrier multiplication, germanium nanocrystals can help achieve the maximum efficiency of solar cells.

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 5:34 am on February 13, 2015 Permalink | Reply
    Tags: , , Nanotechnology, , ,   

    From phys.org: “Gold nanotubes launch a three-pronged attack on cancer cells” 

    physdotorg
    phys.org

    Feb 13, 2015

    1
    Pulsed near infrared light (shown in red) is shone onto a tumour (shown in white) that is encased in blood vessels. The tumour is imaged by multispectral optoacoustic tomography via the ultrasound emission (shown in blue) from the gold nanotubes. Credit: Jing Claussen (Ithera Medical, Germany)

    Scientists have shown that gold nanotubes have many applications in fighting cancer: internal nanoprobes for high-resolution imaging; drug delivery vehicles; and agents for destroying cancer cells.

    The study, published today in the journal Advanced Functional Materials, details the first successful demonstration of the biomedical use of gold nanotubes in a mouse model of human cancer.

    Study lead author Dr Sunjie Ye, who is based in both the School of Physics and Astronomy and the Leeds Institute for Biomedical and Clinical Sciences at the University of Leeds, said: “High recurrence rates of tumours after surgical removal remain a formidable challenge in cancer therapy. Chemo- or radiotherapy is often given following surgery to prevent this, but these treatments cause serious side effects.

    Gold nanotubes – that is, gold nanoparticles with tubular structures that resemble tiny drinking straws – have the potential to enhance the efficacy of these conventional treatments by integrating diagnosis and therapy in one single system.”

    The researchers say that a new technique to control the length of nanotubes underpins the research. By controlling the length, the researchers were able to produce gold nanotubes with the right dimensions to absorb a type of light called ‘near infrared’.

    The study’s corresponding author Professor Steve Evans, from the School of Physics and Astronomy at the University of Leeds, said: “Human tissue is transparent for certain frequencies of light – in the red/infrared region. This is why parts of your hand appear red when a torch is shone through it.

    “When the gold nanotubes travel through the body, if light of the right frequency is shone on them they absorb the light. This light energy is converted to heat, rather like the warmth generated by the Sun on skin. Using a pulsed laser beam, we were able to rapidly raise the temperature in the vicinity of the nanotubes so that it was high enough to destroy cancer cells.”

    In cell-based studies, by adjusting the brightness of the laser pulse, the researchers say they were able to control whether the gold nanotubes were in cancer-destruction mode, or ready to image tumours.

    In order to see the gold nanotubes in the body, the researchers used a new type of imaging technique called ‘multispectral optoacoustic tomography’ (MSOT) to detect the gold nanotubes in mice, in which gold nanotubes had been injected intravenously. It is the first biomedical application of gold nanotubes within a living organism. It was also shown that gold nanotubes were excreted from the body and therefore are unlikely to cause problems in terms of toxicity, an important consideration when developing nanoparticles for clinical use.

    Study co-author Dr James McLaughlan, from the School of Electronic & Electrical Engineering at the University of Leeds, said: “This is the first demonstration of the production, and use for imaging and cancer therapy, of gold nanotubes that strongly absorb light within the ‘optical window’ of biological tissue.

    “The nanotubes can be tumour-targeted and have a central ‘hollow’ core that can be loaded with a therapeutic payload. This combination of targeting and localised release of a therapeutic agent could, in this age of personalised medicine, be used to identify and treat cancer with minimal toxicity to patients.”

    The use of gold nanotubes in imaging and other biomedical applications is currently progressing through trial stages towards early clinical studies.

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 7:26 pm on February 9, 2015 Permalink | Reply
    Tags: , , , Nanotechnology,   

    From Rice: “Nano-antioxidants prove their potential” 

    Rice U bloc

    Rice University

    February 9, 2015
    Mike Williams

    Rice-led study shows how particles quench damaging superoxides

    Injectable nanoparticles that could protect an injured person from further damage due to oxidative stress have proven to be astoundingly effective in tests to study their mechanism.

    Scientists at Rice University, Baylor College of Medicine and the University of Texas Health Science Center at Houston (UTHealth) Medical School designed methods to validate their 2012 discovery that combined polyethylene glycol-hydrophilic carbon clusters — known as PEG-HCCs — could quickly stem the process of overoxidation that can cause damage in the minutes and hours after an injury.

    1
    A polyethylene glycol-hydrophilic carbon cluster developed at Rice University has the potential to quench the overexpression of damaging superoxides through the catalytic turnover of reactive oxygen species that can harm biological functions. Illustration by Errol Samuel

    The tests revealed a single nanoparticle can quickly catalyze the neutralization of thousands of damaging reactive oxygen species molecules that are overexpressed by the body’s cells in response to an injury and turn the molecules into oxygen. These reactive species can damage cells and cause mutations, but PEG-HCCs appear to have an enormous capacity to turn them into less-reactive substances.

    The researchers hope an injection of PEG-HCCs as soon as possible after an injury, such as traumatic brain injury or stroke, can mitigate further brain damage by restoring normal oxygen levels to the brain’s sensitive circulatory system.

    The results were reported today in the Proceedings of the National Academy of Sciences.

    “Effectively, they bring the level of reactive oxygen species back to normal almost instantly,” said Rice chemist James Tour. “This could be a useful tool for emergency responders who need to quickly stabilize an accident or heart attack victim or to treat soldiers in the field of battle.” Tour led the new study with neurologist Thomas Kent of Baylor College of Medicine and biochemist Ah-Lim Tsai of UTHealth.

    PEG-HCCs are about 3 nanometers wide and 30 to 40 nanometers long and contain from 2,000 to 5,000 carbon atoms. In tests, an individual PEG-HCC nanoparticle can catalyze the conversion of 20,000 to a million reactive oxygen species molecules per second into molecular oxygen, which damaged tissues need, and hydrogen peroxide while quenching reactive intermediates.

    Tour and Kent led the earlier research that determined an infusion of nontoxic PEG-HCCs may quickly stabilize blood flow in the brain and protect against reactive oxygen species molecules overexpressed by cells during a medical trauma, especially when accompanied by massive blood loss.

    Their research targeted traumatic brain injuries, after which cells release an excessive amount of the reactive oxygen species known as a superoxide into the blood. These toxic free radicals are molecules with one unpaired electron that the immune system uses to kill invading microorganisms. In small concentrations, they contribute to a cell’s normal energy regulation. Generally, they are kept in check by superoxide dismutase, an enzyme that neutralizes superoxides.

    But even mild traumas can release enough superoxides to overwhelm the brain’s natural defenses. In turn, superoxides can form such other reactive oxygen species as peroxynitrite that cause further damage.

    “The current research shows PEG-HCCs work catalytically, extremely rapidly and with an enormous capacity to neutralize thousands upon thousands of the deleterious molecules, particularly superoxide and hydroxyl radicals that destroy normal tissue when left unregulated,” Tour said.

    “This will be important not only in traumatic brain injury and stroke treatment, but for many acute injuries of any organ or tissue and in medical procedures such as organ transplantation,” he said. “Anytime tissue is stressed and thereby oxygen-starved, superoxide can form to further attack the surrounding good tissue.”

    The researchers used an electron paramagnetic resonance spectroscopy technique that gets direct structure and rate information for superoxide radicals by counting unpaired electrons in the presence or absence of PEG-HCC antioxidants. Another test with an oxygen-sensing electrode, peroxidase and a red dye confirmed the particles’ ability to catalyze superoxide conversion.

    “In sharp contrast to the well-known superoxide dismutase, PEG-HCC is not a protein and does not have metal to serve the catalytic role,” Tsai said. “The efficient catalytic turnover could be due to its more ‘planar,’ highly conjugated carbon core.”

    The tests showed the number of superoxides consumed far surpassed the number of possible PEG-HCC bonding sites. The researchers found the particles have no effect on important nitric oxides that keep blood vessels dilated and aid neurotransmission and cell protection, nor was the efficiency sensitive to pH changes.

    “PEG-HCCs have enormous capacity to convert superoxide to oxygen and the ability to quench reactive intermediates while not affecting nitric oxide molecules that are beneficial in normal amounts,” Kent said. “So they hold a unique place in our potential armamentarium against a range of diseases that involve loss of oxygen and damaging levels of free radicals.”

    The study also determined PEG-HCCs remain stable, as batches up to 3 months old performed as good as new.

    Graduate student Errol Samuel and alumna Daniela Marcano, both of Rice, and Vladimir Berka, a senior research scientist at UTHealth, are lead authors of the study. Co-authors are Rice alumnus Austin Potter; alumnus Brittany Bitner and associate professor Robia Pautler of Baylor College of Medicine; instructor Gang Wu of UTHealth and Roderic Fabian of Baylor College of Medicine and the Michael E. DeBakey Veterans Affairs Medical Center.

    Kent is a professor of neurology and director of stroke research and education at Baylor College of Medicine and chief of neurology and a member of the Center for Translational Research on Inflammatory Diseases at the DeBakey Center. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of materials science and nanoengineering and of computer science and a member of Rice’s Richard E. Smalley Institute for Nanoscale Science and Technology. Tsai is a professor of hematology at UTHealth and adjunct professor of biochemistry and cell biology at Rice.

    The Mission Connect Mild Traumatic Brain Injury Consortium from the Department of Defense and the National Institutes of Health, the Alliance for NanoHealth and UTHealth supported the research.

    See the full article here.

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    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
  • richardmitnick 5:28 pm on February 9, 2015 Permalink | Reply
    Tags: , , , , Nanotechnology   

    From LBL: “New Design Tool for Metamaterials” 

    Berkeley Logo

    Berkeley Lab

    February 9, 2015
    Lynn Yarris (510) 486-5375

    1
    Confocal microscopy confirmed that the nonlinear optical properties of metamaterials can be predicted using a
    theory about light passing through nanostructures.

    Metamaterials – artificial nanostructures engineered with electromagnetic properties not found in nature – offer tantalizing future prospects such as high resolution optical microscopes and superfast optical computers. To realize the vast potential of metamaterials, however, scientists will need to hone their understanding of the fundamental physics behind them. This will require accurately predicting nonlinear optical properties – meaning that interaction with light changes a material’s properties, for example, light emerges from the material with a different frequency than when it entered. Help has arrived.

    Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have shown, using a recent theory for nonlinear light scattering when light passes through nanostructures, that it is possible to predict the nonlinear optical properties of metamaterials.

    “The key question has been whether one can determine the nonlinear behavior of metamaterials from their exotic linear behavior,” says Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division and an international authority on metamaterial engineering who led this study. “We’ve shown that the relative nonlinear susceptibility of large classes of metamaterials can be predicted using a comprehensive nonlinear scattering theory. This will allow us to efficiently design metamaterials with strong nonlinearity for important applications such as coherent Raman sensing, entangled photon generation and frequency conversion.”

    2
    Xiang Zhang, Haim Suchowski and Kevin O’Brien were part of the team that discovered a way to predict thenon-linear optical properties of metamaterials. (Photo by Roy Kaltschmidt)

    Zhang, who holds the Ernest S. Kuh Endowed Chair at UC Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley (Kavli ENSI), is the corresponding author of a paper describing this research in the journal Nature Materials. The paper is titled Predicting nonlinear properties of metamaterials from the linear response. The other authors are Kevin O’Brien, Haim Suchowski, Junsuk Rho, Alessandro Salandrino, Boubacar Kante and Xiaobo Yin.

    The unique electromagnetic properties of metamaterials stem from their physical structure rather than their chemical composition. This structure, for example, provides certain metamaterials with a negative refractive index, an optical property in which the phase front of light moving through a material propagates backward towards the source. The phase front light moving through natural materials always propagates forward, away from its source.

    Zhang and his group have already exploited the linear optical properties of metamaterials to create the world’s first optical invisibility cloak and mimic black holes. Most recently they used a nonlinear metamaterial with a refractive index of zero to generate “phase mismatch–free nonlinear light,” meaning light waves moved through the material gaining strength in all directions. However, engineering nonlinear metamaterials remains in its infancy, with no general conclusion on the relationship between linear and nonlinear properties.

    3
    Metamaterial arrays whose geometry varied gradually from a symmetric bar to an asymmetric U-shape were used to compare the predictive abilities of Miller’s rule and a non-linear light scattering theory.

    For the past several decades, scientists have estimated the nonlinear optical properties in natural crystals using a formulation known as “Miller’s rule,” for the physicist Robert Miller who authored it. In this new study, Zhang and his group found that Miller’s rule doesn’t work for a number of metamaterials. That’s the bad news. The good news is that a nonlinear light scattering theory, developed for nanostructures by Dutch scientist Sylvie Roke, does.

    “From the linear properties, one calculates the nonlinear polarization and the mode of the nanostructure at the second harmonic,” says Kevin O’Brien, co-lead author of the Nature Materials paper and a member of Zhang’s research group. “We found the nonlinear emission is proportional to the overlap integral between these, not simply determined by their linear response.”

    Zhang, O’Brien, Suchowski, and the other contributors to this study evaluated Miller’s rule and the nonlinear light scattering theory by comparing their predictions to experimental results obtained using a nonlinear stage-scanning confocal microscope.

    “Nonlinear stage-scanning confocal microscopy is critical because it allows us to rapidly measure the nonlinear emission from thousands of different nanostructures while minimizing the potential systematic errors, such as intensity or beam pointing variations, often associated with tuning the wavelength of an ultrafast laser,” O’Brien says.

    The researchers used confocal microscopy to observe the second harmonic generation from metamaterial arrays whose geometry was gradually shifted from a symmetric bar-shape to an asymmetric U-shape. Second harmonic light is a nonlinear optical property in which photons with the same frequency interact with a nonlinear material to produce new photons at twice the energy and half the wavelength of the originals. It was the discovery of optical second harmonic generation in 1961 that started modern nonlinear optics.

    “Our results show that nonlinear scattering theory can be a valuable tool in the design of nonlinear metamaterials not only for second-order but also higher order nonlinear optical responses over a broad range of wavelengths,” O’Brien says. “We’re now using these experimental and theoretical techniques to explore other nonlinear processes in metamaterials, such as parametric amplification and entangled photon generation.”

    This research was supported by the DOE Office of Science.

    See the full article here.

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