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  • richardmitnick 10:40 am on July 30, 2015 Permalink | Reply
    Tags: Nanotechnology, , , ,   

    From MIT: “How to look for a few good catalysts” 


    MIT News

    July 30, 2015
    David L. Chandler

    New research shows non-wetting surfaces promote chemical reaction rates.

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    Materials that have good wetting properties, as illustrated on the left, where droplets spread out flat, tend to have hydroxyl groups attached to the surface, which inhibits catalytic activity. Materials that repel water, as shown at right, where droplets form sharp, steep boundaries, are more conducive to catalytic activity, as shown by the reactions among small orange molecules. Illustration: Xiao Renshaw Wang

    Two key physical phenomena take place at the surfaces of materials: catalysis and wetting. A catalyst enhances the rate of chemical reactions; wetting refers to how liquids spread across a surface.

    Now researchers at MIT and other institutions have found that these two processes, which had been considered unrelated, are in fact closely linked. The discovery could make it easier to find new catalysts for particular applications, among other potential benefits.

    “What’s really exciting is that we’ve been able to connect atomic-level interactions of water and oxides on the surface to macroscopic measurements of wetting, whether a surface is hydrophobic or hydrophilic, and connect that directly with catalytic properties,” says Yang Shao-Horn, the W.M. Keck Professor of Energy at MIT and a senior author of a paper describing the findings in the Journal of Physical Chemistry C. The research focused on a class of oxides called perovskites that are of interest for applications such as gas sensing, water purification, batteries, and fuel cells.

    Since determining a surface’s wettability is “trivially easy,” says senior author Kripa Varanasi, an associate professor of mechanical engineering, that determination can now be used to predict a material’s suitability as a catalyst. Since researchers tend to specialize in either wettability or catalysis, this produces a framework for researchers in both fields to work together to advance understanding, says Varanasi, whose research focuses primarily on wettability; Shao-Horn is an expert on catalytic reactions.

    “We show how wetting and catalysis, which are both surface phenomena, are related,” Varanasi says, “and how electronic structure forms a link between both.”

    While both effects are important in a variety of industrial processes and have been the subject of much empirical research, “at the molecular level, we understand very little about what’s happening at the interface,” Shao-Horn says. “This is a step forward, providing a molecular-level understanding.”

    “It’s primarily an experimental technique” that made the new understanding possible, explains Kelsey Stoerzinger, an MIT graduate student and the paper’s lead author. While most attempts to study such surface science use instruments requiring a vacuum, this team used a device that could study the reactions in humid air, at room temperature, and with varying degrees of water vapor present. Experiments using this system, called ambient pressure X-ray photoelectron spectroscopy, revealed that the reactivity with water is key to the whole process, she says.

    The water molecules break apart to form hydroxyl groups — an atom of oxygen bound to an atom of hydrogen — bonded to the material’s surface. These reactive compounds, in turn, are responsible for increasing the wetting properties of the surface, while simultaneously inhibiting its ability to catalyze chemical reactions. Therefore, for applications requiring high catalytic activity, the team found, a key requirement is that the surface be hydrophobic, or non-wetting.

    “Ideally, this understanding helps us design new catalysts,” Stoerzinger says. If a given material “has a lower affinity for water, it has a higher affinity for catalytic activity.”

    Shao-Horn notes that this is an initial finding, and that “extension of these trends to broader classes of materials and ranges of hydroxyl affinity requires further investigation.” The team has already begun further exploration of these areas. This research, she says, “opens up the space of materials and surfaces we might think about” for both catalysis and wetting.

    The research team also included graduate student Wesley Hong, visiting scientist Livia Giordano, and postdocs Yueh-Lin Lee and Gisele Azimi at MIT; Ethan Crumlin and Hendrik Bluhm at Lawrence Berkeley National Laboratory; and Michael Biegalski at Oak Ridge National Laboratory. The work was supported by the National Science Foundation and the U.S. Department of Energy.

    See the full article here.

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  • richardmitnick 4:04 pm on July 28, 2015 Permalink | Reply
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    From BNL: “New Computer Model Could Explain how Simple Molecules Took First Step Toward Life” 

    Brookhaven Lab

    July 28, 2015
    Alasdair Wilkins

    Two Brookhaven researchers developed theoretical model to explain the origins of self-replicating molecules

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    Brookhaven researchers Sergei Maslov (left) and Alexi Tkachenko developed a theoretical model to explain molecular self-replication.

    Nearly four billion years ago, the earliest precursors of life on Earth emerged. First small, simple molecules, or monomers, banded together to form larger, more complex molecules, or polymers. Then those polymers developed a mechanism that allowed them to self-replicate and pass their structure on to future generations.

    We wouldn’t be here today if molecules had not made that fateful transition to self-replication. Yet despite the fact that biochemists have spent decades searching for the specific chemical process that can explain how simple molecules could make this leap, we still don’t really understand how it happened.

    Now Sergei Maslov, a computational biologist at the U.S. Department of Energy’s Brookhaven National Laboratory and adjunct professor at Stony Brook University, and Alexei Tkachenko, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN), have taken a different, more conceptual approach. They’ve developed a model that explains how monomers could very rapidly make the jump to more complex polymers. And what their model points to could have intriguing implications for CFN’s work in engineering artificial self-assembly at the nanoscale. Their work is published in the July 28, 2015 issue of The Journal of Chemical Physics.

    To understand their work, let’s consider the most famous organic polymer, and the carrier of life’s genetic code: DNA. This polymer is composed of long chains of specific monomers called nucleotides, of which the four kinds are adenine, thymine, guanine, and cytosine (A, T, G, C). In a DNA double helix, each specific nucleotide pairs with another: A with T, and G with C. Because of this complementary pairing, it would be possible to put a complete piece of DNA back together even if just one of the two strands was intact.

    While DNA has become the molecule of choice for encoding biological information, its close cousin RNA likely played this role at the dawn of life. This is known as the RNA world hypothesis, and it’s the scenario that Maslov and Tkachenko considered in their work.

    The single complete RNA strand is called a template strand, and the use of a template to piece together monomer fragments is what is known as template-assisted ligation. This concept is at the crux of their work. They asked whether that piecing together of complementary monomer chains into more complex polymers could occur not as the healing of a broken polymer, but rather as the formation of something new.

    “Suppose we don’t have any polymers at all, and we start with just monomers in a test tube,” explained Tkachenko. “Will that mixture ever find its way to make those polymers? The answer is rather remarkable: Yes, it will! You would think there is some chicken-and-egg problem—that, in order to make polymers, you already need polymers there to provide the template for their formation. Turns out that you don’t really.”

    Instilling memory

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    A schematic drawing of template-assisted ligation, shown in this model to give rise to autocatalytic systems. No image credit.

    Maslov and Tkachenko’s model imagines some kind of regular cycle in which conditions change in a predictable fashion—say, the transition between night and day. Imagine a world in which complex polymers break apart during the day, then repair themselves at night. The presence of a template strand means that the polymer reassembles itself precisely as it was the night before. That self-replication process means the polymer can transmit information about itself from one generation to the next. That ability to pass information along is a fundamental property of life.

    “The way our system replicates from one day cycle to the next is that it preserves a memory of what was there,” said Maslov. “It’s relatively easy to make lots of long polymers, but they will have no memory. The template provides the memory. Right now, we are solving the problem of how to get long polymer chains capable of memory transmission from one unit to another to select a small subset of polymers out of an astronomically large number of solutions.”

    According to Maslov and Tkachenko’s model, a molecular system only needs a very tiny percentage of more complex molecules—even just dimers, or pairs of identical molecules joined together—to start merging into the longer chains that will eventually become self-replicating polymers. This neatly sidesteps one of the most vexing puzzles of the origins of life: Self-replicating chains likely need to be very specific sequences of at least 100 paired monomers, yet the odds of 100 such pairs randomly assembling themselves in just the right order is practically zero.

    “If conditions are right, there is what we call a first-order transition, where you go from this soup of completely dispersed monomers to this new solution where you have these long chains appearing,” said Tkachenko. “And we now have this mechanism for the emergence of these polymers that can potentially carry information and transmit it downstream. Once this threshold is passed, we expect monomers to be able to form polymers, taking us from the primordial soup to a primordial soufflé.”

    While the model’s concept of template-assisted ligation does describe how DNA—as well as RNA—repairs itself, Maslov and Tkachenko’s work doesn’t require that either of those was the specific polymer for the origin of life.

    “Our model could also describe a proto-RNA molecule. It could be something completely different,” Maslov said.

    Order from disorder

    The fact that Maslov and Tkachenko’s model doesn’t require the presence of a specific molecule speaks to their more theoretical approach.

    “It’s a different mentality from what a biochemist would do,” said Tkachenko. “A biochemist would be fixated on specific molecules. We, being ignorant physicists, tried to work our way from a general conceptual point of view, as there’s a fundamental problem.”

    That fundamental problem is the second law of thermodynamics, which states that systems tend toward increasing disorder and lack of organization. The formation of long polymer chains from monomers is the precise opposite of that.

    “How do you start with the regular laws of physics and get to these laws of biology which makes things run backward, which make things more complex, rather than less complex?” Tkachenko queried. “That’s exactly the jump that we want to understand.”

    Applications in nanoscience

    The work is an outgrowth of efforts at the Center for Functional Nanomaterials, a DOE Office of Science User Facility, to use DNA and other biomolecules to direct the self-assembly of nanoparticles into large, ordered arrays. While CFN doesn’t typically focus on these kinds of primordial biological questions, Maslov and Tkachenko’s modeling work could help CFN scientists engaged in cutting-edge nanoscience research to engineer even larger and more complex assemblies using nanostructured building blocks.

    “There is a huge interest in making engineered self-assembled structures, so we were essentially thinking about two problems at once,” said Tkachenko. “One is relevant to biologists, and second asks whether we can engineer a nanosystem that will do what our model does.”

    The next step will be to determine whether template-aided ligation can allow polymers to begin undergoing the evolutionary changes that characterize life as we know it. While this first round of research involved relatively modest computational resources, that next phase will require far more involved models and simulations.

    Maslov and Tkachenko’s work has solved the problem of how long polymer chains capable of information transmission from one generation to the next could emerge from the world of simple monomers. Now they are turning their attention to how such a system could naturally narrow itself down from exponentially many polymers to only a select few with desirable sequences.

    “What we needed to show here was that this template-based ligation does result in a set of polymer chains, starting just from monomers,” said Tkachenko. “So the next question we will be asking is whether, because of this template-based merger, we will be able to see specific sequences that will be more ‘fit’ than others. So this work sets the stage for the shift to the Darwinian phase.”

    This work was supported by the DOE Office of Science.

    See the full article here.

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 12:59 pm on July 24, 2015 Permalink | Reply
    Tags: , , Nanotechnology   

    From BNL: “New Technique to Synthesize Nanostructured Nanowires” 

    Brookhaven Lab

    July 20, 2015
    Justin Eure

    Method for growing ‘hybrid’ crystals at the nanoscale incorporates quantum dots into a host nanowire with perfect junctions between the components

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    IBM scientist Frances Ross (left) with Brookhaven Lab scientists Dong Su (center) and Eric Stach in the Center for Functional Nanomaterials.

    A new approach to self-assemble and tailor complex structures at the nanoscale, developed by an international collaboration led by the University of Cambridge and IBM, opens opportunities to tailor properties and functionalities of materials for a wide range of semiconductor device applications.

    The researchers have developed a method for growing combinations of different materials in a needle-shaped crystal called a nanowire. Nanowires are small structures, only a few billionths of a metre in diameter. Semiconductors can be grown into nanowires, and the result is a useful building block for electrical, optical, and energy harvesting devices. The researchers have found out how to grow smaller crystals within the nanowire, forming a structure like a crystal rod with an embedded array of gems. Details of the new method are published in the journal Nature Materials.

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    Electron microscope images showing the formation of a nickel silicide nanoparticle (colored yellow) in a silicon nanowire. Credit: Stephan Hofmann

    “The key to building functional nanoscale devices is to control materials and their interfaces at the atomic level,” said Dr. Stephan Hofmann of the Department of Engineering, one of the paper’s senior authors. “We’ve developed a method of engineering inclusions of different materials so that we can make complex structures in a very precise way.”

    Nanowires are often grown through a process called Vapour-Liquid-Solid (VLS) synthesis, where a tiny catalytic droplet is used to seed and feed the nanowire, so that it self-assembles one atomic layer at a time. VLS allows a high degree of control over the resulting nanowire: composition, diameter, growth direction, branching, kinking and crystal structure can be controlled by tuning the self-assembly conditions. As nanowires become better controlled, new applications become possible.

    The technique that Hofmann and his colleagues from Cambridge and IBM developed can be thought of as an expansion of the concept that underlies conventional VLS growth. The researchers use the catalytic droplet not only to grow the nanowire, but also to form new materials within it. These tiny crystals form in the liquid, but later attach to the nanowire and then become embedded as the nanowire is grown further. This catalyst mediated docking process can ‘self-optimise’ to create highly perfect interfaces for the embedded crystals.

    To unravel the complexities of this process, the research team used two customised electron microscopes, one at IBM’s TJ Watson Research Center and a second at Brookhaven National Laboratory. This allowed them to record high-speed movies of the nanowire growth as it happens atom-by-atom. The researchers found that using the catalyst as a ‘mixing bowl’, with the order and amount of each ingredient programmed into a desired recipe, resulted in complex structures consisting of nanowires with embedded nanoscale crystals, or quantum dots, of controlled size and position.

    “The technique allows two different materials to be incorporated into the same nanowire, even if the lattice structures of the two crystals don’t perfectly match,” said Hofmann. “It’s a flexible platform that can be used for different technologies.”

    Possible applications for this technique range from atomically perfect buried interconnects to single-electron transistors, high-density memories, light emission, semiconductor lasers, and tunnel diodes, along with the capability to engineer three-dimensional device structures.

    “This process has enabled us to understand the behaviour of nanoscale materials in unprecedented detail, and that knowledge can now be applied to other processes,” said Hofmann.

    See the full article here.

    Please help promote STEM in your local schools.

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 2:24 pm on July 23, 2015 Permalink | Reply
    Tags: , Nanotechnology,   

    From Nautilus: “The Ambiguous Colors of Nanotechnology” 

    Nautilus

    Nautilus

    July 23, 2015
    By Jeanne Carstensen, photos by Peter Earl McCollough

    Kate Nichols leans her delicate face against the glass of a chemical fume hood in a University of California, Berkeley lab, peering into a beaker filled with a pale yellow liquid—“like a well hydrated person’s pee,” she says, laughing. The yellow brew is a fresh batch of silver nanoparticles. Over the next week, the liquid will turn green, then turquoise, then blue as the particles morph in shape from spheroids to prisms under the influence of time and fluorescent light. Post-docs and grad students elsewhere in the nanotech lab are synthesizing nanoparticles for research on artificial photosynthesis and quantum dot digital displays. But not Nichols. She isn’t a scientist, but an artist, gripped by color.

    About 15 miles away, in her studio in San Francisco’s Mission District, brightly colored pigments sit on a crowded shelf next to the nanopaints she made in the lab: vials of yellowish and brown solutions containing varying sizes and concentrations of silver nanoparticles. On a nearby wall opposite a large oil painting of close-up fish scales hangs a group of small sculptures she calls “Figments.” Each is made of two triangular pieces of glass covered in nanoparticle paint, and joined by a hinge. They look like eerie birds, or perhaps mutant butterflies, brightening or darkening depending on the light around them and the angle of the viewer, so that they seem to weave in and out of perceptual awareness.

    The scene at her studio is in some sense not so different from the lamp-lit workspace of a Renaissance painter experimenting with new colors. “A lot of pigments were discovered by happy accidents,” explains Philip Ball, author of the book Bright Earth: Art and the Invention of Color. “We understand these mechanisms now, but then it was hands-on experimentation. It seems like [Nichols is doing] the same now with these [nanomaterials].” It’s doubtful any Renaissance painters, though, had an apprenticeship quite like this: Nichols, 34, has spent seven years as artist in residence at a world-class nanotech lab, mastering technically challenging synthesis techniques and learning about colloidal chemistry and optical physics. In the process, she has transformed not just her art, but also the way she looks at color itself.

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    Morpho Butterfly

    Nichols’ journey from the studio to the lab has been driven by what she describes as an “almost maniacal obsession with mimesis.” As a young figurative painter, she was intrigued by the ability of Northern Renaissance painters to capture the luminosity of human skin. So in 2002 she dropped out of Kenyon College to study 15th-century oil painting and paint-making techniques as an apprentice to artist Will Wilson in San Francisco. She learned to make her own paints by mixing pigments with oils she concocted out of linseed oil, lead oxide, and mastic resin, following centuries-old recipes.

    Around this time, Nichols became fixated on the Morpho butterfly. Entranced with its flickering blue-green iridescence—the hue shifting subtly as the insect flits through the air—she yearned to capture this luminous marvel of nature on her canvas. But how? She remembered what a science professor had explained to her in college: The Morpho’s color is structural. It doesn’t arise from pigmentation, but from the light scattering off nanoscale structures embedded in its wings.

    Pigments absorb particular bandwidths of light depending on their chemical composition; whatever is not absorbed is reflected, and it is this reflected light that determines the color we perceive. Structural color isn’t chemical: Instead, tiny structures, often smaller than a single wavelength of light, redirect and slow light waves down, causing them to interfere with each other in ways that depend on the shape, size, and spacing of the scattering structures, as well as on the angle of the incoming light and the position of the observer. In the case of the Morpho, these structures scatter blue light most strongly; its hue shimmers and shifts to lighter or darker blue as the butterfly moves, producing iridescence. Structural color is also at work in peacock feathers, fish scales, and beetle casings.

    Nichols often had the radio on while painting in her studio, and in 2007 heard reports about developments in nanotechnology research on NPR. She began to wonder if it would be possible to make nanomaterials in the lab that would allow her to use structural color in her art. Using her oil technique she could already paint a photorealistic depiction of a Morpho butterfly, but she wanted a deeper mimesis: a blue created from the interaction of light with nanostructures akin to those on the butterfly’s wings.

    On a whim, she wrote to Paul Alivisatos, a nanotechnology expert from UC Berkeley. To her surprise, after just one interview he invited her to join his lab as artist in residence. It was “a very easy” decision to take on Nichols, Alivisatos told me. “I think a scientist is on a personal journey that is very similar to what an artist takes. They each have to struggle to find what is truly beautiful. I always respect people who like to take those quests.”

    Still, when Alivisatos first showed her the wet lab and realized she had never even been in a lab before, he “thought she might get cold feet.” The techniques involved in synthesizing nanomaterials “are quite demanding,” said Alivisatos, who is also the Director of Lawrence Berkeley National Lab. “But she’s been remarkably persistent.”

    After joining the lab in late 2008 Nichols spent long days tagging along with “very generous” graduate students and post-docs. One of those was Jill Millstone, now an assistant professor of chemistry at the University of Pittsburgh. Nichols, who was 27 at the time, hadn’t studied any chemistry since high school. But Millstone said she “picked up on all of the nuances very quickly” regarding everything from mathematical calculations to pipette technique. “She embraced the language of science and the spirit of the way we approach problems,” Millstone added. “That made her melt into the fabric of the lab. She didn’t stick out as an artist.” For her part, Nichols says she found the learning process in the lab to be “similar to her experience of being a painter’s apprentice.”

    At the core of her training were nanoparticles, microscopic particles generally measuring between one and 100 nanometers (one-billionth of a meter). To put this infinitesimal realm into perspective, a water molecule measures about 0.3 nanometers; a human hair is approximately 90,000 nanometers wide. Nanoparticles of metals (such as silver or gold) or semiconductors (such as cadmium sulfide or silicon) exhibit different, electrical, physical, and (especially interesting for Nichols) optical properties than they do in bulk. In addition, the way they interact with light can be controlled by changing their size and shape. To make such tiny structures in a controlled and repeatable way takes a combination of theory and technique, physics and chemistry, and meticulous attention to detail. Nichols understood that she had an opportunity to create materials that would serve as “a bridge between the nanoscopic and visible worlds”—but she was starting from zero.

    She began to fill her lab notebooks with chemical equations and extensive notes for synthesizing nanoparticles made from a variety of materials, including silver, gold, and cadmium. Eventually she settled on silver as her primary material because of its safety and the colors it produced. At first she focused on prism-shaped silver nanoparticles, which displayed beautiful blues and greens in the vial. But she was “disappointed that it looked great in the bottle but if I put it on a glass surface it looked like my dirty windshield.” She couldn’t figure out how to get the silver nanoprisms she had made to adhere to glass the way she wanted. And after a year of solid lab work, she didn’t have any art to show for it. “I had to get knocked on my ass,” she said, remembering the many frustrations.

    Finally, in late 2009, she decided to “listen to the particles.” Instead of using them like paint, she suspended them in sealed glass capillaries, which she attached to each other to create sculptures. They looked a little like ethereal organ pipes, or perhaps clusters of icicles, filled with turquoise liquid. Over time, as light caused the prisms to take on a more rounded shape, the particles turned blue.

    The sculptures were a start, but she wasn’t satisfied. She continued to experiment and eventually found a way to create a paint based on another kind of silver nanoparticle, shaped like soccer balls. The key was their compatibility with a medium. Their specific surface chemistry meant she could suspend the pseudo spheres in organic solvents such as hexane, and apply them to glass. “The important step for her was getting to the stage where she could develop the material,” Alivisatos said. “First, she had to make the material and then have a process where she could embed it so it was stable. Just getting all that to work was hard.”

    By late 2010 Nichols was able to consistently make silver nanopaints and start experimenting with them artistically. The Leonardo Museum in Salt Lake City learned about her experimentations through her 2010 TED talk and commissioned her to create a series of art works, which she called Through the Looking Glass. They consist of abstract, ghostly pools of brown, gold, orange, and purple colors on several superimposed pieces of glass, like large lab slides. These colors shift depending on where you stand and on the light falling on them, because the particles in the nanopaint transmit light in the brown-orange range, but scatter blues and purples. They tend to appear only blue and green on glass with a black background, which eliminates transmitted light, an effect she would explore later.

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    Look twice: A detail from a 2013 work by Nichols called “Doppelganger,” which uses silver nanoparticles on glass. The image, which evokes the scintillation of fish scales, shifts with the viewer’s position.

    Success for a nanoscale scientist veers toward precision. The goal of synthesis is to create nanoparticles with the narrowest possible size distribution, allowing the most exact expression of a specific color for the highest-performing bio-imaging tool or information display or laser. Today artists can also get very precise. Ultramarine, one of the only materials available for producing blue pigment in the Middle Ages, was made from grinding up lapis lazuli, a precious stone that was only available from what is today Afghanistan. It was rare and extremely expensive. Now a fine artist has many blues to choose from for oil, acrylic, and watercolor. An industrialist in need of a blue for a Frisbee or toothpaste tube can dip into the over 9,000-page Color Index International. As Ball points out, poetic names such as Prussian Blue are in the minority, having been joined by chemically informative names such as C.I. VAT RED 13, a kind of red. “The ambiguities of older terminology are banished, and undoubtedly some of the magic goes with them.” The quantum dot industry also uses a prosaic naming system for the hundreds of colors in its quantum gamut: the letters QD, plus a number denoting its wavelength. QD680, for example, “is not a very beautiful name like ultramarine,” Alivisatos said. “But it does tell you exactly what it is.”

    Nichols, on the other hand, brought her artist’s sensibility to the lab. The more she explored nanocolor, the more she was intrigued not by its precision, but by its ambivalence. The colors she coaxed out of the lab and into her artwork can’t be described with a single number. Her silver nanopaints are a purposefully “dirty” mix of particles of different sizes, varying from about five to 30 nanometers and scattering light over a range of the blue-green spectrum; she controls the distribution with a centrifuge. Some of her paints include gold as well, which adds reds. In a sense, each vial of Nichols’ paint contains a palette of colors, a mix of particles that interact with light in a variety of ways. Nichols likens the distinction between her “dirty” mixes and the formulas used for scientific purposes to the difference between sound reverberating through a wooden piano and a synthesizer. She’s attracted to the former, “the messier signal that comes with things that exist in the physical world.”

    Nichols is, as far as I have been able to determine, the only artist to synthesize her own nanopaint in the lab. But what Nichols calls “nanocraftsmanship” has a long history. Nanoparticles of gold and silver have been used in art for thousands of years in ceramic glazes to lend iridescence and, most famously, in stained glass. The vibrant colors of the windows in medieval churches such as Sainte-Chapelle in Paris that glow in intense hues are created by nanoparticles embedded in the glass—silver particles for yellow and gold for ruby red. The color of the windows changes, as well, with the time of day and angle of light striking the particles.

    The Lycurgus Cup, a glass chalice made by the Romans in the fourth century A.D. that today sits in the British Museum, looks green under reflected daylight, and red when light is transmitted through the cup. By 1990, scientists discovered that Roman craftsmen had embedded colloidal gold and silver nanoparticles into the glass, and that the effect was due to the same phenomenon (called surface plasmon resonance) that Nichols plays with on the Berkeley campus. These early nanocraftsmen arrived at their technologies through experimentation, and could not have known the science behind it.

    Nichols also includes photography and Victorian mirror making, which involves a silver-based recipe “strikingly similar to my nanoparticle synthesis,” in the lineage of nanocraftsmanship. The silver particles in these processes aren’t as small as those in her nanopaints, but they have a similar ambivalent, multifaceted relationship with light.

    As artists begin to intentionally explore the artistic possibilities for using synthesized nanoparticles in their art, exciting new questions about color and how we perceive it will arise. “I think there’s no doubt that the number of different colors that can be purposefully made is much larger,” Alivisatos said. But what artists will do with this expanded palette is still an open question. “We’ve only begun to explore the ways these effects could be used artistically to communicate with color,” said Ball, “and to do everything that artists do to make us think about the visual world around us.”

    Sculptor Anish Kapoor hasn’t ventured into the lab like Nichols but he has recently added a “super black” commercial nanopaint to his palette. Made by Surrey NanoSystems out of vertically aligned carbon nanotubes that trap over 99 percent of incoming light, “Vantablack” has applications such as camouflaging military aircraft. Kapoor has compared looking at the nanopaint to staring into a black hole. He told the BBC that a space painted with the substance is “so dark that as you walk in you lose all sense of where you are, what you are, and especially all sense of time.”

    Nichols’ emphasis on the ambivalent qualities of metal silver nanoparticles could tickle the senses in other ways. Scott Taylor, who is a chief operating officer at Maxis, a division of Electronic Arts, and thinks about perception for his work on the SimCity videogame series, was so attracted to the dynamic nature of her art that he has bought several pieces, including one of the “Figments” series. He said he loves that how it looks depends on “whether I see it out of my peripheral vision or straight on, how the light hits it, what I am thinking at the moment.”

    Nichols’ investigations into structural color have the power to inspire the same sense of wonder that her inspiration, the Morpho butterfly, often does. Her pieces at The Leonardo Museum were very layered, said Jann Haworth, the creative director. “First people saw the beauty, but then they went deeper, into the science of how something in nature could create such magic. It’s like a quest. You understand, then you don’t. It’s almost mystical.”

    The nanopaints Nichols has developed so far are only a nano-sized sampling of the artistic possibilities in this new color realm. “If we’re seeing new visual effects who knows how we will respond to them,” Ball said. “We don’t know how that’s going to be perceived.”

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    A new perspective: A portrait of Kate Nichols in her studio.Peter Earl McCullough

    Back in her studio, Nichols is working with some nanoparticle paint on a piece of glass. It’s hard to believe that the yellowish liquid she pours out was made in Alivisato’s nanotechnology lab. It looks like a thin stain or maybe a kind of finger paint—and she treats it as such, letting it flow onto the glass and then manipulating it with broken pieces of glass, and her gloved hand. When she feels the piece is done, she’ll cover it with another piece of glass. She has learned to sense how the pieces will look after the solvent dries and under different light conditions. But she’s often surprised, “and that is what’s delightful and maddening about working with this material,” she laughs.

    I ask her about some dark glass pieces on the wall. Unlike the clear pieces she showed at The Leonardo, these have a black backing to block transmitted light. They look a little like ghostly black-and-white negatives with flickers of blues and greens in different streaks and patches, depending on how you look at it. As I always do when I observe her nano art, I walk around, exploring how it changes. Then I lean in close. “What color is this anyway?”

    She points out a “blue like a gaslight, something more like the silver of silverware, and a green quality but still in blues.” But, she adds, “the question is insufficient.” After working with nanoparticles that look “yellow here and blue there, that change right in front of my eyes,” she thinks about a material’s “particular relationship with light” instead of its color. There is no simple answer to my question. In the last several years, she has brought this sensibility into all of her artwork. Whether painting in traditional oils, making mirrored surfaces, or working with her nanopaint, Nichols crafts “surfaces to catch, scatter, bend, and transmit light in ways that allow us to experience light’s ambivalent nature,” as she described in her 2012 TEDx talk.

    As I continue to circle around the dark glass piece in the afternoon light of the studio, I see new forms and colors that I hadn’t noticed before. Like a Morpho butterfly, the piece is alive with light. It makes me think of all the marvelous things that happen when the sun’s rays fall to Earth.

    See the full article here.

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 8:26 am on May 15, 2015 Permalink | Reply
    Tags: , , , , Nanotechnology   

    From BNL: “Intense Lasers Cook Up Complex, Self-Assembled Nanomaterials” 

    Brookhaven Lab

    May 13, 2015
    Justin Eure

    New technique developed at Brookhaven Lab makes self-assembly 1,000 times faster and could be used for industrial-scale solar panels and electronics

    1
    Brookhaven Lab scientist Kevin Yager (left) and postdoctoral researcher Pawel Majewski with the new Laser Zone Annealing instrument at the Center for Functional Nanomaterials.

    Nanoscale materials feature extraordinary, billionth-of-a-meter qualities that transform everything from energy generation to data storage. But while a nanostructured solar cell may be fantastically efficient, that precision is notoriously difficult to achieve on industrial scales. The solution may be self-assembly, or training molecules to stitch themselves together into high-performing configurations.

    Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a laser-based technique to execute nanoscale self-assembly with unprecedented ease and efficiency.

    “We design materials that build themselves,” said Kevin Yager, a scientist at Brookhaven’s Center for Functional Nanomaterials (CFN). “Under the right conditions, molecules will naturally snap into a perfect configuration. The challenge is giving these nanomaterials the kick they need: the hotter they are, the faster they move around and settle into the desired formation. We used lasers to crank up the heat.”

    Yager and Brookhaven Lab postdoctoral researcher Pawel Majewski built a one-of-a-kind machine that sweeps a focused laser-line across a sample to generate intense and instantaneous spikes in temperature. This new technique, called Laser Zone Annealing (LZA), drives self-assembly at rates more than 1,000 times faster than traditional industrial ovens. The results are described in the journal ACS Nano.

    “We created extremely uniform self-assembled structures in less than a second,” Majewski said. “Beyond the extraordinary speed, our laser also reduced the defects and degradations present in oven-heated materials. That combination makes LZA perfect for carrying small-scale laboratory breakthroughs into industry.”

    The scientists prepared the materials and built the LZA instrument at the CFN. They then analyzed samples using advanced electron microscopy at CFN and x-ray scattering at Brookhaven’s now-retired National Synchrotron Light Source (NSLS)—both DOE Office of Science User Facilities.

    “It was enormously gratifying to see that our predictions were accurate—the enormous thermal gradients led to a correspondingly enormous acceleration!” Yager said.

    2
    Illustration of the Lazer Zone Annealing instrument showing the precise laser (green) striking the un-assembled polymer (purple). The extreme thermal gradients produced by the laser sweeping across the sample cause rapid and pristine self-assembly.

    Ovens versus lasers

    Imagine preparing a complex cake, but instead of baking it in the oven, a barrage of lasers heats it to perfection in an instant. Beyond that, the right cooking conditions will make the ingredients mix themselves into a picture-perfect dish. This nanoscale recipe achieves something equally extraordinary and much more impactful.

    The researchers focused on so-called block copolymers, molecules containing two linked blocks with different chemical structures and properties. These blocks tend to repel each other, which can drive the spontaneous formation of complex and rigid nanoscale structures.

    “The price of their excellent mechanical properties is the slow kinetics of their self-assembly,” Majewski said. “They need energy and time to explore possibilities until they find the right configuration.”

    In traditional block copolymer self-assembly, materials are heated in a vacuum-sealed oven. The sample is typically “baked” for a period of 24 hours or longer to provide enough kinetic energy for the molecules to snap into place—much too long for commercial viability. The long exposure to high heat also causes inevitable thermal degradation, leaving cracks and imperfections throughout the sample.

    The LZA process, however, offers sharp spikes of heat to rapidly excite the polymers without the sustained energy that damages the material.

    “Within milliseconds, the entire sample is beautifully aligned,” Yager said. “As the laser sweeps across the material, the localized thermal spikes actually remove defects in the nanostructured film. LZA isn’t just faster, it produces superior results.”

    LZA generates temperatures greater than 500 degrees Celsius, but the thermal gradients—temperature variations tied to direction and location in a material—can reach more than 4,000 degrees per millimeter. While scientists know that higher temperatures can accelerate self-assembly, this is the first proof of dramatic enhancement by extreme gradients.

    Built from scratch

    “Years ago, we observed a subtle hint that thermal gradients could improve self-assembly,” Yager said. “I became obsessed with the idea of creating more and more extreme gradients, which ultimately led to building this laser setup, and pioneering a new technique.”

    The researchers needed a high concentration of technical expertise and world-class facilities to move the LZA from proposal to execution.

    “Only at the CFN could we develop this technique so quickly,” Majewski said. “We could do rapid instrument prototyping and sample preparation with the on-site clean room, machine shop, and polymer processing lab. We then combined CFN electron microscopy with x-ray studies at NSLS for an unbeatable evaluation of the LZA in action.”

    Added Yager, “The ability to make new samples at the CFN and then walk across the street to characterize them in seconds at NSLS was key to this discovery. The synergy between these two facilities is what allowed us to rapidly iterate to an optimized design.”

    The scientists also developed a new microscale surface thermometry technique called melt-mark analysis to track the exact heat generated by the laser pulses and tune the instrument accordingly.

    “We burned a few films initially before we learned the right operating conditions,” Majewski said. “It was really exciting to see the first samples being rastered by the laser and then using NSLS to discover exactly what happened.”

    Future of the technique

    The LZA is the first machine of its kind in the world, but it signals a dramatic step forward in scaling up meticulously designed nanotechnology. The laser can even be used to “draw” structures across the surface, meaning the nanostructures can assemble in well-defined patterns. This unparalleled synthesis control opens the door to complex applications, including electronics.

    “There’s really no limit to the size of a sample this technique could handle,” Yager said. “In fact, you could run it in a roll-to-roll mode—one of the leading manufacturing technologies.”

    The scientists plan to further develop the new technique to create multi-layer structures that could have immediate impacts on anti-reflective coatings, improved solar cells, and advanced electronics.

    This research and operations at CFN and NSLS were funded by the DOE Office of Science.

    See the full article here.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 7:56 am on May 14, 2015 Permalink | Reply
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    From MIT: “Researchers build new fermion microscope” 


    MIT News

    May 13, 2015
    Jennifer Chu

    1
    Graduate student Lawrence Cheuk adjusts the optics setup for laser cooling of sodium atoms. Photo: Jose-Luis Olivares/MIT

    2
    Laser beams are precisely aligned before being sent into the vacuum chamber. Photo: Jose-Luis Olivares/MIT

    3
    Sodium atoms diffuse out of an oven to form an atomic beam, which is then slowed and trapped using laser light. Photo: Jose-Luis Olivares/MIT

    4
    A Quantum gas microscope for fermionic atoms. The atoms, potassium-40, are cooled during imaging by laser light, allowing thousands of photons to be collected by the microscope. Credit: Lawrence Cheuk/MIT

    5
    The Fermi gas microscope group: (from left) graduate students Katherine Lawrence and Melih Okan, postdoc Thomas Lompe, graduate student Matt Nichols, Professor Martin Zwierlein, and graduate student Lawrence Cheuk. Photo: Jose-Luis Olivares/MIT

    Instrument freezes and images 1,000 individual fermionic atoms at once.

    Fermions are the building blocks of matter, interacting in a multitude of permutations to give rise to the elements of the periodic table. Without fermions, the physical world would not exist.

    Examples of fermions are electrons, protons, neutrons, quarks, and atoms consisting of an odd number of these elementary particles. Because of their fermionic nature, electrons and nuclear matter are difficult to understand theoretically, so researchers are trying to use ultracold gases of fermionic atoms as stand-ins for other fermions.

    But atoms are extremely sensitive to light: When a single photon hits an atom, it can knock the particle out of place — an effect that has made imaging individual fermionic atoms devilishly hard.

    Now a team of MIT physicists has built a microscope that is able to see up to 1,000 individual fermionic atoms. The researchers devised a laser-based technique to trap and freeze fermions in place, and image the particles simultaneously.

    The new imaging technique uses two laser beams trained on a cloud of fermionic atoms in an optical lattice. The two beams, each of a different wavelength, cool the cloud, causing individual fermions to drop down an energy level, eventually bringing them to their lowest energy states — cool and stable enough to stay in place. At the same time, each fermion releases light, which is captured by the microscope and used to image the fermion’s exact position in the lattice — to an accuracy better than the wavelength of light.

    With the new technique, the researchers are able to cool and image over 95 percent of the fermionic atoms making up a cloud of potassium gas. Martin Zwierlein, a professor of physics at MIT, says an intriguing result from the technique appears to be that it can keep fermions cold even after imaging.

    “That means I know where they are, and I can maybe move them around with a little tweezer to any location, and arrange them in any pattern I’d like,” Zwierlein says.

    Zwierlein and his colleagues, including first author and graduate student Lawrence Cheuk, have published their results today in the journal Physical Review Letters.

    Seeing fermions from bosons

    For the past two decades, experimental physicists have studied ultracold atomic gases of the two classes of particles: fermions and bosons — particles such as photons that, unlike fermions, can occupy the same quantum state in limitless numbers. In 2009, physicist Marcus Greiner at Harvard University devised a microscope that successfully imaged individual bosons in a tightly spaced optical lattice. This milestone was followed, in 2010, by a second boson microscope, developed by Immanuel Bloch’s group at the Max Planck Institute of Quantum Optics.

    These microscopes revealed, in unprecedented detail, the behavior of bosons under strong interactions. However, no one had yet developed a comparable microscope for fermionic atoms.

    “We wanted to do what these groups had done for bosons, but for fermions,” Zwierlein says. “And it turned out it was much harder for fermions, because the atoms we use are not so easily cooled. So we had to find a new way to cool them while looking at them.”

    Techniques to cool atoms ever closer to absolute zero have been devised in recent decades. Carl Wieman, Eric Cornell, and MIT’s Wolfgang Ketterle were able to achieve Bose-Einstein condensation in 1995, a milestone for which they were awarded the 2001 Nobel Prize in physics. Other techniques include a process using lasers to cool atoms from 300 degrees Celsius to a few ten-thousandths of a degree above absolute zero.

    A clever cooling technique

    And yet, to see individual fermionic atoms, the particles need to be cooled further still. To do this, Zwierlein’s group created an optical lattice using laser beams, forming a structure resembling an egg carton, each well of which could potentially trap a single fermion. Through various stages of laser cooling, magnetic trapping, and further evaporative cooling of the gas, the atoms were prepared at temperatures just above absolute zero — cold enough for individual fermions to settle onto the underlying optical lattice. The team placed the lattice a mere 7 microns from an imaging lens, through which they hoped to see individual fermions.

    However, seeing fermions requires shining light on them, causing a photon to essentially knock a fermionic atom out of its well, and potentially out of the system entirely.

    “We needed a clever technique to keep the atoms cool while looking at them,” Zwierlein says.

    His team decided to use a two-laser approach to further cool the atoms; the technique manipulates an atom’s particular energy level, or vibrational energy. Each atom occupies a certain energy state — the higher that state, the more active the particle is. The team shone two laser beams of differing frequencies at the lattice. The difference in frequencies corresponded to the energy between a fermion’s energy levels. As a result, when both beams were directed at a fermion, the particle would absorb the smaller frequency, and emit a photon from the larger-frequency beam, in turn dropping one energy level to a cooler, more inert state. The lens above the lattice collects the emitted photon, recording its precise position, and that of the fermion.

    Zwierlein says such high-resolution imaging of more than 1,000 fermionic atoms simultaneously would enhance our understanding of the behavior of other fermions in nature — particularly the behavior of electrons. This knowledge may one day advance our understanding of high-temperature superconductors, which enable lossless energy transport, as well as quantum systems such as solid-state systems or nuclear matter.

    “The Fermi gas microscope, together with the ability to position atoms at will, might be an important step toward the realization of a quantum computer based on fermions,” Zwierlein says. “One would thus harness the power of the very same intricate quantum rules that so far hamper our understanding of electronic systems.”

    Zwierlein says it is a good time for Fermi gas microscopists: Around the same time his group first reported its results, teams from Harvard and the University of Strathclyde in Glasgow also reported imaging individual fermionic atoms in optical lattices, indicating a promising future for such microscopes.

    Zoran Hadzibabic, a professor of physics at Trinity College, says the group’s microscope is able to detect individual atoms “with almost perfect fidelity.”

    “They detect them reliably, and do so without affecting their positions — that’s all you want,” says Hadzibabic, who did not contribute to the research. “So far they demonstrated the technique, but we know from the experience with bosons that that’s the hardest step, and I expect the scientific results to start pouring out.”

    This research was funded in part by the National Science Foundation, the Air Force Office of Scientific Research, the Office of Naval Research, the Army Research Office, and the David and Lucile Packard Foundation.

    See the full article here.

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  • richardmitnick 7:16 am on May 8, 2015 Permalink | Reply
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    From MIT: “Plugging up leaky graphene” 


    MIT News

    May 8, 2015
    Jennifer Chu

    1
    In a two-step process, engineers have successfully sealed leaks in graphene. First, the team fabricated graphene on a copper surface (top left) — a process that can create intrinsic defects in graphene, shown as cracks on the surface. After lifting the graphene and depositing it on a porous surface (top right), the transfer creates further holes and tears. In a first step (bottom left), the team used atomic layer deposition to deposit hafnium (in gray) to seal intrinsic cracks, then plugged the remaining holes (bottom left) with nylon (in red), via interfacial polymerization.
    Courtesy of the researchers.

    For faster, longer-lasting water filters, some scientists are looking to graphene —thin, strong sheets of carbon — to serve as ultrathin membranes, filtering out contaminants to quickly purify high volumes of water.

    Graphene’s unique properties make it a potentially ideal membrane for water filtration or desalination. But there’s been one main drawback to its wider use: Making membranes in one-atom-thick layers of graphene is a meticulous process that can tear the thin material — creating defects through which contaminants can leak.

    Now engineers at MIT, Oak Ridge National Laboratory, and King Fahd University of Petroleum and Minerals (KFUPM) have devised a process to repair these leaks, filling cracks and plugging holes using a combination of chemical deposition and polymerization techniques. The team then used a process it developed previously to create tiny, uniform pores in the material, small enough to allow only water to pass through.

    Combining these two techniques, the researchers were able to engineer a relatively large defect-free graphene membrane — about the size of a penny. The membrane’s size is significant: To be exploited as a filtration membrane, graphene would have to be manufactured at a scale of centimeters, or larger.

    In experiments, the researchers pumped water through a graphene membrane treated with both defect-sealing and pore-producing processes, and found that water flowed through at rates comparable to current desalination membranes. The graphene was able to filter out most large-molecule contaminants, such as magnesium sulfate and dextran.

    Rohit Karnik, an associate professor of mechanical engineering at MIT, says the group’s results, published in the journal Nano Letters, represent the first success in plugging graphene’s leaks.

    “We’ve been able to seal defects, at least on the lab scale, to realize molecular filtration across a macroscopic area of graphene, which has not been possible before,” Karnik says. “If we have better process control, maybe in the future we don’t even need defect sealing. But I think it’s very unlikely that we’ll ever have perfect graphene — there will always be some need to control leakages. These two [techniques] are examples which enable filtration.”

    Sean O’Hern, a former graduate research assistant at MIT, is the paper’s first author. Other contributors include MIT graduate student Doojoon Jang, former graduate student Suman Bose, and Professor Jing Kong.

    A delicate transfer

    “The current types of membranes that can produce freshwater from saltwater are fairly thick, on the order of 200 nanometers,” O’Hern says. “The benefit of a graphene membrane is, instead of being hundreds of nanometers thick, we’re on the order of three angstroms — 600 times thinner than existing membranes. This enables you to have a higher flow rate over the same area.”

    O’Hern and Karnik have been investigating graphene’s potential as a filtration membrane for the past several years. In 2009, the group began fabricating membranes from graphene grown on copper — a metal that supports the growth of graphene across relatively large areas. However, copper is impermeable, requiring the group to transfer the graphene to a porous substrate following fabrication.

    However, O’Hern noticed that this transfer process would create tears in graphene. What’s more, he observed intrinsic defects created during the growth process, resulting perhaps from impurities in the original material.

    Plugging graphene’s leaks

    To plug graphene’s leaks, the team came up with a technique to first tackle the smaller intrinsic defects, then the larger transfer-induced defects. For the intrinsic defects, the researchers used a process called “atomic layer deposition,” placing the graphene membrane in a vacuum chamber, then pulsing in a hafnium-containing chemical that does not normally interact with graphene. However, if the chemical comes in contact with a small opening in graphene, it will tend to stick to that opening, attracted by the area’s higher surface energy.

    The team applied several rounds of atomic layer deposition, finding that the deposited hafnium oxide successfully filled in graphene’s nanometer-scale intrinsic defects. However, O’Hern realized that using the same process to fill in much larger holes and tears — on the order of hundreds of nanometers — would require too much time.

    Instead, he and his colleagues came up with a second technique to fill in larger defects, using a process called “interfacial polymerization” that is often employed in membrane synthesis. After they filled in graphene’s intrinsic defects, the researchers submerged the membrane at the interface of two solutions: a water bath and an organic solvent that, like oil, does not mix with water.

    In the two solutions, the researchers dissolved two different molecules that can react to form nylon. Once O’Hern placed the graphene membrane at the interface of the two solutions, he observed that nylon plugs formed only in tears and holes — regions where the two molecules could come in contact because of tears in the otherwise impermeable graphene — effectively sealing the remaining defects.

    Using a technique they developed last year, the researchers then etched tiny, uniform holes in graphene — small enough to let water molecules through, but not larger contaminants. In experiments, the group tested the membrane with water containing several different molecules, including salt, and found that the membrane rejected up to 90 percent of larger molecules. However, it let salt through at a faster rate than water.

    The preliminary tests suggest that graphene may be a viable alternative to existing filtration membranes, although Karnik says techniques to seal its defects and control its permeability will need further improvements.

    “Water desalination and nanofiltration are big applications where, if things work out and this technology withstands the different demands of real-world tests, it would have a large impact,” Karnik says. “But one could also imagine applications for fine chemical- or biological-sample processing, where these membranes could be useful. And this is the first report of a centimeter-scale graphene membrane that does any kind of molecular filtration. That’s exciting.”

    De-en Jiang, an assistant professor of chemistry at the University of California at Riverside, sees the defect-sealing technique as “a great advance toward making graphene filtration a reality.”

    “The two-step technique is very smart: sealing the defects while preserving the desired pores for filtration,” says Jiang, who did not contribute to the research. “This would make the scale-up much easier. One can produce a large graphene membrane first, not worrying about the defects, which can be sealed later.”

    This research was supported in part by the Center for Clean Water and Clean Energy at MIT and KFUPM, the U.S. Department of Energy, and the National Science Foundation.

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

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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
    Tags: , , , Nanotechnology   

    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.

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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