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  • richardmitnick 11:02 am on September 22, 2014 Permalink | Reply
    Tags: , Electron Beam Technology, , Nanotechnology   

    From FNAL- “Feature Breakthrough: nanotube cathode creates more electron beam than large laser system 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Monday, Sept. 22, 2014
    Troy Rummler

    Lasers are cool, except when they’re clunky, expensive and delicate.

    So a collaboration led by RadiaBeam Technologies, a California-based technology firm actively involved in accelerator R&D, is designing an electron beam source that doesn’t need a laser. The team led by Luigi Faillace, a scientist at RadiaBeam, is testing a carbon nanotube cathode — about the size of a nickel — in Fermilab’s High-Brightness Electron Source Lab (HBESL) that completely eliminates the need for a room-sized laser system currently used to generate the electron beam.

    Fermilab was sought out to test the experimental cathode because of its capability and expertise for handling intense electron beams, one of relatively few labs that can support this project.

    Tests have shown that the vastly smaller cathode does a better job than the laser. Philippe Piot, a staff scientist in the Fermilab Accelerator Division and a joint appointee at Northern Illinois University, says tests have produced beam currents a thousand to a million times greater than the one generated with a laser. This remarkable result means that electron beam equipment used in industry may become not only less expensive and more compact, but also more efficient. A laser like the one in HBESL runs close to half a million dollars, Piot said, about hundred times more than RadiaBeam’s cathode.

    The technology has extensive applications in medical equipment and national security, as an electron beam is a critical component in generating X-rays. And while carbon nanotube cathodes have been studied extensively in academia, Fermilab is the first facility to test the technology within a full-scale setting.

    “People have talked about it for years,” said Piot, “but what was missing was a partnership between people that have the know-how at a lab, a university and a company.”

    Piot and Fermilab scientist Charles Thangaraj are partnering with RadiaBeam Technologies staff Luigi Faillace and Josiah Hartzell and Northern Illinois University student Harsha Panuganti and researcher Daniel Mihalcea. A U.S. Department of Energy Small Business Innovation Research grant, a federal endowment designed to bridge the R&D gap between basic research and commercial products, funds the project. The work represents the kind of research that will be enabled in the future at the Illinois Accelerator Research Center — a facility that brings together Fermilab expertise and industry.

    hp
    Harsha Panunganti of Northern Illinois University works on the laser system (turned off here) normally used to create electron beams from a photocathode. Photo: Reidar Hahn

    The new cathode appears at first glance like a smooth black button, but at the nanoscale it resembles, in Piot’s words, “millions of lightning rods.”

    tubre
    The dark carbon-nanotube-coated area of this field emission cathode is made of millions of nanotubes that function like little lightning rods. At Fermilab’s High-Brightness Electron Source Lab, scientists have tested this cathode in the front end of an accelerator, where a strong electric field siphons electrons off the nanotubes to create an intense electron beam. Photo: Reidar Hahn

    “When you apply an electric field, the field lines organize themselves around the rods’ extremities and enhance the field,” Piot said. The electric field at the peaks is so intense that it pulls streams of electrons off the cathode, creating the beam.

    Traditionally, lasers strike cathodes in order to eject electrons through photoemission. Those electrons form a beam by piggybacking onto a radio-frequency wave, synchronized to the laser pulses and formed in a resonance cavity. Powerful magnets focus the beam. The tested nanotube cathode requires no laser as it needs only the electric field already generated by the accelerator to siphon the electrons off, a process dubbed field emission.

    The intense electric field, though, has been a tremendous liability. Piot said critics thought the cathode “was just going to explode and ruin the electron source, and we would be crying because it would be dead.”

    One of the first discoveries Piot’s team made when they began testing in May was that the cathode did not, in fact, explode and ruin everything. The exceptional strength of carbon nanotubes makes the project feasible.

    Still, Piot continues to study ways to optimize the design of the cathode to prevent any smaller, adverse effects that may take place within the beam assembly. Future research also may focus on redesigning an accelerator that natively incorporates the carbon nanotube cathode to avoid any compatibility issues.

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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  • richardmitnick 3:31 pm on September 12, 2014 Permalink | Reply
    Tags: , , Nanotechnology   

    From DESY: “Scientists watch nanoparticles grow” 

    DESY
    DESY

    27.03.2014
    No Writer Credit

    Analysis allows tailoring materials for switchable windows and solar cells

    With DESY’s X-ray light source PETRA III, Danish scientists observed the growth of nanoparticles live. The study shows how tungsten oxide nanoparticles are forming from solution. These particles are used for example for smart windows, which become opaque at the flick of a switch, and they are also used in particular solar cells. The team around lead author Dr. Dipankar Saha from Århus University present their observations in the scientific journal Angewandte Chemie – International Edition.
    Zoom (17 KB)

    nano
    Top: Structure of the ammonium metatungstate dissolved in water on atomic length scale. The octahedra consisting of the tungsten ion in the centre and the six surrounding oxygen ions partly share corners and edges. Bottom: Structure of the nanoparticles in the ordered crystalline phase. The octahedra exclusively share corners. Credit: Dipankar Saha/Århus University

    For their investigation, the scientists built a small reaction chamber, which is transparent for X-rays. “We use fine capillaries of sapphire or fused silica which are easily penetrable by X-rays,” said Professor Bo Iversen, head of the research group. In these capillaries, the scientists transformed so-called ammonium metatungstate dissolved in water into nanoparticles at high temperature and high pressure. With the brilliant PETRA III X-ray light, the chemists were able to track the growth of small tungsten trioxide particles (WO3) with a typical size of about ten nanometres from the solution in real time.

    “The X-ray measurements show the building blocks of the material,” said co-author Dr. Ann-Christin Dippel from DESY, scientist at beamline P02.1, where the experiments were carried out. “With our method, we are able to observe the structure of the material at atomic length scale. What is special here is the possibility of following the dynamics of the growth process,” Dippel points out. “The different crystal structures that form in these nanoparticles are already known. But now we can track in real-time the transformation mechanism of molecules to nanocrystals. We do not only see the sequence of the process but also why specific structures form.”

    On the molecular level, the basic units of many metal-oxygen compounds like oxides are octahedra, which consist of eight equal triangles. These octahedra may share corners or edges. Depending on their configuration, the resulting compounds have different characteristics. This is not only true for tungsten trioxide but is basically applicable to other materials.

    The octahedra units in the solutions grow up to nanoparticles, with a ten nanometre small particle including about 25 octahedra. “We were able to determine that at first, both structure elements exist in the original material, the connection by corners and by edges,” said Saha. “In the course of the reaction, the octahedra rearrange: the longer you wait, the more the edge connection disappears and the connection by corners becomes more frequent. The nanoparticles which developed in our investigations have a predominantly ordered crystal structure.”

    In the continuous industrial synthesis, this process occurs so quickly, that it mainly produces nanoparticles with mixed disordered structures. “Ordered structures are produced when nanoparticles get enough time to rearrange,” said Saha. “We can use these observations for example to make available nanoparticles with special features. This method is also applicable to other nanoparticles.”

    See the full article here.

    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

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  • richardmitnick 3:27 pm on September 11, 2014 Permalink | Reply
    Tags: , , , Nanotechnology   

    From M.I.T Tech: “A Super-Strong and Lightweight New Material” 

    MIT Technology Review
    M.I.T Technology Review

    September 11, 2014
    Katherine Bourzac

    Nanostructured ceramics could be used to build lighter, stronger airplanes and batteries.

    A new type of material, made up of nanoscale struts crisscrossed like the struts of a tiny Eiffel Tower, is one of the strongest and lightest substances ever made.

    mtl
    Tiny trusses: A scanning electron microscope image of the new material reveals its ceramic nano-lattices

    If researchers can figure out how to make the stuff in large quantities, it could be used as a structural material for making planes and trucks, as well as in battery electrodes.

    Researchers led by Caltech materials scientist Julia Greer found that by carefully designing nanoscale struts and joints, they could make ceramics, metals, and other materials that can recover after being crushed, like a sponge. The materials are very strong and light enough to float through the air like a feather. The work is published today in the journal Science.

    In conventional materials, strength, weight, and density are correlated. Ceramics, for example, are strong but also heavy, so they can’t be used as structural materials where weight is critical—for example, in the bodies of cars. And when ceramics fail, they tend to fail catastrophically, shattering like glass.

    But at the nanoscale the same rules do not apply. In this size range, the structural and mechanical properties of ceramics become less tied to properties such as weight, and they can be altered more precisely.

    “For ceramics, smaller is tougher,” says Greer, who was named one of MIT Technology Review’s 35 Innovators Under 35 in 2008 for her work on nanoscale mechanics. This means that nanoscale trusses made from ceramic materials can be both very light—unsurprising, since they are mostly air—and extremely strong.

    In 2011, working with researchers at HRL Laboratories, a private engineering research company, Greer created one of the lightest materials ever made, a microlattice of hollow metal tubes. She later chose to take on the greater challenge of making ceramics with similar properties. This required fine-tuning structures at the nanoscale, meaning the materials are even more difficult to produce.

    To make the ceramic nano-trusses, Greer’s lab uses a technique called two-photon interference lithography. It’s akin to a very low-yield 3-D laser printer.

    First they use this method to create the desired structure, a lattice, out of a polymer. The polymer lattice is then coated with a ceramic such as alumina. Oxygen plasma etches out the polymer, leaving behind a lattice of hollow ceramic tubes.

    Greer’s lab showed that by changing the thickness of the tube walls, it’s possible to control how the material fails. When the walls are thick, the ceramic shatters under pressure as expected. But trusses with thinner walls, just 10 nanometers thick, buckle when compressed and then recover their shape.

    “You don’t expect these materials to recover—you expect them to be brittle and to fracture,” says Christopher Spadaccini, an engineer who specializes in materials manufacturing at the U.S. Department of Energy’s Lawrence Livermore National Laboratory in California.

    The new materials might be particularly interesting for use in batteries, notes Nicholas Fang, a mechanical engineer at MIT who is also working on nanostructured ceramics. Nanostructures have a very high surface area and are lightweight, a combination that could make for a fast-charging battery that stores a lot of energy in a convenient package. In fact, Greer says she is collaborating with German electronics company Bosch to apply her designs to lithium-ion batteries.

    See the full article here.

    The mission of MIT Technology Review is to equip its audiences with the intelligence to understand a world shaped by technology.

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  • richardmitnick 1:49 pm on September 3, 2014 Permalink | Reply
    Tags: , , , , Nanotechnology, Peptoids   

    From LBL: “Peptoid Nanosheets at the Oil/Water Interface” 

    Berkeley Logo

    Berkeley Lab

    September 3, 2014
    Lynn Yarris (510) 486-5375

    From the people who brought us peptoid nanosheets that form at the interface between air and water, now come peptoid nanosheets that form at the interface between oil and water. Scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed peptoid nanosheets – two-dimensional biomimetic materials with customizable properties – that self-assemble at an oil-water interface. This new development opens the door to designing peptoid nanosheets of increasing structural complexity and chemical functionality for a broad range of applications, including improved chemical sensors and separators, and safer, more effective drug delivery vehicles.

    Supramolecular assembly at an oil-water interface is an effective way to produce 2D nanomaterials from peptoids because that interface helps pre-organize the peptoid chains to facilitate their self-interaction,” says Ron Zuckermann, a senior scientist at the Molecular Foundry, a DOE nanoscience center hosted at Berkeley Lab. “This increased understanding of the peptoid assembly mechanism should enable us to scale-up to produce large quantities, or scale- down to screen many different nanosheets for novel functions.”

    nano
    Peptoid nanosheets are among the largest and thinnest free-floating organic crystals ever made, with an area-to-thickness equivalent of a plastic sheet covering a football field. Peptoid nanosheets can be engineered to carry out a wide variety of functions.
    two
    Ron Zuckerman and Geraldine Richmond led the development of peptoid nanosheets that form at the interface between oil and water, opening the door to increased structural complexity and chemical functionality for a broad range of applications.

    Zuckermann, who directs the Molecular Foundry’s Biological Nanostructures Facility, and Geraldine Richmond of the University of Oregon are the corresponding authors of a paper reporting these results in the Proceedings of the National Academy of Sciences (PNAS). The paper is titled Assembly and molecular order of two-dimensional peptoid nanosheets at the oil-water interface. Co-authors are Ellen Robertson, Gloria Olivier, Menglu Qian and Caroline Proulx.

    Peptoids are synthetic versions of proteins. Like their natural counterparts, peptoids fold and twist into distinct conformations that enable them to carry out a wide variety of specific functions. In 2010, Zuckermann and his group at the Molecular Foundry discovered a technique to synthesize peptoids into sheets that were just a few nanometers thick but up to 100 micrometers in length. These were among the largest and thinnest free-floating organic crystals ever made, with an area-to-thickness equivalent of a plastic sheet covering a football field. Just as the properties of peptoids can be chemically customized through robotic synthesis, the properties of peptoid nanosheets can also be engineered for specific functions.

    “Peptoid nanosheet properties can be tailored with great precision,” Zuckermann says, “and since peptoids are less vulnerable to chemical or metabolic breakdown than proteins, they are a highly promising platform for self-assembling bio-inspired nanomaterials.”

    In this latest effort, Zuckermann, Richmond and their co-authors used vibrational sum frequency spectroscopy to probe the molecular interactions between the peptoids as they assembled at the oil-water interface. These measurements revealed that peptoid polymers adsorbed to the interface are highly ordered, and that this order is greatly influenced by interactions between neighboring molecules.

    “We can literally see the polymer chains become more organized the closer they get to one another,” Zuckermann says.

    ft
    Peptoid polymers adsorbed to the oil-water interface are highly ordered thanks to interactions between neighboring molecules.

    The substitution of oil in place of air creates a raft of new opportunities for the engineering and production of peptoid nanosheets. For example, the oil phase could contain chemical reagents, serve to minimize evaporation of the aqueous phase, or enable microfluidic production.

    “The production of peptoid nanosheets in microfluidic devices means that we should soon be able to make combinatorial libraries of different functionalized nanosheets and screen them on a very small scale,” Zuckermann says. “This would be advantageous in the search for peptoid nanosheets with the molecular recognition and catalytic functions of proteins.”

    Zuckermann and his group at the Molecular Foundry are now investigating the addition of chemical reagents or cargo to the oil phase, and exploring their interactions with the peptoid monolayers that form during the nanosheet assembly process.

    “In the future we may be able to produce nanosheets with drugs, dyes, nanoparticles or other solutes trapped in the interior,” he says. “These new nanosheets could have a host of interesting biomedical, mechanical and optical properties.”

    This work was primarily funded by the DOE Office of Science and the Defense Threat Reduction Agency. Part of the research was performed at the Molecular Foundry and the Advanced Light Source, which are DOE Office of Science User Facilities.

    See the full article here.

    A U.S. Department of Energy National Laboratory Operated by the University of California

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  • richardmitnick 1:46 pm on August 26, 2014 Permalink | Reply
    Tags: , , , , Nanotechnology,   

    From Berkeley Lab: “Competition for Graphene” 

    Berkeley Logo

    Berkeley Lab

    August 26, 2014
    Lynn Yarris (510) 486-5375

    A new argument has just been added to the growing case for graphene being bumped off its pedestal as the next big thing in the high-tech world by the two-dimensional semiconductors known as MX2 materials. An international collaboration of researchers led by a scientist with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has reported the first experimental observation of ultrafast charge transfer in photo-excited MX2 materials. The recorded charge transfer time clocked in at under 50 femtoseconds, comparable to the fastest times recorded for organic photovoltaics.

    “We’ve demonstrated, for the first time, efficient charge transfer in MX2 heterostructures through combined photoluminescence mapping and transient absorption measurements,” says Feng Wang, a condensed matter physicist with Berkeley Lab’s Materials Sciences Division and the University of California (UC) Berkeley’s Physics Department. “Having quantitatively determined charge transfer time to be less than 50 femtoseconds, our study suggests that MX2 heterostructures, with their remarkable electrical and optical properties and the rapid development of large-area synthesis, hold great promise for future photonic and optoelectronic applications.”

    fw
    Feng Wang is a condensed matter physicist with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Physics Department. (Photo by Roy Kaltschmidt)

    Wang is the corresponding author of a paper in Nature Nanotechnology describing this research. The paper is titled Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures. Co-authors are Xiaoping Hong, Jonghwan Kim, Su-Fei Shi, Yu Zhang, Chenhao Jin, Yinghui Sun, Sefaattin Tongay, Junqiao Wu and Yanfeng Zhang.

    MX2 monolayers consist of a single layer of transition metal atoms, such as molybdenum (Mo) or tungsten (W), sandwiched between two layers of chalcogen atoms, such as sulfur (S). The resulting heterostructure is bound by the relatively weak intermolecular attraction known as the van der Waals force. These 2D semiconductors feature the same hexagonal “honeycombed” structure as graphene and superfast electrical conductance, but, unlike graphene, they have natural energy band-gaps. This facilitates their application in transistors and other electronic devices because, unlike graphene, their electrical conductance can be switched off.

    “Combining different MX2 layers together allows one to control their physical properties,” says Wang, who is also an investigator with the Kavli Energy NanoSciences Institute (Kavli-ENSI). “For example, the combination of MoS2 and WS2 forms a type-II semiconductor that enables fast charge separation. The separation of photoexcited electrons and holes is essential for driving an electrical current in a photodetector or solar cell.”

    In demonstrating the ultrafast charge separation capabilities of atomically thin samples of MoS2/WS2 heterostructures, Wang and his collaborators have opened up potentially rich new avenues, not only for photonics and optoelectronics, but also for photovoltaics.

    photo
    Photoluminescence mapping of a MoS2/WS2 heterostructure with the color scale representing photoluminescence intensity shows strong quenching of the MoS2 photoluminescence. (Image courtesy of Feng Wang group)

    “MX2 semiconductors have extremely strong optical absorption properties and compared with organic photovoltaic materials, have a crystalline structure and better electrical transport properties,” Wang says. “Factor in a femtosecond charge transfer rate and MX2 semiconductors provide an ideal way to spatially separate electrons and holes for electrical collection and utilization.”

    Wang and his colleagues are studying the microscopic origins of charge transfer in MX2 heterostructures and the variation in charge transfer rates between different MX2 materials.

    “We’re also interested in controlling the charge transfer process with external electrical fields as a means of utilizing MX2 heterostructures in photovoltaic devices,” Wang says.

    This research was supported by an Early Career Research Award from the DOE Office of Science through UC Berkeley, and by funding agencies in China through the Peking University in Beijing.

    See the full article here.

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  • richardmitnick 12:30 pm on August 22, 2014 Permalink | Reply
    Tags: , , Nanotechnology,   

    From Berkeley Lab: “Shaping the Future of Nanocrystals” 

    Berkeley Logo

    Berkeley Lab

    August 21, 2014
    Lynn Yarris

    The first direct observations of how facets form and develop on platinum nanocubes point the way towards more sophisticated and effective nanocrystal design and reveal that a nearly 150 year-old scientific law describing crystal growth breaks down at the nanoscale.

    Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) used highly sophisticated transmission electron microscopes and an advanced high-resolution, fast-detection camera to capture the physical mechanisms that control the evolution of facets – flat faces – on the surfaces of platinum nanocubes formed in liquids. Understanding how facets develop on a nanocrystal is critical to controlling the crystal’s geometric shape, which in turn is critical to controlling the crystal’s chemical and electronic properties.

    “For years, predictions of the equilibrium shape of a nanocrystal have been based on the surface energy minimization proposal by Josiah Willard Gibbs in the 1870s to describe the equilibrium shape of a water droplet,” says Haimei Zheng, a staff scientist in Berkeley Lab’s Materials Sciences Division who led this study. “For nanocrystals, the idea is that during crystal growth, high-energy facets will grow at a higher rate than low-energy facets and eventually disappear, resulting in a nanocrystal whose shape is configured to minimize surface energy.”

    The research of Zheng and her collaborators showed that at the molecular level, the geometric shape of nanocrystals during synthesis in solution is actually driven by differences in the mobility of ligands across the surfaces of different facets.

    “By choosing ligands that selectively bind on the facets, we should be able to control the shape of the nanocrystal as it grows,” she says. “This would provide a new way to design nanomaterials for advanced applications, including nanostructures for bio-imaging, catalysts for solar conversion, and energy storage.”

    two
    Haimei Zheng and Hong-Gang Liao used TEMs at the National Center for Electron Microscopy and a K2-IS camera to record the first direct observations facet formation in platinum nanocubes. (Photo by Kelly Owen)

    Zheng is the corresponding author of a paper in Science titled Facet Development During Platinum Nanocube Growth. Hong-Gang Liao is the lead author. Co-authors are Danylo Zherebetskyy, Huolin Xin, Cory Czarnik, Peter Ercius, Hans Elmlund, Ming Pan and Lin-Wang Wang.

    The performance of nanocrystals in such surface-enhanced applications as catalysis, sensing and photo-optics is strongly influenced by shape. While significant advances have been made in the synthesis of nanocrystals featuring a variety of shapes – cube, octahedron, tetrahedron, decahedron, icosahedron, etc., – controlling these shapes is often difficult and unpredictable.

    “A major roadblock has been that the atomic pathways of facet development in nanocrystals are mostly unknown due to the lack of direct observation,” Zheng says. “It has been assumed that commonly used surfactants modify the energy of specific facets through preferential adsorption, thereby influencing the relative growth rate of different facets and the shape of the final nanocrystal. However, this assumption was based on post-reaction characterizations that did not account for how facet dynamics evolve during crystal growth.”

    As a crystal undergoes growth, its constituent atoms or molecules fan out along specific directional planes whose coordinates are denoted by a three-digit system called the Miller Index. Facets form when the surfaces along different planes grow at different rates. Three of the most critical facets for determining a crystal’s geometric shape are the so-called “low index facets,” which are designated under the Miller Index as {100}, {110} and {111}.

    image
    Berkeley Lab researchers found that differences in ligand mobility during crystallization cause the low index facets – {100}, {110} and {111} – to stop growing at different times, resulting in the crystal’s final cubic shape. (Image courtesy of Haimei Zheng group)

    Working with platinum, one of the most effective industrial catalysts in use today, Zheng and her collaborators initiated the growth of nanocubes in a thin layer of liquid sandwiched between two silicon nitride membranes. This microfabricated liquid cell can encapsulate and maintain the liquid inside the high vacuum of a transmission electron microscope (TEM) for an extended period of time, enabling in situ observations of single nanoparticle growth trajectories.

    “With the liquid cells, we’re able to use TEMs to observe the growth of nanocrystals that remarkably resemble nanocrystals synthesized in flasks,” Zheng says. “We found that the growth rates of all low index facets are similar until the {100} facets stop growing. The {110} facets will continue to grow until they reach two neighboring {100} facets, at which point they form the edge of a cube whose corners will be filled in by the continued growth of {111} facets. The arrested growth of the {100} facets that triggers this process is determined by ligand mobility on the {100} facets, which is much lower than on the {110} and {111} facets.”

    For their observations, Zeng and her collaborators were able to use several of the TEMs at Berkeley Lab’s National Center for Electron Microscopy (NCEM), a DOE Office of Science user facility, including the TEAM 0.5 instrument, the world’s most powerful TEM. In addition, they were able to use a K2-IS camera from Gatan, Inc., which can capture electron images directly onto a CMOS sensor at 400 frames per second (fps) with 2K-by-2K pixel resolution.

    “The K2-IS camera can also be configured to capture images at up to 1600 fps with appropriate scaling of the field of view, which is critical for observing particles that are moving dynamically in the field of view,” says lead author Liao, a member of Zheng’s research group. “The elimination of the traditional scintillation process during image detection results in significant improvement in both sensitivity and resolution. High resolution imaging is also facilitated by the thin silicon nitride membranes of our liquid cell window, which is about 10 nanometers thick per membrane.”

    The lower ligand mobility and arrested growth of selected facets experimentally observed by Zheng and Liao, were supported by ab initio calculations carried out under the leadership of co-author Wang, a senior scientist with the Materials Sciences Division who heads the Computational Material Science and Nano Science group.

    “At first, we thought the continued growth in the {111} direction might be a result of higher surface energy on the {111} plane,” says co-author Zherebetskyy, a member of Wang’s group. “The experimental observations forced us to consider alternative mechanisms and our calculations show that the relatively low energy barrier on the {111} plane allow the ligand molecules on that plane to be very mobile.”

    Says Wang, “Our collaboration with Haimei Zheng’s group showcases how ab initio calculations can be combined with experimental observations to shed new light on hidden molecular processes.”

    Zheng and her group are now in the process of determining whether the ligand mobility in platinum that shaped the formation of cube-shaped nanocrystals also applies to ligands in other nanomaterials and the formation of nanocrystals in other geometric shapes.

    This research was supported by the DOE Office of Science.

    See the full article here.

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  • richardmitnick 3:51 pm on August 13, 2014 Permalink | Reply
    Tags: , , Nanotechnology   

    From Livermore Lab: “It’s nanotubular: New material could be used for energy storage and conversion” 


    Lawrence Livermore National Laboratory

    08/13/2014
    Anne M Stark

    Lawrence Livermore researchers have made a material that is 10 times stronger and stiffer than traditional aerogels of the same density.

    This ultralow-density, ultrahigh surface area bulk material with an interconnected nanotubular makeup could be used in catalysis, energy storage and conversion, thermal insulation, shock energy absorption and high energy density physics.

    Ultralow-density porous bulk materials have recently attracted renewed interest due to many promising applications.

    Unlocking the full potential of these materials, however, requires realization of mechanically robust architectures with deterministic control over form, cell size, density and composition, which is difficult to achieve by traditional chemical synthesis methods, according to LLNL’s Monika Biener, lead author of a paper appearing on the cover of the July 23 issue of Advanced Materials.

    mag
    Lawrence Livermore National Laboratory researchers have made a material that is 10 times stronger and stiffer than traditional aerogels of the same density, which is detailed in a featured story appearing on the cover of Advanced Materials.

    Biener and colleagues report on the synthesis of ultralow-density, ultrahigh surface area bulk materials with interconnected nanotubular morphology. The team achieved control over density (5 to 400 mg/cm3), pore size (30 um to 4 um) and composition by atomic layer deposition (ALD) using nanoporous gold as a tunable template.

    “The materials are thermally stable and, by virtue of their narrow unimodal pore size distributions and their thin-walled, interconnected tubular architecture, about 10 times stronger and stiffer than traditional aerogels of the same density,” Biener said.

    The three-dimensional nanotubular network architecture developed by the team opens new opportunities in the fields of energy harvesting, catalysis, sensing and filtration by enabling mass transport through two independent pore systems separated by a nanometer-thick 3D membrane.

    Other Livermore authors include Jianchao Ye, Theodore Baumann, Y. Morris Wang, Swanee Shin, Juergen Biener and Alex Hamza.

    The paper titled Ultra-Strong and Low-Density Nanotubular Bulk Materials with Tunable Feature Size” can be found on the Web.

    See the full article here.

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  • richardmitnick 9:32 am on August 7, 2014 Permalink | Reply
    Tags: , , Nanotechnology,   

    From physicsworld.com: “Molecular seeds sprout identical carbon nanotubes” 

    physicsworld
    physicsworld.com

    Aug 7, 2014
    Hamish Johnston

    The first effective technique for growing a batch of single-walled carbon nanotubes (SWCNTs) that all have the same molecular structure has been developed by scientists in Switzerland. The new process involves using “seed molecules” on a platinum substrate to grow SWCNTs with the desired structure. The breakthrough could be extremely important to those developing electronic devices based on SWCNTs because nanotubes with different structures can have very different electronic properties.

    tube
    Up, up and away: growing a nanotube from a seed molecule

    An SWCNT can be thought of as an atomically thin sheet of carbon that has been rolled up to form a tube about 1 nm thick, resembling a drinking straw. The carbon sheet always has the same honeycomb structure, which it shares with graphene. However, there are about a hundred different ways that the edges of the sheet can join together to make a tube, and this defines whether an SWCNT conducts electricity like a metal or a semiconductor. In the case of semiconducting nanotubes, the size of the electronic band gap also depends on how the edges are joined.

    Electronic devices based on SWCNTs could, in principle, be used to create transistors and other components that are smaller, faster and more energy efficient than those based on silicon. But before that can happen, scientists have to come up with reliable ways of producing batches of SWCNTs with identical structures.
    Costly separation

    Careful control of how SWCNTs are prepared can limit the number of different structures to as few as five. Then SWCNTs with the desired structure can be separated from a mixture. However, this is a very costly process with a structurally pure sample of SWCNTs costing about $1000 per milligram from a chemical supplier. As a result, scientists are very keen on developing methods for producing batches containing just one structure.

    This latest work was done by Juan Ramon Sanchez-Valencia and colleagues at the Swiss Federal Laboratories for Material Sciences and Technology (Empa) in Zürich.

    grow
    Grown from seed

    The new technique is based on the fact that, unlike a drinking straw, the tips of SWCNTs are capped by carbon atoms and each species has a cap with a different structure. The team used the established technique of organic chemical synthesis to create cap molecules with the same structure as the cap of the desired structural species of SWCNT. These cap molecules are placed on a platinum surface, which is heated in the presence of a carbon-rich gas such as ethylene. The platinum surface acts as a catalyst, pulling carbon atoms from the gas and passing them to the cap molecules. This steady supply of carbon molecules attaches itself to the bottom of a cap and pushes it up from surface, creating an SWCNT with the desired structure.

    Metallic armchairs

    The cap molecules were designed to seed SWCNTs with the “(6,6) armchair” structure. This much-studied type of nanotube is of interest to device designers because it conducts electricity like a metal. The SWCNTs were grown to several hundred nanometres in length before they were analysed using scanning tunnelling microscopy (STM) and Raman spectroscopy. This revealed that the SWCNTS were all of the same type and were free of structural defects.

    “The clever thing about this is that they predesign the cap and that cap then defines the nanotube type,” explains SWCNT expert James Tour at Rice University in the US, who was not involved in the research. Although the team did not show that the technique can create other types of SWCNTs by using different cap molecules, Tour says that this possibility “seems to be implied and it is likely that that would be the case”.

    Making tonnes of nanotubes

    An important benefit of the new technique is that 1 kg of seed molecules could, in principle, produce 5 tonnes of SWCNTs, each 10 μm in length. On the downside, a platinum surface measuring about 30 km2 would be needed to grow such a quantity of SWCNTs.

    An additional challenge facing anyone wanting to use the technique to produce commercial quantities of SWCNTs is how to deal with the entanglement of neighbouring nanotubes. This occurs before the SWCNTs reach a usable length, and disentangling nanotubes can be a tricky process.

    The new technique is described in Nature.

    See the full article here.

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
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  • richardmitnick 9:09 pm on August 4, 2014 Permalink | Reply
    Tags: , Nanotechnology, ,   

    From physicsworld.com: “Silicon nanorods bend light in new directions” 

    physicsworld
    physicsworld.com

    Aug 4, 2014
    Tim Wogan

    Ultrathin coatings that arbitrarily manipulate the phase and polarization of electromagnetic waves have been created by researchers in the US. The coatings are made from silicon nanorods using a technique that is compatible with industrial processes such as photolithography. The researchers say that the coatings could be used in new types of optical components that are much less bulky than traditional lenses. The technique could even be used to bend light in ways not possible with conventional lenses.

    swirl
    Swirling nanorods: an axicon lens made of silicon

    Fermat’s principle – the rule that light travels along the path of least time – says that electromagnetic waves travel along the path on which they accumulate the least phase. In a medium of higher refractive index, the wavelength shortens and so a wave accumulates more phase across the same distance. A wave therefore bends towards the normal to reduce the distance travelled in the medium and the phase accumulated.

    Manipulative metasurface

    In a conventional optical component such as a lens, phase accumulates continuously as the wave propagates and this determines the nature of the wave that emerges from the lens. However, if the phase of a wave could be changed discontinuously at a surface (called a metasurface), then the wave could, in principle, be manipulated in ways not possible with conventional optics.

    While this is straightforward in theory, the challenge facing physicists is how to create such a phase discontinuity using real materials. In 2011 researchers at Harvard University led by Federico Capasso and Zeno Gaburro covered a surface with V-shaped gold antennas so that the surface could be used to introduce any desired phase shift to optical waves passing through it. While this allows the arbitrary redirection of visible light, there are two major problems with this approach. First, the metallic nature of the surface means that most of the visible light is lost as it travels through the surface. Second, thin layers of metal are very difficult to work with and incompatible with the complementary metal-oxide semiconductor (CMOS) process used to make modern electronic devices.

    In the new research, Mark Brongersma and colleagues at Stanford University in California use lossless silicon optical antennas. When illuminated by a particular frequency of light (which can be selected by varying its diameter), the antenna will resonate strongly. This causes the light wave to pick up a phase shift that depends on the relative orientations of its polarization axes to the antenna. By appropriately tailoring the orientations and distances between the antennas, the surface can impart any desired phase shift to the light. This allowed the researchers to reproduce the functions of a bulk lens with a single layer of nanorods just 100 nm thick.

    Axicons and Bessel beams

    The team was able to create various types of “lenses” using this technique. These include traditional focusing lenses and an axicon. The latter is a specialized type of conical lens that transforms an ordinary laser beam into a Bessel beam – a ring-shaped beam used in optical tweezers and eye surgery.

    Optics expert John Pendry of Imperial College London is impressed. “If anyone in the electronics or photonics game wanted to use a material, it would have to be silicon,” he explains. “You can lay down silicon extremely flat and shape it very precisely. Metals are nowhere near silicon in terms of the precision and the control you can exert over them; so, if you can translate a technology like metasurfaces into a silicon environment, you’re on to a real winner because you can hook on to this bandwagon that’s been rolling for half a century now.”

    In the experiment, the metasurfaces were fabricated by electron-beam lithography, but team member Erez Hasman, now at the Technion-Israel Institute of Technology in Haifa, says that commercial companies could produce large quantities using industrial processes such as photolithography. “I think that Intel or other companies based on CMOS technology can implement such a metasurface now,” he says.

    “The theoretical concept is not surprising at this point, but the fact that they built it and it works is interesting,” agrees Andrea Alù, an expert on metasurfaces at the University of Texas at Austin. He looks forward to the development of optical components that are not possible with normal lenses. Hasman suggests that one of the first such uses might be to interface waveguides with free space. “In general, the modes of a laser resonator or a waveguide are very complex and different from the modes of free space,” he says. Coupling the two together to allow signals to pass between them, he explains, is very difficult using a lens or a prism but should be no problem using the 2D metasurface.

    The research is published in Science.

    See the full article here.

    PhysicsWorld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

    We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.
    IOP Institute of Physics

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  • richardmitnick 4:24 pm on August 1, 2014 Permalink | Reply
    Tags: , , , Nanotechnology   

    From Carnegie Mellon: “Carnegie Mellon Chemists Create Nanofibers Using Unprecedented New Method” 

    Carnegie Mellon University logo
    Carnegie Mellon university

    Thursday, July 31, 2014

    Jocelyn Duffy, jhduffy@andrew.cmu.edu, 412-268-9982

    Researchers from Carnegie Mellon University have developed a novel method for creating self-assembled protein/polymer nanostructures that are reminiscent of fibers found in living cells. The work offers a promising new way to fabricate materials for drug delivery and tissue engineering applications. The findings were published in the July 28 issue of Angewandte Chemie International Edition.

    ribbin
    No legend, no image credit.

    “We have demonstrated that, by adding flexible linkers to protein molecules, we can form completely new types of aggregates. These aggregates can act as a structural material to which you can attach different payloads, such as drugs. In nature, this protein isn’t close to being a structural material,” said Tomasz Kowalewski, professor of chemistry in Carnegie Mellon’s Mellon College of Science.

    The building blocks of the fibers are a few modified green fluorescent protein (GFP) molecules linked together using a process called click chemistry. An ordinary GFP molecule does not normally bind with other GFP molecules to form fibers. But when Carnegie Mellon graduate student Saadyah Averick, working under the guidance of Krzysztof Matyjaszewski, the J.C. Warner Professor of Natural Sciences and University Professor of Chemistry in CMU’s Mellon College of Science, modified the GFP molecules and attached PEO-dialkyne linkers to them, they noticed something strange — the GFP molecules appeared to self-assemble into long fibers. Importantly, the fibers disassembled after being exposed to sound waves, and then reassembled within a few days. Systems that exhibit this type of reversible fibrous self-assembly have been long sought by scientists for use in applications such as tissue engineering, drug delivery, nanoreactors and imaging.

    “This was purely curiosity-driven and serendipity-driven work,” Kowalewski said. “But where controlled polymerization and organic chemistry meet biology, interesting things can happen.”

    The research team observed the fibers using confocal light microscopy, confirmed their assembly using dynamic light scattering and studied their morphology using atomic force microscopy (AFM). They also observed that the fibers were fluorescent, indicating that the GFP molecules retained their 3-D structure while linked together.

    To determine what processes were driving the self-assembly, Matyjaszewski and Kowalewski turned to Anna Balazs, Distinguished Professor of Chemical Engineering and the Robert v. d. Luft Professor at the University of Pittsburgh. A leading expert in modeling the dynamics and mechanical properties of mesoscale systems, Balazs ran a computer simulation of the GFP molecules’ self-assembly process using a technique called dissipative particle dynamics, a type of coarse-grained molecular dynamics method. The simulation confirmed the modified GFP’s tendency to form fibers and revealed that the self-assembly process was driven by the interaction of hydrophobic patches on the surfaces of individual GFP molecules. In addition, Balazs’s simulated fibers closely corresponded with what Kowalewski observed using AFM imaging.

    “Our protein-polymer system gives us an atomically precise, very well-defined nanoscale building object onto which we can attach different handles in very precisely defined positions. It can be used in a way that wasn’t ever intended by biology,” Kowalewski said.

    In addition to Averick, Balazs, Kowalewski and Matyjaszewski, co-authors of the study include Carnegie Mellon’s Orsolya Karacsony and Jacob Mohin, University of Pittsburgh’s Xin Yong and Nicholas M. Moellers, Oregon State University’s Bradley F. Woodman and Ryan A. Mehl, and Zhejiang University’s Weipu Zhu. The research was supported by the U.S. Department of Energy, National Science Foundation, Carnegie Mellon’s CRP Consortium and Oregon State University.

    See the full article here.

    Carnegie Mellon University (CMU) is a global research university with more than 12,000 students, 95,000 alumni, and 5,000 faculty and staff.
    CMU has been a birthplace of innovation since its founding in 1900.
    Today, we are a global leader bringing groundbreaking ideas to market and creating successful startup businesses.
    Our award-winning faculty members are renowned for working closely with students to solve major scientific, technological and societal challenges. We put a strong emphasis on creating things—from art to robots. Our students are recruited by some of the world’s most innovative companies.
    We have campuses in Pittsburgh, Qatar and Silicon Valley, and degree-granting programs around the world, including Africa, Asia, Australia, Europe and Latin America.


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