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  • richardmitnick 7:25 am on June 30, 2016 Permalink | Reply
    Tags: , , Argonne APS, Color,   

    From Argonne: “X-rays reveal the photonic crystals in butterfly wings that create color” 

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    News from Argonne National Laboratory

    June 10, 2016 [This just appeared in social media.]
    Louise Lerner


    Access mp4 video here .

    Scientists used X-rays to discover what creates one butterfly effect: how the microscopic structures on the insect’s wings reflect light to appear as brilliant colors to the eye.

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    Researchers used powerful X-rays to take a molecular look at how the Kaiser-i-Hind butterfly’s wings reflect in brilliant iridescent green. Image: Shutterstock/Butterfly Hunter.

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    When you look very close up at a butterfly wing, you can see this patchwork map of lattices with slightly different orientations (colors added to illustrate the domains). Scientists think this structure, and the irregularities along the edges where they meet, helps create the brilliant “sparkle” of the wings. Image courtesy Ian McNulty/Science

    The results, published today in Science Advances, could help researchers mimic the effect for reflective coatings, fiber optics or other applications.

    We’ve long known that butterflies, lizards and opals all use complex structures called photonic crystals to scatter light and create that distinctive iridescent look. But we knew less about the particulars of how these natural structures grow and what they look like at very, very small sizes—and how we might steal their secrets to make our own technology.

    A powerful X-ray microscope at the Advanced Photon Source, a U.S. Department of Energy Office of Science User Facility, provided just such a view to scientists from the University of California-San Diego, Yale University and the DOE’s Argonne National Laboratory.

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    They took a tiny piece of a wing scale from the vivid green Kaiser-i-Hind butterfly, Teinopalpus imperialis, and ran X-ray studies to study the organization of the photonic crystals in the scale.

    At sizes far too small to be seen by the human eye, the scales look like a flat patchwork map with sections of lattices, or “domains,” that are highly organized but have slightly different orientations.

    “This explains why the scales appear to have a single color,” said UC-San Diego’s Andrej Singer, who led the work. “We also found tiny crystal irregularities that may enhance light-scattering properties, making the butterfly wings appear brighter.”

    These occasional irregularities appear as defects where the edges of the domains met each other.

    “We think this may indicate the defects grow as a result of the chirality —the left or right-handedness—of the chitin molecules from which butterfly wings are formed,” said coauthor Ian McNulty, an X-ray physicist with the Center for Nanoscale Materials at Argonne, also a DOE Office of Science User Facility.

    These crystal defects had never been seen before, he said.

    Defects sound as though they’re a problem, but they can be very useful for determining how a material behaves—helping it to scatter more green light, for example, or to concentrate light energy in other useful ways.

    “It would be interesting to find out whether this is an intentional result of the biological template for these things, and whether we can engineer something similar,” he said.

    The observations, including that there are two distinct kinds of boundaries between domains, could shed more light on how these structures assemble themselves and how we could mimic such growth to give our own materials new properties, the authors said.

    The X-ray studies provided a unique look because they are non-destructive—other microscopy techniques often require slicing the sample into paper-thin layers and staining it with dyes for contrast, McNulty said.

    “We were able to map the entire three-micron thickness of the scale intact,” McNulty said. (Three microns is about the width of a strand of spider silk.)

    The wing scales were studied at the 2-ID-B beamline at the Advanced Photon Source. The results are published in an article, Domain morphology, boundaries, and topological defects in biophotonic gyroid nanostructures of butterfly wing scales, in Science Advances. Other researchers on the study were Oleg Shpyrko, Leandra Boucheron and Sebastian Dietze (UC-San Diego); David Vine (Argonne/Berkeley National Laboratory); and Katharine Jensen, Eric Dufresne, Richard Prum and Simon Mochrie (Yale).

    The research was supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences.

    See the full article here .

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit http://science.energy.gov/user-facilities/basic-energy-sciences/.

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    • Bill 9:19 am on July 10, 2016 Permalink | Reply

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      Like

  • richardmitnick 12:24 pm on November 30, 2015 Permalink | Reply
    Tags: Argonne APS, Intermediate Energy X-ray (IEX) beamline,   

    From APS at ANL: “Novel intermediate energy X-ray beamline opening for researchers” 

    News APS at Argonne National Laboratory

    November 20, 2015
    John Spizzirri

    Researchers working to create next-generation electronic systems and to understand the fundamental properties of magnetism and electronics to tackle grand challenges such as quantum computing have a new cutting-edge tool in their arsenal. The Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility located at Argonne National Laboratory, recently unveiled a new capability: the Intermediate Energy X-ray (IEX) beamline at sector 29.

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    Intermediate Energy X-ray (IEX) beamline at sector 29

    Using relatively low-energy X-rays, the IEX beamline at the APS will help illuminate electronic ordering and emergent phenomena in ordered materials to better understand the origins of distinct electronic properties. Another important feature for users is a greater ability to adjust X-ray parameters to meet experimental needs.

    Currently in commissioning phase, the IEX beamline begins its first user runs in January 2016. With its state-of-the-art electromagnetic insertion device, highly adaptive X-ray optics, and compatible endstation techniques for X-ray photoelectron spectroscopy and scattering, it opens a new era for X-ray research in sciences ranging from condensed matter physics and materials science to molecular chemistry.

    “The nice thing about having both spectroscopy and scattering techniques available here is that there are different communities addressing the same science questions with different approaches,” said Jessica McChesney, an assistant physicist and beamline scientist at the APS who is responsible for operating the beamline and starting the user program. “We hope people will actually work together and talk to each other, and drive the science that way.”

    “The idea is, we’re going to look at electronic order in materials that may one day end up in your cell phone, either as battery materials, interconnects, or in the logic,” McChesney added. “Possibly one day, when we have spintronic devices, the materials may be something we studied here.”

    Conventional electronics use current, or the flow of electrons, while spintronics relies on the flow of the electrons’ spins, not just their charges. Other materials that can be studied at the IEX beamline include high-temperature superconductors, magnetic materials, and polymer self-assemblies.

    The new beamline was built to meet the specific requirements of its two shared scientific endstations that offer users varied but complementary techniques. Using Einstein’s discovery of the photoelectric effect, the angle-resolved photoemission spectroscopy (ARPES) endstation measures the energy and angle of emitted electrons and, by using conservation of energy and momentum, can reveal what the properties of these photoemitted electrons were before they left the material. The resonant soft X-ray scattering (RSXS) uses resonance, the tuning of the X-ray beam to a specific electronic excitation, to scatter off of an ordered electronic state to determine electron density.

    “So there was this freak convergence of a lot of different things: the right combination of science, geography, and technology all at the same time.”

    How it all started

    Like the formation of a new particle in a collider, it was the research trajectory of two scientists that forged the foundations for IEX beamline. Physicists Juan Carlos Campuzano of the University of Illinois at Chicago (UIC) and Peter Abbamonte of the University of Illinois in Urbana Champaign (UIUC) both studied the complicated dynamics of high-temperature superconducting materials.

    By 1985, Campuzano had already proposed a similar, but less advanced, beamline at the Swiss Light Source, in Villingen, Switzerland, while Abbamonte, as a postdoc, had been on the team that pioneered the RSXS endstation, at Brookhaven National Laboratory in Upton, NY. Eventually, both took jobs within the University of Illinois system and were seeking an intermediate energy X-ray source in the Midwest to conduct their research.

    Given the challenges presented by these superconducting materials, they decided a better, brighter beamline was in order. They wrote a proposal that garnered funding from the National Science Foundation (NSF), which suggested they build the instrument at the newly established APS at Argonne, where Campuzano held a joint appointment.

    They reached out to APS beamline scientist George Srajer, now deputy associate laboratory director for Photon Sciences, to forge a partnership with DOE to fine-tune the concept and secure the remaining funding. A beamline was born.

    “So there was this freak convergence of a lot of different things: the right combination of science, geography, and technology all at the same time,” said Abbamonte, now professor of physics at UIUC.

    “There is no other like it in the world.”

    Making the beamline unique

    With several similar beamlines in Japan and Europe already operating, the toughest challenge in requesting funds for and building the new IEX beamline at the APS was to create something unique, noted Campuzano.

    “And it doesn’t seem like a big deal, but deciding what not to do was very important,” added Abbamonte. “You build a $15 million machine and people want to make it do everything. But that ends up costing more and the experiment that is supposed to do everything ends up doing nothing, because the more versatile an instrument is the more difficult it is to make it work. So we decided to focus and pick a few really important things.”

    A key feature unique to IEX at the APS is the beamline’s insertion device (ID), the magnetic system responsible for shaping the properties of X-rays provided to the beamline.

    According to Srajer, there is no other like it in the world.

    The ID is an electromagnetic variable polarizing undulator (EMVPU), operating in a range of 250 to 2,500 electron volts (eV). Like a fixed magnet device, users can change the energy of the X-rays and polarization at the sample. But the new ID also allows the source to run in quasi-periodic mode, which suppresses the higher harmonics in the X-ray beamline, resulting in a much higher signal-to-noise ratio that is ideal for detecting small signals in a large background.

    One advantage to developing a lower-energy beamline at a high-energy storage ring is that the intensity produced by the undulator is rather flat across the whole 250- to 2500-eV energy range. This minimizes the need for normalization, unlike at lower-energy storage rings where users must switch between the different undulator harmonics.

    To accurately deliver the X-rays produced by the ID to the endstations required the complicated design and manufacturing of X-ray optics that precisely adjust X-ray parameters, such as focus, energy resolution, and coherence fraction. Users can further tailor the X-ray beam for a given experiment by selecting between one of three gratings in the monochromator, optimizing the total intensity or flux (109–1012 photons per second) and energy resolution (5–300 milli-electron volts [meV]).

    A means to the end(stations)

    Superconductors with transition temperatures above the temperature of liquid nitrogen hold the promise of practical applications, such as the efficient production and transport of electricity. However, how those moderate- to high-temperature superconductors function is not well understood.

    When Campuzano and Abbamonte joined forces to develop the IEX beamline, their shared interest in high-temperature superconductivity became the focal point for the design of its two scientific endstations. Years of collective work in photoemission spectroscopy and X-ray scattering, respectively, would culminate in a powerful combination of tools located in one place.

    Campuzano was already using ultraviolet ARPES and was considered one of the leading experts in the field when he set his sights to building a new APS beamline.

    “We already knew that low-energy photons released electrons mostly from the surface of a material, which is not necessarily representative of what’s going on inside it,” said Campuzano. “The way to get around that was to build a beamline that had much higher-energy photons, soft X-rays.”

    The IEX ARPES experimental station, designed and built by Campuzano’s team at UIC, uses photons in a relatively high-energy range of 1000 eV to probe electrons deeper within a solid. As electrons absorb incoming photons, they are ejected from the structure. This lets users better analyze the dynamics of electron, the electronic excitations, in a sample.

    By understanding what happens to the electronic structure when macroscopic properties are changed, scientists get a better idea of how they can manipulate those properties to their advantage, whether it’s finding the best remnant magnetic fields for spintronics or determining transition temperatures in superconductors.

    Where ARPES lets researchers know how electrons propagate in a material, the RSXS endstation lets them know where those electrons are located. Designed and built by Abbamonte’s team at UIUC, resonant soft X-ray scattering is a photon-in-photon-out technique that yields real-space information about electronic ordering and information about correlation lengths.

    For Abbamonte, the technique is central to his research in determining whether heterogeneity is relevant for optimizing superconductivity.

    “Set the beam energies to the right resonance value, and when the photons hit the sample, they’ll scatter in all different directions because of this heterogeneity that we’re interested in,” he explained. “Then you use an angle-resolving detector to scan and measure the angle dependence of the light to back out what the form of that heterogeneity is.”

    In addition to the traditional microchannel plate angle-resolving detector, the RSXS endstation is equipped with a two-dimensional energy-resolving detector, another of the highly unique applications on this beamline. Considered among the most sensitive energy-resolving detectors in the world, it is based on transition-edge sensor (TES) technology pioneered by the National Institute of Standards and Technology (NIST) for cosmology applications, such as research in cosmic microwave background radiation.

    This is the first time TES technology has been used for scattering, and could prove 1000 times more sensitive to heterogeneity than any previous technology.

    The development of IEX was jointly funded by DOE and NSF.

    See the full article here .

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    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 1:52 pm on November 7, 2014 Permalink | Reply
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    From FNAL: “Multilaboratory collaboration brings new X-ray detector to light” 


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    Friday, Nov. 7, 2014
    Troy Rummler

    A collaboration blending research in DOE’s offices of High-Energy Physics (HEP) with Basic Energy Sciences (BES) will yield a one-of-a-kind X-ray detector. The device boasts Brookhaven Lab sensors mounted on Fermilab integrated circuits linked to Argonne Lab data acquisition systems. It will be used at Brookhaven’s National Synchrotron Light Source II and Argonne’s Advanced Photon Source. Lead scientists Peter Siddons, Grzegorz Deptuch and Robert Bradford represent the three laboratories.

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    “This partnership between HEP and BES has been a fruitful collaboration, advancing detector technology for both fields,” said Brookhaven’s Peter Siddons.

    team
    These researchers work on the VIPIC prototype. Peter Siddons of Brookhaven National Laboratory (fifth from the left), Grzegroz Deptuch of Fermilab (third from the right) and Robert Bradford of Argonne National Laboratory (far right) lead the effort. Photo courtesy of Argonne National Laboratory

    This detector is filling a need in the X-ray correlation spectroscopy (XCS) community, which has been longing for a detector that can capture dynamic processes in samples with microsecond timing and nanoscale sensitivity. Available detectors have been designed largely for X-ray diffraction crystallography and are incapable of performing on this time scale.

    det
    The 64-by-64 pixel VIPIC prototype, pictured with a sensor on the bottom and solder bump-bonding bump on top, ready to be received on the printed circuit board. Photo: Reidar Hahn

    In 2006, Fermilab’s Ray Yarema began investigating 3-D integrated chip technology, which increases circuit density, performance and functionality by vertically stacking rather than laterally arranging silicon wafers. Then in 2008 Deptuch, a member of Yarema’s group and Fermilab ASIC [Application Specific Integrated Circuit] Group leader since 2011, met with Siddons, a scientist at Brookhaven, at a medical imaging conference. They discussed applying 3-D technology to a new, custom detector project, which was later given the name VIPIC (vertically integrated photon imaging chip). Siddons was intrigued by the 3-D opportunities and has since taken the lead on leveraging Fermilab expertise toward the longstanding XCS problem. As a result, the development of the device at Fermilab — where 97 percent of research funds come through HEP — receives BES funding.

    A 64-by-64-pixel VIPIC prototype tested at Argonne this summer flaunted three essential properties: timing resolution within one microsecond; continuous new-data acquisition with simultaneous old-data read-out; and selective transmission of only pixels containing data.

    The results achieved with the prototype have attracted attention from the scientific community.

    Deptuch noted that this partnership between BES and HEP reflects the collaborative nature of such efforts at the national labs.

    “It truly is a cooperative effort, combining the expertise from three national laboratories toward one specific goal,” he said.

    The team will grow their first VIPIC prototype tiled, seamless array of chips on a sensor to form a 1-megapixel detector. The collaboration is targeting a completion date of 2017 for the basic functionality detector. Ideas for expanded capabilities are being discussed for the future.

    See the full article here.

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  • richardmitnick 4:19 pm on June 9, 2014 Permalink | Reply
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    From Berkeley Lab: “Berkeley Lab Researchers Create Nanoparticle Thin Films That Self-Assemble in One Minute” 

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    June 9, 2014
    Lynn Yarris

    The days of self-assembling nanoparticles taking hours to form a film over a microscopic-sized wafer are over. Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have devised a technique whereby self-assembling nanoparticle arrays can form a highly ordered thin film over macroscopic distances in one minute.

    three
    Upon solvent annealing, supramolecules made from gold nanoparticles and block copolymers will self-assemble into highly ordered thin films in one minute.

    Ting Xu, a polymer scientist with Berkeley Lab’s Materials Sciences Division, led a study in which supramolecules based on block copolymers were combined with gold nanoparticles to create nanocomposites that under solvent annealing quickly self-assembled into hierarchically-structured thin films spanning an area of several square centimeters. The technique is compatible with current nanomanufacturing processes and has the potential to generate new families of optical coatings for applications in a wide number of areas including solar energy, nanoelectronics and computer memory storage. This technique could even open new avenues to the fabrication of metamaterials, artificial nanoconstructs that possess remarkable optical properties.

    TX
    Ting Xu holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry. (Photo by Roy Kaltschmidt)

    “Our technique can rapidly generate amazing nanoparticle assemblies over areas as large as a silicon wafer,” says Xu, who also holds a joint appointment with the University of California (UC) Berkeley’s Departments of Materials Sciences and Engineering, and Chemistry. “You can think of it as pancake batter that you can spread over a griddle, wait one minute and you have a pancake ready to eat.”

    Xu is the corresponding author of a paper describing this research in Nature Communications titled Rapid fabrication of hierarchically structured supramolecular nanocomposite thin films in one minute. Co-authors are Joseph Kao, Kari Thorkelsson, Peter Bai, Zhen Zhang and Cheng Sun.

    Nanoparticles function as artificial atoms with unique optical, electrical and mechanical properties. If nanoparticles can be induced to self-assemble into complex structures and hierarchical patterns, similar to what nature does with proteins, it would enable mass-production of devices a thousand times smaller those used in today’s microtechnology.

    Xu and her research group have been steadily advancing towards this ultimate goal. Most recently their focus has been on the use of block copolymer-based supramolecular solutions to direct the self-assembly of nanoparticle arrays. A supramolecule is a group of molecules that act as a single molecule able to perform a specific set of functions. Block copolymers are long sequences or “blocks” of one type of monomer bound to blocks of another type of monomer that have an innate ability to self-assemble into well-defined arrays of nano-sized structures over macroscopic distances.

    “Block copolymer-based supramolecules self-assemble and form a wide range of morphologies that feature microdomains typically a few to tens of nanometers in size,” Xu says. “As their size is comparable to that of nanoparticles, the microdomains of supramolecules provide an ideal structural framework for the self-assembly of nanoparticle arrays.”

    afm
    AFM phase image shows a 50-nm nanocomposite thin film in lithographically patterned trenches that formed unidirectional nanoparticle arrays over macroscopic distances in just over a minute. The bright circular dots represent the 5 nm gold nanoparticles as illustrated by the schematic.

    In the supramolecular technique devised by Xu and her colleagues, arrays of gold nanoparticles were incorporated into solutions of supramolecules to form films that were about 200 nanometers thick. Through solvent annealing, using chloroform as the solvent, the nanoparticle arrays organized into three-dimensional cylindrical microdomains that were packed into distorted hexagonal lattices in parallel orientation with the surface. This display of hierarchical structural control in nanoparticle self-assembly was impressive but was only half the game.

    “To be compatible with nanomanufacturing processes, the self-assembly fabrication process must also be completed within a few minutes to minimize any degradation of nanoparticle properties caused by exposure to the processing environment,” Xu says.

    She and her group systematically analyzed the thermodynamics and kinetics of self-assembly in their supramolecular nanocomposite thin films upon exposure to solvent vapor. They found that by optimizing a single parameter, the amount of solvent, assembly kinetics could be precisely tailored to produce hierarchically structured thin films in a single minute.

    “By constructing our block copolymer-based supramolecules from small molecules non-covalently attached to polymer side chains, we changed the energy landscape so that solvent content became the most important factor,” Xu says. “This enabled us to achieve fast-ordering of the nanoparticle arrays with the addition of only a very small amount of solvent, about 30-percent of the fraction of a 200 nanometer thick film.”

    two
    Joseph Kao and Kari Thorkelsson helped devise a technique whereby self-assembling nanoparticle arrays can form a highly ordered thin film over macroscopic distances in one minute. (Photo by Roy Kaltschmidt)

    The optical properties of nanocomposite thin films depend on the properties of individual nanoparticles and on well-defined inter-particle distances along different directions. Given that the dimensions of the gold nanoparticle arrays are at least one order of magnitude smaller than the wavelengths of visible light, the supramolecular technique of Xu and her colleagues has strong potential to be used for making metamaterials. These artificial materials have garnered a lot of attention in recent years because their electromagnetic properties are unattainable in natural materials. For example, a metamaterial can have a negative index of refraction, the ability to bend light backwards, unlike all materials found in nature, which bend light forward.

    “Our gold nanocomposite thin films exhibit strong wavelength- dependent optical anisotropy that can be tailored simply by varying the solvent treatment,” Xu says. “This presents a viable alternative to lithography for making metamaterials.”

    While Xu and her colleagues used gold nanoparticles in their films, the supramolecular approach is compatible with nanoparticles of other chemical compositions as well.

    “We should be able to create a library of nanoparticle assemblies engineered for light manipulation and other properties,” Xu says, “using a technique that is compatible with today’s most widely used nanomanufacturing processes, including blade coating, ink-jet printing and dynamic zone annealing.”

    This research was funded by the DOE Office of Science and made use of the Advanced Photon Source at Argonne National Laboratory, a DOE Office of Science user facility.

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    See the full article here.

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  • richardmitnick 4:16 pm on March 21, 2014 Permalink | Reply
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    From Argonne APS: “A Layered Nanostructure Held Together By DNA” 

    News from Argonne National Laboratory

    March 18, 2014
    David Lindley

    Dreaming up nanostructures that have desirable optical, electronic, or magnetic properties is one thing. Figuring out how to make them is another. A new strategy uses the binding properties of complementary strands of DNA to attach nanoparticles to each other and builds up a layered thin-film nanostructure through a series of controlled steps. Investigation at the U.S. Department of Energy Office of Science’s Advanced Photon Source has revealed the precise form that the structures adopted, and points to ways of exercising still greater control over the final arrangement.

    dna
    DNA

    The idea of using DNA to hold nanoparticles was devised more than 15 years ago by Chad Mirkin and his research team at Northwestern University. They attached short lengths of single-stranded DNA with a given sequence to some nanoparticles, and then attached DNA with the complementary sequence to others. When the particles were allowed to mix, the “sticky ends” of the DNA hooked up with each other, allowing for reversible aggregation and disaggregation depending on the hybridization properties of the DNA linkers.

    sticky
    Nanoparticles linked by complementary DNA strands form a bcc superlattice when added layer-by-layer to a DNA coated substrate. When the substrate DNA is all one type, the superlattice forms at a different orientation (top row) than if the substrate has both DNA linkers (bottom row). GISAXS scattering patterns (right) and scanning electron micrographs (inset) reveal the superlattice structure. No image credit.

    Recently, this DNA “smart glue” has been utilized to assemble nanoparticles into ordered arrangements resembling atomic crystal lattices, but on a larger scale. To date, nanoparticle superlattices have been synthesized in well over 100 crystal forms, including some that have never been observed in nature.

    However, these superlattices are typically polycrystalline, and the size, number, and orientation of the crystals within them is generally unpredictable. To be useful as metamaterials, photonic crystals, and the like, single superlattices with consistent size and fixed orientation are needed.

    Northwestern researchers and a colleague at Argonne National Laboratory have devised a variation on the DNA-linking procedure that allows a greater degree of control.

    The basic elements of the superlattice were gold nanoparticles, each 10 nanometers across. These particles were made in two distinct varieties, one adorned with approximately 60 DNA strands of a certain sequence, while the other carried the complementary sequence.

    The researchers built up thin-film superlattices on a silicon substrate that was also coated with DNA strands. In one set of experiments, the substrate DNA was all of one sequence – call it the “B” sequence – and it was first dipped into a suspension of nanoparticles with the complementary “A” sequence.

    When the A and B ends connected, the nanoparticles formed a single layer on the substrate. Then the process was repeated with a suspension of the B-type nanoparticles, to form a second layer. The whole cycle was repeated, as many as four more times, to create a multilayer nanoparticle superlattice in the form of a thin film.

    Grazing incidence small-angle x-ray scattering (GISAXS) studies carried out at the X-ray Science Division 12-ID-B beamline at the Argonne Advanced Photon Source revealed the symmetry and orientation of the superlattices as they formed. Even after just three half-cycles, the team found that the nanoparticles had arranged themselves into a well-defined, body-centered cubic (bcc) structure, which was maintained as more layers were added.

    In a second series of experiments, the researchers seeded the substrate with a mix of both the A and B types of DNA strand. Successive exposure to the two nanoparticle types produced the same bcc superlattice, but with a different vertical orientation. That is, in the first case, the substrate lay on a plane through the lattice containing only one type of nanoparticle, while in the second case, the plane contained an alternating pattern of both types (see the figure).

    To get orderly superlattice growth, the researchers had to conduct the process at the right temperature. Too cold, and the nanoparticles would stick to the substrate in an irregular fashion, and remain stuck. Too hot, and the DNA linkages would not hold together.

    But in a temperature range of a couple of degrees on either side of about 40° C (just below the temperature at which the DNA sticky ends detach from each other), the nanoparticles were able to continuously link and unlink from each other. Over a period of about an hour per half-cycle, they settled into the bcc superlattice, the most thermodynamically stable arrangement.

    GISAXS also revealed that although the substrate forced superlattices into specific vertical alignments, it allowed the nanoparticle crystals to form in any horizontal orientation. The researchers are now exploring the possibility that by patterning the substrate in a suitable way, they can control the orientation of the crystals in both dimensions, increasing the practical value of the technique.

    See the full article here.

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  • richardmitnick 5:24 pm on March 5, 2014 Permalink | Reply
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    From ARGONNE APS: “Squeezing Out the Hidden Lives of Electrons” 

    News from Argonne National Laboratory

    FEBRUARY 26, 2014
    Jenny Morber

    In our daily lives we tend to think of electrical conductivity as largely static: Copper is a good choice for conduction; clay is not. But heat up that copper wire, and electron conduction slows. Give a flake of that ceramic a good squeeze, and conduction may perk up. Conductivity is determined by much more than simple chemistry. Metal-to-insulator transitions have excited and perplexed researchers for over a century, and they continue to provide fodder for research today. The key to understanding what causes changes in material conductivity lies in teasing out contributions from structural atomic arrangements and electron interactions. Researchers using high-energy x-rays from the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS) have managed to disentangle these components in vanadium sesquioxide (V2O3), an extensively studied model solid. By decoupling the effects of spin, charge, and lattice variables in V2O3, the team is uncovering a mechanism that has eluded researchers for six decades.

    graph
    Electrical resistance as a function of pressure in V2O3. As pressure increases from 5 GPa, resistance decreases as expected. At 12.5 GPa the sharp increase in resistance is an unexpected result of electron-lattice interactions. At ~33 GPa, the material’s corundum hexagonal structure changes to monoclinic, and resistance rises more sharply due to electron-electron interactions. Here the material is on the cusp of a metal-to-insulator transition.

    With measurements performed at the LERIX instrument at X-ray Science Division (XSD) beamline 20-ID and the High Pressure Collaborative Access Team (HP-CAT) beamline 16-ID, both at the APS, and calculations from the XSD Theory Group, the researchers have identified a structural phase change in V2O3 that occurs under great pressure, but without the usual metal-to-insulator transition. The interplay between crystal structure and electronic properties underlies almost every modern device, from pressure sensors to superconducting high speed trains.

    Under normal conditions, V2O3 is a black metallic solid with a corundum crystal structure, like that of rubies and sapphires. With changes in temperature it undergoes spectacular metal-to-insulator transitions, often with changes in magnetic behavior as well. These unusual properties make V2O3 a material of choice in devices that include temperature sensors and current regulators.

    Researchers had previously reported interesting behavior in V2O3 as temperature changed and pressure remained constant. Here the team tested the opposite condition, monitoring the material’s resistance while increasing the pressure at a constant temperature.

    At first everything seemed normal—as the pressure increased the material’s resistance also decreased. But around 12.5 GPa the resistance began to rise. This result was unexpected. Even more unusual, at greater pressures near 33 GPa, the material’s structure changed from corundum to a more compact monoclinic arrangement of atoms, but this change was not accompanied by a corresponding spike in resistance (see the figure). The material remained metallic. Previously, all corundum to monoclinic changes in structure had been accompanied by a simultaneous transition from metallic to insulating behavior.

    To understand what was happening, the researchers performed inelastic x-ray scattering measurements and compared the results with theoretical simulations. Because inelastic x-ray spectroscopy measures the unoccupied vanadium electron valence states, these measurements provide a more detailed picture of electron screening interactions.

    While the resistivity measurements clearly showed changes at 12.5 GPa, the inelastic x-ray spectra showed no differences up to the phase change pressure of 33 GPa. This means that the early changes in resistance were due not to changes in electron correlations, but to interactions between electrons and the lattice (or phonons).

    At high pressure the electronic structure changed drastically in the inelastic x-ray spectra, suggesting an increase in electron correlations, but not quite enough to tip the material into the category of an insulator. At such high pressure, V2O3 is on the verge of becoming an insulator, but can’t quite make the change due to competing effects from the lattice.

    This work adds another clue to our understanding of how long-range atomic arrangement and local electron interactions work competitively to manifest metal-to-insulator transitions in solids.

    The next step will be to explore electron correlations in V2O3 by using more advanced techniques, such as the resonant x-ray inelastic scattering method with temperature, as another parameter to extend the unique phase diagram of V2O3.

    See the full article here.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 8:17 am on November 16, 2013 Permalink | Reply
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    From APS at Argonne Lab: “The Most Detailed Picture Yet of a Key AIDS Protein” 

    News from Argonne National Laboratory

    November 14, 2013
    No Writer Credit

    The first atomic-level structure of the tripartite HIV (human immunodeficiency virus) envelope protein—long considered one of the most difficult targets in structural biology and of great value for medical science—has been determined by scientists using data obtained at three synchrotron x-ray light sources including the U.S. Department of Energy (DOE) Office of Science’s Advanced Photon Source.

    hiv
    The structure of the human immunodeficiency virus envelope protein, shown here bound by broadly neutralizing antibodies against two distinct sites of vulnerability. (Courtesy of The Scripps Research Institute)

    The new findings provide the most detailed picture yet of the acquired immune deficiency syndrome (AIDS)-causing virus’s complex envelope, including sites that future vaccines will try to mimic to elicit a protective immune response.

    “Most of the prior structural studies of this envelope complex focused on individual subunits; but we’ve needed the structure of the full complex to properly define the sites of vulnerability that could be targeted, for example with a vaccine,” said Ian A. Wilson of The Scripps Research Institute (TSRI) and a senior author of the new research that included colleagues from TSRI; Weill Cornell Medical College; the Ragon Institute of MGH, MIT, and Harvard; and the Academic Medical Center (The Netherlands). The findings were published in two papers in Science Express, the early online edition of the journal Science, on October 31, 2013.

    See the full article here.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 12:54 pm on June 26, 2013 Permalink | Reply
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    From Argonne Lab APS: “Organic Polymers Show Sunny Potential” 

    Argonne National Laboratory

    JUNE 25, 2013
    No Writer Credit

    “A new version of solar cells created by laboratories at the Rice and Pennsylvania State universities, with an assist from the U.S. Department of Energy Office of Science’s Advanced Photon Source at Argonne National Laboratory and Advanced Light Source at Lawrence Berkeley National Laboratory, could open the door to research on a new class of solar energy devices.

    grid
    Researchers at Rice and Pennsylvania State universities have created solar cells based on block copolymers, self-assembling organic materials that arrange themselves into distinct layers. Image courtesy of the Gomez Laboratory

    The photovoltaic devices created in a project led by Rice chemical engineer Rafael Verduzco and Penn State chemical engineer Enrique Gomez are based on block copolymers, self-assembling organic materials that arrange themselves into distinct layers. They easily outperform other cells with polymer compounds as active elements.

    The discovery is detailed online in the American Chemical Society journal Nano Letters.”

    See the full article here.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 11:03 am on June 21, 2013 Permalink | Reply
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    From Argonne Lab: “A Further Understanding of Superconductivity” 

    Argonne National Laboratory

    JUNE 10, 2013
    No Writer Credit

    “A crucial ingredient of high-temperature superconductivity can be found in a class of materials that is entirely different than conventional superconductors. That discovery is the result of research by an international team of scientists working at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS).

    ‘There have been more than 60,000 papers published on high-temperature superconductive material since its discovery in 1986, said Jak Chakhalian, professor of physics at the University of Arkansas (UA) and a co-author of a new paper published on May 13, 2013, in Scientific Reports. ‘Unfortunately, as of today we have zero theoretical understanding of the mechanism behind this enigmatic phenomenon. In my mind, high-temperature superconductivity is the most important unsolved mystery of condensed matter physics.’

    Superconductivity is a phenomenon that occurs in certain materials when cooled to extremely low temperatures such as -435° F. High temperature superconductivity occurs above -396 F, and has been seen up to -218 F in HgBa2Ca2Cu3O8. In both cases, electrical resistance drops to zero and complete expulsion of magnetic fields occurs.

    sc
    The entire crystal structure of the chemical compound CaCu3Cr4O12, an A-site ordered perovskite.No image credit.

    Because superconductors have the ability to transport large electrical currents and produce high magnetic fields, they have long held great potential for electronic devices and power transmission.”

    See the full article here.

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 5:25 pm on April 10, 2013 Permalink | Reply
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    From Argonne APS: "Protein Structure Could Lead to Better Treatments for HIV, Early Aging" 

    News from Argonne National Laboratory

    APRIL 9, 2013
    No Writer Credit

    “Researchers have determined the molecular structure of a protein whose mutations have been linked to several early aging diseases, and side effects for common human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) medications. This breakthrough could eventually help researchers develop new treatments for these early-aging diseases and redesign AIDS medications to avoid side effects such as diabetes. The research was carried out at the Southeastern Regional Collaborative Access Team(SER-CAT) facility at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory.

    ribbon
    Ribbon diagram of the Ste24p protease.

    The researchers from the University of Virginia School of Medicine, the Hauptman-Woodward Medical Research Institute, and the University of Rochester School of Medicine and Dentistry determined the molecular structure of the enzyme Ste24p. Their Membrane Protein Structural Biology Consortium is funded by the National Institutes of Health Protein Structure Initiative, which supports the determination of molecular structures of biomedically important target proteins. Their findings were published March 29 in the journal Science.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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