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The research was done at the National Synchrotron Light Source (NSLS), a source of extremely bright x-rays that operated at the U.S. Department of Energy's Brookhaven National Laboratory from 1982-2014. It has since been replaced by NSLS-II, a new DOE Office of Science User Facility that produces x-ray beams 10,000 times brighter than its predecessor facility. "The method used here—spatially resolved x-ray micro-diffraction—could be used to study all types of mammalian hair to look for differences and similarities across species and human ethnic groups, and could also have commercial applications," said NSLS-II physicist Kenneth Evans-Lutterodt, who helped conduct the research at NSLS with Vesna Stanic, a scientist at the Brazilian Synchrotron Light Laboratory. The work was a follow-up from a previous study exploring the physical properties of commercial hair products. Before attempting to study the effects of these multi-component products on hair, Stanic and Evans-Lutterodt were curious to understand the molecular arrangements of untreated hair. So they began by collecting samples from young males who had never chemically treated their hair. Stanic, a small angle x-ray scattering (SAXS) expert, and Evans-Lutterodt, a micro-beam diffraction expert, then developed an experimental configuration and technique at beamline X13B of NSLS that allowed them to get good quality data on hair. Two techniques were key to this experiment. First, the scientists cut cross-sections of the hairs that were just 30-microns thick. Beaming x-rays along the axis of these thin "disk" samples allowed them to obtain separate signals from different regions of the hair. Using an x-ray kinoform lens, they created an x-ray beam with extremely narrow dimensions—a mere 300 nanometers, or billionths of a meter—smaller than any previously reported experiments on hair. The kinoform lens was fabricated with the help of Aaron Stein of the Center for Functional Nanomaterials (CFN) at Brookhaven Lab. "Very few x-ray diffraction experiments have used small x-ray beams on a single hair," Evans-Lutterodt said. "Also, the elements that make up hair—carbon, oxygen and hydrogen—produce weak scattering signals. These low signal levels made it a challenge to distinguish between the regions of hair, because they have very similar, but not identical structures." With these techniques, the team resolved the molecular structure of each of the three known regions of human hair—the cuticle, the cortex and the medulla—and discovered a completely new region between the cortex and the cuticle. They refer to this new region as the intermediate region. In this region, the alpha-keratin molecules that make up hair acquire an ordered orientation, as opposed to being randomly positioned as they are in the cortex. Additionally, the scientists discovered that the cuticle has a diffraction signal—a type of x-ray derived "fingerprint"—that is characteristic of beta-keratin sheets, and quite different from the spaghetti-like alpha-keratin form found in the cortex. The researchers expect to continue their work both in Brazil and in the U.S., possibly at NSLS-II. They would like to look at hair from different ethnicities, as well as hair from different species, and ultimately, compare those findings to hair that has been treated with commercial hair products. "We hope to use NSLS-II because brighter beams will allow us to have better spatial resolution, provide a better signal to noise ratio, and help us study more samples from different species more quickly," Stanic said. The techniques developed for this research will also advance the capabilities of x-ray imaging to help optimizing the usefulness of NSLS-II for studying other biological samples. Explore further: A Kinoform's Best Friend: Diamond Refractive Lenses for Nanofocusing


« Wind River and Ricardo partnering on autonomous driving systems | Main | Ford and IBM working on pilot platform for real-time streaming analytics to improve mobility » Lithium nickel manganese cobalt oxide (NMC) is one of the more promising chemistries for better lithium batteries, especially for electric vehicle applications, but scientists have been struggling to get higher capacity out of them. Now, a team of scientists from the US Department of Energy’s (DOE) Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and SLAC National Accelerator Laboratory has found that using a simple technique called spray pyrolysis can help to overcome one of the biggest problems associated with NMC cathodes—surface reactivity, which leads to material degradation. An open-access paper on their work is published in the journal Nature Energy. The team was led Berkeley Lab battery scientist Marca Doeff, who has been studying NMC cathodes for about seven years. The facilities used were the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC and the Center for Functional Nanomaterials (CFN) at Brookhaven, both DOE Office of Science User Facilities. The Berkeley Lab researchers made a particle structure that has two levels of complexity where the material is assembled in a way that it protects itself from degradation, explained Brookhaven Lab physicist and Stony Brook University adjunct assistant professor Huolin Xin, who helped characterize the nanoscale details of the cathode material at Brookhaven Lab’s Center for Functional Nanomaterials (CFN). X-ray imaging performed by scientists at the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC along with Xin’s electron microscopy at CFN revealed spherical particles of the cathode material measuring microns in diameter made up of lots of smaller, faceted nanoscale particles stacked together like bricks in a wall. The characterization techniques revealed important structural and chemical details that explain why these particles perform so well. Lithium-ion rechargeable batteries work by shuttling lithium ions between positive and negative electrodes bathed in an electrolyte solution. As lithium moves into the cathode, chemical reactions generate electrons that can be routed to an external circuit for use. Recharging requires an external current to run the reactions in reverse, pulling the lithium ions out of the cathode and sending them to the anode. Reactive metals such as nickel have the potential to make great cathode materials—except that they are unstable and tend to undergo destructive side reactions with the electrolyte. So the team experimented with ways to incorporate nickel but protect it from these destructive side reactions. They sprayed a solution of lithium, nickel, manganese, and cobalt mixed at a certain ratio through an atomizer nozzle to form tiny droplets, which then decomposed to form a powder. Repeatedly heating and cooling the powder triggered the formation of tiny nanosized particles and the self-assembly of these particles into the larger spherical, sometimes hollow, structures. X-ray spectroscopy revealed that the outer surface of the spheres was relatively low in nickel and high in unreactive manganese, while the interior was rich in nickel. To determine how Li ions were still able to enter the material to react with the nickel, Xin’s group at the CFN ground up the larger particles to form a powder composed of much smaller clumps of the nanoscale primary particles with some of the interfaces between them still intact. Using an aberration-corrected scanning transmission electron microscope—a scanning transmission electron microscope outfitted with a pair of “glasses” to improve its vision—the scientists saw that the particles had facets which allowed them to pack tightly together to form coherent interfaces with no mortar or cement between the bricks. But there was a slight misfit between the two surfaces, with the atoms on one side of the interface being ever so slightly offset relative to the atoms on the adjoining particle. The packing of atoms at the interfaces between the tiny particles is slightly less dense than the perfect lattice within each individual particle, so these interfaces basically make a highway for lithium ions to go in and out, Xin said. The smaller lithium ions can move along these highways to reach the interior structure of the wall and react with the nickel, but much larger electrolyte molecules can’t get in to degrade the reactive material. Using a spectroscopy tool within their microscope, the CFN scientists produced nanoscale chemical fingerprints that revealed there was some segregation of nickel and manganese even at the nanoscale, just as there was in the micron-scale structures. The researchers do not know yet if this is functionally significant, but they think it could be beneficial and want to study this further, Xin said. For example, he said, perhaps the material could be made at the nanoscale to have a manganese skeleton to stabilize the more reactive, less-stable nickel-rich pockets. Such a combination might provide a longer lifetime for the battery along with the higher charging capacity of the nickel. We’re not the first ones who have come up with idea of decreasing nickel on the surface. But we were able to do it in one step using a very simple procedure. We still want to increase the nickel content even further, and this gives us a possible avenue for doing that. The more nickel you have, the more practical capacity you may have at voltages that are practical to use. In future experiments, the researchers plan to probe the NMC cathode with X-rays while it’s charging and discharging to see how its structure and chemistry change. They also hope to improve the material’s safety: As a metal oxide, it could release oxygen during operation and potentially cause a fire. This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office, of the US Department of Energy. The Center for Functional Nanomaterials at Brookhaven Lab and the Stanford Synchrotron Radiation Lightsource at SLAC are both DOE Office of Science User Facilities supported by the DOE Office of Science (BES). Brookhaven National Laboratory is supported by the Office of Science of the US Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States.


News Article | April 11, 2016
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Harnessing the power of the sun and creating light-harvesting or light-sensing devices requires a material that both absorbs light efficiently and converts the energy to highly mobile electrical current. Finding the ideal mix of properties in a single material is a challenge, so scientists have been experimenting with ways to combine different materials to create "hybrids" with enhanced features. In two just-published papers, scientists from the U.S. Department of Energy's Brookhaven National Laboratory, Stony Brook University, and the University of Nebraska describe one such approach that combines the excellent light-harvesting properties of quantum dots with the tunable electrical conductivity of a layered tin disulfide semiconductor. The hybrid material exhibited enhanced light-harvesting properties through the absorption of light by the quantum dots and their energy transfer to tin disulfide, both in laboratory tests and when incorporated into electronic devices. The research paves the way for using these materials in optoelectronic applications such as energy-harvesting photovoltaics, light sensors, and light emitting diodes (LEDs). According to Mircea Cotlet, the physical chemist who led this work at Brookhaven Lab's Center for Functional Nanomaterials, a DOE Office of Science User Facility, "Two-dimensional metal dichalcogenides like tin disulfide have some promising properties for solar energy conversion and photodetector applications, including a high surface-to-volume aspect ratio. But no semiconducting material has it all. These materials are very thin and they are poor light absorbers. So we were trying to mix them with other nanomaterials like light-absorbing quantum dots to improve their performance through energy transfer." One paper, recently published in the journal ACS Nano, describes a fundamental study of the hybrid quantum dot/tin disulfide material by itself. The work analyzes how light excites the quantum dots (made of a cadmium selenide core surrounded by a zinc sulfide shell), which then transfer the absorbed energy to layers of nearby tin disulfide. "We have come up with an interesting approach to discriminate energy transfer from charge transfer, two common types of interactions promoted by light in such hybrids," says Prahlad Routh, a graduate student from Stony Brook University working with Cotlet and co-first author of the ACS Nano paper. "We do this using single nanocrystal spectroscopy to look at how individual quantum dots blink when interacting with sheet-like tin disulfide. This straightforward method can assess whether components in such semiconducting hybrids interact either by energy or by charge transfer." The researchers found that the rate for non-radiative energy transfer from individual quantum dots to tin disulfide increases with an increasing number of tin disulfide layers. But performance in laboratory tests isn't enough to prove the merits of potential new materials. So the scientists incorporated the hybrid material into an electronic device, a photo-field-effect-transistor, a type of photon detector commonly used for light sensing applications. As described in a paper published online in Applied Physics Letters, the hybrid material dramatically enhanced the performance of the photo-field-effect transistors — resulting in a photocurrent response (conversion of light to electric current) that was 500 percent better than transistors made with the tin disulfide material alone. "This kind of energy transfer is a key process that enables photosynthesis in nature," says Chang-Yong Nam, a materials scientist at Center for Functional Nanomaterials and co-corresponding author of the APL paper. "Researchers have been trying to emulate this principle in light-harvesting electrical devices, but it has been difficult particularly for new material systems such as the tin disulfide we studied. Our device demonstrates the performance benefits realized by using both energy transfer processes and new low-dimensional materials." Cotlet concludes, "The idea of 'doping' two-dimensional layered materials with quantum dots to enhance their light absorbing properties shows promise for designing better solar cells and photodetectors." Former Brookhaven Lab staff members Huidong Zang, Huang Yuan, Eli Sutter, and Peter Sutter, and Jia-Shiang Wang, a Stony Brook University graduate student with working with Cotlet, also contributed to this work.  The research was funded by the DOE Office of Science. Source: Brookhaven National Laboratory


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Using bundled strands of DNA to build Tinkertoy-like tetrahedral cages, scientists at the U.S. Department of Energy's Brookhaven National Laboratory have devised a way to trap and arrange nanoparticles in a way that mimics the crystalline structure of diamond. The achievement of this complex yet elegant arrangement, as described in a paper published today in Science, may open a path to new materials that take advantage of the optical and mechanical properties of this crystalline structure for applications such as optical transistors, color-changing materials, and lightweight yet tough materials. "We solved a 25-year challenge in building diamond lattices in a rational way via self-assembly," says Oleg Gang, a physicist who led this research at the Center for Functional Nanomaterials (CFN) at Brookhaven Lab in collaboration with scientists from Stony Brook University, Wesleyan University, and Nagoya University in Japan. The scientists employed a technique developed by Gang that uses fabricated DNA as a building material to organize nanoparticles into 3D spatial arrangements. They used ropelike bundles of double-helix DNA to create rigid, three-dimensional frames, and added dangling bits of single-stranded DNA to bind particles coated with complementary DNA strands. "We're using precisely shaped DNA constructs made as a scaffold and single-stranded DNA tethers as a programmable glue that matches up particles according to the pairing mechanism of the genetic code — A binds with T, G binds with C," says Wenyan Liu of the CFN, the lead author on the paper. "These molecular constructs are building blocks for creating crystalline lattices made of nanoparticles." As Liu explains, "Building diamond superlattices from nano- and micro-scale particles by means of self-assembly has proven remarkably difficult. It challenges our ability to manipulate matter on small scales." The reasons for this difficulty include structural features such as a low packing fraction — meaning that in a diamond lattice, in contrast to many other crystalline structures, particles occupy only a small part of the lattice volume — and strong sensitivity to the way bonds between particles are oriented. "Everything must fit together in just such a way without any shift or rotation of the particles' positions," Gang said. "Since the diamond structure is very open, many things can go wrong, leading to disorder." "Even to build such structures one-by-one would be challenging," Liu adds, "and we needed to do so by self-assembly because there is no way to manipulate billions of nanoparticles one-by-one." Gang's previous success using DNA to construct a wide range of nanoparticle arrays suggests that a DNA-based approach might work in this instance. The team first used the ropelike DNA bundles to build tetrahedral "cages" — a 3D object with four triangular faces. They added single-stranded DNA tethers pointing toward the interior of the cages using T,G,C,A sequences that matched up with complementary tethers attached to gold nanoparticles. When mixed in solution, the complementary tethers paired up to "trap" one gold nanoparticle inside each tetrahedron cage. The arrangement of gold nanoparticles outside the cages was guided by a different set of DNA tethers attached at the vertices of the tetrahedrons. Each set of vertices bound with complementary DNA tethers attached to a second set of gold nanoparticles. When mixed and annealed, the tetrahedral arrays formed superlattices with long-range order where the positions of the gold nanoparticles mimics the arrangement of carbon atoms in a lattice of diamond, but at a scale about 100 times larger. "Although this assembly scenario might seem hopelessly unconstrained, we demonstrate experimentally that our approach leads to the desired diamond lattice, drastically streamlining the assembly of such a complex structure," Gang says. The proof is in the images. The scientists used cryogenic transmission electron microscopy (cryo-TEM) to verify the formation of tetrahedral frames by reconstructing their 3D shape from multiple images. Then they used in-situ small-angle x-ray scattering (SAXS) at the National Synchrotron Light Source (NSLS), and cryo scanning transmission electron microscopy (cryo-STEM) at the CFN, to image the arrays of nanoparticles in the fully constructed lattice. "Our approach relies on the self-organization of the triangularly shaped blunt vertices of the tetrahedra (so called 'footprints') on isotropic spherical particles. Those triangular footprints bind to spherical particles coated with complementary DNA, which allows the particles to coordinate their arrangement in space relative to one another. However, the footprints can arrange themselves in a variety of patterns on a sphere. It turns that one particular placement is more favorable, and it corresponds to the unique 3D placement of particles that locks the diamond lattice," Gang says. The team supported their interpretation of the experimental results using theoretical modeling that provided insight about the main factors driving the successful formation of diamond lattices. "This work brings to the nanoscale the crystallographic complexity seen in atomic systems," says Gang, who noted that the method can readily be expanded to organize particles of different material compositions. The group has demonstrated previously that DNA-assembly methods can be applied to optical, magnetic, and catalytic nanoparticles as well, and will likely yield the long-sought novel optical and mechanical materials scientists have envisioned. "We've demonstrated a new paradigm for creating complex 3D-ordered structures via self-assembly. If you can build this challenging lattice, the thinking is you can build potentially a variety of desired lattices," he says. This work was funded by the DOE Office of Science (BES). CFN and NSLS are DOE Office of Science User Facilities.


Home > Press > Scientists guide gold nanoparticles to form 'diamond' superlattices: DNA scaffolds cage and coax nanoparticles into position to form crystalline arrangements that mimic the atomic structure of diamond Abstract: Using bundled strands of DNA to build Tinkertoy-like tetrahedral cages, scientists at the U.S. Department of Energy's Brookhaven National Laboratory have devised a way to trap and arrange nanoparticles in a way that mimics the crystalline structure of diamond. The achievement of this complex yet elegant arrangement, as described in a paper published February 5, 2016, in Science, may open a path to new materials that take advantage of the optical and mechanical properties of this crystalline structure for applications such as optical transistors, color-changing materials, and lightweight yet tough materials. "We solved a 25-year challenge in building diamond lattices in a rational way via self-assembly," said Oleg Gang, a physicist who led this research at the Center for Functional Nanomaterials (CFN) at Brookhaven Lab in collaboration with scientists from Stony Brook University, Wesleyan University, and Nagoya University in Japan. The scientists employed a technique developed by Gang that uses fabricated DNA as a building material to organize nanoparticles into 3D spatial arrangements. They used ropelike bundles of double-helix DNA to create rigid, three-dimensional frames, and added dangling bits of single-stranded DNA to bind particles coated with complementary DNA strands. "We're using precisely shaped DNA constructs made as a scaffold and single-stranded DNA tethers as a programmable glue that matches up particles according to the pairing mechanism of the genetic code-A binds with T, G binds with C," said Wenyan Liu of the CFN, the lead author on the paper. "These molecular constructs are building blocks for creating crystalline lattices made of nanoparticles." The difficulty of diamond As Liu explained, "Building diamond superlattices from nano- and micro-scale particles by means of self-assembly has proven remarkably difficult. It challenges our ability to manipulate matter on small scales." The reasons for this difficulty include structural features such as a low packing fraction-meaning that in a diamond lattice, in contrast to many other crystalline structures, particles occupy only a small part of the lattice volume-and strong sensitivity to the way bonds between particles are oriented. "Everything must fit together in just such a way without any shift or rotation of the particles' positions," Gang said. "Since the diamond structure is very open, many things can go wrong, leading to disorder." "Even to build such structures one-by-one would be challenging," Liu added, "and we needed to do so by self-assembly because there is no way to manipulate billions of nanoparticles one-by-one." Gang's previous success using DNA to construct a wide range of nanoparticle arrays suggested that a DNA-based approach might work in this instance. DNA guides assembly The team first used the ropelike DNA bundles to build tetrahedral "cages"-a 3D object with four triangular faces. They added single-stranded DNA tethers pointing toward the interior of the cages using T,G,C,A sequences that matched up with complementary tethers attached to gold nanoparticles. When mixed in solution, the complementary tethers paired up to "trap" one gold nanoparticle inside each tetrahedron cage. The arrangement of gold nanoparticles outside the cages was guided by a different set of DNA tethers attached at the vertices of the tetrahedrons. Each set of vertices bound with complementary DNA tethers attached to a second set of gold nanoparticles. When mixed and annealed, the tetrahedral arrays formed superlattices with long-range order where the positions of the gold nanoparticles mimics the arrangement of carbon atoms in a lattice of diamond, but at a scale about 100 times larger. "Although this assembly scenario might seem hopelessly unconstrained, we demonstrate experimentally that our approach leads to the desired diamond lattice, drastically streamlining the assembly of such a complex structure," Gang said. The proof is in the images. The scientists used cryogenic transmission electron microscopy (cryo-TEM) to verify the formation of tetrahedral frames by reconstructing their 3D shape from multiple images. Then they used in-situ small-angle x-ray scattering (SAXS) at the National Synchrotron Light Source (NSLS, https://www.bnl.gov/ps/), and cryo scanning transmission electron microscopy (cryo-STEM) at the CFN, to image the arrays of nanoparticles in the fully constructed lattice. "Our approach relies on the self-organization of the triangularly shaped blunt vertices of the tetrahedra (so called 'footprints') on isotropic spherical particles. Those triangular footprints bind to spherical particles coated with complementary DNA, which allows the particles to coordinate their arrangement in space relative to one another. However, the footprints can arrange themselves in a variety of patterns on a sphere. It turns that one particular placement is more favorable, and it corresponds to the unique 3D placement of particles that locks the diamond lattice," Gang said. The team supported their interpretation of the experimental results using theoretical modeling that provided insight about the main factors driving the successful formation of diamond lattices. Sparkling implications "This work brings to the nanoscale the crystallographic complexity seen in atomic systems," said Gang, who noted that the method can readily be expanded to organize particles of different material compositions. The group has demonstrated previously that DNA-assembly methods can be applied to optical, magnetic, and catalytic nanoparticles as well, and will likely yield the long-sought novel optical and mechanical materials scientists have envisioned. "We've demonstrated a new paradigm for creating complex 3D-ordered structures via self-assembly. If you can build this challenging lattice, the thinking is you can build potentially a variety of desired lattices," he said. ### This work was funded by the DOE Office of Science. CFN and NSLS are DOE Office of Science User Facilities. About Brookhaven National Laboratory Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation for the State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit applied science and technology organization. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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