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  • richardmitnick 4:24 pm on November 18, 2014 Permalink | Reply
    Tags: , , , X-ray Microscopy,   

    From BNL: “Organic Crystal Film Grown on New Substrate Breaks Performance Record” 

    Brookhaven Lab

    November 18, 2014
    Laura Mgrdichian

    The study is an important step toward realizing mainstream organic electronic devices

    Many future electronic devices may be based not on standard conductors and semiconductors but rather on small organic (carbon-based) molecules and polymers. These organic electronics will have several advantages over conventional electronics, including being cheaper to fabricate, physically bendable and flexible, and, in some cases, can be created using printing methods – perhaps even in your own home.

    The field of organic electronics is still in its infancy, however, and scientists have much to learn before organic electronic devices are part of our everyday lives. One obstacle researchers have faced is how to successfully grow high-quality crystals of an organic molecule on top of a conventional substrate – without using a complex growth process or chemically modifying the substrate first. Solving this problem is the necessary first step to creating organic electronic circuits and devices.

    im
    Organic two-dimensional heterostructure of rubrene/h-BN

    Recently, a research group made some significant headway. Working in part at the National Synchrotron Light Source (NSLS), scientists from Columbia University, Harvard University, Brookhaven Lab, and Japan’s National Institute for Materials Science grew a high-quality, high-performing film of rubrene, an organic semiconductor, onto a substrate of hexagonal boron nitride, a layered crystalline material with hexagonally shaped molecular units (similar to graphite carbon). Their work, which they discuss in the May 14, 2014, edition of the journal Advanced Materials, is notable both due to the high-quality crystalline nature of the film and because the substrate is a new player in the field of organic electronics development.

    “The interface between the substrate and the molecular film is very important. It governs the initial nucleation during the growth of the film and also has a big impact on how the film will carry charge,” says Columbia researcher Phillip Kim, one of the paper’s authors. “Our film/substrate heterostructure yielded the highest mobility observed yet in similar systems. It is comparable to those of free-standing single crystals and represents a record for organic films grown on any substrates.”

    When paired with organic materials, conventional substrates like silicon oxide, glass, and plastic are too disordered at the molecular level and also don’t have molecular structures that are similar enough to the organic compounds. In materials science terms, they lack an “epitaxial” relationship. This discourages proper film growth and results in lower-quality films that lack long-range order. In everyday terms, this is kind of like trying to build a layer of Lego bricks on Lego board that doesn’t have an ordered grid of nubs.

    Kim and his colleagues showed that hexagonal boron nitride (h-BN) has many advantages as a substrate for organic electronics. Using an approach called “van der Waals epitaxy,” a method that takes advantage of the weak van der Waals force between molecules, the group grew rubrene films varying from 5 to 1000 nanometers thick. They studied each sample’s structure and charge-carrying ability using several methods.

    Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images suggested that the film was formed of large single-crystal domains. Selected area electron diffraction (SAED), which can be performed inside a transmission electron microscope, also confirmed this. But because SAED provides only local structural information, the group used grazing x-ray diffraction at NSLS beamline X9 to get a broader “view” of the structure. The x-ray data showed sharp, intense peaks, indicating that the sample contained a high-quality crystal structure.

    To study how the film carries charge, graphene electrical contacts were incorporated into the growth process, resulting in a field-effect transistor structure. Measuring the current across it showed that electrons traveling within it are highly mobile, meaning they don’t run into too many barriers caused by a “choppy” molecular structure.

    “Our study highlights the advantages of h-BN and similar materials over commonly used substrates to achieve high-performance organic electronic devices,” said Kim. “More generally, this approach to film growth – van der Waals epitaxy – could be used to fabricate organic/inorganic structures that can be readily expanded to numerous other organic and layered materials for various electronic applications.”

    This research was supported by: the Center for Redefining Photovoltaic Efficiency Through Molecule Scale Control, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences; the FAME Center, one of six centers of STARnet, a Semiconductor Research Corporation program sponsored by MARCO and DARPA; the Nano Material Technology Development Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning; the Basic Science Research Program through the National Research Foundation of Korea; the U.S. Department of Energy, Office of Basic Energy Sciences, under the Extreme Science and Engineering Discovery Environment, supported by the National Science Foundation.

    See the full article here.

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 9:04 am on October 9, 2014 Permalink | Reply
    Tags: , , X-ray Microscopy   

    From DESY: “How ceramics get super-tough” 

    DESY
    DESY

    09.10.2014
    No Writer Credit

    Scientists find new toughening mechanism

    Researchers have identified a previously unknown mechanism that makes a rare kind of ceramics super-tough. The findings may show a way to compose super-hard and super-tough ceramics for industrial application, as the team around DESY scientist Dr. Nori Nishiyama reports in the journal Scientific Reports.

    image
    At the fractures wormlike structures made of amorphous silica form (center). Credit: Nori Nishiyama/DESY

    The researchers investigated a material called stishovite, a rare version of silica that forms under high pressure for instance in meteorite impacts and inside the earth below about 300 kilometres of depth. Stishovite is a ceramic of the oxide group. “It is the hardest oxide known to date, even harder than ruby or sapphire,” says Nishiyama. While ceramics in general can be very hard, they tend to be very brittle also, breaking easily. Its brittleness prevented stishovite from being used industrially.

    But in 2012, Nishiyama and co-workers had synthesized nanocrystals of stishovite and could show that bulk stishovite made up of such nanocrystals is not only very hard, but also becomes very tough, reaching the toughness of zirconia, the toughest ceramic known. The reason for this toughening of stishovite remained elusive until recently.

    With a clever combination of electron microscopy and X-ray investigations at DESY’s synchrotron light source PETRA III (beamline P02.1) and at the Japanese synchrotron light source SPring-8, the researchers could now identify the previously unknown mechanism that makes nanocrystalline stishovite so exceptionally tough. Stishovite forms under high pressure and is only metastable under ambient conditions. Metastable means that if enough energy is added in some form (for instance via a fracture or via high temperature), it switches to a different configuration.

    petra iii
    Petra III

    SPring8 Japan
    SPring-8

    Stishovite uses the energy from a fracture to switch from a tetragonal crystal into amorphous silica, as the researchers found. “Actually, the transformation from stishovite to amorphous silica resembles the melting of ice,” explains Nishiyama. “Both are crystal-to-amorphous transformations that occur outside the stability field.”

    The scientists had produced nanocrystalline bulk stishovite and ripped it apart. They then looked at the fracture sites with an electron microscope. The investigation revealed worm like silica structures that proved to be an amorphous phase of silica. “These ‘worms’ have diameters of some tens of nanometres,” says Nishiyama. Using X-ray spectroscopy the team could show that about half of the surface in the fracture area is covered by amorphous silica. The more amorphous silica was present, the tougher the fracture area got. This result indicates that the fracture-induced transition to amorphous silica indeed caused the toughening of the stishovite.

    “This transition instantaneously doubles the volume of the material, effectively pushing against the fracture and stopping it short,” explains Nishiyama. In a similar way zirconia gets its toughness. On a fracture, it switches from one crystal structure (tetragonal) to another (monoclinic), expanding its volume by 4 per cent. “The transition now observed in stishovite expands the volume by 100 per cent,” underlines Nishiyama. “It may be possible to create ceramics composites for industrial use that can exploit the toughening mechanism of stishovite.”

    The work was supported by the Japan Science and Technology Agency (JST) within the program “Precursory Research Embryonic Science and Technology” (PRESTO) under the program title “New Materials Science and Element Strategy” (research supervisor Prof. Hideo Hosono).

    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 5:10 pm on September 22, 2014 Permalink | Reply
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    From BNL:”Growth of an Ultra-thin Layered Structure Offers Surprises” 

    Brookhaven Lab

    September 22, 2014
    Laura Mgrdichian

    Many new technologies are based on ultra-thin layered structures that are “grown” using precise deposition techniques. Understanding and ultimately controlling this growth at the atomic level – particularly at the interfaces between these layers, where key properties arise – is essential to imparting these structures with properties tailored to possible applications.

    Researchers from the University of Vermont recently investigated an example of “heteroepitaxial” growth, in which one material is grown on the surface of a second material that has a similar crystal structure as the first. They studied a system of bismuth ferrite (BiFeO3, or BFO) grown on strontium titanate (SrTiO3, or STO). The research is published in the February 20, 2014, edition of Physical Review Letters.

    two
    Simulated “maps” for growing bismuth ferrite on strontium titanate

    BFO is a target for materials science researchers because of its diverse ferroelectric properties and possible applications in developing technologies such as nonvolatile memory and data storage. At the National Synchrotron Light Source, the researchers discovered that the BFO forms clusters that grow and coalesce into a single layer in an unexpected way. They found that their data agree well with the “interrupted coalescence model” (ICM) of layer growth. This finding was a bit of a surprise, but they propose that the model may be applicable to other layered systems.

    BNL NSLS
    BNL NSLS Interior
    NSLS

    “In this system, we saw compact, two-dimensional islands come together efficiently over a range of length scales,” said the study’s corresponding scientist, University of Vermont physicist Randall Headrick. “However, the kinetics of the growth process behave more like droplets than what we expected to observe, which was single-layer clusters that grow exponentially in time. This growth mode has implications for the structure of interfaces and ferroelectric domains in these materials, which will have an impact on domain switching in devices.”

    Headrick and his colleagues used a technique called sputter deposition to apply the BFO atoms to the STO surface and “watched” the growth of the BFO layer using x-ray diffraction at NSLS beamline X21. They saw the BFO quickly form islands of varying sizes, with an average size of about 20 nanometers. The small clusters retained their compact shape as they coalesced into bigger clusters. But, this coalescence was kinetically “frozen” when the clusters reached a critical size, leading to the formation of large connected irregularly shaped regions. In the spaces between, smaller islands continued to form and dot the area.

    The group confirmed these observations by studying the final layered structure with atomic force microscopy and additional x-ray diffraction measurements.

    afm
    Atomic Force Microscope at Rutgers University

    This work was supported by the
    Office of Basic Energy Sciences within the U.S. Department of Energy’s Office of Science.

    See the full article here.

    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 8:38 am on September 12, 2014 Permalink | Reply
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    From Stanford: “Stanford engineers help describe key mechanism in energy and information storage” 

    Stanford University Name
    Stanford University

    September 11, 2014
    Bjorn Carey

    By observing how hydrogen is absorbed into individual palladium nanocubes, Stanford materials scientists have detailed a key step in storing energy and information in nanomaterials. The work could inform research that leads to longer-lasting batteries or higher-capacity memory devices.

    block
    The palladium nanocubes viewed through a transmission electron microscope. Each black dot is a palladium atom.

    The ideal energy or information storage system is one that can charge and discharge quickly, has a high capacity and can last forever. Nanomaterials are promising to achieve these criteria, but scientists are just beginning to understand their challenging mechanisms.

    Now, a team of Stanford materials scientists and engineers has provided new insight into the storage mechanism of nanomaterials that could facilitate development of improved batteries and memory devices.

    The team, led by Jennifer Dionne, assistant professor of materials science and engineering at Stanford, and consisting of Andrea Baldi, Tarun Narayan and Ai Leen Koh, studied how metallic nanoparticles composed of palladium absorbed and released hydrogen atoms.

    Previously, scientists have studied hydrogen absorption in ensembles of metallic nanoparticles, but this approach makes it difficult to infer information about how the individual nanoparticles behave. The new study reveals that behavior by measuring the hydrogen content in individual palladium nanoparticles exposed to increasing pressures of hydrogen gas.

    The group’s experimental findings are consistent with a mechanism recently proposed for energy storage in lithium ion batteries, underscoring the interest for the broader scientific community. The work is detailed online in the journal Nature Materials.

    The finding was made possible by the use of a specialized transmission electron microscope (TEM) that allowed the team to detect, with near atomic-scale resolution, the process by which hydrogen entered the nanomaterial.

    “Electron microscopy must ordinarily be conducted in high vacuum,” said co-author Ai Leen Koh, a research scientist with the Stanford Nano Shared Facilities. “But the unique capabilities of Stanford’s environmental TEM obviates this requirement, enabling the study of individual nanoparticles both in vacuum and while immersed in a reactive gas.”
    Stretching metal

    The researchers synthesized palladium nanocubes and then dispersed them onto a very thin membrane. After placing the membrane in the TEM, the engineers flowed hydrogen gas past the palladium nanoparticles and gradually increased its pressure.

    At sufficiently high pressures of hydrogen, the gas molecules dissociate on the surface of the nanocubes and individual hydrogen atoms enter into the spaces between the palladium crystals. Interestingly, the absorption and desorption processes appear to be quite sudden.

    “You can think of it like popcorn,” said co-lead author Tarun Narayan, a graduate student in Dionne’s group. “It’s a very binary process, and a pretty sharp transition. Either the hydrogen is in the palladium or it’s not, and it enters and leaves at predictable pressures. And that’s quite important for a good energy storage system.”

    As the hydrogen enters the palladium nanostructure, the material’s volume increases by about 10 percent. This expansion significantly alters the way in which the particle interacts with the electron beam; this disruption indicates the amount of hydrogen absorbed. Because the nanocubes are single-crystalline and effectively “unbound” from the membrane, the researchers were able to study and measure the storage mechanism in unprecedented detail.

    “You have to stretch the palladium to put the hydrogen inside, but you have to pay energy to make it stretch,” said Andrea Baldi, a postdoctoral researcher in Dionne’s group. “Knowing that cost is very important for any battery designs, and because our nanostructures are not glued to a substrate, we’re able to quantify that stretch more accurately than ever before.”
    Next up: Palladium spheres

    Despite the stress of repeated expansion and contraction, the nanocrystals of palladium were not damaged by hydrogen absorption and desorption, as usually happens in larger specimens.

    “At the nanoscale, materials behave quite differently than they do in bulk,” said Dionne, the senior author. “Their increased surface area to volume ratio can significantly impact their mechanical flexibility and, consequently, their ability to charge and discharge ions or atoms.”

    In particular, this research indicates that nanoparticles can load more easily and at much lower pressures than bulk materials. Further, because they have a higher resistance to elastic stress, the formation of defects in these materials is suppressed.

    “Our results suggest that particles in this size regime don’t develop defects even if charged and discharged with hydrogen multiple times,” Narayan said. “Other researchers are starting to see this in lithium ion battery research as well, and we think a lot of what we’ve learned can be applied to that research.”

    Because of its fast storage speeds, stability and ease-of-loading, the hydrogenation of palladium is an excellent model system to study general energy and information storage mechanisms. Palladium, however, is not a likely material for widespread energy storage – it is too heavy and expensive. Yet, the researchers believe the results could be replicated with other systems involving storing hydrogen in metals.

    The next steps involve applying the newly developed single-particle method to a wide range of nanostructures – spheres and rods, for example – to study how storage can be affected by the shape, size and crystallinity of a nanoparticle. Furthermore, they plan to use the electron microscope to determine exactly where atoms or ions are preferentially absorbed within a singe nanoparticle.

    Dionne is an affiliate of the Stanford Institute for Materials and Energy Sciences (SIMES) and SLAC National Accelerator Laboratory. The research was supported by funding from the National Science Foundation, the Air Force Office of Scientific Research, the U.S. Department of Energy, a Young Energy Scientist Fellowship and a Hellman Fellowship.

    See the full article here.

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 5:03 pm on September 10, 2014 Permalink | Reply
    Tags: , , , , X-ray Microscopy   

    From LBL: “Advanced Light Source Sets Microscopy Record” 

    Berkeley Logo

    Berkeley Lab

    September 10, 2014
    Lynn Yarris (510) 486-5375

    A record-setting X-ray microscopy experiment may have ushered in a new era for nanoscale imaging. Working at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), a collaboration of researchers used low energy or “soft” X-rays to image structures only five nanometers in size. This resolution, obtained at Berkeley Lab’s Advanced Light Source (ALS), a DOE Office of Science User Facility, is the highest ever achieved with X-ray microscopy.

    LBL Advanced Light Source
    LBL ALS

    image
    Ptychographic image using soft X-rays of lithium iron phosphate nanocrystal after partial dilithiation. The delithiated region is shown in red.

    Using ptychography, a coherent diffractive imaging technique based on high-performance scanning transmission X-ray microscopy (STXM), the collaboration was able to map the chemical composition of lithium iron phosphate nanocrystals after partial dilithiation. The results yielded important new insights into a material of high interest for electrochemical energy storage.

    “We have developed diffractive imaging methods capable of achieving a spatial resolution that cannot be matched by conventional imaging schemes,” says David Shapiro, a physicist with the ALS. “We are now entering a stage in which our X-ray microscopes are no longer limited by our optics and we can image at nearly the wavelength of our X-ray light.”

    Shapiro is the lead and corresponding author of a paper reporting this research in Nature Photonics. The paper is titled “Chemical composition mapping with nanometer resolution by soft X-ray microscopy.” (See below for a full list of co-authors and their affiliations.)

    ds
    David Shapiro with the STXM instruments at ALS beamline 5.3.2.1. (Photo by Roy Kaltschmidt)

    In ptychography (pronounced tie-cog-raphee), a combination of multiple coherent diffraction measurements is used to obtain 2D or 3D maps of micron-sized objects with high resolution and sensitivity. Because of the sensitivity of soft x-rays to electronic states, ptychography can be used to image chemical phase transformations and the mechanical consequences of those transformations that a material undergoes.

    “Until this work, however, the spatial resolution of ptychographic microscopes did not surpass that of the best conventional systems using X-ray zone plate lenses,” says Howard Padmore, leader of the Experimental Systems Group at the ALS and a co-author of the Nature Photonics paper. “The problem stemmed from the fact that ptychography was primarily developed on hard X-ray sources using simple pinhole optics for illumination. This resulted in a low scattering cross-section and low coherent intensity at the sample, which meant that exposure times had to be extremely long, and that mechanical and illumination stabilities were not good enough for high resolution.”

    Key to the success of Shapiro, and his collaborators were the use of soft X-rays which have wavelengths ranging between 1 to 10 nanometers, and a special algorithm that eliminated the effect of all incoherent background signals. Ptychography measurements were recorded with the STXM instruments at ALS beamline 11.0.2, which uses an undulator x-ray source, and ALS beamline 5.3.2.1, which uses a bending magnet source. A coherent soft X-ray beam would be focused onto a sample and scanned in 40 nanometer increments. Diffraction data would then be recorded on an X-ray CCD (charge-coupled device) that allowed reconstruction of the sample to very high spatial resolution.

    “Throughout the ptychography scans, we maintained the sample and focusing optic in relative alignment using an interferometric feedback system with a precision comparable to the wavelength of the X-ray illumination,” Shapiro says.

    Lithium iron phosphate is widely studied for its use as a cathode material in rechargeable lithium-ion batteries. In using their ptychography technique to map the chemical composition of lithium iron phosphate crystals, Shapiro and his collaborators found a strong correlation between structural defects and chemical phase propagation.

    “Surface cracking in these crystals was expected,” Shapiro says, “but there is no other means of visualizing the correlation of those cracks with chemical composition at these scales. The ability to visualize the coupling of the kinetics of a phase transformation with the mechanical consequences is critical to designing materials with ultimate durability.”

    Shapiro and his colleagues have already begun applying their ptychography technique to the study of catalytic and magnetic films, magnetotactic bacteria, polymer blends and green cements.
    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas.

    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas.

    For the chemical mapping of lithium iron phosphate they used the STXM instrument at ALS beamline 5.3.2.1 which required up to 800 milliseconds of exposure to the X-ray beam for each scan. Next year, they anticipate using a new ALS beamline called COSMIC (COherent Scattering and MICroscopy), which will feature a high brightness undulator x-ray source coupled to new high-frame-rate CCD sensors that will cut beam exposure times to only a few milliseconds and provide spatial resolution at the wavelength of the radiation.

    image2
    In this soft X-ray ptychography set-up, a 60 nm width outer-zone-plate focuses a coherent soft X-ray beam onto the sample, which is scanned in 40 nm increments to ensure overlap of the probed areas. – See more at: http://newscenter.lbl.gov/2014/09/10/advanced-light-source-sets-microscopy-record/#sthash.6DLMbCxp.dpuf

    “If visible light microscopes could only achieve a resolution that was 50 times the wavelength of visible light, we would not be able to see most single celled organisms,” Shapiro says. “Where would the life sciences be with such a limitation? We are now approaching the point where we will have X-ray microscopes of comparable quality to today’s visible light instruments for the study of nanomaterials.”

    Co-authoring the Nature Photonics paper in addition to Shapiro and Padmore were Young-Sang Yu, Tolek Tyliszczak, Jordi Cabana, Rich Celestre, Weilun Chao, David Kilcoyne, Stefano Marchesini, Tony Warwick and Lee Yang of Berkeley Lab; Konstantin Kaznatcheev of Brookhaven National Laboratory; Shirley Meng of the University of San Diego; and Filipe Maia of Uppsala University in Sweden.

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

    See the full article here.

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

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  • richardmitnick 12:59 pm on September 9, 2014 Permalink | Reply
    Tags: , , , , X-ray Microscopy   

    From SLAC: “Buckyballs and Diamondoids Join Forces in Tiny Electronic Gadget” 


    SLAC Lab

    September 9, 2014
    Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

    Scientists Craft Two Exotic Forms of Carbon into a Molecule for Steering Electron Flow

    Scientists have married two unconventional forms of carbon – one shaped like a soccer ball, the other a tiny diamond – to make a molecule that conducts electricity in only one direction. This tiny electronic component, known as a rectifier, could play a key role in shrinking chip components down to the size of molecules to enable faster, more powerful devices.

    dd
    An international team led by researchers at SLAC National Accelerator Laboratory and Stanford University joined two offbeat carbon molecules – diamondoids, the square cages at left, and buckyballs, the soccer-ball shapes at right – to create “buckydiamondoids,” center. These hybrid molecules function as rectifiers, conducting electrons in only one direction, and could help pave the way to molecular electronic devices. (Manoharan Lab/Stanford University)

    “We wanted to see what new, emergent properties might come out when you put these two ingredients together to create a ‘buckydiamondoid,’” said Hari Manoharan of the Stanford Institute for Materials and Energy Sciences (SIMES) at the Department of Energy’s SLAC National Accelerator Laboratory. “What we got was a basically a one-way valve for conducting electricity – clearly more than the sum of its parts.”

    The research team, which included scientists from Stanford University, Belgium, Germany and Ukraine, reported its results September 9, 2014, in Nature Communications.

    Two Offbeat Carbon Characters Meet Up

    Many electronic circuits have three basic components: a material that conducts electrons; rectifiers, which commonly take the form of diodes, to steer that flow in a single direction; and transistors to switch the flow on and off. Scientists combined two offbeat ingredients – buckyballs and diamondoids – to create the new diode-like component.

    Buckyballs – short for buckminsterfullerenes – are hollow carbon spheres whose 1985 discovery earned three scientists a Nobel Prize in chemistry. Diamondoids are tiny carbon cages bonded together as they are in diamonds, but weighing less than a billionth of a billionth of a carat. Both are subjects of a lot of research aimed at understanding their properties and finding ways to use them.

    In 2007, a team led by researchers from SLAC and Stanford discovered that a single layer of diamondoids on a metal surface can efficiently emit a beam of electrons. Manoharan and his colleagues wondered: What would happen if they paired an electron-emitting diamondoid with another molecule that likes to grab electrons? Buckyballs are just that sort of electron-grabbing molecule.

    A Very Small Valve for Channeling Electron Flow

    For this study, diamondoids were produced in the SLAC laboratory of SIMES researchers Jeremy Dahl and Robert Carlson, who are world experts in extracting the tiny diamonds from petroleum. They were then shipped to Germany, where chemists at Justus-Liebig University figured out how to attach them to buckyballs.

    The resulting buckydiamondoids, which are just a few nanometers long, were tested in SIMES laboratories at Stanford. A team led by graduate student Jason Randel and postdoctoral researcher Francis Niestemski used a scanning tunneling microscope to make images of the hybrid molecules and measure their electronic behavior. They discovered the hybrid is an excellent rectifier: The electrical current flowing through the molecule was up to 50 times stronger in one direction, from electron-spitting diamondoid to electron-catching buckyball, than in the opposite direction. This is something neither component can do on its own.

    ball
    An image made with a scanning tunneling microscope shows hybrid buckydiamondoid molecules on a gold surface. The buckyball end of each molecule is attached to the surface, with the diamondoid end sticking up; both are clearly visible. The area shown here is 5 nanometers on a side. (H. Manoharan et al, Nature Communications)

    image
    Illustration of a buckydiamondoid molecule under a scanning tunneling microscope (STM). The sharp metallic tip of the STM ends in a single atom; as it scans over a sample, electrons tunnel from the tip into the sample. In this study the STM made images of the buckydiamondoids and probed their electronic properties. (SLAC National Accelerator Laboratory)

    While this is not the first molecular rectifier ever invented, it’s the first one made from just carbon and hydrogen, a simplicity researchers find appealing, said Manoharan, who is an associate professor of physics at Stanford. The next step, he said, is to see if transistors can be constructed from the same basic ingredients.

    “Buckyballs are easy to make – they can be isolated from soot – and the type of diamondoid we used here, which consists of two tiny cages, can be purchased commercially,” he said. “And now that our colleagues in Germany have figured out how to bind them together, others can follow the recipe. So while our research was aimed at gaining fundamental insights about a novel hybrid molecule, it could lead to advances that help make molecular electronics a reality.”

    Other research collaborators came from the Catholic University of Louvain in Belgium and Kiev Polytechnic Institute in Ukraine. The primary funding for the work came from the U.S. Department of Energy Office of Science.

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 1:30 pm on September 4, 2014 Permalink | Reply
    Tags: , , , X-ray Microscopy   

    From PNNL: “Birth of a mineral” 


    PNNL Lab

    September 04, 2014
    Mary Beckman, PNNL, (509) 375-3688

    One of the most important molecules on earth, calcium carbonate crystallizes into chalk, shells and minerals the world over. In a study led by the Department of Energy’s Pacific Northwest National Laboratory, researchers used a powerful microscope that allows them to see the birth of crystals in real time, giving them a peek at how different calcium carbonate crystals form, they report September 5 in Science.

    The results might help scientists understand how to lock carbon dioxide out of the atmosphere as well as how to better reconstruct ancient climates.

    “Carbonates are most important for what they represent, interactions between biology and Earth,” said lead researcher James De Yoreo, a materials scientist at PNNL. “For a decade, we’ve been studying the formation pathways of carbonates using high-powered microscopes, but we hadn’t had the tools to watch the crystals form in real time. Now we know the pathways are far more complicated than envisioned in the models established in the twentieth century.”

    Earth’s Reserve

    Calcium carbonate is the largest reservoir of carbon on the planet. It is found in rocks the world over, shells of both land- and water-dwelling creatures, and pearls, coral, marble and limestone. When carbon resides within calcium carbonate, it is not hanging out in the atmosphere as carbon dioxide, warming the world. Understanding how calcium carbonate turns into various minerals could help scientists control its formation to keep carbon dioxide from getting into the atmosphere.

    Calcium carbonate deposits also contain a record of Earth’s history. Researchers reconstructing ancient climates delve into the mineral for a record of temperature and atmospheric composition, environmental conditions and the state of the ocean at the time those minerals formed. A better understanding of its formation pathways will likely provide insights into those events.

    To get a handle on mineral formation, researchers at PNNL, the University of California, Berkeley, and Lawrence Berkeley National Laboratory [LBNL] examined the earliest step to becoming a mineral, called nucleation. In nucleation, molecules assemble into a tiny crystal that then grows with great speed. Nucleation has been difficult to study because it happens suddenly and unpredictably, so the scientists needed a microscope that could watch the process in real time.

    Come to Order

    In the 20th century, researchers established a theory that crystals formed in an orderly fashion. Once the ordered nucleus formed, more molecules added to the crystal, growing the mineral but not changing its structure. Recently, however, scientists have wondered if the process might be more complicated, with other things contributing to mineral formation. For example, in previous experiments they’ve seen forms of calcium carbonate that appear to be dense liquids that could be sources for minerals.

    Researchers have also wondered if calcite forms from less stable varieties or directly from calcium and carbonate dissolved in the liquid. Aragonite and vaterite are calcium carbonate minerals with slightly different crystal architectures than calcite and could represent a step in calcite’s formation. The fourth form called amorphous calcium carbonate — or ACC, which could be liquid or solid, might also be a reservoir for sprouting minerals.

    To find out, the team created a miniature lab under a transmission electron microscope at the Molecular Foundry, a DOE Office of Science User Facility at LBNL. In this miniature lab, they mixed sodium bicarbonate (used to make club soda) and calcium chloride (similar to table salt) in water. At high enough concentrations, crystals grew. Videos of nucleating and growing crystals recorded what happened:

    tem
    transmission electron microscope at LBNL

    Morphing Minerals

    The videos revealed that mineral growth took many pathways. Some crystals formed through a two-step process. For example, droplet-like particles of ACC formed, then crystals of aragonite or vaterite appeared on the surface of the droplets. As the new crystals formed, they consumed the calcium carbonate within the drop on which they nucleated.

    Other crystals formed directly from the solution, appearing by themselves far away from any ACC particles. Multiple forms often nucleated in a single experiment — at least one calcite crystal formed on top of an aragonite crystal while vaterite crystals grew nearby.

    What the team didn’t see in and among the many options, however, was calcite forming from ACC even though researchers widely expect it to happen. Whether that means it never does, De Yoreo can’t say for certain. But after looking at hundreds of nucleation events, he said it is a very unlikely event.

    “This is the first time we have directly visualized the formation process,” said De Yoreo. “We observed many pathways happening simultaneously. And they happened randomly. We were never able to predict what was going to come up next. In order to control the process, we’d need to introduce some kind of template that can direct which crystal forms and where.”

    In future work, De Yoreo and colleagues plan to investigate how living organisms control the nucleation process to build their shells and pearls. Biological organisms keep a store of mineral components in their cells and have evolved ways to make nucleation happen when and where needed. The team is curious to know how they use cellular molecules to achieve this control.

    This work was supported by the Department of Energy Office of Science.

    See the full article here.

    Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy National Laboratories, managed by the Department of Energy’s Office of Science. The main campus of the laboratory is in Richland, Washington.

    PNNL scientists conduct basic and applied research and development to strengthen U.S. scientific foundations for fundamental research and innovation; prevent and counter acts of terrorism through applied research in information analysis, cyber security, and the nonproliferation of weapons of mass destruction; increase the U.S. energy capacity and reduce dependence on imported oil; and reduce the effects of human activity on the environment. PNNL has been operated by Battelle Memorial Institute since 1965.

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  • richardmitnick 12:30 pm on August 22, 2014 Permalink | Reply
    Tags: , , , X-ray Microscopy   

    From Berkeley Lab: “Shaping the Future of Nanocrystals” 

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    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.

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

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  • richardmitnick 7:36 pm on July 22, 2014 Permalink | Reply
    Tags: , , , , X-ray Microscopy,   

    From SLAC: “Bringing High-energy X-rays into Better Focus” 


    SLAC Lab

    July 22, 2014
    SLAC-invented Etching Process Builds Custom Nanostructures for X-ray Optics

    Scientists at the Department of Energy’s SLAC National Accelerator Laboratory have invented a customizable chemical etching process that can be used to manufacture high-performance focusing devices for the brightest X-ray sources on the planet, as well as to make other nanoscale structures such as biosensors and battery electrodes.

    “The tools researchers use to manipulate X-rays today are very limited,” said Anne Sakdinawat, an associate staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) who developed the new “V-MACE” process with Chieh Chang, an SSRL research associate.

    scan
    Scanning electron microscope image of a cleaved spiral zone plate, a type of X-ray optic, created using a chemical etching technique that was developed at SLAC. (Chieh Chang, Anne Sakdinawat)

    “Our new technique for fabricating high performance X-ray optics involves just a few chemicals in a simple, easy-to-implement, one-step technology,” Sakdinawat said. “It offers significant advantages in many far-ranging applications.” The patent-pending technique is detailed in the June 27 edition of Nature Communications.

    Focusing X-rays, particularly higher-energy or “hard” X-rays, is particularly challenging at the nanoscale, though it is key to the success of many scientific studies at two of SLAC’s DOE Office of Science user facilities, SSRL and the Linac Coherent Light Source (LCLS) X-ray laser.

    It is also of great interest for commercial applications such as X-ray microscopy, complex electronics, and biomedical devices and imaging tools.

    Existing tools for focusing hard X-rays, such as specialized mirrors and sequences of concave metal structures that form lenses, are generally limited in how they can shape the X-ray light. Focusing the highest-energy X-rays to produce crisp images remains a challenge, as the focusing tools themselves generally lack nanoscale precision and sap away much of the X-ray energy.

    “It’s been technologically very difficult to fabricate structures that offer both high resolution and high efficiency,” Sakdinawat said, and the effectiveness of the structures, which are examples of X-ray “diffractive optics,” is typically based on the height and precision of their features.

    The new fabrication technique is adapted from a process used to create hairlike silicon wires for research on advanced batteries and electronics. It can fabricate structures up to 100 times as tall as they are wide, with dimensions accurate to billionths of a meter. The technique reduces the need to stack multiple layers to create tall structures.

    The researchers used the etching technique to build tall, precise X-ray diffractive optics, called zone plates, whose thinly spaced lines, symmetric rings or spiral patterns alternately obstruct or phase-shift X-rays and allow them to pass through in a way that separates and refocuses them. This improves the focus and produces higher-quality images.

    zone
    Scanning electron microscope (SEM) image of a zone plate pattern produced using a chemical etching technique invented at SLAC. (Chieh Chang, Anne Sakdinawat)

    zone2
    This scanning electron microscope image shows a cross-sectional view of a zone plate produced using a patent-pending chemical etching technique called “V-MACE” developed at SLAC. (Chieh Chang, Anne Sakdinawat)

    “Basically, this is like an artificial crystal,” Sakdinawat said, diffracting the X-ray light in a predictable pattern, as a crystal would. “You can basically manipulate the light in whatever fashion you want – you can shape the light in different ways,” she said, based on the design of the optics and the needs of the experiment.

    Sakdinawat and Chang tested and imaged a sample zone plate at SSRL, and they hope to construct similar plates for use in experiments at SSRL and LCLS.

    The same technique can be used to build other types of precise silicon and metal-coated nanostructures, such as filtration devices, thermoelectric devices that can create electricity from heat and components for tiny bio-sensors that can be embedded in the body, and researchers are working to tailor the process to suit the needs of government agencies and corporate partners.

    “We’re trying to expand into other fields,” Sakdinawat said. “There are many different applications for this.”

    See the full article here.

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
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  • richardmitnick 9:10 am on June 9, 2014 Permalink | Reply
    Tags: , , X-ray Microscopy,   

    From D.O.E Pulse: “Nanoscope to probe chemistry on the molecular scale” 

    pulse

    D.O.E. Pulse

    June 9, 2014
    Kate Greene, 510.486.4404, kgreene@lbl.gov

    For years, scientists have had an itch they couldn’t scratch. Even with the best microscopes and spectrometers, it’s been difficult to study and identify molecules at the so-called mesoscale, a region of matter that ranges from 10 to 1000 nanometers in size. Now, with the help of broadband infrared light from the Advanced Light Source (ALS) synchrotron at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab), researchers have developed a broadband imaging technique that looks inside this realm with unprecedented sensitivity and range.

    sheet

    This peptoid nanosheet, produced by Gloria Olivier and Ron Zuckerman at Berkeley Lab, is less than 8 nanometers thick at points. SINS makes it possible to acquire spectroscopic images of these ultra-thin nanosheets for the first time.

    By combining atomic force microscopy with infrared synchrotron light, researchers from Berkeley Lab and the University of Colorado have improved the spatial resolution of infrared spectroscopy by orders of magnitude, while simultaneously covering its full spectroscopic range, enabling the investigation of variety of nanoscale, mesoscale, and surface phenomena that were previously difficult to study.

    The new technique, called Synchrotron Infrared Nano-Spectroscopy or SINS, will enable in-depth study of complex molecular systems, including liquid batteries, living cells, novel electronic materials and stardust.

    “The big thing is that we’re getting full broadband infrared spectroscopy at 100 to 1000 times smaller scale,” says Hans Bechtel, principal scientific engineering associate at Berkeley Lab. “This is not an incremental achievement. It’s really revolutionary.”

    In a Proceedings of the National Academy of Sciences paper published May 6 online, titled Ultra-broadband infrared nano-spectroscopic imaging, Berkeley Lab’s Bechtel and Michael Martin, a Berkeley Lab staff scientist, and colleagues from Markus Raschke’s group at the University of Colorado at Boulder describe SINS. They demonstrate the nanoscope’s ability to capture broadband spectroscopic data over a variety of samples, including a semiconductor-insulator system, a mollusk shell, proteins, and a peptoid nanosheet. Martin says these demonstrations just “scratch the surface” of the potential of the new technique.

    Synchronizing Scopes

    SINS combines two pre-existing infrared technologies: a newer technique called infrared scattering-scanning near-field optical microscopy (IR s-SNOM) and an old laboratory standby, known even to college chemistry students, called Fourier Transform Infrared Spectroscopy (FTIR). A clever melding of these two tools, combined with the intense infrared light of the synchrotron at Berkeley Lab gives the researchers the ability to identify clusters of molecules sized as small as 20 to 40 nanometers.

    Experimental setup for SINS that includes the synchrotron light source, an atomic force microscope, a rapid-scan Fourier transform infrared spectrometer, a beamsplitter, mirrors and a detector.

    The new approach overcomes long-standing barriers with pre-existing microscopy techniques that often involve demanding technical and sample preparation requirements. Infrared spectroscopy uses low-energy light, is minimally invasive, and is applicable under ambient conditions, making it an excellent tool for chemical and molecular identifications in systems that are static as well as those that are living and dynamic. The technique works by shining low-energy infrared light onto a molecular sample. Molecules can be thought of as systems of balls (atoms) and springs (bonds between atoms) that vibrate with characteristic wiggles; they absorb infrared radiation at frequencies that correspond to their natural vibrating modes. The output from this absorption is a spectrum, often called a fingerprint, which shows distinctive peaks and dips, depending on the bonds and atoms present in the sample.

    But infrared spectroscopy has its challenges too. While it works well for bulk samples, traditional infrared spectroscopy can’t resolve molecular composition below about 2000 nanometers. The major hurdle is the diffraction limit of light, which is the fundamental barrier that determines the smallest focus spot of light and is particularly troublesome for the large wavelengths of infrared light. In recent years, though, the diffraction limit has been overcome by a technique called scattering-scanning near-field optical microscopy, or s-SNOM, which involves shining light onto a metallic tip. The tip acts as an antenna for the light, directing it to a tiny region at its apex just tens of nanometers wide.

    This trick is what’s used in IR s-SNOM, where infrared light is coupled to a metallic tip. The challenge with IR s-SNOM, however, is that researchers have been relying on infrared light produced by lasers. Lasers emit a large number of photons needed for the technique, but because they operate in a narrow wavelength band, they can only probe a narrow range of molecular vibrations. In other words, laser light simply can’t give you the flexibility to explore a spectrum of mixed molecules.

    A spectral-linescan of a blue mussel shell, which transitions from calcite to aragonite, illustrates the spatial resolution and spectroscopic range capabilities of the SINS technique. The image shows two simultaneously acquired vibrational modes across the transition region.

    Bechtel, Martin and Raschke’s team saw the opportunity to use Berkeley Lab’s ALS to overcome the laser limitation. The lab’s synchrotron produces broadband infrared light with a high-photon count that can be focused to the diffraction limit. The researchers coupled the synchrotron light to a metallic tip with an apex of about 20 nanometers, focusing the infrared beam onto the samples. The resulting spectrum is analyzed with a modified FTIR instrument.

    “This is actually one of very few examples where synchrotron light has been coupled to scanning probe microscopy,” says Raschke. “Moreover, the implementation of the technique at the synchrotron brings chemical nano-spectroscopy and -imaging out of the lab of a few laser science experts and makes it available for a broader scientific community at a user facility.”

    From mollusks to moon rocks

    The team demonstrated the technique by confirming the spectroscopic signature of silicon dioxide on silicon and by illustrating the sharp chemical transition that occurs within the shells of the blue mussel (M. edulis). Additionally, the researchers looked at proteins and a peptoid nanosheet, an engineered, ultra-thin film of proteins with medical and pharmacological applications.

    Martin is excited for the potential of SINS, which is available for researchers from any institution to use. In particular he’s interested in a closer look at battery systems, with the hope that understanding battery chemistry on the mesoscale could provide insight into better performance. Further out, he expects SINS to be useful for a range of biochemistry as well. “This hints at a dream I’ve had in my mind, to look at the surface of a cell, inside the bi-layer membrane, the channels, and receptors,” says Martin. “If we could put a SINS tip on a living cell, we could watch biochemistry happen in real time.”

    Bechtel, for his part, is intrigued by the possibility of using SINS for the study of lunar rocks, meteorites and stardust. These extraterrestrial materials have a molecular diversity that is difficult to resolve on the nanoscale, particularly in a non-destructive manner for these rare samples. A better understanding of the makeup of moon rocks and dust from space could provide clues to the formation of the planets and solar system.

    Raschke is using the technique to study the processes that limit the performance of organic solar cells. He is looking to further improve the flexibility of the technique such that it can be applied under variable and controlled atmospheric and low-temperature conditions. Among other tweaks, he plans to increase the sensitivity of the technique with the ultimate goal of performing singe-molecule chemical spectroscopy.
    This research was supported by the DOE’s Office of Science.

    See the full article here.

    DOE Pulse highlights work being done at the Department of Energy’s national laboratories. DOE’s laboratories house world-class facilities where more than 30,000 scientists and engineers perform cutting-edge research spanning DOE’s science, energy, National security and environmental quality missions. DOE Pulse is distributed twice each month.

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