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  • richardmitnick 7:30 pm on December 4, 2014 Permalink | Reply
    Tags: , Argonne National laboratory APS, ,   

    From ANL: “Atomic ‘mismatch’ creates nano ‘dumbbells'” 

    News APS at Argonne National Laboratory

    December 4, 2014
    Jared Sagoff

    Like snowflakes, nanoparticles come in a wide variety of shapes and sizes. The geometry of a nanoparticle is often as influential as its chemical makeup in determining how it behaves, from its catalytic properties to its potential as a semiconductor component.

    Thanks to a new study from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, researchers are closer to understanding the process by which nanoparticles made of more than one material – called heterostructured nanoparticles – form. This process, known as heterogeneous nucleation, is the same mechanism by which beads of condensation form on a windowpane.

    Heterostructured nanoparticles can be used as catalysts and in advanced energy conversion and storage systems. Typically, these nanoparticles are created from tiny “seeds” of one material, on top of which another material is grown. In this study, the Argonne researchers noticed that the differences in the atomic arrangements of the two materials have a big impact on the shape of the resulting nanoparticle.

    “Before we started this experiment, it wasn’t entirely clear what’s happening at the interface when one material grows on another,” said nanoscientist Elena Shevchenko of Argonne Center for Nanoscale Materials, a DOE Office of Science user facility.

    In this study, the researchers observed the formation of a nanoparticle consisting of platinum and gold. The researchers started with a platinum seed and grew gold around it. Initially, the gold covered the platinum seed’s surface uniformly, creating a type of nanoparticle known as “core-shell.” However, as more gold was deposited, it started to grow unevenly, creating a dumbbell-like structure.

    m
    This picture combines a transmission electron microscope image of a nanodumbbell with a gold domain oriented in direction. The seed and gold domains in the dumbbell in the image on the right are identified by geometric phase analysis. Image credit: Soon Gu Kwon.

    Thanks to state-of-the-art X-ray analysis provided by Argonne’s Advanced Photon Source (APS), a DOE Office of Science user facility, the researchers identified the cause of the dumbbell formation as “lattice mismatch,” in which the spacing between the atoms in the two materials doesn’t align.

    “Essentially, you can think of lattice mismatch as having a row of smaller boxes on the bottom layer and larger boxes on the top layer. When you try to fit the larger boxes into the space for a smaller box, it creates an immense strain,” said Argonne physicist Byeongdu Lee.

    While the lattice mismatch is only fractions of a nanometer, the effect accumulates as layer after layer of gold forms on the platinum. The mismatch can be handled by the first two layers of gold atoms – creating the core-shell effect – but afterwards it proves too much to overcome. “The arrangement of atoms is the same in the two materials, but the distance between atoms is different,” said Argonne postdoctoral researcher Soon Gu Kwon. “Eventually, this becomes unstable, and the growth of the gold becomes unevenly distributed.”

    As the gold continues to accumulate on one side of the seed nanoparticle, small quantities “slide” down the side of the nanoparticle like grains of sand rolling down the side of a sand hill, creating the dumbbell shape.

    The advantage of the Argonne study comes from the researchers’ ability to perform in situ observations of the material in realistic conditions using the APS. “This is the first time anyone has been able to study the kinetics of this heterogeneous nucleation process of nanoparticles in real-time under realistic conditions,” said Argonne physicist Byeongdu Lee. “The combination of two X-ray techniques gave us the ability to observe the material at both the atomic level and the nanoscale, which gave us a good view of how the nanoparticles form and transform.” All conclusions made based on the X-ray studies were further confirmed using atomic-resolution microscopy in the group of Professor Robert Klie of the University of Illinois at Chicago.

    This analysis of nanoparticle formation will help to lay the groundwork for the formation of new materials with different and controllable properties, according to Shevchenko. “In order to design materials, you have to understand how these processes happen at a very basic level,” she said.

    The research was funded in part by the National Science Foundation and the University of Illinois at Chicago Research Resources Center.

    An article based on the research, Heterogeneous nucleation and shape transformation of multicomponent metallic nanostructures,” appeared in the Nov. 2 online issue of Nature Materials.

    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future.

    With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. 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.

    See the full article here.

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

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

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  • richardmitnick 2:21 pm on August 29, 2014 Permalink | Reply
    Tags: , Argonne National laboratory APS, Space Dust,   

    From ANL: “Mysteries of space dust revealed” 

    News from Argonne National Laboratory

    August 29, 2014
    This story was originally reported by Kate Greene of Berkeley National Laboratory.

    The first analysis of space dust collected by a special collector onboard NASA’s Stardust mission and sent back to Earth for study in 2006 suggests the tiny specks open a door to studying the origins of the solar system and possibly the origin of life itself.

    NASA Stardust spacecraft
    NASA/Stardust

    This is the first time synchrotron light sources have been used to look at microscopic particles caught in the path of a comet. The Advanced Photon Source, the Advanced Light Source, and the National Synchrotron Light Source at the U.S. Department of Energy’s Argonne, Lawrence Berkeley and Brookhaven National Laboratories, respectively, enabled analysis that showed that the dust, which likely originated from beyond our solar system, is more complex in composition and structure than previously imagined.

    “Fundamentally, the solar system and everything in it was ultimately derived from a cloud of interstellar gas and dust,” says Andrew Westphal, physicist at the University of California, Berkeley’s Space Sciences Laboratory and lead author on the paper published this week in Science titled Evidence for interstellar origin of seven dust particles collected by the Stardust spacecraft. “We’re looking at material that’s very similar to what made our solar system.”

    The analysis tapped a variety of microscopy techniques including those that rely on synchrotron radiation. “Synchrotrons are extremely bright light sources that enable light to be focused down to the small size of these particles while providing unprecedented chemical identification,” said Hans Bechtel, principal scientific engineering associate at Berkeley Lab.

    The APS helped the researchers create a map of the locations and abundances of the different elements in each tiny particle, said Argonne physicist Barry Lai, who was involved with the analysis at the APS.

    “The Advanced Photon Source was unique in the capability to perform elemental imaging and analysis on such small particles — just 500 nanometers or less across,” Lai said. (That is so small that about 1,000 of them could fit in the period at the end of a sentence.) “This provided an important screening tool for differentiating the origin of each particle.”

    Researchers used the scanning transmission x-ray and Fourier transform infrared microscopes at the ALS. The X-ray microscope ruled out tens of interstellar dust candidates because they contained aluminum, not found in space or other substances and possibly knocked off the spacecraft and embedded in the aerogel. The infrared spectroscopy helped to identify sample contamination that could ultimately be subtracted later.

    “Almost everything we’ve known about interstellar dust has previously come from astronomical observations — either ground-based or space-based telescopes,” says Westphal. But telescopes don’t tell you about the diversity or complexity of interstellar dust, he says. “The analysis of these particles captured by Stardust is our first glimpse into the complexity of interstellar dust, and the surprise is that each of the particles are quite different from each other.”

    Westphal, who is also affiliated with Berkeley Lab’s Advanced Light Source, and his 61 co-authors, including researchers from the University of Chicago and the Chicago Field Museum of Natural History, found and analyzed a total of seven grains of possible interstellar dust and presented preliminary findings. All analysis was non-destructive, meaning that it preserved the structural and chemical properties of the particles. While the samples are suspected to be from beyond the solar system, he says, potential confirmation of their origin must come from subsequent tests that will ultimately destroy some of the particles.

    “Despite all the work we’ve done, we have limited the analyses on purpose,” Westphal explains. “These particles are so precious. We have to think very carefully about what we do with each particle.”

    Between 2000 and 2002, the Stardust spacecraft, on its way to meet a comet named Wild 2, exposed the special collector to the stream of dust coming from outside our solar system. The mission objectives were to catch particles from both the comet coma as well as from the interstellar dust stream. When both collections were complete, Stardust launched its sample capsule back to earth where it landed in northwestern Utah. The analyses of Stardust’s cometary sample have been widely published in recent years, and the comet portion of the mission has been considered a success.

    This new analysis is the first time researchers have looked at the microscopic particles collected en route to the comet. Both types of dust were captured by the spacecraft’s sample-collection trays, made of an airy material called aerogel separated by aluminum foil. Three of the space-dust particles (a tenth the size of comet dust) either lodged or vaporized within the aerogel while four others produced pits in the aluminum foil leaving a rim residue that fit the profile of interstellar dust.

    Much of the new study relied on novel methods and techniques developed specifically for handling and analyzing the fine grains of dust, which are more than a thousand times smaller than a grain of sand. These methods are described in twelve other papers available now and next week in the journal of Meteoritics & Planetary Science.

    One of the first research objectives was to simply find the particles within the aerogel. The aerogel panels were essentially photographed in tiny slices by changing the focus of the camera to different depths, which resulted in millions of images eventually stitched together into video. With the help of a distributed science project called Stardust@home [running on BOINC software from SSL], volunteer space enthusiasts from around the world combed through video, flagging tracks they believed were created by interstellar dust. More than 100 tracks have been found so far, but not all of these have been analyzed. Additionally, only 77 of the 132 aerogel panels have been scanned. Still, Westphal doesn’t expect more than a dozen particles of interstellar dust will be seen.

    The researchers found that the two larger dust particles from the aerogel have a fluffy composition, similar to that of a snowflake, says Westphal. Models of interstellar dust particles had suggested a single, dense particle, so the lighter structure was unexpected. They also contain crystalline material called olivine, a mineral made of magnesium, iron, and silicon, which suggest the particles came from disks or outflows from other stars and were modified in the interstellar medium.

    Three of the particles found in the aluminum foil were also complex, and contain sulfur compounds, which some astronomers believe should not occur in interstellar dust particles. Study of further foil-embedded particles could help explain the discrepancy.

    Westphal says that team will continue to look for more tracks as well as take the next steps in dust analysis. “The highest priority is to measure relative abundance of three stable isotopes of oxygen,” he says. The isotope analysis could help confirm that the dust originated outside the solar system, but it’s a process that would destroy the precious samples. In the meantime, Westphal says, the team is honing their isotope analysis technique on artificial dust particles called analogs. “We have to be super careful,” he says. “We’re doing a lot of work on analogs to practice, practice, practice.”

    The Advanced Photon Source is currently in the process of designing a proposed upgrade that would increase its ability to do such analyses, Lai said.

    “With the APS upgrade, we would be able to increase the spatial resolution and to image faster — effectively scanning a larger area of the aerogel in a shorter time,” he said.

    Since just over half of the aerogels have been checked for particles, there are plenty more waiting to be analyzed.

    This research was supported by NASA, the Klaus Tschira Foundation, the Tawani Foundation, the German Science Foundation, and the Funds for Scientific Research, Flanders, Belgium. In addition to ALS, the research made use of the National Synchrotron Light Source at Brookhaven National Laboratory and the Advanced Photon Source at Argonne. All three x-ray light sources are DOE Office of Science User Facilities.

    Brookhaven NSLS
    Brookhaven NSLS

    Berkeley Advanced Light Source
    LBL ALS

    See the full article here.

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

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

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

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  • richardmitnick 9:05 pm on July 7, 2014 Permalink | Reply
    Tags: , Argonne National laboratory APS, ,   

    From Argonne Lab: “Unprecedented detail of intact neuronal receptor offers blueprint for drug developers “ 

    News from Argonne National Laboratory

    July 7, 2014
    Tona Kunz

    Scientists succeeded in obtaining an unprecedented view of a type of brain-cell receptor that is implicated in a range of neurological illnesses, including Alzheimer’s disease, Parkinson’s disease, depression, schizophrenia, autism, and ischemic injuries associated with stroke.

    cell
    The NMDA receptor is a massive, multi-subunit complex. CSHL researchers found that it looks much like a hot air balloon. The upper, balloon-like portion of the structure is found outside the cell and responds to chemical messengers. Those messengers act like a key to unlock the lower portion of the receptor. This lower portion, corresponding to the basket of the hot air balloon, is embedded in the neuron’s membrane. It creates a narrow channel that allows ions, or electrically charged atoms, to flow into the cell. These many subunit interactions are potential targets for drug discovery.

    The team of biologists at Cold Spring Harbor Laboratory used the U.S. Department of Energy’s Advanced Photon Source at Argonne National Laboratory to get an atomic-level picture of the intact NMDA (N-methyl, D-aspartate) receptor should serve as template and guide for the design of therapeutic compounds.

    The NMDA receptor is a massive multi- subunit complex that integrates both chemical and electrical signals in the brain to allow neurons to communicate with one another. These conversations form the basis of memory, learning, and thought, and critically mediate brain development. The receptor’s function is tightly regulated: both increased and decreased NMDA activities are associated with neurological diseases.

    Despite the importance of NMDA receptor function, scientists have struggled to understand how it is controlled. In work published recently in Science, CSHL Associate Professor Hiro Furukawa and Erkan Karakas, Ph.D., a postdoctoral investigator, use a type of molecular photography known as X-ray crystallography to determine the structure of the intact receptor. Their work identifies numerous interactions between the four subunits of the receptor and offers new insight into how the complex is regulated. The X-ray work was done with the National Institute for General Medical Sciences and National Cancer Institute Collaborative Access Team (GM/CA) beamline at the APS and a beamline at SPring 8.

    “Previously, our group and others have crystallized individual subunits of the receptor – just fragments – but that simply was not enough,” says Furukawa. “To understand how this complex functions you need to see it all together, fully assembled.”

    For such a large complex, this was a challenging task. Using an exhaustive array of protein purification methods, Furukawa and Karakas were able to isolate the intact receptor. Their crystal structure reveals that the receptor looks much like a hot air balloon. “The ‘basket’ is what we call the transmembrane domain. It forms an ion channel that allows electrical signals to propagate through the neuron,” explains Furukawa.

    An ion channel is like a gate in the neuronal membrane. Ions, small electrically charged atoms, are unable to pass through the cell membrane. When the ion channel “gate” is closed, ions congregate outside the cell, creating an electrical potential across the cell membrane.

    When the ion channel “gate” opens, ions flow in and out of the cell through the channel pores. This generates an electrical current that sums up to create pulses that rapidly propagate through the neuron. But the current can’t jump from one neuron to the next. Rather, the electrical pulse triggers the release of chemical messengers, called neurotransmitters. These molecules traverse the distance between the neurons and bind to receptors, such as the NMDA receptor, on the surface of neighboring cells. There, they act much like a key, unlocking ion channels within the receptor and propelling the electrical signal across another neuron and, ultimately, across the brain.

    The “balloon” portion of the receptor that Furukawa describes is found outside the cell. This is the region that binds to neurotransmitters. The structure of the assembled multi-subunit receptor complex, including the elusive ion channel, helps to explain some of the existing data about how NMDA receptors function. “We are able to see how one domain on the exterior side of the receptor directly regulates the ion channel within the membrane,” says Furukawa. “Our structure shows why this particular domain, called the amino terminal domain, is important for the activity of the NMDA receptor, but not for other related receptors.”

    This information will be critical as scientists work to develop drugs that control the NMDA receptor. “Our structure defines the interfaces where multiple subunits and domains contact one another,” says Furukawa. “In the future, these will guide the design of therapeutic compounds to treat a wide range of devastating neurological diseases.”

    This work was supported by the National Institutes of Health, a Mirus Research Award, and the Robertson Research Fund of Cold Spring Harbor Laboratory.

    Crystal structure of a heterotetrameric NMDA receptor ion channel appears online in Science on May 30, 2014. The authors are Erkan Karakas and Hiro Furukawa. The paper can be obtained online at: http://www.sciencemag.org

    The APS beamline is funded by the National Institutes of Health’s National Institute of General Medical Sciences and the National Cancer Institute. The APS is funded by the U.S. Department of Energy’s Office of Science.

    See the full article here.

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

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

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

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  • richardmitnick 4:16 am on May 7, 2014 Permalink | Reply
    Tags: , Argonne National laboratory APS, , ,   

    From APS at Agonne Lab: “Advanced Photon Source to remain leader in protein structure research for years” 

    News from APS at Argonne National Laboratory

    May 5, 2014
    Brian Grabowski

    Proteins are involved in virtually every process in all living cells on the planet, be it a bacterium or yourself. In humans, antibodies defend against invading bacteria, viruses and other infectious agents. Insulin helps regulate how your body uses carbohydrates and fats. Lactase helps digest lactose from dairy products.

    ps
    The world’s first protein characterization research facility directly attached to a light source will open in the near future at the Advanced Photon Source. The Advanced Protein Characterization Facility will use state-of-the-art robotics for gene cloning, protein expression, protein purification and protein crystallization.

    But scientists know the structures and functions of only a small fraction of the proteins in living systems. The vast majority remain a mystery. The backlog of uncharacterized proteins grows quickly every day as scientists continue to determine the genetic makeups of thousands of new organisms, using astonishingly efficient techniques of genome sequencing.

    No X-ray facility in the world has supported more protein structure research and characterized more proteins than the Advanced Photon Source (APS) at the U.S. Department of Energy’s Argonne National Laboratory. Soon this 2/3-mile-in-circumference X-ray instrument will get a boost in efficiency that likely will translate into a big boon for the discovery of new pharmaceuticals and the control of genetic disorders and other diseases, as well as advancing the biotech industry.

    The world’s first protein characterization research facility directly attached to a light source will open in the near future at the APS. The Advanced Protein Characterization Facility (APCF) will use state-of-the-art robotics for gene cloning, protein expression, protein purification and protein crystallization.

    robotics
    Not beautiful, but very efficient

    “The net result will be more protein structures analyzed per year, higher resolution structures and more research into protein function,” said Andrzej Joachimiak, an Argonne Distinguished Fellow who also is director of the Structural Biology Center’s (SBC’s) Sector 19 beamlines and the Midwest Center for Structural Genomics. “This facility has been designed to integrate systems biology and molecular biology with gene cloning, protein expression, protein purification, protein crystallization and crystal testing and delivery to the APS. There is nothing like this anywhere in the world right now.”

    When a new protein structure is discovered and verified, the data are deposited in the Protein Data Bank repository to make it available to researchers around the world. For the last 11 consecutive years, the APS has been far and away the world leader in protein structure deposits. The APS has 14 beamlines dedicated to the study of protein crystals through a technique called macromolecular crystallography.

    “Two Nobel Prizes for Chemistry were awarded in the past four years for APS-based research involving crystallography,” said Joachimiak, “One Nobel Prize was for research into the structure and function of ribosomes on SBC’s 19-ID beamline, and another was awarded in 2012 for studies of G-protein-coupled receptors at a GM/CA-CAT micro-focus beamline.”

    Ribosomes make proteins in all living cells. Improved knowledge about bacterial ribosomes, for example, is speeding development of new antibiotics that combat bacterial infections by interfering with protein production. G-protein-coupled receptor (GPCR) proteins help cells stay in constant communication with each other, thereby facilitating resource sharing. When normal cells become cancerous, GPCRs are changed, too. The change can corrupt the lines of communication, allowing the cancerous cells to grow without limits. The first discovery of the structure of a human GPCR was made at the APS as part of the Nobel Prize-winning research. In fact, the structure was captured at the exact moment the GPCR was signaling across a cell membrane.

    The APCF will be available for use by the more than 5,500 scientists who visit the APS annually, but it will have a particularly strong connection to Argonne’s SBC and the beamline it operates at Sector 19. In 2013, more than 660 crystallographers used the SBC facility to collect data on hundreds of projects, including proteins from the Ebola virus. More than 4,100 protein structures have been deposited into the Protein Data Bank from SBC.

    Protein structures are analyzed by crystalling the proteins and then placing the single crystals into an X-ray beam for analysis using X-ray diffraction. The results depend on the quality of both the protein crystal and the X-ray beam. The APS provides some of the most brilliant X-ray beams in the Western Hemisphere. Additionally, the APS generates a highly parallel beam, which enables tight focusing of the X-rays. Staff at the National Institute of General Medical Sciences and National Cancer Institute structural biology facility (GM/CA-CAT) beamline capitalized on this and created the world’s first micro X-ray beam at the request of visiting researchers. “The micro-beam was essential for the GPCR research,” said Joachimiak.

    The crystallography capabilities of the APS will increase with a planned upgrade. “After the upgrade, the brilliance of the X-ray beam will increase by two to three orders of magnitude,” Joachimiak said. “The beam will be more parallel, too, so we will be able to focus down to a very small beam size. This beam will also be two to three times more intense. The upgrade should help ensure APS leadership in macromolecular crystallography for many years to come.”

    See the full article here.

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

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

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

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  • richardmitnick 2:10 pm on May 6, 2014 Permalink | Reply
    Tags: , Argonne National laboratory APS,   

    From Argonne Lab: “Scientists find x-rays can cause reversible resistance changes” 

    News from Argonne National Laboratory

    May 6, 2014
    Jared Sagoff

    Usually, when we think of a device that has defects, it means it’s time to throw it out. However, for several types of materials, imperfections are what actually make them function in the first place. Finding ways to control defects in a material without irrevocably damaging it could yield new information in the quest for an array of improved devices.

    Synchrotron X-rays are frequently used to image a wide range of different materials, but they can also cause chemical changes as well. In a new study, researchers at the U.S. Department of Energy’s Argonne National Laboratory looked at how a material’s electrical resistance changes when it is irradiated with these high-energy X-rays.

    In the experiment, the researchers looked at titanium dioxide, a material known for exhibiting multiple resistive states induced by defect movement. This behavior, known as resistive switching, could offer scientists a mechanism that may hold the key to potential new computer memories and even artificial neurons, according to Argonne materials scientist Seungbum Hong, who led the study along with Argonne physicist Jung Ho Kim.

    “It’s not easy to make a nanoscale device that switches reliably between resistive states,” Hong said. “In order to design reliable resistive switching materials, you need to understand and control the defect at the nanoscale.”

    When the titanium dioxide cell was exposed to the X-rays generated by Argonne’s Advanced Photon Source, the scientists found the existence of a photovoltaic-like effect, which changes the resistance by orders of magnitude, depending on the intensity of the oncoming X-rays. This effect, combined with an X-ray irradiation-induced phase transition, triggers a non-volatile reversible resistance change – that is, the change in resistance can be observed even after the X-rays are turned off.

    Argonne APS
    Advanced Photon Source at Argonne Lab

    “This result was somewhat serendipitous, in that people had known that X-rays could damage these materials, but they hadn’t been looking for this kind of reversible change,” Kim said.

    An article based on the research, titled X-ray Irradiation Induced Reversible Resistance Change in Pt/TiO2/Pt Cells, appeared in the January 13 edition of ACS Nano. Two other Argonne physicists, Jeff Eastman and John Freeland, also contributed to the study.

    This research was funded by the U.S. Department of Energy’s Office of Science.

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

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

    See the full article here.

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

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