Quantum spin Hall effect in two-dimensional transition metal dichalcogenides

Exotic states materialize with supercomputers. Materials with novel electrical properties discovered using XSEDE computational resources Stampede and Lonestar supercomputers of TACC

UNIVERSITY OF TEXAS AT AUSTIN, TEXAS ADVANCED COMPUTING CENTER

The science team included Ju Li, Liang Fu, Xiaofeng Qian, and Junwei Liu, experts in topological phases of matter and two-dimensional materials research at the Massachusetts Institute of Technology (MIT). They calculated the electronic structures of the materials using the Stampede and Lonestar supercomputers of the Texas Advanced Computing Center.

The computational allocation was made through XSEDE, the Extreme Science and Engineering Discovery Environment, a single virtual system funded by the National Science Foundation (NSF) that scientists use to interactively share computing resources, data and expertise. The study was funded by the U.S. Department of Energy and the NSF.

This picture tells quite a story to scientists. It's a portrait of what they call a topological insulator, materials that conduct only at their edges. Technically it shows the edge density of states calculated for a monolayer transition metal dichalcogenide in the 1T'-MoS2 structural phase.

There's a black gap between the purple blobs at the bottom and top. What's more, there's crisscrossing reddish lines that bridge the gap. The lines indicate the edge state of the material, allowing electrons to cross the gap and conduct electricity. CREDIT: (Credit: Qian et. al.) USAGE RESTRICTIONS: None

"To me, national computing resources like XSEDE, or specifically the Stampede and Lonestar supercomputers, are extremely helpful to computational scientists," Xiaofeng Qian said. In January 2015, Qian left MIT to join Texas A&M University as the first tenure-track assistant professor at its newly formed Department of Materials Science and Engineering.

What Qian and colleagues did was purely theoretical work, using Stampede for part of the calculations that modeled the interactions of atoms in the novel materials, two-dimensional transition metal dichalcogenides (TMDC). Qian used the molecular dynamics simulation software Vienna Ab initio Simulation Package to model a unit cell of atoms, the basic building block of the crystal lattice of TMDC.

"If you look at the unit cell, it's not large. They are just a few atoms. However, the problem is that we need to predict the band structure of charge carriers in their excited states in the presence of spin-orbit coupling as accurately as possible," Qian said.

Scientists diagram the electronic band structure of materials to show the energy ranges an electron is allowed, with the band gap showing forbidden zones that basically block the flow of current. Spin-orbit coupling accounts for the electromagnetic interactions between electron's spin and magnetic field generated from the electron's motion around the nucleus.

"We found a very convenient method to control the topological phase transition in these quantum spin Hall interlayers."
Xiaofeng Qian, Assistant Professor in the Department of Materials Science and Engineering at Texas A&M University.

The complexity lies in the details of these interactions, for which Qian applied many-body perturbation theory with the GW approximation, a state-of-the-art first principles method, to calculate the quasiparticle electronic structures for electrons and holes. The 'G' is short for Green's Function and 'W' for screened Coulomb interaction, Qian explained.

"In order to carry out these calculations to obtain reasonable convergence in the results, we have to use 96 cores, sometimes even more," Qian said. "And then we need them for 24 hours. The Stampede computer is very efficient and powerful. The work that we have been showing is not just one material; we have several other materials as well as different conditions. In this sense, access to the resources, especially Stampede, is very helpful to our project."

The big picture for Qian and his colleagues is the hunt for new kinds of materials with extraordinarily useful properties. Their target is room-temperature quantum spin Hall insulators, which are basically near-two-dimensional materials that block current flow everywhere except along their edges. "Along the edges you have the so-called spin up electron flow in one direction, and at the same time you have spin down electrons and flows away in the opposite direction," Qian explained. "Basically, you can imagine, by controlling the injection of charge carriers, one can come up with spintronics, or electronics."

The scientists in this work proposed a topological field-effect transistor, made of sheets of hexagonal boron interlaced with sheets of TMDC. "We found a very convenient method to control the topological phase transition in these quantum spin Hall interlayers," Qian said. "This is very important because once we have this capability to control the phase transition, we can design some electronic devices that can be controlled easily through electrical fields."

Media Contact: Faith Singer-Villalobos faith@tacc.utexas.edu 512-232-5771

Quantum spin Hall effect in two-dimensional transition metal dichalcogenides. More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2015/03/quantum-spin-hall-effect-in-two.html

Exotic states materialize with supercomputers. Materials with novel electrical properties discovered using XSEDE computational resources Stampede and Lonestar supercomputers of TACC.

Scientists used supercomputers to find a new class of materials that possess an exotic state of matter known as the quantum spin Hall effect. The researchers published their results in the journal Science in December 2014, where they propose a new type of transistor made from these materials.

Photon transport enhanced by transverse Anderson localization in disordered superlattices

A breakthrough by a team of researchers from UCLA, Columbia University and other institutions could lead to the more precise transfer of information in computer chips, as well as new types of optical materials for light emission and lasers.

The researchers were able to control light at tiny lengths around 500 nanometers — smaller than the light’s own wavelength — by using random crystal lattice structures to counteract light diffraction. The discovery could begin a new phase in laser collimation — the science of keeping lasers precise and narrow instead of spreading out.

The study’s principal investigator was Chee Wei Wong, associate professor of electrical engineering at the UCLA Henry Samueli School of Engineering and Applied Science.

Artist’s depiction of light traveling through a photonic crystal superlattice, where holes have been randomly patterned. The result is a more narrow beam of light. Image by Nicoletta Barolini

Think of shining a flashlight against a wall. As the light moves from the flashlight and approaches the wall, it spreads out, a phenomenon called diffraction. The farther away the light source is held from the wall, the more the beam diffracts before it reaches the wall.

The same phenomenon also happens on a scale so small that distances are measured in nanometers — a unit equal to one-billionth of a meter. For example, light could be used to carry information in computer chips and optical fibers. But when diffraction occurs, the transfer of data isn’t as clean or precise as it could be.

Technology that prevents diffraction and more precisely controls the light used to transfer data could therefore lead to advances in optical communications, which would enable optical signal processing to overcome physical limitations in current electronics and could enable engineers to create improved optical fibers for use in biomedicine.

To control light on the nanoscale, the researchers used a photonic crystal superlattice, a lattice structure made of crystals that allows light through. The lattice was a disorderly pattern, with thousands of nanoscale heptagonal, square and triangular holes. These holes, each smaller than the wavelength of the light traveling through the structure, serve as guideposts for a beam of light.

Engineers had understood previously that uniformly patterned holes can control the spatial diffraction somewhat. But the researchers found in the new study that the structures with the most disorderly patterns were best able to trap and collimate the beam into a narrow path, and that the structure worked over a broad part of the infrared spectrum.

The study’s lead author was Pin-Chun Hsieh, who was advised by Wong during his doctoral studies at Columbia University’s Fu Foundation School of Engineering and Applied Science.

The effect of disorder, known as Anderson localization, was first proposed in 1958 by Nobel laureate Philip Anderson. It is the physical phenomenon that explains the conductance of electrons and waves in condensed matter physics.

The new study was the first to examine transverse Anderson localization in a chip-scale photonic crystal media. It was published online today by Nature Physics.

“This study allows us to validate the theory of Anderson localization in chip-scale photonics, through engineered randomness in an otherwise periodic structure,” Wong said. “What Pin-Chun has observed provides a new path in controlling light propagation at the wavelength scale, that is, delivering structure arising out of randomness.”

Hsieh, who also is chairman and majority owner of Taiwan-based Quantumstone Research, said the findings are completely counterintuitive because one might think that disorder in the structures would lead the light to spread out more. “This effect, based on intuition gained from electronic systems, where introduced impurities can turn an insulator into a semiconductor, shows unequivocally that controlling disorder can arrest transverse transport, and really reduce the spreading of light.”

The numerical simulation was performed at University College London, and the sample fabrication was carried out at the Brookhaven National Laboratory in New York and at National Cheng Kung University in Taiwan.

The research was supported primarily by a grant from the U.S. Office of Naval Research. Additional support was provided by the National Science Foundation, the Department of Energy and the government of the United Kingdom. Hsieh is supported by a scholarship from Taiwan’s Department of Education.

Media Contact Matthew Chin mchin@support.ucla.edu 310-206-0680

Photon transport enhanced by transverse Anderson localization in disordered superlattices. More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2015/02/photon-transport-enhanced-by-transverse.html

A breakthrough by a team of researchers from UCLA, Columbia University and other institutions could lead to the more precise transfer of information in computer chips, as well as new types of optical materials for light emission and lasers.

The researchers were able to control light at tiny lengths around 500 nanometers — smaller than the light’s own wavelength — by using random crystal lattice structures to counteract light diffraction.

Turning biological cells to stone 'Zombie' method hardens biostructures for mass production

Turning biological cells to stone. 'Zombie' method hardens biostructures for mass production.

ALBUQUERQUE, N.M. -- Changing flesh to stone sounds like the work of a witch in a fairy tale.

But a new technique to transmute living cells into more permanent materials that defy rot and can endure high-powered probes is widening research opportunities for biologists who are developing cancer treatments, tracking stem cell evolution or even trying to understand how spiders vary the quality of the silk they spin.

The simple, silica-based method also offers materials scientists the ability to "fix" small biological entities like red blood cells into more commercially useful shapes. And, at least in theory, the method can transmute naturally grown objects like livers and spleens from livestock into non-organic "zombie" replicas that function simultaneously at a variety of length-scales, from macro to nano, in more sophisticated ways than the most advanced machinery can produce.

A Potential Battery Terminal? This image shows the complex multiscale structure of a carbonized mouse spleen. Credit: Sandia National Laboratories. Usage Restrictions: professional media

Related news release: Turning biological cells to stone improves cancer and stem cell research.

"Why go to the trouble of making objects if nature will do it for you?" asks lead investigator Bryan Kaehr, of the Department of Energy's Sandia National Laboratories.

The unusual method has been the subject of papers in Proceedings of the National Academy of Sciences, the Journal of the American Chemical Society (JACS), and on Dec. 8, Nature Communications.

The initial insight came when Kaehr and then-University of New Mexico (UNM) postdoctoral student Jason Townson discovered that the silica slurry they were using had an unexpected property: At a reasonably low pH level, the silica molecules, instead of clotting with each other, bound only to surfaces against which they rested, forming the thinnest of coatings.

Kaehr wondered if a similar coating on biological cells would strengthen cell structures so they could be examined for longer periods with more powerful tools. So the researchers put cultured tissue cells in a silica solution and let the mix harden overnight. Then they raised the temperature to burn off the biomaterial. What remained, astonishingly, were perfectly replicated cells, like little row houses of glass.

But the replicated cells were so sturdy that Kaehr surmised that the slurry must have coated the cells inside as well as out. Breaking a row of cells as one would a tiny pane of glass, the team examined their interiors with an electron microscope. They found they had indeed replicated the nanoscopic organelles of the cell as well as its exterior. They had discovered a way to create a near-perfect silica counterfeit of a biological organism, from its overall shape down to its nanostructures.

This initial result is already being used by biologists in Finland to create three-dimensional models that preserve the different stages of stem cells as they evolve to their final form, said Sandia fellow and paper co-author Jeff Brinker, who is also a UNM professor.

Townson, now on the faculty at UNM, uses the method to research the movements of cancer-fighting nanoparticles inserted into chicken cells prior to their conversion to silica. "With optical microscopy, it is difficult to form an image of the interactions of nanoparticles with cells while preserving a three-dimensional context," he said. Bioreplication, where the sample can be mechanically dissected and investigated with electron microscopes, offers better 3-D resolution at the nanoscale.

The method also is being used in England's Oxford University to study the internal biological changes by which spiders create different types of silk, adjusting their mechanisms on the fly (so to speak) to create thicker or stickier strands, said Brinker.


Blood as a possible raw material

In the JACS article, Kaehr and colleagues showed they could use the silica technique to make permanent alterations in natural objects. They introduced chemicals that transformed red blood cells from life-saver-like objects to spiky spheres. By introducing the silica slurry to the dish containing the altered red blood cells and letting the mixture harden, Kaehr and colleagues made the change permanent. Burning off the protoplasmic original, the team was left with microparticles that might be useful in rubber composites created by tire companies that routinely insert silica spheres in their tire mix for additional strength. Manufacturers would no longer need an energy-consuming factory to make the inserted material which, by bioreplication, would form cheaply and easily, Kaehr said.

Said Kaehr. "Our method has good potential over traditional silica additives, and its raw material -- blood -- is considered a waste product in the meat industry. "

In addition to food industry waste products, he said, "there's a huge amount of harmless bacteria out there we could co-opt to create still other shapes." Bacteria are harder to harvest, he said, because they are protected by a double sheath against silica invasion, but it could be done.

In the Nature Communications paper, Kaehr and colleagues took the same technique a step further. They took a liver, submerged it in a silica solution and then heated it anaerobically to come up with a hardened, carbonized, exact duplicate of the liver, from centimeter to nanometer scales. "We let nature do the work," he said, "because we don't yet know how to build an object accurately across six length scales, from centimeter to nanometers.

"Think about electrodes in batteries," he said. "That's a three-dimensional question. Now in livers and spleens, for example, evolution has already optimized absorption and diffusion in a three-dimensional organization. The liver is a marvelously effective organ with tremendous surface area for absorption and an unparalleled ability to release materials in channels ranging from large arteries to capillaries a few micrometers wide.

"If we transfer the hierarchical structure of a liver to an electrode, rather than having just a passive piece of solid material, we would have greater surface area per volume, greater energy storage, and have a creation that is already optimized to output fluids and small particles to much larger highways like large veins and arteries."

The carbonized method also can be used to better examine cancers and other growths without the often tedious and expensive processes normally necessary to "fix," process and stabilize the organic material for examination to prevent it from falling apart under electron-beam analysis. Carbon, because it conducts electricity instead of absorbing it, is not weakened and destroyed like protoplasm.

This creative consideration of the possibilities of the natural world in new and dizzying ways is in line with Kaehr's research sponsor --DOE's Office of Science, which is interested in "the exploration, discovery and design of biomimetic materials," he said. Portions of this work were performed at the Center for Integrated Nanotechnologies, a DOE Office of Science User Facility jointly led by Los Alamos and Sandia National Laboratories.

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Sandia and UNM have applied for a joint patent on the set of methods.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.


Contact: Neal Singer nsinger@sandia.gov 505-845-7078 DOE / Sandia National Laboratories@SandiaLabs

Nanomimics of Host Cell Membranes Block Invasion and Expose Invasive Malaria Parasites

Nanomimics of Host Cell Membranes Block Invasion and Expose Invasive Malaria Parasites.

For many infectious diseases no vaccine currently exists. In addition, resistance against currently used drugs is spreading rapidly. To fight these diseases, innovative strategies using new mechanisms of action are needed. The malaria parasite Plasmodium falciparum that is transmitted by the Anopheles mosquito is such an example. Malaria is still responsible for more than 600,000 deaths annually, especially affecting children in Africa (WHO, 2012).

Artificial bubbles with receptors

Malaria parasites normally invade human red blood cells in which they hide and reproduce. They then make the host cell burst and infect new cells. Using nanomimics, this cycle can now be effectively disrupted: The egressing parasites now bind to the nanomimics instead of the red blood cells.

After maturation, malaria parasites (yellow) are leaving an infected red blood cell and are efficiently blocked by nanomimics (blue). (Fig: Modified with permission from ACS).

Researchers of groups led by Prof. Wolfgang Meier, Prof. Cornelia Palivan (both at the University of Basel) and Prof. Hans-Peter Beck (Swiss TPH) have successfully designed and tested host cell nanomimics. For this, they developed a simple procedure to produce polymer vesicles – small artificial bubbles – with host cell receptors on the surface. The preparation of such polymer vesicles with water-soluble host receptors was done by using a mixture of two different block copolymers. In aqueous solution, the nanomimics spontaneously form by self-assembly.

Blocking parasites efficiently

Usually, the malaria parasites destroy their host cells after 48 hours and then infect new red blood cells. At this stage, they have to bind specific host cell receptors. Nanomimics are now able to bind the egressing parasites, thus blocking the invasion of new cells. The parasites are no longer able to invade host cells, however, they are fully accessible to the immune system.

The researchers examined the interaction of nanomimics with malaria parasites in detail by using fluorescence and electron microscopy. A large number of nanomimics were able to bind to the parasites and the reduction of infection through the nanomimics was 100-fold higher when compared to a soluble form of the host cell receptors. In other words: In order to block all parasites, a 100 times higher concentration of soluble host cell receptors is needed, than when the receptors are presented on the surface of nanomimics.

“Our results could lead to new alternative treatment and vaccines strategies in the future”, says Adrian Najer first-author of the study. Since many other pathogens use the same host cell receptor for invasion, the nanomimics might also be used against other infectious diseases. The research project was funded by the Swiss National Science Foundation and the NCCR “Molecular Systems Engineering”.

Original source: Adrian Najer, Dalin Wu, Andrej Bieri, Françoise Brand, Cornelia G. Palivan, Hans-Peter Beck, and Wolfgang Meier
Nanomimics of Host Cell Membranes Block Invasion and Expose Invasive Malaria Parasites. ACS Nano, Publication Date (Web): 29 November 2014 | DOI: 10.1021/nn5054206

Further information: Prof. Wolfgang Meier, University of Basel, Department of Chemistry, phone: +41 61 267 38 02, email: wolfgang.meier@unibas.ch

On-the-fly decoding luminescence lifetimes in the microsecond region for lanthanide-encoded suspension arrays

WEST LAFAYETTE, Ind. — A research team using tunable luminescent nanocrystals as tags to advance medical and security imaging have successfully applied them to high-speed scanning technology and detected multiple viruses within minutes.

The research, led by Macquarie University in Sydney, Australia and Purdue University, builds on the team's earlier success in developing a way to control the length of time light from a luminescent nanocrystal lingers, which introduced the dimension of time in addition to color and brightness in optical detection technology.

Detection based on the lifetime of the light from a nanocrystal as well as its specific color exponentially increases the possible combinations and unique tags that could be created for biomedical screens.

"We now are able to build a huge library of lifetime color-coded microspheres to perform multiple medical tasks or diagnoses at the same time," said Yiqing Lu, a researcher at Macquarie University, who led the research. "The time saved by omitting the need to grow or amplify a culture sample for testing and eliminating the need to run multiple tests will save future patients precious time so treatment can begin, which can be life-saving when managing aggressive diseases."

Ebola virus virion. Created by CDC microbiologist Cynthia Goldsmith, this colorized transmission electron micrograph (TEM) revealed some of the ultrastructural morphology displayed by an Ebola virus virion.

This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #10816

The technology could enable screens that identify thousands of different target molecules simultaneously, said J. Paul Robinson, the Professor of Cytomics in Purdue's College of Veterinary Medicine and professor in Purdue's Weldon School of Biomedical Engineering, who was involved in the research.

"This is the second part of the puzzle," said Robinson, who led the biological testing of the technology. "Now we've successfully measured the lifetimes of these tags on the fly at thousands of samples per second. The next step is to perform such high-throughput testing within a liquid, like water, blood or urine. That will open the door to widespread biological use and clinical applications, as well as the detection of pathogens in food or water."

Robinson's research focuses on flow cytometry, the analysis of cells that are contained in a liquid flowing past a laser beam. In addition to developing instrumentation to measure the tags, he plans to explore the technology's health care and biodetection applications.

The research team attached unique tags to DNA strands of HIV, Ebola virus, Hepatitis B virus and Human Papillomavirus 16. The tags were accurately read and distinguished at high speeds in suspension arrays. The team's work is detailed in a paper that will be published in the next issue of Nature Communications and is currently available online.

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Dayong Jin, an Australian Research Council Future Fellow, and a professor of photonics at Macquarie ARC Centre for nanoscale BioPhotonics (CNBP), led the design and manufacture of the nanoparticles, which the researchers named tau-dots.

In addition to Jin, Lu and Robinson, paper co-authors include Jie Lu, Jiangbo Zhao, Ewa M. Goldys, and James A. Piper of Macquarie; Janet Cusido and Francisco M. Raymo of the University of Miami; Jingli Yuan of Dalian University of Technology in Dalian, China; , Sean Yang and Robert C. Leif of Newport Instruments in San Diego; and Yujing Huo of Tsinghua Univesity in Beijing, China.

Contact: Elizabeth K. Gardner ekgardner@purdue.edu 765-494-2081 Purdue University www.twitter.com/PurdueResearch

On-the-fly decoding luminescence lifetimes in the microsecond region for lanthanide-encoded suspension arrays.

Ebola virus virion. Created by CDC microbiologist Cynthia Goldsmith, this colorized transmission electron micrograph (TEM) revealed some of the ultrastructural morphology displayed by an Ebola virus virion.

More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/10/on-fly-decoding-luminescence-lifetimes.html

NRL syntheses potassium superoxide (KO2) to rapidly form oxide nanoparticles from simple salt solutions in water

Scientists at the U.S. Naval Research Laboratory (NRL) Materials Science and Technology Division have developed a novel one-step process using, for the first time in these types of syntheses, potassium superoxide (KO2) to rapidly form oxide nanoparticles from simple salt solutions in water.

"Typically, the synthesis of oxide nanoparticles involves the slow reaction of a weak oxidizing agent, such as hydrogen peroxide, with dilute solutions of metal salts or complexes in both aqueous and non-aqueous solvent systems," said Dr. Thomas Sutto, NRL research chemist. "The rapid exothermic reaction of potassium superoxide with the salt solutions results in the formation of insoluble oxide or hydroxide nanoparticulates."

An important advantage of this method is the capability of creating bulk quantities of materials. NRL has demonstrated that large quantities (over 10 grams) of oxide nanoparticles can be prepared in a single step, which is approximately four orders of magnitude higher yield than many other methods. The metal concentrations, usually in the millimolar (mM) amount, need to be low in order to prevent aggregation of the nanoparticles into larger clusters that could significantly limit the amount of material that can be prepared at any one time.

Oxide nanoparticles have been shown to be crucial components in numerous applications to include electronic and magnetic devices, energy storage and generation, and medical applications such as magnetic nanoparticles for use in magnetic resonance imaging (MRI). In all of these applications, particle size is critical to the utility and function of oxide nanoparticles—decreased particles size results in increased surface area, which can significantly improve the performance of the oxide nanoparticle.

This figure illustrates the ease with which grams of many different types of oxide nanoparticles can be prepared in a single step. The first row of sample vials shows the initial salt solutions of the different elements. The second row shows the product after reaction with potassium superoxide (KO2) and the addition of methanol. The bottom row shows the grams of nanoparticles after being purified by centrifugation.
(Photo: U.S. Naval Research Laboratory)

In order to demonstrate the broad scale applicability of this new method, oxide or hydroxide nanoparticles have been prepared from representative elements from across the periodic table to rapidly produce nanometer sized oxides or hydroxides. In addition to the elements converted to oxide nanoparticles in the above illustration, it has also been shown that oxide nanoparticles can be prepared from second and third row transition metals, and even semi-metals such as tin, bismuth, thallium and lead.

One exciting aspect of this technique is that it can also be used to produce blends of nanoparticles. This has been demonstrated by preparing more complex materials, such as lithium cobalt oxide—a cathode material for lithium batteries; bismuth manganese oxide—a multiferroic material; and a 90 degrees Kelvin (K) superconducting Yttrium barium copper oxide material. As such, this new synthetic route to oxide nanoparticles also shows great promise for a multitude of other catalytic, electrical, magnetic, or electrochemical processes, from novel cathodes to solution preparation of other types of ceramic materials.

About the U.S. Naval Research Laboratory. The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.

NRL syntheses potassium superoxide (KO2) to rapidly form oxide nanoparticles from simple salt solutions in water. More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/09/nrl-syntheses-potassium-superoxide-ko2.html

Scientists at the U.S. Naval Research Laboratory (NRL) Materials Science and Technology Division have developed a novel one-step process using, for the first time in these types of syntheses, potassium superoxide (KO2) to rapidly form oxide nanoparticles from simple salt solutions in water.

"Typically, the synthesis of oxide nanoparticles involves the slow reaction of a weak oxidizing agent, such as hydrogen peroxide, with dilute solutions of metal salts or complexes in both aqueous and non-aqueous solvent systems

Reference Material (RM) 8027

World's smallest reference material is big plus for nanotechnology.

If it's true that good things come in small packages, then the National Institute of Standards and Technology (NIST) can now make anyone working with nanoparticles very happy. NIST recently issued Reference Material (RM) 8027, the smallest known reference material ever created for validating measurements of these man-made, ultrafine particles between 1 and 100 nanometers (billionths of a meter) in size.

RM 8027 consists of five hermetically sealed ampoules containing one milliliter of silicon nanoparticles—all certified to be close to 2 nanometers in diameter—suspended in toluene. To yield the appropriate sizes for the new RM, the nanocrystals are etched from a silicon wafer, separated using ultrasound and then stabilized within an organic shell. Particle size and chemical composition are determined by dynamic light scattering, analytical centrifugation, electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS), a powerful technique that can measure elements at concentrations as low as several parts per billion.

"For anyone working with nanomaterials at dimensions 5 nanometers or less, our well-characterized nanoparticles can ensure confidence that their measurements are accurate," says NIST research chemist Vytas Reipa, leader of the team that developed and qualified RM 8027.

A structural model of a typical silicon nanocrystal (yellow) was stabilized within an organic shell of cyclohexane (blue). Credit: NIST Usage Restrictions: None

Silicon nanoparticles such as those in RM 8027 are being studied as alternative semiconductor materials for next-generation photovoltaic solar cells and solid-state lighting, and as a replacement for carbon in the cathodes of lithium batteries. Another potential application comes from the fact that silicon crystals at dimensions of 5 nanometers or less fluoresce under ultraviolet light. Because of this property, silicon nanoparticles may one day serve as easily detectable "tags" for tracking nanosized substances in biological, environmental or other dynamic systems.

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RM 8027 maybe ordered from the NIST Standard Reference Materials Program by phone, (301) 975-2200; by fax, (301) 948-3730; or online at http://www.nist.gov/srm.

Contact: Michael E. Newman michael.newman@nist.gov 301-975-3025 National Institute of Standards and Technology (NIST) @usnistgov

Reference Material (RM) 8027. The National Institute of Standards and Technology (NIST) can now make anyone working with nanoparticles very happy. NIST recently issued Reference Material (RM) 8027, the smallest known reference material ever created for validating measurements of these man-made, ultrafine particles between 1 and 100 nanometers (billionths of a meter) in size.

More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/09/reference-material-rm-8027.htm

Generic epitaxial graphene biosensors for ultrasensitive detection of cancer risk biomarker

An ultrasensitive biosensor made from the wonder material graphene has been used to detect molecules that indicate an increased risk of developing cancer.

The biosensor has been shown to be more than five times more sensitive than bioassay tests currently in use, and was able to provide results in a matter of minutes, opening up the possibility of a rapid, point-of-care diagnostic tool for patients.

The biosensor has been presented today, 19 September, in IOP Publishing's journal 2D Materials.

To develop a viable bionsensor, the researchers, from the University of Swansea, had to create patterned graphene devices using a large substrate area, which was not possible using the traditional exfoliation technique where layers of graphene are stripped from graphite.

Instead, they grew graphene onto a silicon carbide substrate under extremely high temperatures and low pressure to form the basis of the biosensor. The researchers then patterned graphene devices, using semiconductor processing techniques, before attaching a number of bioreceptor molecules to the graphene devices. These receptors were able to bind to, or target, a specific molecule present in blood, saliva or urine.

This is an illustration of an epitaxial graphene channel biosensor for detection of targeted 8-hydroxydeoxyguanosine (8-OHdG) biomarker. (A) Schematic of MLEG device (B) Thin film of covalently attached nitro phenyl (PhNO2) groups on the MLEG channel. (C) Attachment of the 'bioreceptor' antibody anti-8-OHdG to the amine terminated MLEG channel and subsequent detection of 8-OHdG.

Credit: 2D Materials. Usage Restrictions: Credit to 2D Materials must be given and, if reproducing online, a link to the paper must be included: iopscience.iop.org/

The molecule, 8-hydroxydeoxyguanosine (8-OHdG), is produced when DNA is damaged and, in elevated levels, has been linked to an increased risk of developing several cancers. However, 8-OHdG is typically present at very low concentrations in urine, so is very difficult to detect using conventional detection assays, known as enzyme-linked immunobsorbant assays (ELISAs).

In their study, the researchers used x-ray photoelectron spectroscopy and Raman spectroscopy to confirm that the bioreceptor molecules had attached to the graphene biosensor once fabricated, and then exposed the biosensor to a range of concentrations of 8-OHdG.

When 8-OHdG attached to the bioreceptor molecules on the sensor, there was a notable difference in the graphene channel resistance, which the researchers were able to record.

Results showed that the graphene sensor was capable of detecting 8-OHdG concentrations as low as 0.1 ng mL-1, which is almost five times more sensitive compared with ELISAs. The graphene biosensor was also considerably faster at detecting the target molecules, completing the analysis in a matter of minutes.

Moving forward, the researchers highlight the potential of the biosensor to diagnose and monitor a whole range of diseases as it is quite simple to substitute the specific receptor molecules on the graphene surface.

Co-author of the study Dr Owen Guy said: "Graphene has superb electronic transport properties and has an intrinsically high surface-to-volume ratio, which make it an ideal material for fabricating biosensors.

Now that we've created the first proof-of-concept biosensor using epitaxial graphene, we will look to investigate a range of different biomarkers associated with different diseases and conditions, as well as detecting a number of different biomarkers on the same chip."

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Contact: Michael Bishop michael.bishop@iop.org 01-179-301-032 Institute of Physics @PhysicsNews

Generic epitaxial graphene biosensors for ultrasensitive detection of cancer risk biomarker

An ultrasensitive biosensor made from the wonder material graphene has been used to detect molecules that indicate an increased risk of developing cancer.

More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/09/generic-epitaxial-graphene-biosensors.html

Scanning tunneling microscopy/spectroscopy of picene thin films formed on Ag(111)

The future face of molecular electronics. Thin layer of picene molecules attached to a silver surface maintain their structure and function, demonstrating potential for electronic applications.

WASHINGTON, D.C., September 16, 2014 --The emerging field of molecular electronics could take our definition of portable to the next level, enabling the construction of tiny circuits from molecular components. In these highly efficient devices, individual molecules would take on the roles currently played by comparatively-bulky wires, resistors and transistors.

A team of researchers from five Japanese and Taiwanese universities has identified a potential candidate for use in small-scale electronics: a molecule called picene. In a paper published September 16 in The Journal of Chemical Physics, from AIP Publishing, they characterize the structural and electronic properties of a thin layer of picene on a silver surface, demonstrating the molecule's potential for electronic applications.

Picene's sister molecule, pentacene, has been widely studied because of its high carrier mobility—its ability to quickly transmit electrons, a critical property for nanoscale electronics. But pentacene, made of five benzene molecules joined in a line, breaks down under normal environmental conditions.

Caption: Zigzag picene is more intact than straight pentacene on silver. Credit: Y. Hasegawa/ISSP, U. Tokyo Usage Restrictions: This image may be used only with appropriate caption and credit.

Enter picene, in which these same five benzene rings are instead bonded together in a W shape. This simple structural change alters some of the molecule's other properties: Picene retains pentacene's high carrier mobility, but is more chemically stable and therefore better suited to practical applications.

To test picene's properties when juxtaposed with a metal, as it would be in an electronic device, the researchers deposited a single layer of picene molecules onto a piece of silver. Then, they used scanning tunneling microscopy, an imaging technique that can visualize surfaces at the atomic level, to closely examine the interface between the picene and the silver.

Though previous studies had shown a strong interaction between pentacene and metal surfaces, "we found that the zigzag-shaped picene basically just sits on the silver," said University of Tokyo researcher Yukio Hasegawa. Interactions between molecules can alter their shape and therefore their behavior, but picene's weak connection to the silver surface left its properties intact.

"The weak interaction is advantageous for molecular [electronics] applications because the modification of the properties of molecular thin film by the presence of the [silver] is negligible and therefore [the] original properties of the molecule can be preserved very close to the interface," said Hasegawa.

A successful circuit requires a strong connection between the electronic components—if a wire is frayed, electrons can't flow. According to Hasegawa, picene's weak interactions with the silver allow it to deposit directly on the surface without a stabilizing layer of molecules between, a quality he said is "essential for achieving high-quality contact with metal electrodes."

Because picene displays its high carrier mobility when exposed to oxygen, the researchers hope to investigate its properties under varying levels of oxygen exposure in order to elucidate a molecular mechanism behind the behavior.

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Contact: Jason Socrates Bardi jbardi@aip.org 240-535-4954 Amtoperican Institute of Physics @AIP_Publishing

Scanning tunneling microscopy/spectroscopy of picene thin films formed on Ag(111)

The emerging field of molecular electronics could take our definition of portable to the next level, enabling the construction of tiny circuits from molecular components. In these highly efficient devices, individual molecules would take on the roles currently played by comparatively-bulky wires, resistors and transistors.

More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/09/scanning-tunneling-microscopyspectrosco.html

Functionalized Graphene Nanoribbon Films as a Radiofrequency and Optically Transparent Material

Nanoribbon film keeps glass ice-free. Rice University lab refines deicing film that allows radio frequencies to pass

Rice University scientists who created a deicing film for radar domes have now refined the technology to work as a transparent coating for glass.

The new work by Rice chemist James Tour and his colleagues could keep glass surfaces from windshields to skyscrapers free of ice and fog while retaining their transparency to radio frequencies (RF).

The technology was introduced this month in the American Chemical Society journal Applied Materials and Interfaces.

The material is made of graphene nanoribbons, atom-thick strips of carbon created by splitting nanotubes, a process also invented by the Tour lab. Whether sprayed, painted or spin-coated, the ribbons are transparent and conduct both heat and electricity.

Last year the Rice group created films of overlapping nanoribbons and polyurethane paint to melt ice on sensitive military radar domes, which need to be kept clear of ice to keep them at peak performance. The material would replace a bulky and energy-hungry metal oxide framework.

This scanning electron microscope image shows a closeup of nanoribbon network in Rice University's high-density graphene nanoribbon film. CREDIT: A.O. Raji/Rice University

The graphene-infused paint worked well, Tour said, but where it was thickest, it would break down when exposed to high-powered radio signals. "At extremely high RF, the thicker portions were absorbing the signal," he said. "That caused degradation of the film. Those spots got so hot that they burned up."

The answer was to make the films more consistent. The new films are between 50 and 200 nanometers thick – a human hair is about 50,000 nanometers thick – and retain their ability to heat when a voltage is applied. The researchers were also able to preserve their transparency. The films are still useful for deicing applications but can be used to coat glass and plastic as well as radar domes and antennas.

In the previous process, the nanoribbons were mixed with polyurethane, but testing showed the graphene nanoribbons themselves formed an active network when applied directly to a surface. They were subsequently coated with a thin layer of polyurethane for protection. Samples were spread onto glass slides that were then iced. When voltage was applied to either side of the slide, the ice melted within minutes even when kept in a minus-20-degree Celsius environment, the researchers reported.

"One can now think of using these films in automobile glass as an invisible deicer, and even in skyscrapers," Tour said. "Glass skyscrapers could be kept free of fog and ice, but also be transparent to radio frequencies. It's really frustrating these days to find yourself in a building where your cellphone doesn't work. This could help alleviate that problem."

Tour noted future generations of long-range Wi-Fi may also benefit. "It's going to be important, as Wi-Fi becomes more ubiquitous, especially in cities. Signals can't get through anything that's metallic in nature, but these layers are so thin they won't have any trouble penetrating."

He said nanoribbon films also open a path toward embedding electronic circuits in glass that are both optically and RF transparent.

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Rice graduate student Abdul-Rahman Raji is lead author of the paper. Co-authors are Rice graduate student Errol Samuel and researcher Sydney Salters, a student at Second Baptist School, Houston; Rice alumnus Yu Zhu, now an assistant professor at the University of Akron, Ohio; and Vladimir Volman, an engineer at Lockheed Martin. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of materials science and nanoengineering and of computer science. He is a member of the Richard E. Smalley Institute for Nanoscale Science and Technology.

The Lockheed Martin Aerospace Co. through the LANCER IV Program, the Office of Naval Research's Multidisciplinary University Research Initiative and the Air Force Office of Scientific Research supported the research.

Functionalized Graphene Nanoribbon Films as a Radiofrequency and Optically Transparent Material.

Rice University scientists who created a deicing film for radar domes have now refined the technology to work as a transparent coating for glass.

The new work by Rice chemist James Tour and his colleagues could keep glass surfaces from windshields to skyscrapers free of ice and fog while retaining their transparency to radio frequencies (RF).

More about this image and story at Nanotechnology Today - http://nanotechnologytoday.blogspot.com/2014/09/functionalized-graphene-nanoribbon.html

Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors

Improved Supercapacitors for Super Batteries, Electric Vehicles

Researchers develop novel supercapacitor architecture that provides two times more energy and power compared to supercapacitors commercially available today

RIVERSIDE, Calif. (www.ucr.edu) — Researchers at the University of California, Riverside have developed a novel nanometer scale ruthenium oxide anchored nanocarbon graphene foam architecture that improves the performance of supercapacitors, a development that could mean faster acceleration in electric vehicles and longer battery life in portable electronics.

The researchers found that supercapacitors, an energy storage device like batteries and fuel cells, based on transition metal oxide modified nanocarbon graphene foam electrode could work safely in aqueous electrolyte and deliver two times more energy and power compared to supercapacitors commercially available today.

The foam electrode was successfully cycled over 8,000 times with no fading in performance. The findings were outlined in a recently published paper, “Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors,” in the journal Nature Scientific Reports.

(a) Schematic illustration of the preparation process of RGM nanostructure foam. SEM images of (b–c) as-grown GM foam (d) Lightly loaded RGM, and (e) heavily loaded RGM.

The paper was written by graduate student Wei Wang; Cengiz S. Ozkan, a mechanical engineering professor at UC Riverside’s Bourns College of Engineering; Mihrimah Ozkan, an electrical engineering professor; Francisco Zaera, a chemistry professor; Ilkeun Lee, a researcher in Zaera’s lab; and other graduate students Shirui Guo, Kazi Ahmed and Zachary Favors.

Supercapacitors (also known as ultracapacitors) have garnered substantial attention in recent years because of their ultra-high charge and discharge rate, excellent stability, long cycle life and very high power density.

These characteristics are desirable for many applications including electric vehicles and portable electronics. However, supercapacitors may only serve as standalone power sources in systems that require power delivery for less than 10 seconds because of their relatively low specific energy.

A team led by Cengiz S. Ozkan and Mihri Ozkan at UC Riverside are working to develop and commercialize nanostructured materials for high energy density supercapacitors.

High capacitance, or the ability to store an electrical charge, is critical to achieve higher energy density. Meanwhile, to achieve a higher power density it is critical to have a large electrochemically accessible surface area, high electrical conductivity, short ion diffusion pathways and excellent interfacial integrity. Nanostructured active materials provide a mean to these ends.

“Besides high energy and power density, the designed graphene foam electrode system also demonstrates a facile and scalable binder-free technique for preparing high energy supercapacitor electrodes,” Wang said. “These promising properties mean that this design could be ideal for future energy storage applications.”
Media Contact

Sean Nealon Tel: (951) 827-1287 E-mail: sean.nealon@ucr.edu Twitter: seannealon Additional Contacts

Cengiz Ozkan Tel: 951-827-5016 E-mail: cozkan@engr.ucr.edu

Structural basis for protein-RNA recognition in telomerase

Arizona Sate University scientists take steps to unlock the secrets to the fountain of youth.

ASU scientists, together with collaborators from the Chinese Academy of Sciences in Shanghai, have published today, in Nature Structural and Molecular Biology, a first of its kind atomic level look at the enzyme telomerase that may unlock the secrets to the fountain of youth.

Telomeres and the enzyme telomerase have been in the medical news a lot recently due to their connection with aging and cancer. Telomeres are found at the ends of our chromosomes and are stretches of DNA which protect our genetic data, make it possible for cells to divide, and hold some secrets as to how we age –and also how we get cancer.

An analogy can be drawn between telomeres at the end of chromosomes and the plastic tips on shoelaces: the telomeres keep chromosome ends from fraying and sticking to each other, which would destroy or scramble our genetic information.

Each time one of our cells divides its telomeres get shorter. When they get too short, the cell can no longer divide and it becomes inactive or dies. This shortening process is associated with aging, cancer and a higher risk of death. The initial telomere lengths may differ between individuals. Clearly, size matters!

Caption: This image depicts telomeres on a chromosome and shows the different components required for telomerase activity as researched by professor Julian Chen of Arizona State University and published on 05/04/14 in Nature Structural and Molecular Biology. Credit: Joshua Podlevsky. Usage Restrictions: None

"Telomerase is crucial for telomere maintenance and genome integrity," explains Julian Chen, professor of chemistry and biochemistry at ASU and one of the project's senior authors. "Mutations that disrupt telomerase function have been linked to numerous human diseases that arise from telomere shortening and genome instability."

Chen continues that, "Despite the strong medical applications, the mechanism for telomerase holoenzyme (the most important unit of the telomerase complex) assembly remains poorly understood. We are particularly excited about this research because it provides, for the first time, an atomic level description of the protein-RNA interaction in the vertebrate telomerase complex."

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The other senior author on the project is professor Ming Lei who has recently relocated from the University of Michigan to Shanghai, China to lead a new National Center for Protein Science (affiliated with the Chinese Academy of Sciences).

The Department of Chemistry and Biochemistry at ASU, in the College of Liberal Arts and Sciences, ranks 6th worldwide for research impact (gauged by the average cites per paper across the department for the decade ending in the 2011 International Year of Chemistry) and in the top eight nationally for research publications in Science and Nature. The department's strong record in interdisciplinary research is also evidenced by its 31st national ranking by the NSF in total and federally financed higher education R&D expenditures in chemistry.

This work was supported by grants from the US National Institutes of Health (RO1GM094450 to J.J.-L.C.), Ministry of Science and Technology of China (2013CB910400 to M.L.), and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB08010201 to M.L.).

Contact: Jenny Green jenny.green@asu.edu 480-965-1430 Arizona State University

In Situ Three-Dimensional Synchrotron X-Ray Nanotomography of the (De)lithiation Processes in Tin Anodes

Nanotechnology Today - In Situ Three-Dimensional Synchrotron X-Ray Nanotomography of the (De)lithiation Processes in Tin Anodes.

UPTON, NY—Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have made the first 3D observations of how the structure of a lithium-ion battery anode evolves at the nanoscale in a real battery cell as it discharges and recharges. The details of this research, described in a paper published in Angewandte Chemie, could point to new ways to engineer battery materials to increase the capacity and lifetime of rechargeable batteries.

"This work offers a direct way to look inside the electrochemical reaction of batteries at the nanoscale to better understand the mechanism of structural degradation that occurs during a battery's charge/discharge cycles," said Brookhaven physicist Jun Wang, who led the research. "These findings can be used to guide the engineering and processing of advanced electrode materials and improve theoretical simulations with accurate 3D parameters."

Chemical reactions in which lithium ions move from a negatively charged electrode to a positive one are what carry electric current from a lithium-ion battery to power devices such as laptops and cell phones. When an external current is applied—say, by plugging the device into an outlet—the reaction runs in reverse to recharge the battery.

These images show how the surface morphology and internal microstructure of an individual tin particle changes from the fresh state through the initial lithiation and delithiation cycle (charge/discharge). Most notable are the expansion in overall particle volume during lithiation, and reduction in volume and pulverization during delithiation. The cross-sectional images reveal that delithiation is incomplete, with the core of the particle retaining lithium surround by a layer of pure tin.

Scientists have long known that repeated charging/discharging (lithiation and delithiation) introduces microstructural changes in the electrode material, particularly in some high-capacity silicon and tin-based anode materials. These microstructural changes reduce the battery's capacity—the energy the battery can store—and its cycle life—how many times the battery can be recharged over its lifetime. Understanding in detail how and when in the process the damage occurs could point to ways to avoid or minimize it.

"It has been very challenging to directly visualize the microstructural evolution and chemical composition distribution changes in 3D within electrodes when a real battery cell is going through charge and discharge," said Wang.

A team led by Vanessa Wood of the university ETH Zurich, working at the Swiss Light Source, recently performed in situ 3D tomography at micrometer scale resolution during battery cell charge and discharge cycles.

Achieving nanoscale resolution has been the ultimate goal.

"For the first time," said Wang, "we have captured the microstructural details of an operating battery anode in 3D with nanoscale resolution, using a new in-situ micro-battery-cell we developed for synchrotron x-ray nano-tomography—an invaluable tool for reaching this goal." This advance provides a powerful new source of insight into microstructural degradation.

Developing a working micro battery cell for nanoscale x-ray 3D imaging was very challenging. Common coin-cell batteries aren't small enough, plus they block the x-ray beam when it is rotated.

"The whole micro cell has to be less than one millimeter in size but with all battery components—the electrode being studied, a liquid electrolyte, and the counter electrode—supported by relatively transparent materials to allow transmission of the x-rays, and properly sealed to ensure that the cell can work normally and be stable for repeated cycling," Wang said. The paper explains in detail how Wang's team built a fully functioning battery cell with all three battery components contained within a quartz capillary measuring one millimeter in diameter.

By placing the cell in the path of high-intensity x-ray beams generated at beamline X8C of Brookhaven's National Synchrotron Light Source (NSLS), the scientists produced more than 1400 two-dimensional x-ray images of the anode material with a resolution of approximately 30 nanometers. These 2D images were later reconstructed into 3D images, much like a medical CT scan but with nanometer-scale clarity. Because the x-rays pass through the material without destroying it, the scientists were able to capture and reconstruct how the material changed over time as the cell discharged and recharged, cycle after cycle.

Using this method, the scientists revealed that, "severe microstructural changes occur during the first delithiation and subsequent second lithiation, after which the particles reach structural equilibrium with no further significant morphological changes."

Specifically, the particles making up the tin-based anode developed significant curvatures during the early charge/discharge cycles leading to high stress. "We propose that this high stress led to fracture and pulverization of the anode material during the first delithiation," Wang said. Additional concave features after the first delithiation further induced structural instability in the second lithiation, but no significant changes developed after that point.

"After these initial two cycles, the tin anode shows a stable discharge capacity and reversibility," Wang said.

"Our results suggest that the substantial microstructural changes in the electrodes during the initial electrochemical cycle—called forming in the energy storage industry—are a critical factor affecting how a battery retains much of its current capacity after it is formed," she said. "Typically a battery loses a substantial portion of its capacity during this initial forming process. Our study will improve understanding of how this happens and help us develop better controls of the forming process with the goal of improving the performance of energy storage devices."

Wang pointed out that while the current study looked specifically at a battery with tin as the anode, the electrochemical cell her team developed and the x-ray nanotomography technique can be applied to studies of other anode and cathode materials. The general methodology for monitoring structural changes in three dimensions as materials operate also launches an opportunity to monitor chemical states and phase transformations in catalysts, other types of materials for energy storage, and biological molecules.

The transmission x-ray microscope used for this study will soon move to a full-field x-ray imaging (FXI) beamline at NSLS-II, a world-class synchrotron facility now nearing completion at Brookhaven Lab. This new facility will produce x-ray beams 10,000 times brighter than those at NSLS, enabling dynamic studies of various materials as they perform their particular functions.

Jiajun Wang and Yu-chen Karen Chen-Wiegart are research associates in Wang's research group and performed the work together.

This research was funded as a Laboratory Directed Research and Development project at Brookhaven Lab and by the DOE Office of Science. The transmission x-ray microscope used in this work was built with funding from the American Recovery and Reinvestment Act.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Contact: Karen McNulty Walsh kmcnulty@bnl.gov 631-344-8350 DOE/Brookhaven National Laboratory.

Optical device turns on and off trillions of times per second with switches that measure 200 nanometers

Nanotechnology Today - An ultra-fast and ultra-small optical switch has been invented that could advance the day when photons replace electrons in the innards of consumer products ranging from cell phones to automobiles.

The new optical device can turn on and off trillions of times per second. It consists of individual switches that are only one five-hundredth the width of a human hair (200 nanometers) in diameter. This size is much smaller than the current generation of optical switches and it easily breaks one of the major technical barriers to the spread of electronic devices that detect and control light: miniaturizing the size of ultrafast optical switches.

The new device was developed by a team of scientists from Vanderbilt University, University of Alabama-Birmingham, and Los Alamos National Laboratory and is described in the March 12 issue of the journal Nano Letters.

The ultrafast switch is made out of an artificial material engineered to have properties that are not found in nature. In this case, the “metamaterial” consists of nanoscale particles of vanadium dioxide (VO2) – a crystalline solid that can rapidly switch back and forth between an opaque, metallic phase and a transparent, semiconducting phase – which are deposited on a glass substrate and coated with a “nanomesh” of tiny gold nanoparticles.

Left: Illustration of terahertz optical switches shows the vanadium dioxide nanoparticles coated with a "nanomesh" of smaller gold particles. Right: Scanning electron microscope image of the switches at two resolutions. (Haglund Lab / Vanderbilt)

The scientists report that bathing these gilded nanoparticles with brief pulses from an ultrafast laser generates hot electrons in the gold nanomesh that jump into the vanadium dioxide and cause it to undergo its phase change in a few trillionths of a second.

“We had previously triggered this transition in vanadium dioxide nanoparticles directly with lasers and we wanted to see if we could do it with electrons as well,” said Richard Haglund, Stevenson Professor of Physics at Vanderbilt, who led the study. “Not only does it work, but the injection of hot electrons from the gold nanoparticles also triggers the transformation with one fifth to one tenth as much energy input required by shining the laser directly on the bare VO2.”

Both industry and government are investing heavily in efforts to integrate optics and electronics, because it is generally considered to be the next step in the evolution of information and communications technology. Intel, Hewlett-Packard and IBM have been building chips with increasing optical functionality for the last five years that operate at gigahertz speeds, one thousandth that of the VO2 switch.

“Vanadium dioxide switches have a number of characteristics that make them ideal for optoelectronics applications,” said Haglund. In addition to their fast speed and small size, they:

• Are completely compatible with current integrated circuit technology, both silicon-based chips and the new “high-K dielectric” materials that the semiconductor industry is developing to continue the miniaturization process that has been a major aspect of microelectronics technology development;
• Operate in the visible and near-infrared region of the spectrum that is optimal for telecommunications applications;
• Generate an amount of heat per operation that is low enough so that the switches can be packed tightly enough to make practical devices: about ten trillionths of a calorie (100 femtojoules) per bit.

“Vanadium dioxide’s amazing properties have been known for more than half a century. At Vanderbilt, we have been studying VO2 nanoparticles for the last ten years, but the material has been remarkably successfully at resisting theoretical explanations,” said Haglund. “It is only in the last few years that intensive computational studies have illuminated the physics that underlies its semiconductor-to-metal transition.”

Vanderbilt graduate students Kannatassen Appavoo and Joyeeta Nag fabricated the metamaterial at Vanderbilt; Appavoo joined forces with University of Alabama, Birmingham graduate student Nathaniel Brady and Professor David Hilton to carry out the ultrafast laser experiments with the guidance of Los Alamos National Laboratory staff scientist Rohit Prasankumar and postdoctoral scholar Minah Seo. The theoretical and computational studies that helped to unravel the complex mechanism of the phase transition at the nanoscale were carried out by postdoctoral student Bin Wang and Sokrates Pantelides, University Distinguished Professor of Physics and Engineering at Vanderbilt.

The university researchers were supported by Defense Threat-Reduction Agency grant HDTRA1-0047, U.S. Department of Energy grant DE-FG02-01ER45916, U.S. Department of Education GAANN Fellowship P200A090143 and National Science Foundation grant DMR-1207241. Portions of the research were performed at the Vanderbilt Institute of Nanoscale Science and Engineering in facilities renovated with NSF grant ARI-R2 DMR-0963361, at the Center for Integrated Nanotechnologies at Los Alamos National Laboratory under USDOE contract DE-AC52-06NA25396) and at Sandia National Laboratories under USDOE contract DE-AC04-94AL85000).

Contact: David Salisbury, (615) 322-NEWS david.salisbury@vanderbilt.edu Vanderbilt University

Nanotechnology could turn shrubbery into supercharged energy producers or sensors for explosives

Nanotechnology Today - Plants have many valuable functions: They provide food and fuel, release the oxygen that we breathe, and add beauty to our surroundings. Now, a team of MIT researchers wants to make plants even more useful by augmenting them with nanomaterials that could enhance their energy production and give them completely new functions, such as monitoring environmental pollutants.

In a new Nature Materials paper, the researchers report boosting plants’ ability to capture light energy by 30 percent by embedding carbon nanotubes in the chloroplast, the plant organelle where photosynthesis takes place. Using another type of carbon nanotube, they also modified plants to detect the gas nitric oxide.

Together, these represent the first steps in launching a scientific field the researchers have dubbed “plant nanobionics.”

Researchers use a near infrared microscope to read the output of carbon nanotube sensors embedded in an Arabidopsis Thaliana plant. Photo Bryce Vickmark

“Plants are very attractive as a technology platform,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering and leader of the MIT research team. “They repair themselves, they’re environmentally stable outside, they survive in harsh environments, and they provide their own power source and water distribution.”

Strano and the paper’s lead author, postdoc and plant biologist Juan Pablo Giraldo, envision turning plants into self-powered, photonic devices such as detectors for explosives or chemical weapons. The researchers are also working on incorporating electronic devices into plants. “The potential is really endless,” Strano says.

Supercharged photosynthesis

The idea for nanobionic plants grew out of a project in Strano’s lab to build self-repairing solar cells modeled on plant cells. As a next step, the researchers wanted to try enhancing the photosynthetic function of chloroplasts isolated from plants, for possible use in solar cells.

Chloroplasts host all of the machinery needed for photosynthesis, which occurs in two stages. During the first stage, pigments such as chlorophyll absorb light, which excites electrons that flow through the thylakoid membranes of the chloroplast. The plant captures this electrical energy and uses it to power the second stage of photosynthesis — building sugars.

Chloroplasts can still perform these reactions when removed from plants, but after a few hours, they start to break down because light and oxygen damage the photosynthetic proteins. Usually plants can completely repair this kind of damage, but extracted chloroplasts can’t do it on their own.

To prolong the chloroplasts’ productivity, the researchers embedded them with cerium oxide nanoparticles, also known as nanoceria. These particles are very strong antioxidants that scavenge oxygen radicals and other highly reactive molecules produced by light and oxygen, protecting the chloroplasts from damage.

The researchers delivered nanoceria into the chloroplasts using a new technique they developed called lipid exchange envelope penetration, or LEEP. Wrapping the particles in polyacrylic acid, a highly charged molecule, allows the particles to penetrate the fatty, hydrophobic membranes that surrounds chloroplasts. In these chloroplasts, levels of damaging molecules dropped dramatically.

Using the same delivery technique, the researchers also embedded semiconducting carbon nanotubes, coated in negatively charged DNA, into the chloroplasts. Plants typically make use of only about 10 percent of the sunlight available to them, but carbon nanotubes could act as artificial antennae that allow chloroplasts to capture wavelengths of light not in their normal range, such as ultraviolet, green, and near-infrared.

With carbon nanotubes appearing to act as a “prosthetic photoabsorber,” photosynthetic activity — measured by the rate of electron flow through the thylakoid membranes — was 49 percent greater than that in isolated chloroplasts without embedded nanotubes. When nanoceria and carbon nanotubes were delivered together, the chloroplasts remained active for a few extra hours.

The researchers then turned to living plants and used a technique called vascular infusion to deliver nanoparticles into Arabidopsis thaliana, a small flowering plant. Using this method, the researchers applied a solution of nanoparticles to the underside of the leaf, where it penetrated tiny pores known as stomata, which normally allow carbon dioxide to flow in and oxygen to flow out. In these plants, the nanotubes moved into the chloroplast and boosted photosynthetic electron flow by about 30 percent.

Yet to be discovered is how that extra electron flow influences the plants’ sugar production. “This is a question that we are still trying to answer in the lab: What is the impact of nanoparticles on the production of chemical fuels like glucose?” Giraldo says.

Lean green machines

The researchers also showed that they could turn Arabidopsis thaliana plants into chemical sensors by delivering carbon nanotubes that detect the gas nitric oxide, an environmental pollutant produced by combustion.

Strano’s lab has previously developed carbon nanotube sensors for many different chemicals, including hydrogen peroxide, the explosive TNT, and the nerve gas sarin. When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube’s fluorescence.

“We could someday use these carbon nanotubes to make sensors that detect in real time, at the single-particle level, free radicals or signaling molecules that are at very low-concentration and difficult to detect,” Giraldo says.

“This is a marvelous demonstration of how nanotechnology can be coupled with synthetic biology to modify and enhance the function of living organisms — in this case, plants,” says James Collins, a professor of biomedical engineering at Boston University who was not involved in the research. “The authors nicely show that self-assembling nanoparticles can be used to enhance the photosynthetic capacity of plants, as well as serve as plant-based biosensors and stress reducers.”

By adapting the sensors to different targets, the researchers hope to develop plants that could be used to monitor environmental pollution, pesticides, fungal infections, or exposure to bacterial toxins. They are also working on incorporating electronic nanomaterials, such as graphene, into plants.

“Right now, almost no one is working in this emerging field,” Giraldo says. “It’s an opportunity for people from plant biology and the chemical engineering nanotechnology community to work together in an area that has a large potential.”

The research was funded primarily by the U.S. Department of Energy.

Contact: Sarah McDonnell s_mcd@mit.edu 617-253-8923 Massachusetts Institute of Technology.

Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces

Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces.

A big step in the development of next-generation fuel cells and water-alkali electrolyzers has been achieved with the discovery of a new class of bimetallic nanocatalysts that are an order of magnitude higher in activity than the target set by the U.S. Department of Energy (DOE) for 2017.

The new catalysts, hollow polyhedral nanoframes of platinum and nickel, feature a three-dimensional catalytic surface activity that makes them significantly more efficient and far less expensive than the best platinum catalysts used in today’s fuel cells and alkaline electrolyzers. This research was a collaborative effort between DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory (ANL).

“We report the synthesis of a highly active and durable class of electrocatalysts by exploiting the structural evolution of platinum/nickel bimetallic nanocrystals,” says Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division, who led the discovery of these new catalysts. “Our catalysts feature a unique hollow nanoframe structure with three-dimensional platinum-rich surfaces accessible for catalytic reactions.

By greatly reducing the amount of platinum needed for oxygen reduction and hydrogen evolution reactions, our new class of nanocatalysts should lead to the design of next-generation catalysts with greatly reduced cost but significantly enhanced activities.”

These schematic illustrations and corresponding transmission electron microscope images show the evolution of platinum/nickel from polyhedra to dodecahedron nanoframes with platinum-enriched skin.

Yang, who also holds appointments with the University of California (UC) Berkeley and the Kavli Energy NanoSciences Institute at Berkeley, is one of the corresponding authors of a paper in Science that describes this research. The paper is titled “Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces.” The other corresponding author is Vojislav Stamenkovic, a chemist with ANL’s Materials Science Division, who led the testing of this new class of electrocatalysts.

Fuel cells and electrolyzers can help meet the ever-increasing demands for electrical power while substantially reducing the emission of carbon and other atmospheric pollutants. These technologies are based on either the oxygen reduction reaction (fuel cells), or the hydrogen evolution reaction (electrolyzers). Currently, the best electrocatalyst for both reactions consists of platinum nanoparticles dispersed on carbon. Though quite effective, the high cost and limited availability of platinum makes large-scale use of this approach a major challenge for both stationary and portable electrochemical applications.

“Intense research efforts have been focused on developing high-performance electrocatalysts with minimal precious metal content and cost,” Yang says. “In an earlier study, the ANL scientists showed that forming a nano-segregated platinum skin over a bulk single-crystal platinum/nickel alloy enhances catalytic activity but the materials cannot be easily integrated into electrochemical devices. We needed to be able to reproduce the outstanding catalytic performance of these materials in nanoparticulates that offered high surface areas.”

Yang and his colleagues at Berkeley accomplished this by transforming solid polyhedral bimetallic nanoparticles of platinum and nickel into hollow nanoframes. The solid polyhedral nanoparticles are synthesized in the reagent oleylamine, then soaked in a solvent, such as hexane or chloroform, for either two weeks at room temperature, or for 12 hours at 120 degrees Celsius. The solvent, with its dissolved oxygen, causes a natural interior erosion to take place that results in a hollow dodecahedron nanoframe. Annealing these dodecahedron nanoframes in argon gas creates a platinum skin on the nanoframe surfaces.

“In contrast to other synthesis procedures for hollow nanostructures that involve corrosion induced by harsh oxidizing agents or applied potential, our method proceeds spontaneously in air,” Yang says. “The open structure of our platinum/nickel nanoframes addresses some of the major design criteria for advanced nanoscale electrocatalysts, including, high surface-to-volume ratio, 3-D surface molecular accessibility, and significantly reduced precious metal utilization.”

In electrocatalytic performance tests at ANL, the platinum/nickel nanoframes when encapsulated in an ionic liquid exhibited a 36-fold enhancement in mass activity and 22-fold enhancement in specific activity compared with platinum nanoparticles dispersed on carbon for the oxygen reduction reaction. These nanoframe electrocatalysts, modified by electrochemically deposited nickel hydroxide, were also tested for the hydrogen evolution reaction and showed that catalytic activity was enhanced by an order-of-magnitude over platinum/carbon catalysts.

“Our results demonstrate the beneficial effects of the hollow nanoframe’s open architecture and surface compositional profile,” Yang says. “Our technique for making these hollow nanoframes can be readily applied to other multimetallic electrocatalysts or gas phase catalysts. I am quite optimistic about its commercial viability.”

Other co-authors of the Science paper in addition to Yang and Stamenkovic are Chen Chen, Yijin Kang, Ziyang Huo, Zhongwei Zhu, Wenyu Huang, Huolin Xin, Joshua Snyder, Dongguo Li, Jeffrey Herron, Manos Mavrikakis, Miaofang Chi, Karren More, Yadong Li, Nenad Markovic and Gabor Somorjai.

This research was funded by the DOE Office of Science.

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

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 www.anl.gov

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Contact: Lynn Yarris lcyarris@lbl.gov 510-486-5375 DOE/Lawrence Berkeley National Laboratory

Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms

Integrated circuit-based electrochemical sensor for spatially resolved detection of redox-active metabolites in biofilms.

New York, NY— A research team led by Ken Shepard, professor of electrical engineering and biomedical engineering at Columbia Engineering, and Lars Dietrich, assistant professor of biological sciences at Columbia University, has demonstrated that integrated circuit technology, the basis of modern computers and communications devices, can be used for a most unusual application—the study of signaling in bacterial colonies.

They have developed a chip based on complementary metal-oxide-semiconductor (CMOS) technology that enables them to electrochemically image the signaling molecules from these colonies spatially and temporally. In effect, they have developed chips that "listen" to bacteria.

"This is an exciting new application for CMOS technology that will provide new insights into how biofilms form," says Shepard. "Disrupting biofilm formation has important implications in public health in reducing infection rates."

Caption: The development of colony biofilms by Pseudomonas aeruginosa is affected by redox-active compounds called phenazines. A phenazine-null mutant forms a hyperwrinkled colony with prominent spokes, while wild-type colonies are more constrained and smooth.

Credit: Hassan Sakhtah, Columbia University. Usage Restrictions: None

The researchers, who include PhD students Dan Bellin (electrical engineering) and Hassan Sakhtah (biology), say that this is the first time integrated circuits have been used for such an application—imaging small molecules electrochemically in a multicellular structure. While optical microscopy techniques remain paramount for studying biological systems (using photons allows for relatively non-invasive interaction to the biological system being studied), they cannot directly detect critical components of physiology, such as primary metabolism and signaling factors.

The team thought there might be a better way to directly detect small molecules through techniques that employ direct transduction to electrons, without using photos as an intermediary. They made an integrated circuit, a chip that, Shepard says, is an "'active' glass slide, a slide that not only forms a solid-support for the bacterial colony but also 'listens' to the bacteria as they talk to each other."

Cells, Dietrich explains, mediate their physiological activities using secreted molecules. The team looked specifically at phenazines, which are secreted metabolites that control gene expression. Their study found that the bacterial colonies produced a phenazine gradient that, they say, is likely to be of physiological significance and contribute to colony morphogenesis.

"This is a big step forward," Dietrich continues. "We describe using this chip to 'listen in' on conversations taking place in biofilms, but we are also proposing to use it to interrupt these conversations and thereby disrupt the biofilm. In addition to the pure science implications of these studies, a potential application of this would be to integrate such chips into medical devices that are common sites of biofilm formation, such as catheters, and then use the chips to limit bacterial colonization."

The next step for the team will be to develop a larger chip that will enable larger colonies to be imaged at higher spatial and temporal resolutions.

"This represents a new and exciting way in which solid-state electronics can be used to study biological systems," Shepard adds. "This is one of the many emerging ways integrated circuit technology is having impact in biotechnology and the life sciences."

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The study was supported by the National Institutes of Health and the National Science Foundation.

Contact: Holly Evarts holly.evarts@columbia.edu 347-453-7408 Columbia University School of Engineering and Applied Science

High Ampacity Power Cables of Tightly Packed and Aligned Carbon Nanotubes

On a pound-per-pound basis, carbon nanotube-based fibers invented at Rice University have greater capacity to carry electrical current than copper cables of the same mass, according to new research.

While individual nanotubes are capable of transmitting nearly 1,000 times more current than copper, the same tubes coalesced into a fiber using other technologies fail long before reaching that capacity.

But a series of tests at Rice showed the wet-spun carbon nanotube fiber still handily beat copper, carrying up to four times as much current as a copper wire of the same mass.

That, said the researchers, makes nanotube-based cables an ideal platform for lightweight power transmission in systems where weight is a significant factor, like aerospace applications.

Scanning electron microscope images show typical carbon nanotube fibers created at Rice University and broken into two by high-current-induced Joule heating. Rice researchers broke the fibers in different conditions – air, argon, nitrogen and a vacuum – to see how well they handled high current. The fibers proved overall to be better at carrying electrical current than copper cables of the same mass. (Credit: Kono Lab/Rice University)

The analysis led by Rice professors Junichiro Kono and Matteo Pasquali appeared online this week in the journal Advanced Functional Materials. Just a year ago the journal Science reported that Pasquali's lab, in collaboration with scientists at the Dutch firm Teijin Aramid, created a very strong conductive fiber out of carbon nanotubes.

Present-day transmission cables made of copper or aluminum are heavy because their low tensile strength requires steel-core reinforcement.

Scientists working with nanoscale materials have long thought there's a better way to move electricity from here to there. Certain types of carbon nanotubes can carry far more electricity than copper. The ideal cable would be made of long metallic "armchair" nanotubes that would transmit current over great distances with negligible loss, but such a cable is not feasible because it's not yet possible to manufacture pure armchairs in bulk, Pasquali said.

In the meantime, the Pasquali lab has created a method to spin fiber from a mix of nanotube types that still outperforms copper. The cable developed by Pasquali and Teijin Aramid is strong and flexible even though at 20 microns wide, it's thinner than a human hair.

Pasquali turned to Kono and his colleagues, including lead author Xuan Wang, a postdoctoral researcher at Rice, to quantify the fiber's capabilities.

Pasquali said there has been a disconnect between electrical engineers who study the current carrying capacity of conductors and materials scientists working on carbon nanotubes. "That has generated some confusion in the literature over the right comparisons to make," he said. "Jun and Xuan really got to the bottom of how to do these measurements well and compare apples to apples."

The researchers analyzed the fiber's "current carrying capacity" (CCC), or ampacity, with a custom rig that allowed them to test it alongside metal cables of the same diameter. The cables were tested while they were suspended in the open air, in a vacuum and in nitrogen or argon environments.

Electric cables heat up because of resistance. When the current load exceeds the cable's safe capacity, they get too hot and break. The researchers found nanotube fibers exposed to nitrogen performed best, followed by argon and open air, all of which were able to cool through convection. The same nanotube fibers in a vacuum could only cool by radiation and had the lowest CCC.

"The outcome is that these fibers have the highest CCC ever reported for any carbon-based fibers," Kono said. "Copper still has better resistivity by an order of magnitude, but we have the advantage that carbon fiber is light. So if you divide the CCC by the mass, we win."

Kono plans to further investigate and explore the fiber's multifunctional aspects, including flexible optoelectronic device applications.

Pasquali suggested the thread-like fibers are light enough to deliver power to aerial vehicles. "Suppose you want to power an unmanned aerial vehicle from the ground," he mused. "You could make it like a kite, with power supplied by our fibers. I wish Ben Franklin were here to see that!"

The paper's co-authors are Rice alumnus Natnael Behabtu and graduate students Colin Young and Dmitri Tsentalovich. Kono is a professor of electrical and computer engineering, of physics and astronomy, and of materials science and nanoengineering. Pasquali is a professor of chemical and biomolecular engineering, chemistry, and materials science and nanoengineering. Tsentalovich, Kono and Pasquali are members of Rice's Richard E. Smalley Institute for Nanoscale Science and Technology.

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The research was supported by the Department of Energy, the National Science Foundation, the Robert A. Welch Foundation, Teijin Aramid BV, the Air Force Office of Scientific Research and the Department of Defense National Defense Science and Engineering Graduate Fellowship.

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy.

With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 2 for "best value" among private universities by Kiplinger's Personal Finance.

Contact: David Ruth david@rice.edu 713-348-6327 Rice University