Other materials science stories that may be of interestPublished on August 27th, 2012 | By: email@example.com
Some developments worth reading about:
Though the concept of high temperature superconductors is more than two decades old, finding and controlling the right materials has been a challenge. Now Yoram Dagan of Tel Aviv University’s Department of Physics and Center for Nanoscience and Nanotechnology has discovered an innovative way to manipulate superconducting materials. By manipulating different types of light, including UV and visible light, Dagan and his fellow researchers are able to alter the critical temperatures of superconducting materials. This finding adds to a growing toolbox for controlling and improving the technology. The research has been published in Angewandte Chemie and featured in Nature Nanotechnology. In the lab, they put a thin layer, one organic molecule thick, atop a superconducting film, approximately 50 nanometers thick. When researchers shined a light on these molecules, the molecules stretched and changed shape, altering the properties of the superconducting film-most importantly, altering the critical temperature at which the material acted as a superconductor. The researchers tested three separate molecules. The first was able to increase the critical temperature of the superconducting film. With the second molecule, they found that shining an ultraviolet light heightened the material’s critical temperature, while visible light lowered it. Finally, with the third molecule, they found that simply by turning a light on, critical temperature was raised-and lowered again when the light was switched off.
Researchers have created a new type of biosensor that can detect minute concentrations of glucose in saliva, tears and urine and might be manufactured at low cost because it does not require many processing steps to produce. “Most sensors typically measure glucose in blood,” says Jonathan Claussen, a former Purdue University doctoral student and now a research scientist at the Naval Research Laboratory. “Many in the literature aren’t able to detect glucose in tears and the saliva. What’s unique is that we can sense in all four different human serums: the saliva, blood, tears and urine. And that hasn’t been shown before.” The sensor has three main parts: layers of graphene nanosheets resembling tiny rose petals; platinum nanoparticles; and the enzyme glucose oxidase. Each petal contains a few layers of stacked graphene. The edges of the petals have dangling, incomplete chemical bonds, defects where platinum nanoparticles can attach. Electrodes are formed by combining the nanosheet petals and platinum nanoparticles. Then the glucose oxidase attaches to the platinum nanoparticles. The enzyme converts glucose to peroxide, which generates a signal on the electrode. “The good thing about these petals is that they can be grown on just about any surface, and we don’t need to use any of these steps, so it could be ideal for commercialization,” says Purdue doctoral student Anurag Kumar.
Fueling nuclear reactors with uranium harvested from the ocean could become more feasible because of a material developed by a team led by the DOE’s Oak Ridge National Lab. The combination of ORNL’s high-capacity reusable adsorbents and a Florida company’s high-surface-area polyethylene fibers creates a material that can rapidly, selectively and economically extract valuable and precious dissolved metals from water. The material, HiCap, vastly outperforms today’s best adsorbents, which perform surface retention of solid or gas molecules, atoms or ions. HiCap also effectively removes toxic metals from water, according to results verified by researchers at Pacific Northwest National Lab. “We have shown that our adsorbents can extract five- to seven-times more uranium at uptake rates seven-times faster than the world’s best adsorbents,” says Chris Janke, one of the inventors and a member of ORNL’s Materials Science and Technology Division. “Our HiCap adsorbents are made by subjecting high-surface area polyethylene fibers to ionizing radiation, then reacting these pre-irradiated fibers with chemical compounds that have a high affinity for selected metals.” After the processing, scientists can place HiCap adsorbents in water containing the targeted material, which is quickly and preferentially trapped. Scientists then remove the adsorbents from the water and the metals are readily extracted using a simple acid elution method. The adsorbent can then be regenerated and reused after being conditioned with potassium hydroxide. Results were presented today at the fall meeting of the American Chemical Society in Philadelphia.
(EE Times) MC10, a Cambridge, Mass., startup specializing in flexible electronics, has signed a one year contract with the Army to develop and test solar cell technology for military use. The technology will take the form of wearable solar panels built into military personnel’s clothing to power up America’s GIs, while decreasing the number of battery packs lugged around. MC10 specializes in re-engineering rigid electronics into flexible forms and has made significant strides in creating human vital stat sensors which have been successfully applied to surgical patients and athletes alike. The sensors are typically a 1-inch flexible patch that tracks temperature, heart rate and hydration. For the necessary flexibility required for solar powered clothing, MC10 uses flexible microgrids of solar cells, connected by gold ribbon wrapped in a soft conducting polymer. The wearable solar cells harness the power of gallium arsenide, the light harvesting metal compound built into high-efficiency solar panels found on rooftops.
A new class of organic materials developed at Northwestern University boasts a very attractive but elusive property: ferroelectricity. The crystalline materials also have a great memory, which could be very useful in computer and cellphone memory applications, including cloud computing. A team of organic chemists discovered they could create very long crystals with desirable properties using just two small organic molecules that are extremely attracted to each other. The attraction between the two molecules causes them to self assemble into an ordered network, order that is needed for a material to be ferroelectric. The starting compounds are simple and inexpensive, making the lightweight materials scalable and very promising for technology applications. In contrast, conventional ferroelectric materials—special varieties of polymers and ceramics—are complex and expensive to produce. The Northwestern materials can be made quickly and are very versatile. The study is published in the journal Nature. These new supramolecular materials derive their properties from the specific interaction, repeated over and over again between two small alternating organic molecules, not from the molecules themselves. The two complementary molecules interact electronically and so strongly that they come close together and form very long crystals. This highly ordered 3D network is based on hydrogen bonds.
A team of scientists led by Carnegie Institution for Science’s Lin Wang has observed a new form of very hard carbon clusters, which are unusual in their mix of crystalline and disordered structure. The material is capable of indenting diamond. This finding has potential applications for a range of mechanical, electronic, and electrochemical uses. The work is published in Science. Wang’s team started with carbon-60 cages. An organic xylene solvent was put into the spaces between the balls and formed a new structure. They then applied pressure to this combination of carbon cages and solvent, to see how it changed under different stresses. At relatively low pressure, the carbon-60’s cage structure remained. But, as the pressure increased, the cage structures started to collapse into more amorphous carbon clusters. However, the amorphous clusters still occupy their original sites, forming a lattice structure. The team discovered that there is a narrow window of pressure, about 320,000 times the normal atmosphere, under which this new structured carbon is created and does not bounce back to the cage structure when pressure is removed. This material was capable of indenting the diamond anvil used in creating the high-pressure conditions. If the solvent used to prepare the new form of carbon is removed by heat treatment, the material loses its lattice periodicity, indicating that the solvent is crucial for maintaining the chemical transition that underlies the new structure. Because there are many similar solvents, it is theoretically possible that an array of similar, but slightly different, carbon lattices could be created using this pressure method.
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