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Image in Focus
Credit: X.-M. Sui and H.D. Wagner, Weizmann Institute of Science
Tough Nanocomposite
TEM image of stretched poly(methyl methacrylate) (PMMA)/single-wall carbon nanotube (SWCNT) electrospun fibers. Unusually large deformation was observed in PMMA electrospun fibers under tension when multiwall or single-wall carbon nanotubes were included as a second phase in the fibers.[Submitted by H. Daniel Wagner, Weizmann Institute of Science]
Reference: Tough nanocomposites: The role of carbon nanotube type, X.-M. Sui, H.D. Wagner,Nano Letters, 9 (4) (2009), 1423-1426.
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Materials in Focus
Crystal/liquid interface made visible
Researchers have captured the first images of what's actually happening in the fuzzy area of the crystal/liquid interface. The data make the waves between the two states of matter visible for the first time. The theory that surface waves move along the crystal/liquid boundary – the intrinsic interface – dates back to 1965 and is well established. The researchers found a way to take a picture of the intrinsic interface, measure it, and show how it fluctuates over time. The visual evidence shows that the fuzzy region between the two states is extremely narrow.
Randomness reigns in crystalline order
 
Credit: Phys. Rev. Lett. |
Other things being equal, nature favors more randomness, but sometimes an orderly pattern lets a system increase its total disorder. In a new report, researchers show that a large group of spheres favors a crystalline arrangement over a disorderly arrangement, even when the spheres are linked into polymer-like chains. They simulated an idealized model in which spheres in the same chain must stay in contact but can otherwise move freely.
Energy Focus
New catalyst for methane to methanol conversion
Scientists have invented a new solid catalyst for converting methane to methanol. The system could eventually provide a smaller-scale alternative to current commercial methods for methanol production from natural gas, which rely on big, expensive industrial facilities for steam reforming of methane to syngas - typically so-called 'megamethanol' plants where there is a large supply of natural gas. Natural gas is often found in smaller quantities in remote locations where its transportation cannot be justified economically.One promising technique used a platinum-based catalyst developed by Periana et al. in which platinum is co-ordinated to a bipyrimidine. This is then dissolved in fuming sulfuric acid - oleum - to carry out the oxidation, which involves sulfur trioxide. However, the expensive platinum proved difficult to recover from solution. Now, a team has created what is in effect a solid Periana catalyst which appears to be recyclable with no loss of platinum. This is a highly porous carbon-nitrogen polymer, with a very similar structural motif to the Periana catalyst, with platinum incorporated into the structure.
Nano Focus
New carbon form, multilayer epitaxial graphene, created
Researchers claim to have found a new form of carbon, made from layers of graphene stacked on top of one another in such a way that each layer is electronically independent. The researchers suggest that the material, dubbed multilayer epitaxial graphene (MEG), could be used in carbon electronics instead of costly single and double layer graphene sheets. The graphene layers were grown from a silicon carbide substrate in such a way that each layer is rotated by 30 degrees with respect to the lower layers. This MEG differs from naturally occurring graphite where each layer is rotated by 60 degrees with respect to the lower layers.
Nanotubes used as electron emitters in x-ray generator
Carbon nanotubes are at the heart of a new x-ray machine that is slated for clinical tests later this year. The machine could perform much better than those used today for x-ray imaging and cancer therapy, say the researchers who developed the technology. They have shown that it speeds up organ imaging, takes sharper images, and could increase the accuracy of radiotherapy so it doesn't harm normal tissue. Instead of a single tungsten emitter, the team uses an array of vertical carbon nanotubes that serve as hundreds of tiny electron guns. While conventionally used tungsten requires time to warm up, the nanotubes emit electrons from their tips instantly when a voltage is applied to them.
Gold nanostars used for gyromagnetic imaging optical contrast
Researchers report details of a new gyromagnetic imaging technique that exploits the light scatter from rotating gold nanoparticles to suppress the background noise associated with optical interrogations of biological tissue. The gold "nanostars", which measure about 100 nm tip to tip, contain an iron-oxide core that causes them to spin when exposed to a rotating magnet. The arms of the nanostar reflect incident light to a camera in effect, twinkling at rates that can be precisely controlled by the speed of the rotating magnetic field. It's the unique signature of the twinkling nanostars that enables them to be picked out from a field of stationary particles, some of which may be brighter than the nanostars.
Bio Focus
Silicon nanowires get biological impulses
Credit: LLNL |
Using silicon wires just 20-40 nm thick, scientists have managed to send and receive signals through a lipid membrane similar to the one that surrounds a living cell. This work could help improve the integration of biological and electronic systems — allowing, for example, the development of electrical probes that can monitor what is happening inside a cell without damaging the cells or disrupting internal biological processes. Combining biological and man-made components has proved tricky. In particular, no one has been able to use electronic devices to control the flow of ions through biological membranes, a crucial process in cell communication. The researchers have been able to accomplish just that by using a silicon nanowire embedded inside a lipid-bilayer membrane. The nanowire was also able to convert the flow of ions across the membrane into an electric signal.
Laser nanopulse triggers protein crystallization
A technique that creates crystals on demand using laser pulses could make it easier to prepare the high-quality crystals needed to study protein structure. Scientists need crystals of proteins and other chemicals to analyse their atomic structure using X-rays, while many industrial processes rely on triggering crystal formation at precisely the right time and place during the production of drugs and other useful compounds. The trickiest part of crystallization is controlling the very first step, where molecules begin to aggregate in an ordered way around a nucleation point, such as a seed crystal or speck of dust. Researchers have now shown that pulses of low-energy laser light can trigger the formation of crystals from a solution of a chemical held within a gel. This enables them to control exactly when and where crystals form without the need for an added nucleation point.
DNA folded into complex nanoscale shapes
Credit: Science |
One way to control shape during the assembly of an object is to design in stresses that cause a planned amount of deformation. Researchers have now designed DNA helix bundles, arranged in honeycomb lattices, in which some of the helices have insertions or deletions relative to the other helices in the bundles. The stresses help the bundles assemble into objects on the scale of tens of nanometers. Both the direction and degree of bending could be controlled, and curvatures as tight as 6 nanometers achieved. Complex shapes, such as square-toothed gears, could be created by combining multiple curved elements.
