NEWS FROM THE WORLD OF MATERIALS

Visit the Materials360^® Plus and the Materials News pages on the MRS Website for continually updated research news and features

Image in Focus

Clandestine Attraction of a Transparent Ceramic
The valence electron density of the hexagonal layered transparent conductor indium zinc oxide, calculated within density functional theory and visualized using VESTA. Additional color rendering was performed using Photoshop. 
[Submitted by Aron Walsh, National Renewable Energy Laboratory, Golden, Colorado, to theScience as Art competition at the 2008 MRS Fall Meeting]

[We invite you to submit your images to the Editor for possible inclusion in this feature]

Materials in Focus

Self-healing concrete for safer, more durable infrastructure
A recently developed concrete material can heal itself when it cracks. Self-healing is possible because the material is designed to bend and crack in narrow hairlines rather than break and split in wide gaps, as traditional concrete behaves. In the lab, self-healed specimens recovered most if not all of their original strength after researchers subjected them to a 3 percent tensile strain.

Bendy, twistable polymer could improve oil refining
A bendy polymer that can recognise and separate aromatic hydrocarbons from aliphatic mixtures has been developed. Researchers built the porous 3D polymer using a flexible 1D polymer made from metal units bound to salen ligands. The resulting structure bends and twists when its polymer chains stretch, triggered by guest molecules entering or leaving the structure.

Ferroelectric oxide formed directly on silicon
Researchers have been able to add ferroelectric capability to an oxide material used in common computer transistors. They took strontium titanate, a normally non-ferroelectric variant of the ferroelectric material , and deposited it on silicon in such a way that the silicon squeezed it into a ferroelectric state. They grew coherently strained strontium titanate (SrTiO₃) films via oxide molecular beam epitaxy in direct contact with silicon, with no interfacial silicon dioxide. They were able to observe ferroelectricity in these ultrathin SrTiO₃ layers by means of piezoresponse force microscopy.

Energy Focus

Potassium improves photochemical characteristics of titania nanotubes
A research team has discovered, serendipitously, that a residue of a process used to build arrays of titania nanotubes—a residue that wasn't even noticed before this—plays an important role in improving the performance of the nanotubes in solar cells that produce hydrogen gas from water. Their results indicate that by controlling the deposition of potassium on the surface of the nanotubes, they can achieve significant energy savings in a promising new alternate energy system. When the research team compared the performance of potassium-bearing nanotubes to similar arrays deliberately prepared without potassium, the former required only about one-third the electrical energy to produce the same amount of hydrogen as an equivalent array of potassium-free nanotubes.

Carbene catalyst converts carbon dioxide from air to methanol 
A novel reaction scheme has been developed by which CO₂ can be efficiently converted into methanol under very mild conditions. The reaction is based on an N-heterocyclic carbene catalyst and a silane as the reducing agent. The basic framework of an N-heterocyclic carbene is a five-membered ring made of two nitrogen and three carbon atoms. Instead of having the usual four bonds, one of these carbon atoms only has two. The two electrons left over in the form of a lone pair, which makes this species highly reactive—reactive enough to attack CO₂.

Nano Focus

Nano-mechanical sensors wired by photonics 
Researchers have demonstrated silicon-based nanocantilevers, smaller than the wavelength of light, that operate on photonic principles eliminating the need for electric transducers and expensive laser setups in nanoelectromechanical system (NEMS) devices. The new study demonstrates how NEMS can be improved by using integrated photonics to sense the cantilever motion. The system can detect deflections in the nano-cantilever sensors as small as 0.0001 Angstroms.

Universal transduction scheme using dielectric forces for NEMS
Chemical analysts today are expected to track down even single molecules. Researchers have now constructed a system of nanostrings made of non-conducting material, where each string can be electrically excited separately. Thousands of these strings can be produced on a small chip. One of the devices that could be created with this system is a highly sensitive "artificial nose" that detects various molecules – pollutants for example – individually.

A zippy route to nanoribbons
Two teams of researchers working independently have reported a new strategy for forming graphene nanoribbons, by longitudinally "unzipping" carbon nanotubes. Compared with other procedures for preparing graphene nanoribbons, which are narrow and elongated one-atom-thick strips of carbon, the new routes are simpler, less expensive, and potentially better suited to making bulk quantities of the material. The first team treated the nanotubes with sulfuric acid and potassium permanganate. The second team partially embedded the nanotubes in a polymer film to hold them in place and then etched them with an argon plasma.

Bio Focus

Spider silk toughness greatly increased by metal infiltration 
Researchers have used atomic-layer deposition to pulse zinc, titanium, and aluminum ions into spider silk. The resulting materials show greatly enhanced toughness over natural spider silk and could be used to make protective clothing or even new structural materials. The protein-metal composites are tougher than the sum of their parts.

AFM reveals hidden differences between normal and cancerous cells 
Using an atomic force microscope, researchers have identified an important difference in the surface properties of normal and cancerous cells. They found that normal cells have "brushes" of one length on their surface while cancerous cells have two brush lengths that have very different densities to the brushes on normal cells. This important variation means that cancer and normal cells may interact very differently with nanoparticles, something that could be exploited for cancer detection and treatment via drug delivery.

Posted in: