Volume 8 Issue 11, November 2009

Field-effect transistors, regardless of whether they use an organic or an inorganic semiconductor, require a gate dielectric with a large relative permittivity. A once-popular layered electrolyte may be just the right material for the job.

Nickel–manganese–gallium foams connected internally by sizeable single-crystalline elements provide magnetic-field-induced strains comparable to free-standing bulk single crystals, and demonstrate feasibility for the application of magnetic shape memory.

Crystalline alloys often fall short in providing certain key properties desired for biomedical applications. But by using metallic glasses instead, problems such as hydrogen evolution can be dramatically reduced in biodegradable magnesium alloys.

Friction measurements on carbon nanotubes show a remarkable anisotropy, the origin of which can be traced to the activation of specific deformation modes of energy dissipation.

Further achievements in the realm of organic and molecular electronics — even at the level of device applications — requires greater understanding of the materials at a fundamental level. This insight can only come with input from researchers in several disciplines working together on the materials from different perspectives.

The magnetic-field-induced strain in magnetic shape-memory alloys can be used in several types of application. However, the strain is high (10%) only in single-crystalline specimens, which are difficult and expensive to obtain. Polycrystalline samples with comparable strain have now been fabricated by introducing pores of similar size to the grains.

Plasmonic biosensors are either based on freely propagating surface plasmons or plasmons localized at nanostructures. Despite advantages such as quantitative detection, localized surface-plasmon sensors have shown lower overall sensitivities. A nanorod metamaterial supporting new plasmonic modes is now shown to considerably outperform earlier plasmonic biosensors by combining and expanding their respective advantages.

Conventional electroanalytical and structure-analysis techniques provide limited information about ionic fluxes in electrochemical systems. A quartz crystal microbalance is now used as a gravimetric probe of the concentration and compositional changes in microporous activated carbon.

When a tip slides on a carbon nanotube, the friction along the transverse direction is much larger than in the parallel direction. It is shown that this behaviour is due to hindered rolling of the tube, and a frictional dissipation that is negligible for a tip sliding along the axis.

Although much effort has been directed towards the separation of single-walled carbon nanotube mixtures, chiral-selective growth is required for scalable production and applications. The chiral distribution of carbon nanotubes can now be altered by varying the composition of nickel–iron nanocatalysts.

The mechanical properties and corrosion behaviour of glassy metals are attractive for biodegradable implants. Magnesium-based glasses are particularly promising but they suffer from hydrogen evolution during corrosion. A distinct reduction in hydrogen evolution is now observed in zinc-rich magnesium glasses showing good tissue compatibility.

One of the attractions in studying oxide heterostructures is the unusual physical phenomena that they enable. It is now demonstrated that the enforced cation ordering in thin oxide superlattices leads to significantly enhanced magnetic ordering temperatures.

Sodium beta-alumina (SBA) compositions are well known as ionic conductors. Nevertheless, ionic and electron conductivities perpendicular to the lattice planes in the material are very low. It is now shown that by exploiting this property, SBAs can be used as transistor gate dielectrics in solution-processed devices using oxide-based and polymer electrodes.

The efficiency of solar cells depends not only on the generated current, but also the photovoltage produced. Ground-state charge-transfer complexes are shown to have an important role in influencing the open-circuit voltage of several polymer–fullerene solar-cell blends; future chemical tuning of the polymers could maximize the complexes’ role in affecting the voltage for increased power-conversion efficiency.

Bioelastomers generally show elasticity similar to that of rubber, which originates from entropic forces linked to deformation. It is now shown that in the egg capsule of a large marine shell, the elasticity is instead based on a structural transition. The results could have a significant impact on engineering protective encapsulating systems inspired by natural elastomers.