Volume 9 Issue 1, January 2010

The realization of electrical sources of surface plasmon polaritons using complementary metal oxide semiconductor technology is a significant step towards silicon-compatible nanoscale photonic devices.

Experiments have shown that the physical characteristics of the matrix surrounding a stem cell can affect its behaviour. This picture gets further complicated by studies of stem cells and their differentiated counterparts that show that the cells' own softness also has a clear role in how they respond to stress.

Most crystalline materials expand when heated. Now, the packing arrangement of an organic dumbbell-shaped molecule is seen to bring about a large thermal contraction of its crystal lattice.

500 years after the first studies on friction, the concepts of superlubricity, wearless sliding and friction control are being realized in laboratories and have become predictable by adequate modelling. The challenge now is to bridge the gap between what is known about these processes on the microscopic and macroscopic scales.

This review discusses glass and mineral dissolution in terms of traditional kinetic studies, and how nanometre-sized cluster oxide ions are now being used to gain mechanistic insight into the structural dynamics that take place during the dissolution process.

Surface plasmon polaritons allow the control of light on a scale much smaller than its wavelength, and thus are important for nanophotonic applications. The demonstration of an electrical source of surface plasmon polaritons compatible with silicon electronics takes a step towards such integrated plasmonic circuits.

According to Fourier theory, thermal transport is a diffusive process. However, this cannot be the case at length scales smaller than the mean free path of the energy carriers. The first experimental study of thermal transport at the nanoscale is now reported in the case of a point-like heat source, providing a quantitative description of the transition between the ballistic and diffusive regimes.

Dye-sensitized solar cells are a promising technology for sustainable energy generation. Most dyes in these types of solar cell act as sensitizers for injecting electrons into n-type semiconductors. But the development of a sensitizer that can efficiently inject holes into p-type semiconductors makes possible the realization of tandem cells that could exploit the two approaches together.

Occasionally, organic crystalline materials contract when heated (negative thermal expansion), and the mechanisms responsible for this phenomenon are poorly understood. The arrangement of dumbbell-shaped molecules in an organic material is shown to give rise to its negative thermal expansion. The packing and intermolecular interactions facilitate a cooperative mechanical response to temperature causing a decrease in lattice dimensions.

Liquid-crystal gel networks of neurofilament assemblies play a key part in the mechanical stability of neuronal processes, and disruptions in the networks are a hallmark of motor-neuron diseases. Under pressure, these networks are shown to undergo an abrupt transition from expanded to condensed states, with distinct mechanical properties, helping to explain possible disruption mechanisms.

Synthesizing magnetic nanostructures, which could potentially be used in spintronic applications, is quite challenging owing to the difficulty in incorporating magnetic impurities in a non-magnetic matrix. It is now shown that up to 10% Mn can be incorporated in CdSe nanoribbons by nucleation-controlled doping, giving rise to very strong magnetic effects.

Molecular sieves made out of cryptomelane-type manganese oxide (OMS-2) have been widely studied, but synthesizing them with a hierarchical nanostructure and precise crystal orientation is very challenging. It is now demonstrated that pulsed-laser deposition of OMS-2 on SrTiO₃ leads to the spontaneous formation of three-dimensional arrays of parallel and inclined fibres. The results open the way for lattice-engineered synthesis of multilayer materials.

Surface-enhanced Raman scattering has been widely used for chemical sensing, even though the large nonlinearity of the effect makes reproducible sensing difficult. A DNA-based assembly technique now offers a means of precise engineering of gap distances in nanoparticle dumbbells for a robust surface-enhanced Raman sensing of DNA and RNA molecules.

Lithium-ion batteries have contributed to the commercial success of portable electronics, and should affect higher-volume applications such as plug-in hybrid electric vehicles. A fluorosulphate insertion positive electrode showing promising electrochemical performance is now reported.

Metal nanoparticles with controlled composition and size are attractive candidates for heterogeneous catalysis. Now, a distillation-like process is shown to result in the synthesis of bimetallic PtRh nanoparticles with precise compositional control and high temperature stability.

Soft embryonic stem cells respond to small localized forces by increasing cell protrusion and spreading; in contrast, cells that are differentiated from them—which are ten times stiffer—do not spread. The deformation of the cell cytoskeleton is thus shown to be an important determinant of cellular response to force.