Articles in 2009

Virtual worlds such as Second Life present an intriguing premise for scientific use. But are the benefits sufficiently clear for widespread uptake?

The concept of using magnetic micro- and nanoparticles for targeting solid tumours with drugs was first proposed over three decades ago, but has yet to translate into a clinical application. Rethinking the mechanistic approach could circumvent the difficulties that have stood in its way.

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.

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.

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.

Biocompatible, lithographically defined, ferromagnetic microdiscs that have a spin-vortex ground state oscillate when activated by an alternating magnetic field. This oscillation compromises the integrity of the cell membrane and initiates programmed cell death in ∼90% of cancer cells in vitro, even with a low-frequency field applied for only ten minutes.

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.

Using a liquid gate has allowed electrically induced superconductivity in a solid specimen by means of carrier accumulation on the surface. But this phenomenon was limited to materials that became superconductors at low carrier density. It is now shown that superconductivity can be induced in a much wider range of materials by using an ionic liquid.

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.

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.

The structure of magnetic nanoparticles has a strong influence on the properties of these materials at present being considered for magnetic-storage applications. It is now shown that size and shape of magnetic nanoparticles such as CoPt affect the transition from an ordered to a disordered phase, highlighting the need to take morphology into account to understand the structural properties.

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.

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.

Direct in situ high-resolution X-ray radiography and tomography observations now reveal instability and metastability domains in cellular solidification of colloidal suspensions and the transition to the stable phase. These results provide important insight into the study of morphological instabilities and could prove significant in the design of various types of nanostructure.

When artificial polypeptides are conjugated to a variety of hydrophobic molecules such as chemotherapeutics, the resulting molecules spontaneously self-assemble into nanoparticles. Delivering the chemotherapeutics to a murine cancer model, the nanoparticles have a fourfold higher maximum tolerated dose than the free drug, and induce nearly complete tumour regression after a single dose.

Grain boundaries are already known to have a large effect on the charge-carrier mobility of molecular semiconductors. Several experimental and computational techniques now show that the orientation of grain boundaries in a perylene diimide semiconductor modulates carrier mobility by two orders of magnitude. The results provide important guidelines for producing device-optimized molecular semiconductors.

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.

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.