Reviews & Analysis

In bulk semiconductors, the absorption of one photon of energy greater than the bandgap leads to one exciton. In quantum dots, however, it could be possible to create multiple excitons from a single high-energy photon, a finding with dramatic implications for the efficiencies of devices such as solar cells.

A comparative study of silica-filled polystyrene and thin polystyrene films offers a new framework both for quantifying the typical shift in the glass-transition temperature of such systems, and prospects for the design of new nanocomposites.

Smart coupling of light-induced molecular motion with a change in surface wettability provides an efficient way to drive a liquid drop up an incline.

A low-power light image projected on a photoconductive layer can initiate non-uniform electric fields over a large area, and allow the manipulation and sorting of particles without wires and electrodes and in the absence of flow.

Progress in all-organic electronic circuits has been hampered by the intrinsic low speed of organic devices. The fabrication of a fast organic rectifying diode opens the gate to novel applications.

The dislocation mechanisms involved in nanoscale deformation have so far been largely studied theoretically from atomistic simulations. High-temperature nanoindentation measurements provide a new quantitative experimental method of studying the onset of nanoscale plasticity.

Commercialization of organic electronics has been limited by the complex processing required to make large-scale devices from single crystals. A new approach exploiting composite phase behaviour facilitates the manufacture of crystalline films from solution for high-quality devices.

Large arrays of vertical laser sources need to emit a coherent output of light. This can be achieved through photonic crystals that mediate the interaction between the lasers in the array.

Most of the outstanding properties of carbon nanotubes rely on them being almost atomically perfect, but the amount of imperfections, and the effect that they have on the tube properties, has, to date, been poorly understood. New work shows that even a very low concentration of missing atom-pairs in the nanotubes has a large effect on their electrical conductance.

An effective route to investigate complex periodic motifs in liquid crystals reveals that molecular packing alone can result in a tricontinuous network of channels separated by two periodic surfaces.

Superconductivity and ferromagnetism do not mix very well. In some magnetic materials, however, they have found a way to coexist. The compromises necessary for their common existence have now been exposed.

The notion that plasticity is governed not by the steady flow of a material under an applied stress, but by the occurrence of intermittent avalanches of defects moving through the material, is gaining increasing acceptance. A new study of plastic deformation in polycrystalline materials suggests that the situation could be even more complex than once thought.

The finding that carbon nanotube–elastomer nanocomposites can either contract or expand reversibly on exposure to light is surprising and hard to explain. But this may create a new avenue for the development of light-controlled actuators.

The discovery of polymorphic crystals that have different mechanical properties could prove valuable in the study of structure–property relationships.

Doping high-temperature superconductors with calcium improves their current-carrying capacity. Two microscopy studies provide insight into how this doping works.