News & Views in 2013

A study on carrier-collection efficiency in various organic photovoltaic systems now reveals that ultrafast relaxation of photoexcitations within the manifold of charge-transfer states does not impede mobile charge carrier generation.

Reversible strains up to 14% driven by changes in temperature or electric field have been realized in a thin film of bismuth ferrite oxide.

The energetic and kinetic behaviours of water-oxidation catalysts deposited on semiconductor electrodes are probed in situ, elucidating the junction formed between them, and transforming the design principles of the catalysts.

Planar patterns of colloidal microparticles have been manufactured with high yield over square centimetre areas by using magnetic-field microgradients in a paramagnetic fluid. This approach could evolve into technology capable of printing three-dimensional objects through programmable and reconfigurable 'magnetic pixels'.

Scanning probe techniques reveal an intricate interplay between the formation of structural domains in strontium titanate and electronic transport effects at oxide interfaces.

Measurements of the structure and organization of intact bone samples show that water plays a significant role in orienting bone apatite crystals, and that such ordering is mediated by an amorphous mineral coating layer.

Mixed-halide organic–inorganic hybrid perovskites are reported to display electron–hole diffusion lengths over 1 μm. This observation provides important insight into the charge-carrier dynamics of this class of semiconductors and increases the expectations for highly efficient and cheap solar cells.

Adult cells can be routinely reprogrammed into pluripotent stem cells by chemical and genetic means, such as the expression of a cocktail of exogenous transcription factors. It is now shown that growing cells on substrates with aligned features such as microgrooves can enhance this process.

Traps in organic semiconducting crystals are healed when a perfluoropolyether oil is deposited on the surface of these materials, thus making possible the detection of intrinsic features of charge-carrier transport in rubrene and tetracene.

Poorly ordered films of conjugated polymers that show high charge mobility recently challenged the idea that disorder is detrimental for electrical conduction. Systematic studies now reveal that long polymeric chains can bridge small crystalline domains thus supporting charge transport on length scales relevant for device operation.

Advances in photochemistry have profoundly impacted the way in which biology is studied. Now, a photoactivated enzymatic patterning method that offers spatiotemporal control over the presentation of bioactive proteins to direct cells in three-dimensional culture significantly expands the available chemical toolbox.

Cells can sense their environment by applying and responding to mechanical forces, yet how these forces are transmitted through the cell's cytoskeleton is largely unknown. Now, a combination of experiments and computer simulations shows how forces applied to the cell cortex are synergistically shared by motor proteins and crosslinkers.

The critical temperature of most superconductors varies with the density of charge carriers, which in turn is most easily tuned by chemical doping. The observation that a specially fabricated two-dimensional superconductor maintains the same critical temperature regardless of doping raises some important questions.

Pristine graphitic surfaces seem to be more hydrophilic than previously assumed because of the unexpected influence of the quick adsorption of hydrocarbons from air.

A study on the subtle interplay between electronic structure and structural defects now explains why the suppression of conduction in the insulating state of bilayer graphene is not as strong as might be expected. It also reveals the possibility of creating graphene-based nanoscale systems with unique electronic properties.

The discovery of a ferroelectric-like structural transition in metallic LiOsO₃ identifies a new class of materials with unconventional properties, providing an exotic playground for theorists and experimentalists.