Volume 12 Issue 12, December 2013

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.

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.

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

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.

The emergence of conductivity at the {001} interface of LaAlO₃ and SrTiO₃ is one of the more celebrated examples of interface engineering. Using a microscopy approach based on a sensitive magnetometry probe, it is now shown that narrow paths of enhanced conductivity occur along the crystallographic axes of the oxide structures.

Clathrate materials have been the subject of intense investigation because of their beneficial properties, in particular their low thermal conductivities. Now, improved thermopower at high temperatures arising from strong electron correlation effects has been achieved in a type-I clathrate containing cerium guest atoms.

For alloys displaying diffusive transport behaviour, understanding the electrochemical factors that control dealloying-induced morphologies could prove important for battery development. Composition, particle size and dealloying rate are now shown to affect morphology evolution in the Li–Sn system, and dealloying is found to be governed by both percolation-dissolution and solid-state-diffusion mechanisms.

Compared with their rigid counterparts, thin-film solar cells grown on flexible substrates usually display lower power-conversion efficiencies. Now, the application of a post-deposition alkaline treatment that modifies the chemical composition of the surfaces of Cu(In,Ga)Se₂ thin films reduces optical losses in these flexible photovoltaic architectures. Furthermore, efficiencies comparable to solar cells based on polycrystalline silicon are achieved.

The LaAlO₃/SrTiO₃ interface plays host to a diverse range of physical phenomena. By imaging the electrostatic landscape with a specially designed detector it is shown that tetragonal domains give rise to a large extrinsic piezoelectricity.

Previous studies have suggested that even in the absence of a graphene bandgap, a relaxation bottleneck at the Dirac point may allow for population inversion and lasing. Now, using time- and angle-resolved photoemission spectroscopy with femtosecond extreme-ultraviolet pulses, it is shown that interband excitations give rise to population inversion, suggesting that terahertz lasing may be possible.

In organic semiconductors, disorder-induced traps can alter the mobility of the charges and introduce noise in transport measurements. It is now shown that simple drop-casting of perfluoropolyether on top of organic single-crystals is an effective strategy for healing charge traps. This method allows the intrinsic transport properties of these materials to be recovered as well as suppressing noise in Hall effect measurements.

Metal fluorides/oxides are promising electrodes for lithium-ion batteries, but the mechanism by which they exhibit additional reversible capacity is still not well understood. By using high-resolution solid-state NMR techniques it is shown that extra capacity in this RuO₂ system is due to the generation of LiOH and its subsequent reversible reaction with Li to form Li₂O and LiH.

The electrochemical reduction of oxygen to hydrogen peroxide requires selective and stable electrocatalysts. It is now shown that Pt–Hg nanoparticles display an order of magnitude improvement in the mass activity for hydrogen peroxide production compared with the best performing catalyst.

Proteins from bone extracellular matrix are known to mediate the organization of apatite crystals in bone. Now, electron microscopy, X-ray scattering and nuclear magnetic resonance measurements of the structure and organization of apatite nanoparticles and intact bone samples show that water also plays a significant role in orienting the apatite crystals, and that such structuring is mediated by a disordered mineral layer that coats the crystalline core of bone apatite.

Somatic cells can be reprogrammed into induced pluripotent stem cells biochemically through the expression of a few transcription factors. It is now shown that aligned microgrooves or nanofibres on cell-adhesive substrates can promote the reprogramming of somatic cells more efficiently through epigenetic regulation of genes related to pluripotency and the mesenchymal-to-epithelial transition. The findings suggest that the epigenetic state can be regulated by variations in cell morphology.