Research articles

It is now shown that femtosecond optical excitation can be used as a tool to investigate the spin-polarization properties of half-metals, and provide a clear distinction between those and metals. Such knowledge is of fundamental importance for the use of these materials in spintronics applications.

Manipulating the properties of semiconducting nanostructures through magnetic doping can lead to interesting fundamental phenomena, as well as potential spintronics or memory devices. The demonstration that the magnetic properties of Mn-doped ZnSe dots can be tuned by adjusting the thickness of a CdSe shell represents a fundamental advance in the field.

Ferroelectric polymers are of interest for use as memory devices for all-organic electronics applications. A fast and efficient embossing technology is now shown not only to lead to high-density arrays of ferroelectric nanocells but also to significantly improve the ferroelectric properties of these structures.

Bridging the gap between theoretical and experimental work to understand the effect of plasticity on the crumpling of thin sheets into a small volume has proved difficult. A realistic numerical model now makes a distinction between elastic and elasto-plastic behaviour.

Understanding the short- and medium-range structure of metallic glasses remains a difficult challenge. The observation that the medium-range order has the characteristics of a fractal network may have broader implications in the understanding of the relation between structure and mechanical properties in metallic glasses.

Electronically active materials made by the self-assembly of alternating layers of zinc oxide and conjugated molecules directly onto an electrode combine the advantages of their inorganic and organic components. They are shown to be stable photoconductors with promising device characteristics.

Nanostructured high-surface-area materials capable of converting energy into mechanical work are promising for use as actuation devices. Surface-chemistry-induced changes of the surface stress in nanoporous gold are now observed on alternate exposure to ozone and carbon monoxide.

The growth kinetics and crystallization behaviour of DNA-directed colloidal systems are not well understood. Now, using experiments and simulations, a single nucleotide mismatch in DNA strands attached to two microsphere species enables the kinetics of crystal growth and segregation as a result of crystallization to be investigated.

Colloidal synthesis can help to precisely control the shape and composition of catalytic metal nanoparticles, but it has so far proved difficult to use these particles in high-temperature reactions. Core–shell structures capable of isolating Pt-mesoporous silica nanoparticles have now been shown to be catalytically active for ethylene hydrogenation and CO oxidation at high temperature.

One of the challenges posed by spin manipulation in organic semiconductors is the difficulty of measuring the spin polarization and the spin diffusion length. This is now elegantly achieved by a low-energy muon spin rotation.

One of the challenges posed by spin manipulation in organic semiconductors is the difficulty of measuring the spin injection from a ferromagnetic contact and the subsequent spin diffusion length. This is now elegantly achieved by a two-photon photoemission experiment.

Phase-change materials are widely used as non-volatile memories, for example in optical data storage, but the search for improved phase-change materials has proved difficult. Based on a fundamental understanding of their bonding characteristics, a systematic prediction of phase-change properties has now become possible.

A long-standing problem with molecular wires is their poor transport properties. Highly conductive and very long wires have now been synthesized by incorporating metal centres into rigid molecular backbones, which shows promise for their use in electronic devices.

Carbon-based structures are being intensively investigated for their use in electronic devices. A pronounced non-volatile switching is now observed in two-terminal devices made from graphitic sheets. The highly reliable switching mechanism is explained by the local breaking and rejoining of atomic bonds in the sheets.

Superconductivity is a complex and fascinating phenomenon, made more so by its coexistence with other collective electronic states. A study of the layered compound 1T-TaS₂ under pressure enables the various states of the material to be investigated and compared with other commonly studied layered superconductors.

Hydrogen generated from splitting water using a catalyst and solar energy is an ideal energy source. A polymeric carbon nitride photocatalyst that is thermally and chemically stable is now shown to produce hydrogen from water even in the absence of noble metal catalysts.

Nanomaterials are effective catalysts for many chemical reactions, however, their catalytic properties are most often determined by ensembles of nanoparticles, and so far only averaged results have been measured. Now, the heterogeneous reactivity and the surface structure dynamics of individual gold nanoparticles are revealed by monitoring single fluorogenic reactions.

Construction of tissue-engineering scaffolds that mimic cardiac anisotropy is a challenge. Now, accordion-like honeycomb scaffolds have been created that can form tissue grafts with preferentially aligned heart cells, and with mechanical properties that closely resemble the anisotropy of native myocardium.

Understanding the corrosion mechanism of aqueous silicate glass is crucial for the long-term durability of nuclear waste glasses. This mechanism is generally thought to be associated with chemical affinity, but it is now demonstrated that morphological transformations also have an important role in the leaching kinetics of these glasses.

According to a neutron-scattering study of the structural and magnetic properties of the pnictide CeFeAsO_1−xF_x, the phase diagram of this material shows considerable similarities with the high-T_c cuprate superconductors. These results are an important addition to the effort to find out where superconductivity in these iron–arsenic alloys arises.