Letters in 2009

In multiferroics ferroelectricity and magnetism are coupled, but the coupling is often rather weak. As is now shown for a perovskite oxide, composite domain walls can lead to a strong coupling of electricity and magnetism, highlighting the importance of domain walls for practical applications using multiferroics.

To use conducting and semiconducting polymers for electronic applications, their fundamental properties need to be understood. It is now demonstrated that the transport mechanism of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) at high carrier densities in field-effect transmitters and electrochemically doped films match those of a one-dimensional metal.

The interaction of water with metal oxides is important for catalysis and biochemistry. Charge rearrangement at the water–anastase (101) interface affects the adsorption of further water molecules, and results in short-range repulsive interactions and locally ordered water-molecule superstructures.

Silver iodide is a well-known ionic conductor. However, it shows superionic conductivity only in its high-temperature phase (above∼150 ^∘C). It is now demonstrated that various sizes of nanoparticles can be synthesized for which the superionic phase is stable down to ∼30 ^∘C. The results suggest promising applications in silver-ion-based electrochemical devices.

Fe-based superconductors have attracted tremendous interest recently. New evidence on BaFe₂As₂ shows that chemical doping and pressure, both of which induce superconductivity, distort the lattice in similar ways. The result provides important information in the quest for an understanding of the mechanism behind superconductivity.

Metal–organic frameworks are highly porous materials that are promising for drug release and gas storage. A liquid-phase-epitaxy approach that prevents interpenetration and retains the pore size is now proposed.

Previous demonstrations of cloaking, where objects are rendered invisible at certain frequencies, have been limited to the microwave regime. Moving us a significant step closer to invisibility in a region that can been seen by humans, a cloaking device has now been demonstrated for a broad range of frequencies in the near-infrared.

The synthesis of highly pure diamond nanocrystals with a very small amount of paramagnetic impurities allows the observation of electron spin-dephasing times of up to 1.8 ms, a record for solid-state materials. The result could have important implications for quantum information processing methods based on diamond.

Solution-based syntheses of nanoscale clusters using biomolecules as links between nanoparticles are frequently inefficient and normally produce many different multimers or isomers of clusters. Dimer nanoclusters and Janus nanoclusters have now been designed and produced in high yields using nanoparticles grafted with single-stranded DNA.

Layered lithium nickel-rich oxides are attractive as cathodes for rechargeable lithium batteries. A concentration-gradient material based on manganese nickel cobalt oxide showing high capacity and thermal stability could prove advantageous for batteries used in plug-in hybrid electric vehicles.

In non-conventional superconductors, the competition of magnetic order and superconductivity seems to be a key element for the origin of superconductivity. Investigation of the newly discovered iron-pnictides superconductors challenges this picture, showing a coexistence of superconductivity and magnetism.

Nanomaterials that can circulate in the body hold great potential to diagnose and treat disease, but suffer from problems such as toxicity. Porous silicon nanoparticles have now been engineered to concomitantly image tumours or organs within the body, deliver therapeutics and resorb in vivo into benign components that clear renally.

In non-conventional superconductors, it is usually found that superconductivity emerges in the vicinity of a critical point where antiferromagnetic order gradually disappears—corresponding to a second-order transition. Investigation of the newly discovered iron pnictide superconductors challenges this picture, showing an abrupt, first-order transition.

Mesoporous materials with tunable, non-oxidic frameworks possess structural characteristics that make them attractive for catalytic and optoelectronic applications. Porous materials based on germanium-rich chalcogenide networks and polarizable surfaces exhibit selectivity for separating hydrogen from methane and carbon dioxide.

Oxide heterostructures offer new functionality based on the interaction of order parameters across the heterostructure interfaces. In particular, it is now demonstrated that superconducting layers can induce giant modulations of magnetization in adjacent ferromagnetic layers.

The possibility of polarizing conducting charges in a material by blocking those with a specific spin direction could lead to efficient spintronic devices. It is now shown that spin polarized-defects in a non-magnetic semiconductor can deplete electrons with opposite spins and turn the semiconductor into an efficient spin filter operating at room temperature.

Thermal annealing of SiC produces graphene layers on an insulating substrate, but the material is highly inhomogeneous. It is now shown that an argon atmosphere during annealing improves uniformity of the graphene layers dramatically and yields better transport characteristics. This is a very important result for the development of graphene-based electronic devices.

Catalytic oxidative dehydrogenation of alkanes is limited by poor activity and/or selectivity. Efficient conversion of propane to propylene is now achieved using sub-nanometre Pt clusters stabilized on alumina supports. The clusters are shown to be substantially more active than conventional catalysts and are highly selective towards propylene formation.

A limiting factor of the power conversion efficiencies of organic photovoltaic devices is low voltage output. Methano derivatives of the trimetallic endohedral fullerene Lu₃N@C₈₀ have now been synthesized and used as the acceptor in organic photovoltaics. The open circuit voltage of the devices is significantly above those made using alternative fullerenes.

Molecular magnets are promising for their use as high-density memory devices. However, maintaining the molecules’ magnetic state when bonded to a substrate has been impossible. The discovery, in sophisticated experiments, that single magnetic molecules can indeed show magnetic hysteresis when wired to a gold surface opens the door to individually address magnetic molecules.