Research articles

Applications of high-temperature superconductivity rely on transporting a large current without dissipation. It is now shown how the inclusion of a combination of two types of defect can be used to control and optimize the performance of the high-temperature superconductor YBa₂Cu₃O₇.

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.

Proteins are usually produced in living cells, but hydrogels that incorporate genes demonstrate that cells aren’t always needed. The gels produce a wide variety of proteins without cells, and with higher yields than the equivalent solution method. Materials-related proteins that have been difficult to produce by other methods can now be made in greater quantities.

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.

Anisotropic superstructures produced by the self-assembly of spherical nanoparticles are realized. Uniformly grafting polymer chains onto inorganic spherical nanoparticles produces particles with amphiphile-like behaviour. Mixing these with monodisperse polymer facilitates the self-assembly of numerous anisotropic nanocomposites.

Polymer crystals have a range of melting temperatures, therefore simultaneous melting and crystallization can take place. New crystals are seeded from some of the initial crystalline material, and as the orientation of the second-generation material is correlated with the starting crystal, orientated arrays of polymer crystals are produced.

Although heterogeneous ice nucleation is investigated in a number of fields, a mechanism for the process remains elusive. Ice with a pentagon-based chain structure is now seen to form on a Cu(110) surface, revealing that the structure of ice–water films can adapt to maximize water–metal bonding and achieve strong hydrogen bonding within the layer.

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.

What drives a phase transition in the heavy-fermion compound URu₂Si₂ is one of the major unsolved problems in condensed-matter physics. Numerical calculations now demonstrate how antiferromagnetic ordering leads to a symmetry breaking that alters the material’s band structure and therefore its electronic properties.

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.

Graphene nanostructures—like nanoribbons or quantum dots—hold great potential for applications. An extensive STM study elucidates how the details of the nanostructure edges heavily influence the electronic properties, which can vary between metallic and semiconducting according to the predominancy of zigzag or armchair edges.

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.

Molecular rotors have seen considerable interest as functional molecules on surfaces or for applications as memory devices. However, it is now shown that molecular rotation may also be used to induce ferroelectricity in a molecule.

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.