Letters in 2012

Because it is an intrinsically slow technique, scanning tunnelling microscopy is not usually useful for studying the dynamics of particles on a surface. This issue is now solved by using scanning noise microscopy, which yields a complete characterization of copper phthalocyanine molecules on Cu(111), ranging from the dynamical processes to the underlying electronic structure at the single-molecule level.

Emulating the spiking phenomena associated with neural activity in technological devices offers the promise of drastically improving their efficiency and scale. The fabrication of a neuristor that consists of nanoscale Mott memristors provides a step towards making such devices practical for integrated circuit applications.

The standard picture of organic photovoltaics predicts that excitons, which are created under light irradiation, thermalize before dissociation into free electrons and holes. Experimental results and calculations on a low-bandgap polymer–fullerene blend now illustrate the dynamics of hot charge-transfer states and their contribution to charge generation in bulk heterojunctions.

Solid-state spin qubits offer promise as building blocks for quantum computers. Now, efficient quantum control is demonstrated over hybrid nuclear–electronic qubits in bismuth-doped silicon, as a consequence of the strong hyperfine interactions in this system.

Rechargeable metal–air batteries are considered particularly attractive due to their potential high-energy densities and simplicity of the underlying cell reaction. A room-temperature sodium–oxygen cell with an ether-based electrolyte demonstrates enhanced current densities using pure carbon cathodes without an added catalyst.

The dynamical properties of single-chain magnets are difficult to control experimentally. The demonstration of a scheme for switching individual spins optically now allows for the study and manipulation of dynamical processes in magnetic nanowires with comparative ease.

The appealing electronic properties of the monolayer semiconductor molybdenum disulphide make it a candidate material for electronic devices. The observation of tightly bound trions in this system—which have no analogue in conventional semiconductors—opens up possibilities for controlling these quasiparticles in future optoelectronic applications.

A critical component for chip-scale integrated photonics would be a non-reciprocal optical waveguide allowing light to travel in only one direction while reflecting it in the opposite one. Inspired by concepts of parity-time-symmetric quantum theories, a periodically modulated dielectric waveguide displaying unidirectional reflection is now demonstrated, reflecting light at telecom frequencies in only one direction.

Determining crystal structures from diffraction experiments can be labour intensive and prone to errors. A hybrid approach combining experimental diffraction data, statistical symmetry information and first principles-based algorithmic optimization is now proposed to automatically solve crystal structures.

The exterior surface of cell membranes in eukaryotes is surrounded by glycans. It is now found that the spatial configuration of these polysaccharide molecules controls the phase behaviour of multiphase lipid membranes—either by stabilizing ordered lipid domains or by suppressing macroscopic lipid phase separation—and that this glycan-induced patterning is thermally reversible.

The poor thermal conductance of interfaces is a significant bottleneck to the integration of nanoscale devices in a range of applications. Now, the thermal conductance at metal/dielectric heterointerfaces is significantly enhanced by the introduction of an organic nanomolecular monolayer.

Metamaterials offer a unique potential to guide the propagation of light. However, existing designs of devices such as invisibility cloaks require a restrictive range of materials parameters for their realization. A new approach to cloak devices now lifts such restrictions allowing for a greater flexibility in device design.

Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage and conversion, and catalysis, but their tendency to grow into larger crystallites is an issue for their stable performance. A strategy based on controlling not only size and composition but also the location of the metal nanoparticles, now reveals the impact of their three-dimensional nanospatial distribution on their catalytic stability.

Altering the composition of the spacer layers present in iron-based superconductors is one strategy for increasing the temperature below which they superconduct. Now, intercalating FeSe with molecular spacer layers is also shown to enhance the superconducting transition temperature.

The atomic structure of nanoparticles considerably influences their properties. A new methodology that is now able to measure the full three-dimensional atomic structure of free-standing nanoparticles will therefore provide a much better connection between their structure and properties.

Optical coatings usually consist of many multilayers of thin films to achieve the desired properties. A new approach using interference effects between an absorbing dielectric film and a metallic substrate now enables ultrathin optical coatings that could also find applications as thin solar cells or photodetectors.

The dynamical processes associated with the magnetization of a material can be drastically altered by the application of a spin current. This study now demonstrates the feasibility of selectively exciting coherent auto-oscillation modes in magnetic nanostructures.

Classically, friction is known to increase with increasing normal load. Scanning probe experiments now show that reversible local delamination of chemically modified graphite can lead to an enhancement in friction as the applied load decreases, resulting in an effectively negative friction coefficient.

Nickel-rich layered lithium transition metal oxides have been investigated as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. Such an oxide with high capacity (215 mA h g^-1), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle, is now proposed.

On application of a focused magnetic field, zinc-doped iron oxide nanoparticles with targeting antibodies attached are shown to activate cell death signalling in a spatially controlled manner. This triggering of apoptosis signalling, via the magnetically activated aggregation of receptors, is observed in both in vitro and in vivo systems.