Articles in 2011

The energy-level alignment at the heterojunction critically influences the performance of organic photovoltaic devices. It is now shown that the surface dipole moments of individual organic semiconductor films can be tuned with surface-segregated monolayers before forming bilayer solar cells by a simple film-transfer method.

Production of chemical fuels by solar energy is an attractive and sustainable solution to our energy problems. A highly active photocathode, consisting of electrodeposited cuprous oxide with platinum nanoparticles is now activated for hydrogen evolution resulting from photelectrochemical water reduction.

Chemical vapour deposition is a promising route for large-scale graphene growth. It is now shown that—through the use of seeds—high-quality, large, single-crystal domains can be grown on a patterned arrangement, and can be used to carefully study the transport across grain boundaries.

The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. A highly efficient solar to electric energy conversion device based on nanostructured thermoelectric materials and high solar concentration is now demonstrated. The results show potential for cost effective solar thermoelectric generation.

Active gels—such as the cytoskeleton—are out-of-equilibrium networks that self-organize in complex, dynamic patterns. The mechanisms by which dynamic structures form are, however, poorly understood. Now, a generic mechanism of structure formation, analogous to nucleation and growth in passive systems, is found in a minimal active-gel consisting of actin filaments, molecular-motor filaments and crosslinkers.

Solution-deposited metal oxides show great potential for large-area electronics, but they generally require high annealing temperatures, which are incompatible with flexible polymeric substrates. Combustion processing is now reported as a new low-temperature route for the deposition of diverse metal oxide films, and high-performance transistors are demonstrated using this method.

Nanofibrous hollow microspheres, formed by the self-assembly of star-shaped biodegradable polymers, are shown to be effective injectable cell carriers for cartilage repair. The microspheres accommodate cells and enhance cartilage regeneration in vivo with respect to various control groups, in particular, indicating smooth integration between the regenerated and host tissue.

A nanocarrier—synthesized by the fusion of liposomes to spherical, nanoporous silica particles and subsequent modification of the lipid bilayer with targeting peptides and fusogenic peptides—shows the targeted delivery and controlled release of chemically diverse multicomponent cargos within the cytosol of certain cancer cells.

The symmetries of crystals are an important factor in the understanding of their properties. The discovery of a new symmetry type, rotation-reversal symmetry, may lead to the discovery of new rotation-based phenomena, for example in multiferroic materials.

Explaining why interactions of metal particles with oxide supports can improve their catalytic performance has proved challenging. The origin and nature of metal–oxide interactions on industrially important platinum–ceria catalysts are now clarified, together with the dependence of the catalytic activity on the structure of the support.

Computer simulations of nematic liquid crystals confined in bicontinuous porous geometries show that frustration and topology lead to multiple, metastable trajectories of defect lines that can be memorized on application of external fields. These topologically enabled metastable states could be exploited to optically functionalize orientationally ordered materials.

The optical properties and biocompatibility of nanovesicles composed of self-assembled porphyrin bilayers are investigated. These nanovesicles—termed porphysomes, with liposome-like structure and loading capacity—are shown to be multimodal contrast agents for photoacoustic tomography and fluorescence imaging in biomedical applications.

Inflatable balloon catheters are widely used in many surgical and diagnostic procedures. Such catheters have now been used as a platform for a collection of components including semiconductor devices, sensors and actuators, and these multifunctional catheters probed for their use in cardiac-related applications.

A potent vaccine-delivery system based on interbilayer-crosslinked multilamellar vesicles is reported. The lipid vesicles enable extracellular co-entrapment of protein antigens and immunostimulatory molecules, which are released in vivo, eliciting endogenous T-cell and antibody responses comparable to those for live vaccines.

Monte Carlo simulations are performed to study the assembly of polyhedrons into various mesophases and crystalline states. The formation of new liquid-crystalline and plastic-crystalline phases is predicted at intermediate volume fractions and, by correlating these results with particle anisotropy and rotational symmetry, guidelines for predicting phase behaviour are proposed.

One of the key loss mechanisms in the operation of organic solar cells is the separation and extraction of the generated charge carriers from the active region. The use of a ferroelectric layer is now shown to create large internal electric fields, resulting in an enhanced carrier extraction and increased device efficiency.

Low-voltage intercalation anodes for lithium batteries are important for future applications in portable electronics and electric vehicles. Using a combination of computational methods along with powder X-ray- and neutron-diffraction techniques, the intercalation process for Li_1+xV_1−xO₂, in particular the key role of non-stoichiometry in switching on intercalation, is clarified.

Metamaterials show many intriguing properties, which are often limited to a narrow range of frequencies. The demonstration of a low-loss broadband metamaterial at radiofrequencies promises applications as enhanced antennas, for example.

A one-pot, high-throughput method for the recombinant polymerization of monomer DNA sequences is reported. The method enables the rapid synthesis of diverse libraries of artificial repetitive polypeptides, exemplified by the isolation of protease-responsive polymers and a family of polypeptides with reversible thermally responsive behaviour.

Devices that can field-ionize gas molecules at low bias voltages are promising for selective gas-sensing applications and for ion-mobility spectrometry. Field ionization is now observed at very low voltage on semiconducting whiskered silicon nanowires.