Volume 10 Issue 3, March 2011

The issues associated with the supply of rare-earth metals are a vivid reminder to all of us that natural resources are limited. Japan's Element Strategy Initiative is a good example of a long-term strategy towards the sustainable use of scarce elements.

The critical shortage of rare-earth elements is a concern for a number of important technologies, but also an opportunity to research alternative materials and technologies, says Alexander King, director of the US Department of Energy's Ames Laboratory.

A study of nitrogen doping of graphene reveals the potential of high-resolution electron microscopy for imaging charge transfer around chemical bonds.

Multilamellar lipid vesicles with crosslinked walls carrying protein antigens in the vesicle core and immunostimulatory drugs in the vesicle walls generate immune responses comparable to the strongest live vector vaccines.

The formation of a two-dimensional electron liquid at the interface between two insulating oxides, now extended to oxides on Si, joins a wealth of observations that reveal how electron transfer between layers is responsible for this unusual effect.

The observation that disorder leads to a transition from metallic to insulating behaviour in the crystalline phase of GeSb₂Te₄ provides a new look at its transport properties, crucial for old and new applications of phase-change materials in non-volatile-memory devices.

The realization of a self-assembled kagome lattice from colloids with attractive hydrophobic patches offers a simple but powerful example of the bottom-up design strategy.

Tunnelling and capacitance spectroscopies are able to image the wavefunctions of electrons in atom-like solid-state systems as they are shaped by an external magnetic field.

The presence of metal centres in synthetic polymers can impart interesting functionality on the resultant material. This Review Article focuses on the use of metal-containing polymers in a diverse range of applications, for example, in emissive and optical materials, in nanomaterials, as sensors, stimuli-responsive gels, catalysts and artifical metalloenzymes.

The occupation of electronic orbitals on the surface and interface of oxide thin films and heterostructures is a key influence over their properties, including magnetism and superconductivity. A new spectroscopy technique now provides the first quantitative, spatially resolved data of orbital occupation in oxide structures.

Magnetic domain walls can be controlled through a spin torque, which is usually influenced by extrinsic factors, such as defects, that pin the domain walls to specific configurations. It is now shown that intrinsic pinning conditions can be achieved, which will facilitate the development of efficient information storage devices based on domain wall control.

Electronic devices based on complex oxides offer the possibility to connect electrical devices with phenomena such as magnetism and superconductivity. However, existing oxide field-effect transistors have drawbacks such as high operation voltage. The demonstration of a metal-base transistor whose geometry makes use of the strong internal electric fields in oxide heterojunctions may now offer a new platform for oxide electronics.

Phase-change materials are used in computer memories for their switching between amorphous and crystalline phases. However, even the crystalline state shows disorder, with extremely small electron mean free paths. The discovery that, depending on annealing temperature, this disorder leads to a metal–insulator transition in the crystalline phase provides a completely new look at the transport properties of these compounds.

Transmission electron microscopy (TEM) has reached unprecedented resolution and can provide structural information down to the single atomic level. It is now shown that a properly designed experimental analysis also allows the charge distribution around a single atomic dopant to be monitored, demonstrating the possibility of TEM to provide electronic as well as structural information.

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.

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.

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.

Actin networks are an excellent model system for studying the mechanical properties of the cell cytoskeleton. Using microscopic methods, actin bundle networks formed in the presence of the crosslinking protein fascin show age-dependent changes in their viscoelastic properties and spontaneous relaxation dynamics in a similar way to glassy, soft materials.

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.

The supply shortages of several important chemical elements poses significant challenges for a broad range of technologies. This focus highlights the scope of the problem, ranging from motors and batteries in electric cars to fertilizers, and points towards solutions to remedy this problem.