Volume 8 Issue 7, July 2009

Ever since invisibility cloaking has left the realm of fiction and been demonstrated for microwave radiation, cloaking in the visible has been the aim. Having reached the near-infrared, we might be there soon.

Bulk polycrystalline organic conductors do not behave like two- or three-dimensional materials but as one-dimensional metals.

DNA provides more than lock-and-key control of assembly. Careful engineering of hairpins and loops provides the means to control the kinetics of particle assembly, allowing structures to be 'glued' together by heating.

A renormalization group study of electric transport in nanocontacts reveals the importance of quantum correlations for achieving a startling ferromagnetic Kondo effect.

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.

A route connecting density functional theory and the numerical renormalization group method represents the first approach to studying atomic contacts—including magnetic elements—at an atomic level. When applied to the case of a nickel impurity in a gold nanowire, the strategy provides a clear connection between the geometry and the transport properties.

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.

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.

Designing and building molecular machines at the nanometre scale is a conceptual and synthetic challenge. Rotation of a single molecule has been observed but controlling the direction of the rotation has so far proved difficult. The step-by-step rotation of a molecular gear mounted on an atomic-scale axis is now controlled by a scanning tunnelling microscope.

The transport and mechanical properties of polymer electrolytes make them important materials for all-solid-state electrochemical devices such as batteries or electrochromic displays. Crystalline polymer electrolytes containing alkali metal salts are now found to exhibit ionic conductivity 1.5 orders of magnitude higher than the best conductor reported so far.

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.

Functionalizing colloidal particles with DNA is a powerful tool for guiding their assembly, using the complementary ‘sticky ends’ of the molecules. However, other attributes of DNA can be used to engineer interactions between particles more subtly. Temperature- or time-controlled formation of loops or hairpins in DNA provides switchable connections for novel materials from particle assemblies.

Hydrogels are hydrated polymer networks with applications in biotechnology and medicine. When created from alpha-helical peptides with engineered peptide sequences, their formation mechanisms can be controlled, leading to diverse properties. For instance, those with hydrogen-bonded networks melt on heating, but those formed through hydrophobic interactions strengthen when warmed.

The mechanisms underlying the fracture of glasses are poorly understood. It is now shown that intrinsic density fluctuations in glass are enhanced during the deformation process, and may therefore be the origin of fracture in glasses. This understanding may lead to the design of glasses with improved mechanical properties.