Articles in 2010

A polymeric hydrogel coating shows impressive antimicrobial activity against both bacteria and fungi. The biocompatible and reusable coating, formed of a polycationic nanoporous hydrogel, is thought to act by drawing anionic sections of phospholipids on bacterial cell membranes into its pores, causing membrane disruption and cell death.

Sodium layered oxides are low-dimensional and strongly correlated systems that have been extensively studied because of their intriguing structural and physical properties. Electrochemical sodium intercalation is now used to investigate their different phase domains and thermal stability.

Strain-induced damage typically limits the bending radius of electronic circuits to a few millimetres. The development of very thin organic transistors and electronic circuit designs that show a bending radius down to 100 μm will enable novel applications with unconventional form factors.

Flexible electronic devices that can be stretched without losing performance have seen increasing functionality. In particular, the demonstration of light-emitting diodes and photodetectors on flexible electronic substrates now opens the door to applications of flexible optoelectronic sheets in biomedicine and robotics.

Hydrophobic surfaces composed of an asymmetric array of polymer nanorods show unidirectional wetting behaviour relative to the orientation of the tilted nanorods. The surfaces, which are smooth on the microscale, can transport water droplets of microlitre capacity by a ratcheting mechanism resulting from the pillared substrate.

Excitons in polycrystalline films of organic semiconductors typically migrate distances of the order of tens of nanometres. Photoconductivity measurements in highly ordered rubrene now show that exciton diffusion can reach the micrometre range, opening a route to designing excitonic circuitry for applications in photocatalysis, photochemical sensing or photovoltaic energy conversion.

In situ spectroscopic analysis of operating solid oxide electrochemical cells has proved to be difficult owing to high-vacuum requirements. Ambient-pressure X-ray photoelectron spectroscopy on single-chamber cells now suggests that surface reaction kinetics and electron transport on the electrodes are co-limiting processes.

Proton conductor oxides are promising materials for their use as electrolytes for reducing the operation temperature of solid-oxide fuel cells. Epitaxially oriented yttrium-doped barium zirconate films now show unprecedented proton conductivity in the 500–700 °C range.

Typically, electronic contributions have a very small effect on infrared absorption in solids. Now, however, a giant-infrared-absorption band of electronic origin has been observed in reduced graphene oxide. The band arises from the coupling of electronic states to the asymmetric stretch mode of a yet-unreported structure, consisting of oxygen atoms aggregated at edges of defects.

Flexible organic electronics could eventually be used to create electronic skin. Films of a pressure-sensitive microstructured elastomer are now used as the dielectric layer in organic field-effect transistors to create highly sensitive devices. The elastomer is also used in a matrix pressure sensor that can detect loads in numerous positions.

Using optical antennas in optoelectronic devices could lead to improved device performance. Photoemission from the inner core of core–shell single-walled nanotube structures where the optical bandgap of the core is smaller than that of the outer shells demonstrates that these structures channel excitons thereby acting as optical concentrators.

The selective reaction of one part of a bifunctional molecule is a fundamental challenge in heterogeneous catalysis. Modifying a supported palladium catalyst with alkanethiol self-assembled monolayers is now shown to increase selectivity for the hydrogenation of 1-epoxy-3-butane to 1-epoxybutane.

Structure–property relationships between material properties and stem cell behaviour are investigated using high-throughput methods. The data identify the optimal substrates within a range of different polymeric surfaces to support the growth and self-renewal of human embryonic stem cells from fully dissociated single cells.

The mixing of metals to form alloys with enhanced properties has been known at least since the Bronze Age, although being able to predict their properties remains difficult. An analytical model using computational input is now able to quantitatively predict the mechanical properties of metal yield stress in solute-strengthened alloys.

Nanoscale porous materials show unique properties that can be important for catalytic, separation and gas-storage applications. A strategy to yield crystalline porous compounds decorated with reactive nitrenes that can chemically trap and convert guest molecules by light stimulation is now reported.

Synthetic solid-state nanopores are of interest at present for their use as single-molecule sensors for characterization and detection of biomolecules. By using self-assembly evaporation and atomic-layer deposition, kinked silica nanopores are shown to exhibit reduction in DNA-translocation velocity and selectivity.

The detailed mechanism of the pH-dependent quenching of semiconductor quantum-dot/dopamine conjugates, confirming quinone as the electron acceptor in the process, is now reported. This electrochemical knowledge of the bioconjugate system is used for the in vitro detection of drug-induced intracellular pH changes.

The conversion of solar energy into electricity usually occurs either electrically or through thermal conversion. A new mechanism, photon-enhanced thermionic emission, which combines electric as well as thermal conversion mechanisms, is now shown to lead to enhanced conversion efficiencies that potentially could even exceed the theoretical limits of conventional photovoltaic cells.

The control of magnetization by electric fields is important for applications in data storage and sensing. An efficient control of exchange bias by electric fields has now been achieved in thin-film devices in which a ferroelectric antiferromagnet is coupled to a ferromagnet.

In the standard model of particle physics the permanent electric dipole moment of particles is zero, although competing theories suggest it must exist to explain the asymmetry of matter and antimatter in the Universe. The design and synthesis of a new multiferroic material may now enable us to search for the electric dipole moment of electrons with unprecedented precision.