Research articles

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.

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.

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.

Silver iodide is a well-known ionic conductor. However, it shows superionic conductivity only in its high-temperature phase (above∼150 ^∘C). It is now demonstrated that various sizes of nanoparticles can be synthesized for which the superionic phase is stable down to ∼30 ^∘C. The results suggest promising applications in silver-ion-based electrochemical devices.

The size distribution of polymer vesicles and phospholipids is usually polydisperse as there are no selection rules for the overall size. A method combining photolithography and molecular self-assembly can now produce giant polymer vesicles with controlled and narrow size distributions.

The high capacity and energy densities of lithium sulphur batteries make them promising for applications, but their widespread realization has been hindered by problems at the interface between the cell components. A conductive mesoporous carbon–sulphur cathode framework capable of constraining sulphur growth and generating electrical contact to the insulating sulphur is now reported.

Stretchable electronics enables applications on arbitrary curved surfaces or on movable parts to be made. Based on a new technique for printing with carbon nanotube pastes, stretchable active matrix displays containing integrated electronic circuits are now realized.

Fe-based superconductors have attracted tremendous interest recently. New evidence on BaFe₂As₂ shows that chemical doping and pressure, both of which induce superconductivity, distort the lattice in similar ways. The result provides important information in the quest for an understanding of the mechanism behind superconductivity.

Metal–organic frameworks are highly porous materials that are promising for drug release and gas storage. A liquid-phase-epitaxy approach that prevents interpenetration and retains the pore size is now proposed.

Free-standing nanoparticle superlattices offer interesting possibilities for the design of devices free from undesired effects of substrates. DNA can now be used to obtain superlattices with control over interparticle spacing, offering an alternative perspective on the synthesis of nanoparticle solids.

Concerns over safety and the inability to control release have hampered progress towards instilling siRNA into mucosal tissue for protection against and treatment of human disease. Nanoparticles made from FDA-approved polymers have now been loaded with large amounts of siRNA and topically applied to vaginal mucosa leading to sustained gene silencing.

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.

Multiferroics offer intriguing opportunities for sensing and information storage applications, although their integration into electronic devices has been difficult owing to a lack of suitable electronic control. Electric modulation of conduction is now achieved for a doped multiferroic, resulting in complete control over the ferroelectric state itself.

Microstructure evolution in complex nonlinear systems, such as quasiperiodic two-phase chessboard structures, is a fascinating fundamental phenomenon. It is demonstrated that under certain conditions a transformation from tweed to nanowire chessboards develops by spinodal decomposition.

A process based on spray-assisted layer-by-layer deposition produces conformal coatings on individual fibres within the bulk porous substrate. Additional processing creates a sublayer with properties that differ from the substrate. The method is used to fabricate a material that acts as both a toxin barrier and a photocatalyst.

The size reduction of thin-film ferroelectric capacitors has been hampered by effects that arise as ferroelectric films reach only a few unit cells in height. However, rather than inevitably resulting in a ‘dead layer’, an enhancement of ferroelectricity at certain metal–oxide interfaces is now predicted.

Explaining the quantitative relationships between processing conditions and oxide-layer geometry for the growth of porous anodic alumina has so far proved difficult. A model for steady-state growth of these amorphous films, incorporating metal and oxygen ions transported by plastic flow and coupled electrical migration, is now proposed.

Discotic liquid crystals are materials with high charge-carrier mobility, which are promising for molecular electronics. They self-organize into stacks, usually with a twist of 30^∘, but the shape and periphery of the molecules can now be altered to produce materials with a twist of 60^∘. Defect-limited mobilities of these materials reach 0.2 cm² V⁻¹ s⁻¹, but the potential defect-free mobility could be up to 10 cm² V⁻¹ s⁻¹.

The synthesis of highly pure diamond nanocrystals with a very small amount of paramagnetic impurities allows the observation of electron spin-dephasing times of up to 1.8 ms, a record for solid-state materials. The result could have important implications for quantum information processing methods based on diamond.

Freezing water containing salts is believed to produce pure ice and a salt hydrate. Neutron-diffraction measurements of the ice phase obtained by recrystallizing the glassy state of LiCl salt solution at high pressure suggests something different. The data reveal an ‘alloyed’ ice VII structure incorporating Li and Cl ions.