Volume 11 Issue 6, June 2012

Memristors are dynamic electronic devices whose nanoscale realization has led to considerable research interest. However, their experimental history goes back two centuries.

It is commonly presumed that the random displacements that particles undergo as a result of the thermal jiggling of the environment follow a normal, or Gaussian, distribution. However, non-Gaussian diffusion in soft materials is more prevalent than expected.

Colloidal particles interacting through DNA linkers can be designed to form solids that melt when either heated or cooled. This scenario widens the temperature window in which colloidal superlattices form by reducing kinetic bottlenecks.

Progress in organic electronics depends on our understanding of the structure–property relationships of organic materials. Resonant scattering of polarized soft X-rays by aromatic carbon bonds has now been used to probe molecular orientation in thin organic semiconductor films down to length scales of 20 nm.

To drive the formation of tubular structures, cells remodel their extracellular microenvironment to induce coordinated migration. It is now found that a mechanical feedback loop, involving the interaction of cell traction forces with collagen fibres, facilitates the formation of long epithelial tubules.

Geometrically frustrated magnets are systems where it is impossible for all magnetic interactions to occur simultaneously. The discovery of frustrated magnetism in a system where the magnetic moments are situated across clusters of transition-metal elements instead of individual ions promises a new approach for controlling such magnetic states.

Ultrafast and intense optical pulses have been used to study spin-density-waves in pnictide compounds, which are known to exhibit unconventional superconductivity. The results show that the magnetic order follows lattice motion, which suggests that a spin–phonon coupling may play an important role in the formation of spin-density-waves and superconductivity.

Understanding how heat is transferred across interfaces is important for the efficiency of micro- and nanoscale electronic devices. Here, it is shown that there is a direct link between the bonding character of an interface and the thermal transport across it.

The substitution of oxygen by hydride anions in oxide materials to form oxyhydrides has been difficult to achieve because it requires highly reducing conditions without transferring an electron from the hydride. An oxyhydride of BaTiO₃ that is electronically conducting, stable in air and water at ambient conditions, and exchangeable with hydrogen gas at 400 °C, has now been prepared.

Although sodium is an abundant element that can be electrochemically and reversibly extracted from and inserted into layered materials, the resulting reversible capacity for storing energy remains low. A manganese–iron–sodium-based electrode is now shown to exhibit a reversible capacity of 190 mAh g⁻¹ due to electrochemically active Fe³⁺/Fe⁴⁺ redox reactions.

The self-assembly of colloidal particles functionalized with complementary DNA strands into crystalline structures has been hampered by kinetic trapping into disordered aggregates, which effectively limits the temperature window where crystallization occurs. A strategy to design DNA-functionalized colloids with a broadened crystallization window is now proposed, and is supported by theory and simulations.

Magnetoelectric composite materials are of interest for sensitive magnetic-field sensors. The realization of a magnetoelectric composite that does not require an applied external magnetic field, but instead relies on internal bias via exchange coupling, promises sensitive sensors even for small magnetic fields.

Studying electrochemical equilibria at interfaces on the atomic scale is crucial for understanding physicochemical processes, but such investigations are currently limited by phase instabilities and instrumentation. A small amount of electron donors in a solid electrolyte is now shown to enable scanning tunnelling microscope measurements and atomically resolved imaging.

Molecular orientation, which critically influences the properties of organic materials, could until now only be characterized if the sample exhibited sufficient crystallinity. Resonant scattering of polarized soft X-rays by aromatic carbon bonds has now been used to probe non-crystalline ordering and molecular orientation in thin films with a resolution down to 20 nm.

Graphene oxide could potentially be used for numerous applications, particularly in electronics. Understanding its structural stability in an ambient atmosphere is essential for the realization of devices. A new study shows that multilayer graphene oxide is in fact metastable at room temperature.

Efficient electrochemical transformation of water to molecular hydrogen and of hydroxyl ions to oxygen in alkaline environments is important for reducing energy losses in water–alkali electrolysers. Insight into the activities of hydr(oxy)oxides on platinum catalyst surfaces for hydrogen and oxygen evolution reactions should prove significant for designing practical alkaline electrocatalysts.