Volume 10 Issue 10, October 2011

Crystalline ice surfaces are found to exhibit an unusually large spread of vacancy formation energies, akin to an amorphous material. The finding has implications for the fundamental understanding of electrostatically frustrated surfaces and for the reactivity and catalytic properties of atmospheric ice.

X-ray illumination can be used to control the arrangement of oxygen atoms in cuprate superconductors, allowing the writing of regions of robust high-transition-temperature superconductivity.

Mimicking the complexity of the extracellular environment in synthetic hydrogels is hard. A simple two-photon excitation strategy to simultaneously immobilize multiple proteins with spatial control in three dimensions shows promise.

The electronic structure in the bulk of a crystal can be unveiled by hard X-ray angle-resolved photoemission spectroscopy.

The arrangement of defects in solid-state phases has an enormous influence on material properties. It is here shown that powerful X-rays can be used to change the properties of an oxide superconductor, thus effectively writing superconducting regions within an insulating matrix. The results open the way to the manipulation of superconductors and potentially other phases.

The coupling between electron spins and phonons could lead to a new typology of electronic devices. The effects of such coupling are now experimentally demonstrated by injecting sound waves into a magnetic strip. The results also help to explain the origin of the spin Seebeck effect, which has been controversial for a while.

The combined magnetic and thermoelectric properties of nanostructures have recently attracted considerable attention. It is now demonstrated that the Seebeck coefficient in a magnetic tunnelling junction is strongly dependent on the magnetic configuration.

Superparamagnetic nanoparticles under an external magnetic field align in the field’s direction to minimize magnetic-dipole interactions. By modulating and fixing the alignment of magnetic nanoparticles in polymeric microcomponents through photopolymerization, magnetic nanocomposite microactuators were programmed to undergo complex motion, such as anisotropic bending and crawling.

With only a few known useful room-temperature multiferroics, other ways of achieving materials showing magnetism as well as electrical polarization are sought. The discovery that the ferroelectric BaTiO₃ also shows magnetism at room temperature at the interface with iron or cobalt marks a new approach to achieving multiferroic properties.

Angle-resolved photoemission spectroscopy is possibly the most widely used technique to probe the electronic structure of crystals. Unfortunately the technique is usually too sensitive to surface properties. It is now demonstrated that by using hard X-rays as the incident radiation it is possible to probe the electronic structure in the bulk.

Organic ligands enhance the stability and the solution processability of semiconductor quantum dots, but they can impede charge transport in films of such nanoparticles. Passivation with atomic ligands now offers an alternative strategy that enables the fabrication of PbS colloidal-quantum-dot solar cells with power-conversion efficiencies of up to 6%.

Increasing the energy density of lithium-ion batteries is crucial for consumer electronics and electric-vehicle applications. A polyanionic material that crystallizes in the triplite structure by substituting 5at.% of Mn for Fe in a fluorosulphate material now exhibits an enhanced potential of 3.90 V for the Fe²⁺/Fe³⁺ redox couple.

Developing oxygen-electrode catalysts with high activity at low cost for renewable energy applications such as water splitting and fuel cells is challenging. A hybrid material of Co₃O₄ nanocrystals grown on reduced graphene oxide exhibits enhanced catalytic performance for the oxygen reduction and oxygen evolution reactions.

Methodologies capable of directly visualizing and detecting gases are important for a wide variety of applications that involve instantaneous decision-making in complex environments and locations. A strategy for the capture and detection of gases by co-operative structural transformations of a flexible porous coordination polymer and fluorescent reporter molecules is now reported.

First-principles calculations show that water molecules at the surface of crystalline ice have high variability in their binding energies. Such an amorphous character of a crystalline surface is unusual, and for ice it is a result of electrostatic frustration and the relaxation of geometric constraints. The findings have consequences for ice catalysis, surface pre-melting and growth.

Bioactive proteins within hydrogel scaffolds used to culture cells can guide cellular activities, but the control of the location of the proteins has proved difficult. Using the multiphoton laser of a confocal microscope, simultaneous patterning of two growth factors, which remain bioactive after immobilization, is now shown in three-dimensional hydrogels. The technique should be applicable to the patterning of a variety of proteins.