Articles in 2013

Experimental realizations of topological insulators are relatively rare at present. Now, a structurally complex bismuth rhodium iodide is synthesized and shown to have a honeycomb-layered structure akin to that of graphene, but made up of bismuth and rhodium sheets.

The application of three-photon excitation to biomedical imaging is demonstrated by combining the three-photon excitation properties of ZnS nanocrystals and the visible emission from Mn²⁺ dopants. The biocompatible, doped nanocrystals are used for high-resolution cellular imaging and in vivo tumour-targeting imaging under non-invasive conditions.

Supercapacitors are electrochemical energy-storage devices that take advantage of electrostatic interactions between high-surface-area nanoporous electrodes and electrolyte ions. Molecular mechanisms at work inside supercapacitor carbon electrodes are now clarified with solid-state nuclear magnetic resonance.

The use of colloidal quantum dots in optical applications is hampered by difficulties in optimizing their physical properties. The synthesis of high-quality quantum dots that simultaneously exhibit narrow emission linewidths and minimal blinking potentially overcomes this problem.

Current strategies for fabricating quantum dots embedded within nanowires suffer from a number of shortcomings. Now, a versatile self-assembly approach is demonstrated for fabricating core–shell GaAs–AlGaAs nanowires with appealing optical properties.

The ultrafast dynamic phenomena associated with thin magnetic films irradiated by a laser pulse have been proposed to occur through a process involving spin transport. The observation that this is also the case when the films are covered by a non-magnetic capping layer provides compelling evidence in favour of this scenario.

The mechanical properties of a spider’s web are spatially mapped using Brillouin light scattering. This non-contact approach can probe the elastic properties of single fibres, intersection points and glue spots within the web, as well as measure how the elastic stiffness changes in supercontracted silk fibres.

Although molybdenum alloys — often used in turbines and fusion reactors — can be easily hardened, they suffer from low ductility and toughness. Now, a nanostructuring processing route that leads to a microstructure consisting of submicrometre grains with nanometric oxide particles uniformly distributed in the grain interior achieves high-strength molybdenum alloys with large tensile elongation at room temperature.

Microneedle arrays coated with a pH-sensitive releasable layer act as an intradermal delivery system for polyelectrolyte films containing bioactive molecules for DNA vaccination. The implanted films co-deliver DNA, transfection agents and adjuvants, promoting local transfection and generating immune responses that can be tuned from days to weeks.

The monitoring of cell survival and functionality following their in vivo transplantation remains a challenge in clinical cell therapy. Now, using magnetic resonance imaging techniques and microcapsules with pH-sensitive components, in vivo cell death and cell viability patterns can be assessed with high anatomical accuracy.

Controlling the charge and spin states of single molecular complexes at metal interfaces is a challenging task. Scanning tunnelling microscopy experiments now show that doping metal phthalocyanines with alkali ions is an effective way to achieve this.

It has been suggested that the cytoplasm of living cells can be described as a porous elastic meshwork bathed in an interstitial fluid. Microindentation tests now show that intracellular water redistribution plays a fundamental role in cellular rheology and that at physiologically relevant timescales cellular responses to mechanical stresses are consistent with such a poroelastic model.

Glasses with extraordinary kinetic stability have been made in the laboratory by physical vapour deposition. A computational algorithm that mimics such a deposition process now reveals that deposition at the temperature at which the configurational entropy vanishes leads to ultrastable glasses that are truly amorphous, pack uniformly and have energies that are equivalent to those of equilibrium supercooled liquids.