Volume 12 Issue 5, May 2013

Topological insulators have generated much interest in condensed-matter physics. The synthesis and characterization of Bi₁₄Rh₃I₉, a so-called weak topological insulator, demonstrates that chemists also have much to offer to the field.

Two-photon luminescence in metallic nanostructures provides a unique signature of the number of plasmonic modes per unit energy and volume, paving the way for more efficient plasmonic sources, detectors and sensors.

Understanding heat flow across interfaces remains an open question for thermal science. Nanocrystal arrays may play a key role in unlocking this mystery.

Stem cells alter their morphology and differentiate to particular lineages in response to biophysical cues from the surrounding matrix. When the matrix is degradable, however, cell fate is morphology-independent and is directed by the traction forces that the cells actively apply after they have degraded the matrix.

Measuring and characterizing dynamic charge density waves in cuprate superconductors is a challenging task. By using a method based on ultrafast spectroscopy, the problem is overcome and detecting the presence and lifetimes of these fluctuations is made possible.

Artificially grown superlattices consisting of iron pnictide materials offer a strategy for tailoring their superconducting properties. The fabrication of compositionally modulated oxygen- and cobalt-doped BaFe₂As₂ heterostructures yields vertically aligned defects that introduce strong vortex pinning sites and enhance the materials’ critical current density.

The tunnelling electroresistance effect that occurs at ferroelectric tunnel junctions could form the basis for a class of potential memory applications. Now, an enhanced effect is observed in a complex oxide interface as a result of a ferroelectrically induced phase transition.

Despite recent progress in the production of bendable thin-film transistors, their development is limited by leakage currents and fragile inorganic oxides. Combining graphene and single-walled carbon nanotube electrodes with a geometrically wrinkled inorganic layer, highly stretchable and transparent field-effect transistors have now been demonstrated.

The optical and electronic performance of inorganic nanocrystal assemblies stabilized by organic ligands has been extensively investigated, whereas less attention has been paid to their thermal transport properties. It is now shown that the thermal conductivity of these composite systems is determined by the vibrational states of both inorganic and ligand regions, as well as by their relative volumes.

The fabrication of microchips with vertically stacked circuits is challenging because they require arrays of electrical interconnections between the circuits, where accessibility is limited. An approach to generate conductive, mechanically stable plug-and-socket interconnections through three-dimensional actin-filament self-organization and selective metallization offers a potential solution to this problem.

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.

Much less exploited than the spectral and spatial properties of surface plasmons (SPs) are their local density of states (SP-LDOS), which rule a number of important nanoscale phenomena. Using two-photon luminescence microscopy, the SP-LDOS in ultrathin gold nanoprisms is now visualized directly, allowing for the SP modal distribution to be tuned.

Although poly(vinylidene fluoride) is a well-known organic ferroelectric, its utilization in microelectronics has been hampered by the difficulty in obtaining uniform thin films. By exploiting a high-temperature deposition approach, smooth and thin films of the ferroelectric δ-phase polymorph of this material are now obtained, showing their potential for capacitors and non-volatile memories.

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 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.

Development of the classical lithium-ion technology based on liquid electrolytes has been limited to a certain extent by the intrinsic instability of liquid electrolytes and their mechanical properties. A multifunctional single-ion polymer electrolyte based on polyanionic block copolymers consisting of polystyrene segments is now shown to exhibit enhanced lithium-ion transport, mechanical properties and electrochemical stability window.

Adhesive interactions between stem cells and the extracellular matrix are known to regulate stem cell differentiation, yet the underlying mechanisms are not well understood. It is now shown that fate decisions of stem cells encapsulated in covalently crosslinked hydrogels are regulated, independently of matrix mechanics and cell morphology, by the cellular tension generated from cell-induced degradation of the hydrogels.