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Here, the utility of large-area graphene as a flexible, biocompatible electrode to stimulate cell growth is demonstrated. Chemical vapor deposition allows the production of highly crystalline, single, double, or few-layered graphene on copper substrates. The subsequent transfer to a biopolymer support, such as polylactic acid (PLA) or polylactic-co-glycolic acid (PLGA) copolymers, provides a unique electrode structure retaining the flexibility and surface properties of the underlying materials with a conductive graphene layer sufficient to enable electrical communication with excitable cells. The growth and compatibility of PC-12 cells on these graphene-biopolymer (GPB) electrodes is influenced more by the underlying polymer than the presence of graphene, demonstrating that the characteristics influencing biocompatibility have been retained after graphene modification. Differentiation of these cells into neural phenotypes is enhanced using electrical stimulation through the graphene conductive layer, confirming that the conductivity of graphene is sufficient to electrically communicate with cells grown on the surface. The process described herein demonstrates that non-conducting, flexible biopolymer surfaces can be easily coated with graphene without changing the biocompatibility of the materials. This could be used to create electrodes from non-conducting materials with optimized cell compatibility with graphene providing electrical properties suitable for stimulation of cells without greatly changing the surface properties. Bilayer graphene, transferred as a layer onto biopolymers, is used as a flexible biological interface material for electrical cell stimulation. Bilayer graphene provides a conductive layer without changing the cytocompatibility of the underlying layer, allowing electrical stimulation of cells on substrates of chosen composition. The production of flexible, biocompatible electrodes is described and the differentiation of neural cells is demonstrated for the first time from a graphene-based electrode. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In the quest to discover the properties of planar semiconductors, two-dimensional molybdenum trioxide and dichalcogenides have recently attracted a large amount of interest. This family, which includes molybdenum trioxide (MoO 3 ), disulphide (MoS 2 ), diselenide (MoSe 2 ) and ditelluride (MoTe 2 ), possesses many unique properties that make its compounds appealing for a wide range of applications. These properties can be thickness dependent and may be manipulated via a large number of physical and chemical processes. In this Feature Article, a comprehensive review is delivered of the fundamental properties, synthesis techniques and applications of layered and planar MoO 3 , MoS 2 , MoSe 2 , and MoTe 2 along with their future prospects.

Blue light-emitting oligotriphenylene nanofibers are synthesized by oxidizing triphenylene using ferric chloride. By adjusting the monomer concentration, the acid used, and the temperature employed, the average diameter and length of the nanofibers can be readily tuned from 50 to 200 nm and 0.5 to 5 μm, respectively. Structural characterization, electrical conductivity, thermal stability, and fluorescence of oligotriphenylene, along with a pro posed nanofiber formation mechanism, are presented. Both oligotriphenylene nanofiber dispersions and oligotriphenylene/polysulfone composite films are developed as fluorescent sensors for detecting traces of nitro-based explosives including nitromethane, nitrobenzene, and 2,4,6-trinitrophenol, as well as an electron-deficient metal ion, Fe(III). The sensors exhibit much better selectivity and sensitivity compared to conventional sensors, with detection limits down to 1.0 nm with a detection range covering ∼4 orders of magnitude. The detection mechanism of the fluorescent sensors is also disscussed.

Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their full potential. Tungsten oxides (WOx) are unique materials that have been rigorously studied for their chromism, photocatalysis, and sensing capabilities. However, they exhibit further important properties and functionalities that have received relatively little attention in the past. This Feature Article presents a general review of nanostructured WOx, their properties, methods of synthesis, and a description of how they can be used in unique ways for different applications. Tungsten oxides (WOx) are unique functional materials that can be obtained in a vast variety of nanostructured forms. This Feature Article presents a comprehensive review on the properties of WOx that goes beyond chromism and photocatalysis, for which they are usually investigated for. This is followed by a survey of their synthesis methods and implementations for different applications.

Dense transition metal borides have recently been identified as superhard materials that offer the possibility of ambient pressure synthesis compared to the conventional high pressure, high temperature approach. This feature article begins with a discussion of the relevant physical properties for this class of compounds, followed by a summary of the synthesis and properties of several transition metal borides. A strong emphasis is placed on correlating mechanical properties with electronic and atomic structure of these materials in an effort to better predict new superhard compounds. It concludes with a perspective of future research directions, highlighting some recent results and presenting several new ideas that remain to be tested.

Thermoelectric power sources have consistently demonstrated their extraordinary reliability and longevity for deep space missions and small unattended terrestrial systems. However, more efficient bulk materials and practical devices are required to improve existing technology and expand into large-scale waste heat recovery applications. Research has long focused on complex compounds that best combine the electrical properties of degenerate semiconductors with the low thermal conductivity of glassy materials. Recently it has been found that nanostructuring is an effective method to decouple electrical and thermal transport parameters. Dramatic reductions in the lattice thermal conductivity are achieved by nanostructuring bulk silicon with limited degradation in its electron mobility, leading to an unprecedented increase by a factor of 3.5 in its performance over that of the parent single-crystal material. This makes nanostructured bulk (nano-bulk) Si an effective high temperature thermoelectric material that performs at about 70% the level of state-of-the-art Si0.8Ge0.2 but without the need for expensive and rare Ge.

The global supercapacitor market has been growing rapidly during the past decade. Today, virtually all commercial devices use activated carbon. In this work, it is shown that laser treatment of activated carbon electrodes results in the formation of microchannels that can connect the internal pores of activated carbon with the surrounding electrolyte. These microchannels serve as electrolyte reservoirs that in turn shorten the ion diffusion distance and enable better interaction between the electrode surfaces and electrolyte ions. The capacitance can be further increased through fast and reversible redox reactions on the electrode surface using a redox-active electrolyte, enabling the operation of a symmetric device at 2.0 V, much higher than the thermodynamic decompostion voltage of water. This simple approach can alleviate the low energy density of supercapacitors which has limited the widespread use of this technology. This work represents a clear advancement in the processing of activated carbon electrodes toward the next-generation of low-cost supercapacitors.