Polyaniline-graphite composites were prepared via in situ emulsion pathway, using different weight ratios of aniline to graphite. These composites were characterized for thermal, electrical, and spectral attributes. The thermal stability ($ 230 C) and electrical conductivity (67.9 S/cm) were improved significantly as compared with polyaniline doped with conventional inorganic dopants such as HCl (140 C and 10 S/cm). Scanning electron micrographs indicated a systematic change in morphology from globular to flaky with increasing amounts of graphite. The relative shifting of UV-visible bands indicates that some interactions exist between doped polyaniline and graphite. Absorptiondominated total electromagnetic interference shielding effectiveness of the order of À33.6 dB suggests that these materials can be used as futuristic microwave shielding materials. The good electrical conductivity and thermal stability make them ideal candidates for preparing conducting composites by melt blending with conventional thermoplastics such as polyethylene, polypropylene, and polystyrene, etc.

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Vertically aligned silicon nanowire (SiNW) arrays have been fabricated over a large area using a silver-assisted single-step electroless wet chemical etching (EWCE) method, which involves the etching of silicon wafers in aqueous hydrofluoric acid (HF) and silver nitrate (AgNO3) solution. A comprehensive systematic investigation on the influence of different parameters, such as the etching time (up to 15 h), solution temperature (10-80 °C), AgNO3 (5-200 mM) and HF (2-22 M) concentrations, and properties of the multi-crystalline silicon (mc-Si) wafers, is presented to establish a relationship of these parameters with the SiNW morphology. A linear dependence of the NW length on the etch time is obtained even at higher temperature (10-50 °C). The activation energy for the formation of SiNWs on Si(100) has been found to be equal to ∼0.51 eV . It has been shown for the first time that the surface area of the Si wafer exposed to the etching solution is an important parameter in determining the etching kinetics in the single-step process. Our results establish that single-step EWCE offers a wide range of parameters by means of which high quality vertical SiNWs can be produced in a very simple and controlled manner. A mechanism for explaining the influence of various parameters on the evolution of the NW structure is discussed. Furthermore, the SiNW arrays have extremely low reflectance (as low as <3% for Si(100) NWs and <12% for mc-Si NWs) compared to ∼35% for the polished surface in the 350-1000 nm wavelength range. The remarkably low reflection surface of SiNW arrays has great potential for use as an effective light absorber material in novel photovoltaic architectures, and other optoelectronic and photonic devices.

A potential driven self-assembly of sodium dodecyl sulfate/tungsten oxide aggregates at the electrolyte-electrode interface followed by template extraction and annealing yielded mesoporous thin films of electrochromic tungsten oxide (WO(3)). Electron microscopy images revealed that the films are characterized by a hitherto unreported hybrid structure comprising nanoparticles and nanorods with a tetragonal crystalline phase of WO(3) with the measured lattice parameters: a = 0.53 nm and c = 0.37 nm. In addition to pentagonal voids characteristic of the tetragonal WO(3) phase at the lattice scale, open channels and pores of 5-10 nm in diameter lie between the nanoparticles, which cumulatively promote rapid charge transport through the film. This resulted in colouration efficiency (η(max)∼90 cm(2) C(-1) at λ = 900 nm) and switching kinetics (colouration time =  3 s and bleaching time =  2 s for a 50% change in transmittance) higher and faster than previously reported values for mesoporous WO(3) films. Repetitive cycling between the clear and blue states has no deleterious effect on the electrochromic performance of the film, which is suggestive of its potential as a cathode in practical electrochromic windows.

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