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The electrocatalytic performance of noble metal nanoparticles depends upon their size, shape, composition, and crystalline facets. Here we demonstrate the shape-dependent electrocatalytic activity of Au nanoparticles toward ascorbic acid oxidation in acidic medium, wherein the catalysis is strongly influenced by the shape of the nanoparticles. The synthesis of (popcorn, tetrapod, and bipod shaped) Au nanoparticles was carried out using a systematic variation of the surfactant concentrations based on the seed-mediated growth technique at room temperature. Due to the facile electrostatic interaction of the positively charged Au nanoparticles with glassy carbon electrode, the modification of the surface with variable-shaped Au nanoparticles is accomplished without involving any binding agents. Among variable-shaped face-centered cubic (fcc) crystalline AuNPs, bipod-shaped Au nanoparticles (GNBipd) exhibit a superior electrocatalytic performance over tetrapod-shaped (GNTepd) and popcorn-shaped (GNPop) nanoparticles as inferred from the differential pulse voltammetry and electrochemical impedance spectroscopy. The results have been explained by invoking the relative surface free energy (?) with preferentially exposed crystal planes, relative surface area (A), zeta potential (?), and the curvature-induced charge density (?q) at the apex for individual variable-shaped gold nanoparticles. � 2015 American Chemical Society.

Mesoporous TiO2 has been obtained by template synthesis. The introduction of a surfactant in the hydrolysis of tetrabutoxytitanium in aqueous ethanol allows the structure of the resulting material to be controlled. The amorphous TiO2 resulting from hydrolysis turns into anatase on being calcined at 300°C. As determined by X-ray diffraction, the anatase crystallite size is 70 nm in the presence of the highest surfactant concentration examined and 210 nm in the absence of a surfactant. Amorphous materials have been characterized by electron microscopy and differential thermal analysis. The ultimate benzene adsorption value has been determined for calcined mesoporous TiO2. © 2010 Pleiades Publishing, Ltd.

The effect of surfactants sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) on the surface roughness, surface morphology and surface topography of electroless nickel (EN)-phosphorus surface protective coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactant concentrations on the surface roughness of coated samples were investigated. It was observed that the surface roughness, surface morphology and surface topography of Ni-P coating were clearly influenced by the addition of surfactants SDS and CTAB. EN deposits with addition of surfactant SDS and CTAB at a concentration of 0.6 g/l produce a smooth surface and the average roughness (Ra) value is 1.715 ?m for SDS and 1.607 ?m for CTAB which is less than the Ra value of EN deposit without surfactant addition (1.885 ?m). The mean average roughness (Ra) value with addition of surfactant is 1.796 ?m. EN deposit with addition of surfactants consists of a significant fraction of particles of nickel. In the presence of SDS, fine nickel particles have dispersed uniformly on the substrate surface resulting in smoother surface finish of the deposited layers. In the presence of CTAB, at lower concentrations (upto 0.6 g/l) coalescence of nickel particles have been deposited on the substrate surface and at the higher concentration (above 0.6 g/l) uniformly improved surface finish of the deposited layer is resulted. The complete experimental details, results obtained and their analysis are presented in this paper. � 2008 Elsevier B.V. All rights reserved.