Catalytic behavior of nickel nanoparticles stabilized by lower alkylammonium bromide in aqueous medium

Heterogeneous synthesis of monodisperse pure nickel nanoparticles in aqueous medium has been carried out using cetyltrimethylammonium bromide and a lower alkylammonium bromide mixture of tetraethylammonium bromide and tetrabutylammonium bromide. The presence of cetyltrimethylammonium bromide alone results in the formation of a mixture of nickel hydroxide and nickel nanoparticles. The particles have been characterized using TEM, EDS, XRD, TGA-DSC and FTIR. The analysis showed that particles are spherical in shape, monodisperse, face-centered-cubic with average size about 15 nm and are stable in air up to 325 degrees C. The nanoparticles have been used as a solid phase catalyst for the reduction of p-nitrophenol in the presence of hydrazine hydrate as reducing agent at different temperatures under varying conditions. The reduction process has been monitored by UV-vis analysis. The present study showed that nanoparticles are not poisoned after their repeated use in reduction of p-nitrophenol to p-aminophenol. TEM analysis also confirms that nanoparticles are stable in the dispersed medium for longer times. (C) 2007 Elsevier B.V. All rights reserved.