Synthesis and Characterization of Nickel Nanoparticles

Metals precipitated from aqueous solutions are of common interest in the field of catalysis. The nanoscale metallic particles are used as catalysts for their better efficiency. Various chemical approaches developed for the preparation of colloidal metals, but reduction of metal salts seems to be the most common. In aqueous medium, stabilization of these nanoparticles is relatively difficult because of oxide and hydroxide formation.To this end heterogeneous synthesis of nickel nanoparticles in aqueous medium has been carried out using a mixture of cetyltrimethylammonium bromide, tetraethylammonium bromide and tetrabutylammonium bromide. heterogeneous nucleation was achieved by adding chloroplatinic acid solution which is reduced and forms tiny metallic Pt particles that act as foreign nuclei for the subsequent growth of nanoparticles. In this case, hydrazine hydrate has been used as a reducing agent to convert Ni ions to metallic Ni nanoparticles. To avoid coagulation of nanoparticles, pH of the solution has been adjusted in the range of 10-12 by adding NaOH solution. At an elevated temperature of 60◦C in a water bath the solution turned black and nickel nanoparticles were formed in about 5 hours. Then the reaction mixture was allowed to cool to room temperature. For a better precipitation of nanoparticles, chloroform-methanol solution was added to the reaction mixture and this solution was then centrifuged to separate the nanoparticles. After the nanoparticles were washed with a chloroform-methanol solution, they were dried under vacuum at room temperature. The nanoparticles have been characterized using XRD, DTG, TEM techniques. These particles have been used as effective catalyst for reduction of compounds with appropriate reduction potentials