Effect of surfactants on the size and shape of cobalt nanoparticles synthesized by thermal decomposition

Cobalt nanoparticles with various morphologies were synthesized by thermal decomposition of cobalt acetate in the presence of various surfactants at 260 degrees C. A combination of surfactants consisting of sufficient amount of oleic acid together with polyvinylpyrrolidone and oleylamine resulted in well-dispersed cubic cobalt nanoparticles of similar to 25 nm in average size. When 1,2-dodecanediol was added as a reducing agent to the surfactant mixture, triangular-prism-shaped nanoparticles of similar to 50 nm in average size were synthesized. Furthermore, an injection of trioctylphosphine into the reactor as an additional surfactant decreased the particle size to similar to 10 nm. The XRD pattern of the prism-like particles corresponded to hexagonal close-packed crystalline phase of cobalt. (C) 2006 American Institute of Physics.