Stable cobalt nanoparticles passivated with oleic acid and triphenylphosphine

H T Yang, C M Shen, Y G Wang, Y K Su, T Z Yang, H J Gao
2003 Nanotechnology  
Monodisperse cobalt nanoparticles (NPs) are synthesized via a high-temperature thermal decomposition method in the presence of oleic acid and triphenylphosphine. The as-synthesized NPs are stable against further deep oxidation when they are kept in heptane (C 7 H 16 ). Time-dependent x-ray photoelectron spectroscopy studies indicate that the oxidation of the as-synthesized cobalt NPs by air is slow and the valence change of cobalt from the Co NP sample kept in heptane under air is not observed
more » ... ir is not observed for 120 days. The cobalt NPs have β-manganese type structure (also called ε-cobalt). Annealing the NPs at 500 • C under Ar (95%) + H 2 (5%) converts these particles from ε-Co to fcc-Co. Two-dimensional (2D) and three-dimensional (3D) self-assembled superlattices of passivated cobalt NPs are formed by slow evaporation of the carrier solvent.
doi:10.1088/0957-4484/15/1/014 fatcat:dfm3uo6jxzgexidmtj4xlvgcde