Mechanochemical Preparation of Cobalt Nanoparticles through a Novel Intramolecular Reaction in Cobalt(II) Complexes

Abstract

A novel solid state reaction involving a series of cobalt(II) hydrazine-azides has been used to prepare metallic cobalt nanoparticles. The reactions of [Co(N2H4)(N3)2], [Co(N2H4)2(N3)2], and [Co(N2H4)(N3)Cl]·H2O via NaOH, KOH as reactants were carried out in the solid state. These complexes undergo an intramolecular two-electron oxidation-reduction reaction at room temperature, producing metallic cobalt nanoparticles (Co1–Co6). The aforementioned complexes contain cobalt(II) that is an oxidizing agent and also hydrazine ligand as a reducing agent. Other products produced include sodium azide and ammonia gas. The cobalt metal nanoparticles were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The synthesized cobalt nanoparticles have similar morphologies; however, their particle size distributions are different.