Protective Agent-Free Synthesis of Colloidal Cobalt Nanoparticles

Spherical colloidal cobalt (Co) nanoparticles of about 2–7 nm were synthesized by hydrazine reduction in ethylene glycol at 80° C. The mean diameter of the Co nanoparticles was varied to some extent by changing the pH, temperature, Co(II) chloride hexahydrate concentration, and amount of hydrazine. The Co particle size was reduced by decreasing Co(II) chloride concentration and increasing amount of hydrazine.