Potential Synthesis of Nickel and Cobalt Nanoparticles via Sonochemical Decomposition and Reduction of Nickelocene and Cobaltocene

We investigate the synthesis of nickel and cobalt nanoparticles at low temperatures (40 °C) via a sonochemical process with nickelocene and cobaltocene as starting materials. The reduction and decomposition behaviors of nickelocene and cobaltocene are studied using ultrasound irradiation for different concentrations of hydrazine. At 5 and 10 vol% of hydrazine, nickel nanoparticles are synthesized from nickelocene by direct hydrazine reduction without intermediate formation. However, at a hydrazine concentration of 50 vol%, nickel nanoparticles are formed from Ni-hydrazine complexes. In contrast, from cobaltocene, microsized cobalt particles are formed by multistep reduction at 50 vol% hydrazine. Because nickelocene is more unstable than cobaltocene, it is assumed that nickel is formed by direct reduction under ultrasound irradiation at low concentrations of hydrazine. This sonochemical process using metallocene is expected to be an eco-friendly synthetic process as it does not require pH control, as in the conventional processes, and can be conducted at 40 °C using a simple apparatus.