Phase-controllable synthesis of CuxS nanocrystals by an ambient pressure tetraethylene glycol solution process

An ambient pressure solution chemical process using tetraethylene glycol as solvent, copper(II) chloride and thioacetamide as precursors, polyvinylpyrrolidone as capping agent synthesized CuxS (x = 1 or 1.8) nanocrystals by injecting Cu(II) precursor solution into thioacetamide precursor solution at 200–280 °C. Influence of the synthesized temperature and refluxing time on the formed phases and growing morphologies of CuxS nanocrystals was investigated based on XRD, TEM, HRTEM and EDX. Optical properties of the synthesized CuxS nanocrystals were characterized. The results showed that single-phase, snowflake-like shaped covellite CuS nanocrystals were formed at injection temperature of 220 °C and below. And single-phase, well-dispersed, polyhedral-shaped digenite Cu1.8S nanoparticles were grown at injection temperature of 260 °C and above. The formation mechanism of the CuS and Cu1.8S nanocrystals in this phase-selective solution synthesis was discussed.