Water-induced thermolytic formation of homogeneous core-shell CuS microspheres and their shape retention on desulfurization

Homogeneous inorganic core-shell microspheres made from hexagonal CuS are synthesized via thermolysis of Cu(R(2)dtc)(2) (R = octyl, dtc = dithiocarbamate) precursor at 130-180 degrees C under N-2 flow, optimally at 180 degrees C for 0.5 h. Scanning electron microscopy (SEM) analyses indicate that the core-shell microspheres have an average diameter of 1.74 mu m (sigma = +/- 12.7%) with a shell thickness of about 225 nm. Their formation is induced by the small amount of water in the precursor. A tentative formation mechanism is speculated. Interestingly, the as-made cupric sulfide CuS microspheres undergo a reduction to tetragonal cuprous sulfide Cu2S microspheres without morphology changes via solid-state annealing at 400 degrees C under N-2 atmosphere. The microspheres made over 400-700 degrees C are invariably tetragonal Cu2S phase.