Phase selective synthesis of copper sulfides by non-hydrolytic sol–gel methods

Copper sulfide nanoparticles have many potential applications, however, difficulties with controlled synthesis of specific polymorphs, and long term stability of phases with desirable properties, have hampered their implementation. In this work, non-hydrolytic sol–gel chemistry was used for precisely controlled synthesis of five different CuxS polymorphs, namely β-chalcocite, α-chalcocite, djurleite, low digenite and covellite. All polymorphs could be obtained as nanoparticles by adjusting reaction conditions. Notably, α-chalcocite nanoparticles were considerably more stable than any previously reported. In addition, continuous phase evolutions between several sets of copper sulfide polymorphs, and intermediate structures between certain structures, were observed. A route to synthesize digenite with an unusual stoichiometry by grinding β-chalcocite, α-chalcocite or djurleite was also discovered.