Solvothermal synthesis of Cu₃BiS₃ enabled by precursor complexing

Copper bismuth sulfide, Cu₃BiS₃, has been prepared by a solvothermal method that relies on precursor complexing to achieve the desired ternary chalcogenide preferentially over possible binary sulfides in the system. The complexing agent L-cystine also simultaneously donates sulfur to the compound when the complexes are dissociated at a single temperature. This low temperature and use of nitrate salts instead of the commonly employed but less "green" chloride salts provide a path toward cleaner methods. The reaction progression has been characterized by X-ray powder diffraction of sequential samples and shows complete reaction of reagents to form the Wittichenite phase. Spectroscopy analysis reveals confirmation of a direct bandgap at approximately 1.5 eV. Microscopy images reveal varying morphology dominated by nanorods and including particles with aspect ratios approaching 1:1. A low-temperature Cu3BiS3 synthesis employing L-cystine as a sulfur source and complexing agent, nitrate salt precursors, and pure ethylene glycol has been demonstrated.