Solvothermal synthesis of CuMS2 (M=Al, In, Fe) nanoparticles and effect of coordinating solvent on the crystalline structure

CuMS2 (M=Al, In, Fe) ternary compounds were synthesized via the facile polyol method in autoclave. Depending on the functional groups of solvent and surfactant, the structure of the nanocrystals can be controlled in the form of wurtzite or chalcopyrite. The chalcopyrite structure was obtained when the precursors solved in the mixture of diethylene glycol, polyethylene glycol 600 and ammonium hydroxide. When the solvent was replaced by ethylene diamine, the wurtzite was obtained along with chalcopyrite (polytypism). The products were characterized by X-Ray Diffraction (XRD) for analysis of structural properties, Transmission Electron Microscopy (TEM) for studying morphological properties, and absorbance spectrophotometer (UV-Vis-NIR) and photoluminescence (PL) for analysis of optical properties. The different optical band gap for CuAlS2 (3.48 eV), CuInS2 (1.51 eV) and CuFeS2 (0.65 eV) could be utilized for absorbance material in a whole range of sunlight wavelengths. The possible formation mechanism was also discussed.