Binuclear Cu-Pyrazinylthiolate\nMolecular Precursor\nas a Gateway to Binary CuS and Ternary CuInS<sub>2</sub>, Cu<sub>2</sub>SnS<sub>3</sub>, and CuSbS<sub>2</sub> Nanoparticles

Copper-based\nbinary and ternary sulfides have attracted\nsignificant\nattention due to their excellent photophysical properties, making\nthem highly promising for high-performance photovoltaic devices. This\nstudy focuses on the synthesis and structural characterization of\nan air-stable binuclear Cu-pyrazinethiolate-phosphine complex, which\nserves as an efficient single-source molecular precursor for the preparation\nof CuS nanoplatelets. Furthermore, the utility of this complex as\na versatile molecular precursor for the preparation of copper-based\nternary sulfides, such as CuInS<sub>2</sub>, Cu<sub>2</sub>SnS<sub>3</sub>, and CuSbS<sub>2</sub>, has been demonstrated. A plausible\nmechanism for the facile formation of these ternary materials is proposed\nbased on the presence of disulfide (S–S) linkages in CuS. The\ncrystal structure, phase purity, and compositions of the nanoparticles\nwere confirmed using powder X-ray diffraction (PXRD), X-ray photoelectron\nspectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and\narea elemental mapping. Electron microscopic studies revealed the\nformation of a two-dimensional (2D) nanoplatelet morphology with varied\nshapes and sizes. Ultraviolet–visible (UV–vis) diffuse\nreflectance spectroscopy showed a slight blue shift in the band gap\nof the nanoparticles compared to their bulk counterparts, which can\nbe attributed to quantum confinement or surface lattice distortion\neffects. The band gap and the pristine nanoparticles were found to\nbe blue-shifted compared to the bulk material. Prototype photoelectrochemical\ncells, fabricated using pristine nanoparticles, exhibit nice photocurrent\ngeneration along with optimum photoswitching, which poses them as\nsuitable materials for clean-energy applications.