Green synthesis of CuS using garlic-derived sulfur: structural, morphological, optical, electrical, and photoresponse characterization with potential for thermoelectric applications.

In this study, we present an environmentally friendly and sustainable green synthesis method for CuS thin films using sulfur sources derived from garlic ( L.). This novel approach facilitates room-temperature sulfurization without the need for surfactants or artificial sulfur compounds, resulting in copper sulfide films with unique nanostructured morphologies. The synthesized CuS films were comprehensively characterized using FESEM, RBS, PIXE, Raman spectroscopy, Hall effect measurements, and DRS to evaluate their morphological, structural, optical, electrical, and photoresponse properties. FESEM analysis revealed well-defined nanostructures with a tubular sea coral-like morphology, while RBS and PIXE confirmed the successful formation and elemental composition of CuS with minimal impurities. Raman spectroscopy indicated the presence of both CuS and CuO phases, suggesting partial oxidation during synthesis. The optical properties assessed DRS demonstrated a significant reduction in the band gap energy from 2.06 eV to 1.63 eV with increasing exposure time, highlighting the tunability of the material. Hall effect measurements confirmed p-type semiconductor behavior with enhanced electrical conductivity over time, and the photoresponse study showed a strong sensitivity to visible light, making the films suitable for optoelectronic applications. Compared to conventional methods, our green synthesis offers a low-cost, scalable, and environmentally friendly alternative, with potential applications in photovoltaics and thermoelectrics. This study highlights the potential of garlic-derived sulfur for sustainable nanomaterial synthesis and paves the way for its integration into energy conversion technologies.