Green synthesis of Cu2S using garlic-derived sulfur: structural, morphological, optical, electrical, and photoresponse characterization with potential for thermoelectric applications

Abstract

In this study, we present an environmentally friendly and sustainable green synthesis method for Cu₂S thin films using sulfur sources derived from garlic (Allium sativum 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 Cu₂S 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 Cu₂S with minimal impurities. Raman spectroscopy indicated the presence of both Cu₂S and Cu₂O phases, suggesting partial oxidation during synthesis. The optical properties assessed via 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.