Influence of Cu doping on the functionality of spray coated SnS₂ thin films and its photocatalytic degradation of dyes and antibacterial activity

Tin sulfide (SnS₂) is a material known for its effective photocatalytic activity due to its affordability and wide light spectrum response. To enhance and optimize its optical and chemical characteristics, doping is a straightforward approach that can improve its photocatalytic efficiency. This work focuses on the effect of Cu doping on the structural, optical, and photocatalytic properties of the thin films prepared by the spray-coating approach. XRD confirms the hexagonal SnS₂ structure. As the amount of Cu added increases, the crystallite size decreases while dislocation density rises. The XPS findings show that a low concentration of copper (2%) within the SnS₂ thin films exhibits both high solubility and exclusively a monovalent state, in contrast to the 4% concentration. The effective band gap is in the range of 1.9–2.2 eV. SEM image reveals a variety of morphologies, and the porosity is reduced with increasing Cu doping. Furthermore, the FTIR study confirms the Sn-S bond present at 753 cm⁻¹. EPR studies reveal the existence of sulfur vacancies in Cu-doped SnS₂. Mechanical properties were also affected, with an observed decrease in microhardness as the dopant concentration increased. The photocatalytic activity of the samples is studied by photocatalytic degradation of malachite green and Congo red dyes under visible light irradiation. Additionally, their antibacterial effect against Escherichia coli was examined. This study shows that an optimal amount of Cu doping can significantly increase the photocatalytic performance of SnS₂ for efficiently decomposing organic pollutants and enhancing antibacterial activities.