Optimized photocatalytic degradation of dyes using Ag and Cu-Doped ZnS quantum dots embedded in PVA membranes

In this study, silver (Ag) and copper (Cu) dual-doped zinc sulfide (ZnS) photocatalysts were synthesized using the coprecipitation method and tested for their efficiency in degrading dyes such as Acid Orange, Auramine O, Methylene Blue, Methyl Orange, Rhodamine B, and Crystal Violet under sunlight. X-ray diffraction (XRD) confirmed a cubic structure with high phase purity, and Ag doping reduced the crystalline size. Transmission electron microscopy (TEM) revealed crumpled quantum dots (QDs), while ultraviolet–visible (UV–Vis) spectroscopy showed bandgaps of 3.73, 3.71, and 3.63 eV for Cu, (Cu, 1 % Ag), and (Cu, 2 % Ag)-doped ZnS QDs, respectively. The inclusion of Ag reduced the bandgap, enhancing photocatalytic performance. The degradation efficiencies were 93.09 %, 99.49 %, and 99.95 % for Cu, (Cu, 1 % Ag), and (Cu, 2 % Ag)-doped ZnS QDs, respectively, after 180 min. Dual doping significantly improved performance over Cu-doped QDs, with a rate constant of 49.99 × 10⁻³ min⁻¹ and an R² value of 0.9374. Ag ions further enhanced activity by reducing electron-hole recombination. Additionally, polyvinyl alcohol (PVA)-embedded ZCA3 QDs demonstrated high reusability over five cycles. The study also investigated the effects of dosage, dye variation, and hemolytic activity.