Multifunctional ZnS-PVA nanocomposites: Photocatalytic removal of Rhodamine B with DFT and antimicrobial activity

A multifunctional ZnS-PVA nanocomposite was synthesized via a facile wet chemical method and evaluated for photocatalytic and antimicrobial applications. The material was comprehensively characterized using PXRD, FT-IR, UV-Vis, PL, SEM, and EDX analyses. Structural studies revealed the coexistence of wurtzite ZnS and zinc blende cubic phases with average crystallite sizes of 4.38 nm and 4.76 nm, respectively, and a direct band gap of 4.75 eV. Photocatalytic performance was assessed through the photocatalytic removal (decolorization) of Rhodamine B (RB) under natural sunlight. The nanocomposite achieved ∼90% dye removal within 120 min under the optimized photocatalytic conditions using 50 mg of catalyst in 100 mL of 20 ppm RB solution at pH 12. Kinetic analysis followed a pseudo-first-order model with an apparent rate constant of (0.01838 ± 0.0004) min −1 . Statistical analyses confirmed the significant influence of pH, catalyst dosage, and initial dye concentration on the RB removal efficiency. Density Functional Theory (DFT) calculations provided insights into the adsorption and interaction of RB with the ZnS−PVA surface, supporting the experimental results. The catalyst exhibited excellent stability and reusability, maintaining activity over five consecutive cycles. In addition to photocatalysis, the ZnS-PVA nanocomposite demonstrated potent antimicrobial activity against the fungus ( Alternaria alternata ) and Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli ). Statistical analysis further confirmed significant differences in microbial susceptibility, with A. alternata exhibiting the highest sensitivity toward the nanocomposite. Overall, the combined experimental, statistical, and theoretical results highlight the ZnS-PVA nanocomposite as a reusable, sunlight-driven photocatalyst and antimicrobial agent, offering an environmentally friendly strategy for pollutant removal and microbial inactivation.