Rubia-inspired biogenic synthesis of Cu–ZnO nanocomposites: dual-modelling of visible light photocatalytic degradation and antibacterial assessment

Cu-doped ZnO nanoparticles (NPs) were synthesised using Rubia cordifolia root extract and their photocatalytic degradation and antimicrobial properties were evaluated. Among all dopant concentrations, UV-VIS analysis of 5 % Cu–ZnO NPs revealed a clean shift towards the visible range with a reduction in the band gap from 3.2 eV for pristine ZnO to 2.98 eV. Formed NPs were identified as wurtzite crystal structure (size of 16.67 nm) having functional group of ZnO, using XRD and FTIR analysis. Highest photocatalytic degradation efficiencies of both Alizarine Red (AZ) (80 %) and Rhodamine B (RhB) (82 %) dyes were by 5 % Cu–ZnO NPs. Statistical modelling and optimization were conducted using Response Surface Methodology (RSM) and Adaptive Neuro-Fuzzy Inference System (ANFIS), resulting in development of models having >90 % predictive accuracy. Furthermore, the biogenic Cu–ZnO nanoparticles exhibits effective antimicrobial properties against both gram-positive (S. aureus) and gram-negative (E. coli) bacteria. The biogenic synthesis approach demonstrated enhanced photocatalytic efficiency and antimicrobial properties, suggesting its potential for environmentally friendly applications.