HEBM-assisted SSR synthesis of copper-doped ZnO nanocrystalline semiconductors: physical properties, dielectric behavior and enhanced antimicrobial efficacy against clinically relevant pathogens

This study explores copper-doped zinc oxide nanoparticles (Cu–ZnO NPs) synthesized via high-energy ball milling–assisted solid-state reaction, optimizing particle size, doping (3–9 wt.% Cu), medium state (solid/liquid), and visible-light activation for antimicrobial efficacy. Structural analysis (XRD, SEM, TEM/EDS) confirmed hexagonal wurtzite ZnO with Cu²⁺ lattice integration, uniform dopant distribution, and particle refinement to ~50 nm post-milling. Bandgap reduction (0.13 eV) enhanced charge mobility and ROS generation. Solid-state NPs exhibited superior antimicrobial activity, achieving inhibition zones of 14.8 mm (Staphylococcus aureus) and 19.7 mm (Staphylococcus epidermidis), outperforming liquid-phase results (p < 0.05). Light activation amplified ROS production, elevating Candida albicans inhibition to 23.0 mm. Size reduction enabled unprecedented inhibition of gram-negative Klebsiella oxytoca (12.4 mm). The synergy of Cu doping, particle refinement, and light activation underscores Cu–ZnO NPs as scalable, tunable antimicrobial agents against resistant pathogens, with potential applications in clinical and industrial settings.