Green synthesis of niobium-doped ZnO nanoparticles using Eucalyptus globulus leaf extract for enhanced photocatalytic dye degradation and antibacterial applications

This study presents a novel green hydrothermal synthesis of niobium (Nb)-doped zinc oxide (ZnO) nanoparticles using Eucalyptus globulus leaf extract as a natural reducing and stabilizing agent. Nb doping was performed at 2 %, 5 %, and 8 % concentrations to optimize photocatalytic and antibacterial performance. Structural and morphological analyses via FTIR, XRD, DLS, EDX, SEM, and UV–Vis spectroscopy confirmed successful synthesis. XRD revealed a hexagonal wurtzite structure with crystallite sizes between 24 and 27 nm, and DLS showed hydrodynamic diameters ranging from 93 to 141 nm. UV–Vis analysis demonstrated a significant band gap reduction from 3.21 eV (pure ZnO) to 2.15 eV for 8 % Nb-doped ZnO, enhancing visible light absorption. The 8 % Nb/ZnO sample achieved 98 % degradation of methylene blue within 120 min under sunlight—outperforming lower doping levels and many reported green-synthesized ZnO systems. Additionally, it exhibited strong antibacterial activity against both Gram-positive and Gram-negative strains. These results highlight the effectiveness of optimized Nb doping and plant-mediated synthesis in producing multifunctional nanomaterials for sustainable water treatment and microbial control.