Phytomediated Synthesis of Zinc Oxide (ZnO) Nanoparticles via Vitex negundo Leaf Extract: Characterization, Antibacterial and Antibiofilm Activity

This study provides evidence for the green synthesis of zinc oxide nanoparticles (ZnO NPs) using Vitex negundo leaf extract. The UV–Visible (UV–Vis) spectrum of ZnO NPs and calcinated ZnO NPs (ZnO-C) showed peaks at 370[Formula: see text]nm and 374[Formula: see text]nm, respectively, confirming zinc ion reduction to zinc oxide. The ZnO NPs and calcinated counterparts were further characterized by FTIR, XRD, FE-SEM and EDX. FTIR results revealed the presence of alcoholic and aromatic groups, like flavonoids, in the leaf extract. The XRD pattern showed a distinctive Wurtzite crystalline phase with a hexagonal shape. The Brunauer–Emmett–Teller (BET) analysis data revealed that ZnO’s surface area and pore size is 22.8[Formula: see text]m 2 /g and 12.9[Formula: see text]nm, whereas ZnO-C exhibited a surface area of 23.5[Formula: see text]m 2 /g and pore size of 13.1[Formula: see text]nm. The SEM data demonstrated numerous irregular and agglomerated flakes fusing to form a roughly spherical morphology with the size, in the range of 15–20[Formula: see text]nm and 11–16[Formula: see text]nm for ZnO and ZnO-C NPs, respectively. The results of the antimicrobial assay by disc diffusion method and MIC testing revealed that ZnO and ZnO-C NPs exhibited moderate to high antimicrobial activity against various microorganisms, indicating their application against bacterial infection. In addition, the ZnO NPs significantly disrupted the biofilm of Bacillus cereus and Pseudomonas aeruginosa, as confirmed by CV assay and fluorescent microscopy.