Enhanced Antimicrobial Activity of Biogenic Zinc Oxide (ZnO) Nanoparticles

This study reports the facile biogenic synthesis of zinc oxide nanoparticles (ZnO NPs) using Tectona grandis (Teak) leaves and Curcuma longa (Curcumin) extracts as eco-friendly capping and reducing agents. Pathogenic bacterium (K. pneumoniae SGGDG) and fungus (Exophiala sp. SGVMC), identified by rRNA gene sequencing, were used for subsequent antimicrobial evaluation. UV–vis spectroscopy monitored the synthesis, revealing significantly faster kinetics with Curcumin (∼0.0083 min⁻¹) compared to Teak extract (∼0.0038 min⁻¹). Advanced characterization (XRD, FESEM, TEM, and FOM) confirmed nanocrystalline ZnO NPs and average crystallite sizes of ∼17.43 nm (Curcumin-capped) and ∼20.45 nm (Teak-coated), validating successful biogenic encapsulation. Crucially, antimicrobial assays demonstrated a remarkable enhancement in efficacy for the biogenically capped ZnO NPs. Curcumin-capped ZnO NPs exhibited superior antibacterial (1.095 cm inhibition) and antifungal (0.764 cm inhibition) activities against both pathogens, outperforming bare ZnO NPs and Teak-coated counterparts. This enhanced activity is attributed to a synergistic effect, likely involving reactive oxygen species generation and membrane disruption. These findings highlight a promising eco-friendly route for developing highly effective antimicrobial nanomaterials, particularly Curcumin-capped ZnO NPs, for diverse biomedical and environmental applications.