Phytochemical-Mediated ZnO Nanoparticles from Chromolaena odorata: Structural Characterisation and Antimicrobial Efficacy against Multidrug-Resistant Clinical Isolates, Nigeria

Abstract

Nanoparticles (NPs), ranging from 1–100 nm, exhibit unique properties due to their compact atomic arrangement, enhancing mechanical, electrical, magnetic, optical, catalytic, and antibacterial characteristics compared to macroscopic materials. The rising threat of multidrug-resistant pathogens necessitates novel antimicrobial agents. This study explores the green synthesis of zinc oxide nanoparticles (ZnO NPs) using Chromolaena odorata leaf extract with zinc acetate dihydrate (Sample A), zinc sulphate (Sample S), and zinc nitrate (Sample N) as precursors. The NPs were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, and ultraviolet-visible (UV-Vis) spectroscopy. XRD revealed wurtzite ZnO structures with crystallite sizes of 9.1–9.2 nm (A), 3.2–15.9 nm (S), and 7.5–38 nm (N). SEM showed spherical (A), irregular (S), and rod-like (N) morphologies, while EDX confirmed Zn and O as primary elements with trace phytochemical-derived elements. FTIR identified phenolic and flavonoid capping, and BET indicated high surface areas (235.505–325.475 m²/g). UV-Vis spectra displayed absorption peaks at 374–383 nm, consistent with ZnO’s bandgap. Antimicrobial assays demonstrated significant activity against multidrug-resistant clinical isolates from Enugu State University Teaching Hospital, Nigeria, including bacteria and Candida albicans, with Sample S’s high surface area correlating with enhanced efficacy. These findings highlight the role of precursor chemistry in tailoring NP properties and underscore the potential of Chromolaena odorata-mediated ZnO NPs as effective antimicrobial agents. The NPs’ biocompatibility and high surface area suggest further applications in wound healing and photocatalysis, warranting future in vivo and mechanistic studies.