Green synthesis, characterization and bioactivity of zinc oxide nanoparticles: Experimental and computational approaches

Abstract

Phyto-mediated nanoparticles (NPs) are known for their high biocompatibility, eco-friendliness, and cost-effectiveness, and they have been gaining significant attention recently. Here, we present a unique method for synthesizing zinc oxide nanoparticles (ZnO NPs) using Datura metel L. leaf extract as capping and reducing agents followed by characterization with X-ray diffraction (XRD), field emission electron microscopy (FESEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and UV–vis spectroscopy. XRD and TEM confirmed the formation of ZnO NPs. XRD reported a decrease in crystallite size from 32.9 to 26.5 nm, with strain proportionately increasing from 3.6 × 10⁻³ to 4.7 × 10⁻³. FESEM elucidated the morphology of the NPs and agglomeration was clear in the micrographs. FTIR identified the functional groups in the Datura metel L. leaf extract and supported the extract's qualitative phytochemical analysis. UV–vis spectroscopy confirmed the optical band gap of ZnO NPs ($E_g\sim$3.98–4.03 eV), further validated by the density function theory (DFT), computed HOMO-LUMO energy gap values. The bacterial isolates extracted from spoiled fruits and vegetables examined using tube techniques and congo red agar (CRA) for analysing phenotypic biofilm formation capability. ZnO NPs exhibited strong anti-biofilm activity against the primary biofilm-forming isolate - Klebsiella pneumoniae. Hence, this investigation demonstrated that the green synthesized ZnO NPs using Datura metel L. leaf extract promise to serve as an antibacterial reagent to avert the microbial spoilage of fruits and vegetables.