Cosmos caudatus extract-intervened zinc oxide nanoparticles: reaction mechanism, molecular docking, and optical properties

Zinc oxide nanoparticles (ZnO NPs) are extensively applied in numerous domains, including photocatalytic, antibacterial, anti-inflammatory, and anticancer applications. Utilization of ZnO NPs in numerous domains has generated increasing demand. Therefore, it is imperative to consider an economical, highly efficient, and sustainable approach. One plausible method for accomplishing these criteria is biological. This study aimed to investigate the reaction mechanism and physical, chemical, morphological, and optical characteristics of ZnO NPs emanated from Cosmos caudatus leaf extract employing a bioreduction approach. Furthermore, molecular docking analysis was conducted to obtain insights into the specific interactions between ZnO NPs and proteins found within microbial cells. X-ray diffraction (XRD) validated the existence of ZnO NPs, bearing a mean crystallite diameter of 50.54 nm. The morphology observed through scanning electron microscopy (SEM) examination exhibited hexagonal-shaped particles with a relatively consistent size distribution. The maximum absorbance was noticed at 385 nm, characterized by a band gap of 3.04 eV. Molecular docking showed that the ligand (ZnO) bound to Escherichia coli and Aspergillus niger which possess bond energies of -3.4 kcal/mol and −2.6 kcal/mol, respectively, and Staphylococcus aureus with −2.3 kcal/mol.