“Green Chemistry Synthesis of Zinc Oxide Nanoparticles Using <i>Rosa indica</i> Leaf Extracts: Its Characterizations &amp; Antibacterial Activity Under Visible Light”

ABSTRACT Zinc oxide nanoparticles (ZnO NPs) possess unique physicochemical properties that have made them highly attractive across various industrial and biomedical fields. However, traditional methods for synthesizing ZnO NPs often involve the use of hazardous chemicals and energy‐intensive processes, raising concerns about their environmental and health impacts. In response to these challenges, green synthesis approaches, particularly those utilizing plant extracts have emerged as eco‐friendly and sustainable alternatives. In the current study, the green synthesis approach was adopted to synthesize ZnO NPs from the extract of Rosa indica leaves. The formation of NPs were confirmed by various characterization techniques. Powder X‐ray diffraction (XRD) indicates that the current ZnO NP exhibit rutile phase with a tetragonal crystal structure and is having an average crystallite size of 38.67 nm. Fourier transform infrared spectroscopy (FT‐IR) projected its Zn─O vibrational modes at 618 cm − 1 and 421 cm − 1 , hence confirms its successful synthesis. Surface morphology studies done by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed nanoparticle formation with porous structure. Energy dispersive X‐ray spectroscopy confirms the presence of Zn and O elements present in the sample. Ultraviolet‐visible absorption spectroscopy was used to investigate the optical band gap in the present sample. From this UV‐Vis data, the band gap was found to be around 3.15 eV. However, this energy gap is slightly blue shifted and is possibly due to its nano‐formation and hence band structure. These NPs were subjected to the photoluminescence (PL) spectroscopy and where we got indications of the possible defect states present in the system. The hydrodynamic diameter and poly dispersive index was determined by dynamic light scattering (DLS) experiments. DLS data suggests particle coalescing behavior. The surface charge in dissolving medium for these NPs was determined by zeta potential technique. The lower value of potential also suggest particle aggregation and is well correlating with other particle size measurements. The ZnO NPs were subjected to antimicrobial activities under different color of lights for various strains like Escherichia coli (EC 25922), Klebsiella pneumonia (KP 700603), and Staphylococcus aureus (ATCC 33591). Different zones of inhibition were observed under different colors of lights. A possible mechanism to explain metal oxide NPs in action is proposed. Further the composite films of ZnO‐PVA were prepared for food packaging applications (here for chicken breast meat). This food packaging studies (for the meat wrapped in these films) was conducted under visible light at room temperature. Here low concentrations of ZnO‐PVA composite films show the best results. From these studies it was concluded that in presence of light, even minimum concentration of ZnO (like NPs or its composite polymer films) can be used to reduce the growth of bacteria.