Biosynthesis and Characterization of <scp>ZnO</scp> Nanoparticles Using <scp> <i>Dillenia indica</i> </scp> L. Sepals Extract and Their Concentration Effects on Properties of <scp>PVA</scp> Nanocomposite Films

ABSTRACT In the present study, biosynthesis of zinc oxide nanoparticles (ZnO NPs) was carried out using the underutilized aqueous sepals extract of Dillenia indica as a natural resource. The synthesized ZnO NPs (0.1%, 0.3%, and 0.5%) were reinforced into a polyvinyl alcohol (PVA) matrix, and their effects on the morphological, thermal, mechanical, and barrier properties of PVA nanocomposite films were reported. The prepared ZnO NPs were characterized to analyze their functional groups, UV absorption properties, crystalline structure, elemental composition, surface morphology, zeta potential, hydrodynamic measurements and antimicrobial activities. The peaks of XRD diffraction were closely aligned with the standard pattern for hexagonal wurtzite ZnO. The mean crystallite size of the ZnO NPs was found to be 12.83 nm. The hydrodynamic diameter of ZnO NPs was 580.2 nm with a polydispersity index (PDI) of 0.606. The maximum antibacterial activity was observed at the concentration of ZnO NPs (0.5%) against E. coli (24.90 ± 0.656 mm) and S. aureus (21.18 ± 0.928 mm). The reinforced effects of ZnO NPs significantly enhanced the tensile strength (TA) of the PVA nanocomposites from 39.736 ± 1.431 MPa to 53.209 ± 0.983 MPa with the addition of 0.3%, respectively. The water vapor permeability (WVP) of the films was significantly decreased from 36.160 ± 1.860 (g·mm/m 2 ·day·kPa) to 10.883 ± 0.552 (g·mm/m 2 ·day·kPa) with increasing ZnO NPs concentration. In conclusion, the antibacterial activity of synthesized ZnO NPs and their positive impact on the properties of PVA nanocomposite films make them suitable for food safety applications.