Phytochemical mediated green synthesis of ZnO nanoparticles using Quercus infectoria Galls: Correlating crystallinity, morphology, and colloidal stability

Phytochemical-mediated green synthesis has emerged as a sustainable and efficient strategy for producing metal oxide nanoparticles with controlled physicochemical properties. In this study, zinc oxide nanoparticles (ZnONPs) were synthesized using aqueous gall extract of Quercus infectoria , a tannin-rich natural source, and the relationship between phytochemical composition and nanoparticle characteristics was systematically investigated. The synthesis was carried out using zinc sulfate under controlled temperature and pH conditions, followed by comprehensive characterization. UV–Visible spectroscopy revealed a characteristic absorption edge in the range of 360–380 nm, confirming the formation of ZnO nanoparticles and corresponding to intrinsic band gap absorption. FTIR analysis indicated the involvement of hydroxyl, carbonyl, and aromatic functional groups in Zn²⁺ chelation, nucleation control, and nanoparticle stabilization. X-ray diffraction (XRD) analysis confirmed the formation of crystalline ZnO with a hexagonal wurtzite structure, and the average crystallite size was determined to be approximately 71.24 nm. Scanning electron microscopy (SEM) images showed quasi-spherical nanoparticles forming aggregated clusters, while dynamic light scattering (DLS) analysis indicated a hydrodynamic diameter of 207.3 nm with a polydispersity index of 0.206. The zeta potential value of −28.3 mV confirmed moderate colloidal stability, attributed to surface-bound phytochemicals. The correlation between crystallite size, particle aggregation, and colloidal behavior highlights the critical role of phytochemical capping in nanoparticle formation. The findings demonstrate that Quercus infectoria galls serve as an effective phytochemical system for ZnO nanoparticle synthesis and provide insight into structure–property relationships in green nanomaterials. This study presents a reproducible and environmentally benign approach with potential for future applications in nanotechnology.