Eco-friendly synthesis of zinc oxide nanoparticles using Dillenia indica leaf extract: Characterization and evaluation of biological properties

Zinc oxide nanoparticles (ZnO NPs) were synthesized using Dillenia indica leaf extract, and their structural, morphological, and functional properties were analyzed. UV-Visible spectroscopy confirmed the presence of ZnO NPs with an absorption peak at ∼360 nm with a band gap energy of 3.20 eV obtained from the UV-Visible reflectance spectra. X-ray diffraction (XRD) patterns revealed a hexagonal wurtzite crystal structure, with average crystallite sizes of 26.69 nm for non-calcined and 25.47 nm for calcined samples. Scanning electron microscopy (SEM) showed spherical morphology with average particle sizes of 32 nm (non-calcined) and 27 nm (calcined). Energy Dispersive X-ray Analysis (EDAX) confirmed zinc and oxygen presence, with a trace of carbon in non-calcined samples indicating phytochemical residues. Dynamic Light Scattering (DLS) exhibited larger hydrodynamic sizes (270.7 nm for non-calcined, 150.7 nm for calcined), while zeta potential values (-50.9 mV non-calcined, -51.7 mV calcined) indicated high colloidal stability. Fourier-transform infrared spectroscopy (FTIR) highlighted organic functional groups in non-calcined samples, which diminished after calcination. The thermal analysis revealed excellent thermal stability of ZnO nanoparticles, with minimal mass loss (2.27%) up to 1200 °C, highlighting their suitability for high-temperature applications. Antimicrobial studies showed moderate activity against Gram-positive bacteria, with non-calcined ZnO NPs exhibiting slightly better performance. The antioxidant assays demonstrated that non-calcined ZnO NPs had superior radical scavenging activity, potentially due to retained bioactive phytochemicals. These findings suggest that the green synthesis of ZnO NPs using D . indica provides a viable method for producing bioactive nanomaterials with potential applications in antimicrobial and antioxidant domains.