Tailoring ZnO Nanoparticles from Vitis, Senna, and Aegle Extracts for Forensic and Optoelectronic Applications

In the present study, ZnO nanoparticles (NPs) were synthesized using natural plant extracts—Vitis vinifera fruit (ZnOS1), Senna auriculata flowers (ZnOS2), and Aegle marmelos leaves (ZnOS3)—as bio-based fuels/surfactants via an ultrasonication-assisted solution combustion method. X-ray diffraction (XRD) analysis confirmed the hexagonal wurtzite crystal structure (space group P63mc) in all three samples, with average crystallite sizes estimated using both Scherrer's equation and the SSP (size-strain plot) method. Scanning electron microscopy revealed agglomerated and non-uniform surface morphology. Ther-mogravimetric analysis (TGA) indicated good thermal stability, supporting the suitability of the synthesized ZnO NPs for high-temperature applications. Optical band gap energies, determined from UV-Vis spectroscopy, were found to be 3.2, 3.17, and 3.12 eV for ZnOS1, ZnOS2, and ZnOS3, respectively. Photoluminescence (PL) spectra recorded at an excitation wavelength of 320 nm showed strong blue emissions, particularly in ZnOS2, suggesting potential use in forensic and security lighting applications. Among the three, ZnOS2 nanoparticles exhibited superior optical and luminescent behavior, along with excellent ridge detail in latent fingerprint development, demonstrating their strong potential for multifunctional and forensic applications.