Green synthesis of TiO2 nanoparticles using <i>Azadirachta indica</i> flower extract and evaluation of their photocatalytic performance

Abstract

Industrial dyes such as methylene blue (MB) and methyl orange (MO) pose significant ecological risks when released into aquatic systems. In this study, titanium dioxide nanoparticles (TiO2 NPs) were synthesized via a green synthesis approach using Azadirachta indica flower extract and titanium tetraisopropoxide. The bioactive compounds in the extract acted as reducing and stabilizing agents, promoting the formation of anatase-phase TiO2. The synthesized nanoparticles were characterized using UV–visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and transmission electron microscopy (TEM). UV–vis analysis confirmed a bandgap energy of 3.2 eV, while XRD results indicated a tetragonal anatase structure. FT-IR spectra showed reduced intensities of N—H and C=O functional groups, confirming the role of biomolecules in nanoparticle stabilization. TEM images revealed predominantly spherical nanoparticles with sizes below 20 nm. Photocatalytic degradation studies demonstrated high efficiency, with maximum degradation of 99.30% for MB at pH 8 and 99.17% for MO at pH 5. The degradation followed first-order kinetics, with rate constants of 0.0403 min−1 for MB and 0.00773 min−1 for MO. These findings highlight the potential of green-synthesized TiO2 nanoparticles as an effective and sustainable photocatalyst for wastewater treatment.