Green Synthesis and Characterization of Titanium Dioxide (TiO₂) Nanoparticles Using Rice Husk Extract

Abstract

Green synthesis of titanium dioxide (TiO₂) nanoparticles has emerged as an environmentally sustainable alternative to conventional chemical methods because it eliminates the use of hazardous reducing agents and utilizes naturally occurring phytochemicals for nanoparticle formation and stabilization. This study synthesized TiO₂ nanoparticles using aqueous rice husk (Oryza sativa) extract and evaluated their physicochemical properties using ultraviolet-visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX), and X-ray fluorescence (XRF). Rice husk extract was prepared by aqueous extraction and reacted with titanium tetraisopropoxide (TTIP), followed by drying at 110 °C and calcination at 500 °C for 2 h. UV–Vis analysis exhibited a characteristic absorption maximum at 374 nm, corresponding to an estimated optical band gap of 3.32 eV, confirming the formation of nanosized TiO₂. FTIR spectra revealed prominent absorption bands at 3332, 1550, 1274, 1021, 820, and 599 cm⁻¹, assigned to O–H, C–O, O–C–O, Ti–O–Ti, and Ti–O functional groups, demonstrating the participation of rice husk phytochemicals during nanoparticle synthesis and stabilization. XRD analysis showed diffraction peaks at 2θ = 25.39°, 27.50°, 36.16°, 41.26°, 48.05°, 53.92°, 54.37°, 56.64°, and 62.85°, confirming the formation of predominantly anatase TiO₂ with a minor rutile phase. SEM micrographs revealed predominantly spherical, agglomerated nanoparticles with rough and porous surface morphology, while EDX analysis identified titanium as the dominant element with 95.97 at.% and 96.71 wt.%. XRF analysis further confirmed high chemical purity, with TiO₂ constituting 87.09 wt.% of the total oxide composition and only trace quantities of other oxides. The excellent agreement among the UV–Vis, FTIR, XRD, SEM–EDX, and XRF analyses confirms the successful green synthesis of highly crystalline and chemically stable TiO₂ nanoparticles. These nanoparticles possess physicochemical characteristics suitable for photocatalysis, wastewater treatment, environmental remediation, antimicrobial coatings, and other sustainable nanotechnology applications..