Studies on the Fe³⁺ doping effect on structural, optical and catalytic properties of hydrothermally synthesized TiO₂ photocatalyst

Objective: Pure TiO₂ and Fe³⁺-TiO₂ nanoparticles have been prepared by a simple hydrothermal method with different Fe³⁺ concentrations. Method: The synthesized nanoparticles are analysed to determine its structural, optical, morphological and compositional properties using X-ray diffraction, Raman, UV-DRS, photoluminescence, Mossbauer, XPS, TEM and SEM/EDS. The EDS micrograph confirms the existence of Fe³⁺ atoms in the TiO₂ matrix with 0.85, 1.52 and 1.87 weight percent. The crystallite size and band gap decrease with increasing Fe³⁺ concentration. The average particle size obtained from TEM is 7-11 nm, in good agreement with XRD results. Raman bands at 640 cm^-1, 517 cm^-1 and 398 cm^-1 further confirm pure phase anatase in all samples. XPS results show the proper substitutions of a few sites of Ti⁴⁺ ions by Fe³⁺ ions in the TiO₂ host lattice. Conclusion: The intensity of PL spectra for Fe³⁺-TiO₂ shows a gradual decrease in the peak intensity with increasing Fe³⁺ concentration in TiO₂, and it indicates a lower recombination rate as the Fe³⁺ ion concentration increases. These nanoparticles are further studied for its photocatalytic activities using malachite green dye under UV, visible and sunlight.