Biogenic Extract-Mediated Synthesis of Mg-Ni Co-Doped TiO2 Nanomaterial: A Sustainable visible light sensitized Catalyst for Dye and Bacterial Decontamination

Abstract

Tuning the optical and structural properties of TiO₂ nanoparticles through Mg and Ni co-doping, utilizing lemon juice as a capping agent via the sol-gel method for effective dye and microbial decontamination under visible light irradiation. The synthesized Nano catalysts were characterized using PXRD, which confirmed the formation of the anatase phase. The narrowing of the band gap was determined by UV-Vis DRS, revealing a reduction from 3.2 eV for undoped TiO₂ to 2.7 eV for MNT-2 and 2.5 eV for MNT-2L2. TEM and SEM techniques were employed to determine the lower particle sizes of MNT-2L2 6.2 nm compare to UDT and MNT2, which exhibited a spherical shape with smooth morphology. BET surface area analysis indicated a significant increase in surface area 61.89 m²/g for UDT, 102.34 for MNT2 and 182.79 m²/g for MNT-2L2.The substitutional doping of Mg and Ni into the TiO₂ lattice was analysed using FTIR and XPS techniques. Additionally, photoluminescence analysis was conducted to evaluate reduced electron-hole recombination and the formation of hydroxyl radicals. The EIS plot was used to examine charge transport and the flat band potential, which lies below the conduction band and hinders electron-hole recombination. Electrochemical analysis was performed to investigate the redox potential, peak current, diffusion coefficient in dark and visible light.VB-XPS measurements were performed to determine the valence band position after doping. Finally, the catalytic efficiency of the MNT-2L2 Nano catalyst was assessed by the degradation of Acid Red 249 dye, achieving complete degradation within 80 minutes. The catalyst was also evaluated for its antibacterial activity, demonstrating a zone of inhibition against Vibrio cholerae comparable to that of standard chloramphenicol.