Effect of Au ions on structural, optical, magnetic, dielectric, and antibacterial properties of TiO_2 dip-coated thin films

摘要

Physical properties of the TiO_2 and Au-doped TiO_2 films fabricated by sol-gel dip-coating route are investigated. The diffraction peaks of XRD spectra confirmed the formation of anatase phase. Crystallite size was found to be decreased by increasing dopant concentration from 12.02 to 10.10 nm. All the thin films annealed in air exhibit significant room-temperature ferromagnetism displaying anatase phase that can be employed in spintronic devices. The saturation magnetization increases from 6.8 to 10.35 emu/cm~3 with the increase in Au concentration. The coercivity values vary between 360.82 and 478.515 Oe and remnant magnetization ranges between 0.46 and 0.71 emu/cm3. Dielectric parameters obeyed Maxwell-Wagner model and Koop's theory and were explained by hopping mechanism. Small values of dielectric constant made them favorable for high-frequency devices. The band gaps of the undoped and Au-doped TiO_2 thin films is in the range 3.5 to 3.38 eV, which are lesser than those of reported pure TiO_2 (3.7 eV) that is favorable for enhancing solar cells efficiency. Au-doped TiO_2 leads to an optimum antimicrobial agent. The pho-tocatalysts having 5 wt% Au exhibit the highest photoactivities. The degradation of methylene blue under sunlight made them promising materials for water treatment.