Effect of precursor concentration of microstructured titanium-di-oxide (TiO2) thin films and their photocatalytic activity

Abstract

TiO2 thin films were synthesised by hydrothermal method on ITO coated glass substrate at a hydrothermal temperature of 160 °C for 24 h with different titanium precursor amount (0.3 ml, 0.5 ml, 0.7 ml, 1 ml). The band gap energy of prepared thin films varies from 3.2 eV to 3.6 eV. A sharp peak was observed at about 280 nm in the absorption spectrum, revealing a large band gap in the UV region. Reflectance spectra show high value with decreasing wavelength. XRD analysis confirms the presence of a TiO2 thin film phase. FESEM images of the thin films show sieve-like porous layered morphology. On the increasing amount of precursor, the porosity of the thin films increases. We calculated porosity from the transmittance data and the refractive index from the reflectance data. Particle sizes of the thin films were roughly found to lie between 10 nm–40 nm. Sharp emission at 440 nm is due to electron transition mediated by defect states. Small peaks between 450 nm–500 nm are assigned to free electron recombination from conduction band to the ground state. The visible light photocatalytic degradation rate of Methylene Blue (MB) is highest for the TiO2 thin film whose precursor amount is 0.5 ml. The kinetic rate of degradation and porosity is also greater for the same sample.