Surface and photocatalytic properties of TiO2 thin films prepared by non-aqueous surfactant assisted sol-gel method

Abstract

Titanium dioxide (TiO2) thin films are prepared on glass substrates using sol-gel spin coating method. Titanium tetraisopropoxide (TTIP) precursor is used to prepare TiO2 sol-gels using Ethanol solvent. Acetyl acetone (AcAc) and Acetic acid (AA) are used as modifiers and Cetyltrimethylammonium Bromide (CTAB) surfactant as pore-forming agent. A clear transparent TiO2 sol-gel is obtained without precipitation only when both AA and AcAc are present in the TiO2 sol. A worm-like structure is observed in the film at 0.1 M TTIP and changed to the flake-like structure in the film at 0.4 M TTIP. The TiO2 thin films are non-porous and porous when CTAB is below and above the concentration of 0.8 g per 0.01 mol TTIP. The critical micelle concentrationis found to exist between 0.6 to 0.8 g CTAB per 0.01 mol TTIP. Grazing Incidence X-ray diffraction and Raman analysis confirm the presence of anatase phase in the 3 and 4 times coated TiO2 thin films. The field emission scanning electron microscopy analysis shows that a highly homogeneous and uniform thin film is obtained with TiO2 sol-gel composition of 0.2 M TTIP, 0.1 M AcAc, 0.09 M AA and 1 g of CTAB per 0.01 mol TTIP. The photocatalytic activity of the TiO2 films is determined by investigating the photodegradation of methylene blue (MB) in aqueous solution. The TiO2 thin film with 110.7 nm and 145.3 nm thickness showed 42.6 % and 58.4 % degradation of MB, respectively, at 60 min of photocatalytic reaction under UV light irradiation.