Sol gel derived photocatalytic porous TiO₂ thin films

Transparent porous TiO₂ thin film was spin-coated on glass substrates from a sol gel solution containing titanium alkoxide as precursor. Polyethylene glycol (PEG), with different molecular weight, was added to the coating solution as a structure-directing agent, and the films thus prepared were transparent, crack free and nanoporous. The surface morphology of the films has been observed by field emission gun-scanning electron microscope (FEG-SEM), the crystal structure characterized by X-ray diffraction (XRD) and the photocatalytic activity of the TiO₂ thin films evaluated. All the films are hydrophilic. The decomposition of PEG during high temperature treating is considered to be responsible for the generation of porous structure in the films as compared with TiO₂ film without addition of the polymer, and higher molecular weight leads to larger pore size and specific surface area. XRD shows that all TiO₂ films display the characteristic diffraction peaks of a TiO₂ anatase structure at 550 °C. The photocatalytic activity of the TiO₂ thin films as evaluated by the decomposition of methyl orange was increased with the PEG molecular weight increased.