Photocatalytic effect of the sol–gel derived nanoporous TiO2 transparent thin films

Abstract Photocatalytically active nanoporous anatase TiO2 films were deposited on glass plates by a sol–gel process conducted in the presence of polyethylene glycol (PEG). The films in different stages of the formation process were characterized by field emission scanning electron microscope, thermogravimetry–differential thermal analysis, ultraviolet–visible (UV–visible) spectroscopy and X-ray diffraction. The as-deposited TiO2/PEG composite films were smooth and dense, and were made nanoporous after the embedded PEG was thermally removed during calcination. The higher the content of PEG the larger was the resultant pore size. There were no cracks in the films common to films prepared in the presence of PEG, and the thermal stability of the films were also improved by the PEG addition. UV–visible spectroscopy showed that the calcination of PEG–TiO2 films also resulted in red shifting the absorption band of TiO2. The films were active in the photooxidation of iodide and methyl orange, and demonstrated an activity increase that scaled with the increase in the PEG content in the sol–gel preparation.