Photocatalytic thin films of TiO2 formed by a sol–gel process using titanium tetraisopropoxide as the precursor

Thin TiO2 films were prepared with the dip-coating technique by using sols deriving from titanium tetraisopropoxide. TiO2 films were formed on glass substrates previously covered by a SiO2 layer obtained from a tetraethylortosilicate sol. The films, after a thermal treatment at 673 K, mainly consisted of TiO2 anatase. The samples were characterised by X-ray diffraction, UV–Vis spectroscopy, scanning electron microscopy and atomic force microscopy. The photoactivity of the various films was tested by using as probe reaction the photo-oxidation of 2-propanol in gas-solid regime. The photoreactivity results indicated that the TiO2 films were efficient for degrading 2-propanol under UV illumination, propanone being the only compound detected as intermediate product. Films prepared by using Degussa P25 appeared to be more photoactive, but the coating was easily detached by wiping.