A PROMOTING EFFECT OF NH4F ADDITION ON THE PHOTOCATALYTIC ACTIVITY OF SOL-GEL TIO2 FILMS

The photoreactivity of sol-gel (SG)-TiO2 films was enhanced significantly with addition of a small amount of ammonium fluoride (AF) into the SG-starting solution. The rate of the TiO2 photoinduced oxidation of an overlying methylsiloxane monolayer reached a maximum near [AF]/[Ti] molar ratio of 1.35 × 10−2. The apparent rate constant was as much as 8.2 times greater than of AF non-added system. X-Ray diffraction analyses clearly indicated that the principal factor is the improvement in the anatase crystallinity caused by F− ions.