The photoreactivity of sol-gel (SG)-TiO₂ films was enhanced significantly with addition of a small amount of trifluoroacetic acid (TFA) into the starting solution. The promoting effect was confirmed in two separate experiments of the methylsiloxane monolayer oxidation and the photocurrent measurements. The results of film characterization indicated that the absorption coefficient for ultraviolet light ( < 360="" nm)="" increases="" due="" to="" film="" densification="" and="" the="" crystallinity="" is="" improved="" upon="" f="" doping.="" the="" improvement="" in="" the="" photoreactivity="" was="" ultimately="" attributed="" to="" the="" increase="" in="" the="" rate="" at="" which="" the="" photogenerated="" charge="" carriers="" reach="" the="" surface="" in="" the="" photostationary="">