Studying TiO2 coatings on silica-covered glass by O2 photosorption measurements and FTIR–ATR spectrometry: Correlation with the self-cleaning efficacy

Self-cleaning coatings on glass plates covered with a thin silica barrier layer were formed from anatase nanoparticles mixed with Ti and Si organic salts, and subsequent calcination. UV irradiation of these coatings exposed to O2 produced either a gradual increase or decrease in O2 pressure P (1–120 Pa). For each coating the initial P value, Psat, separating the domains of a net photoadsorption or a net photodesorption was regarded as characterizing the O2 photosorption capacity. Psat was found to be correlated to the self-cleaning efficacy evaluated by optically following the removal rate of an organic layer issued from hexadecanoic acid sprayed on the coating. The unfavorable role of SiO2 (used to better anchor the coating) with respect to electron transfer between O2 and the UV-irradiated coatings is discussed, taking into account the fact that an FTIR–ATR study showed the existence of Si–O–Ti bonds in the coatings.