Self-cleaning properties of TiO2-coated glass: Degradation, under simulated solar light, of palmitic (hexadecanoic) acid and fluoranthene layers deposited on the glass surface

The self-cleaning property of glass arises from a thin transparent TiO2 coa ting. Under solar UV light, TiO2 becomes capable of degrading organics at i ts surface. Our objectives were: to assess the self-cleaning efficiency wit h respect to the removal of compounds representative of organic deposits; t o identify and, if possible, quantify the intermediate products formed duri ng the destruction of these organic layers both to complete the data concer ning the self-cleaning properties and to have an insight into the photocata lytic degradation pathways. Our target compounds were palmitic (hexadecanoi c) acid and fluoranthene: both are present in the atmospheric solid particl es and come from various sources. The removal rates of layers of these comp ounds sprayed on the self-cleaning glass were found to be sufficient for th e expected application The identified intermediates (about 40 for each comp ound) show the gradual splitting of the palmitic acid chain and the oxidati ve openings of the aromatic rings of fluoranthene. In the case of palmitic acid the products give some indications about the photocatalytic mechanism About 20% of the organic carbon contained in the initial compounds was tran sformed into volatile carbonyl products In the case of fluoranthene, this p ercentage was less than for the degradation on TiO2-free glass.