Spectroscopic and Mass-Spectrometric Study of Acridine Orange Photodegradation on the Surface of Mesoporous TiO2, SiO2 /TiO2 and SiO2 Films (original) (raw)

The efficiency of nanosized mesoporous TiO 2 , SiO 2 /TiO 2 and SiO 2 films as photocatalytic coverings has been demonstrated by the example of adsorbed acridine orange (AO) dye photodegradation in air. SiO 2-and TiO 2-based functional coatings were prepared via template assisted sol-gel method. The films were characterized by electron microscopy (SEM, TEM), FTIR and UV-Vis spectroscopy. Hydrophylic properties of prepared films were estimated from the water contact angle measurements. Electronic spectra and LDI mass-spectra changes accompanying AO photodegradation under the UV-exposure were investigated and main photodestruction products have been determined. We suggest the photobleach of adsorbed AO on the surface of researched films is a result of the oxidation reaction of dye molecule with the oxygen species such as singlet oxygen and OH • radical produced in the gas phase in presence of titania as well as in presence of sensitizer AO on silica surface. The observed photobleach of AO on the SiO 2 and SiO 2 /TiO 2 films proceeds through the photooxidative Ndemethylation of dimethylaminogroup in dye. Electronic and laser desorption/ionisation mass spectra give evidence that efficient photobleach of AO localized at the surface of anatase films proceeds through the following steps: 1-N-demethylation; 2-photodimerization; 3-photodegradation. Pure commercial TiO 2 P25 (S sp = 50 m 2 /g) does not adsorb some dyes (i.e. Rhodamine 6G (R6G), and process of a mineralization occurs on interface of TiO 2-solution R6G (3). However binary titania-silica catalyst with 10 % TiO 2 and S sp =100 m 2 /g adsorbs R6G from the solution, and process of its mineralization passes much more effectively compared with those on pure TiO 2 powders and coatings (7-10, 13-15). Mesoporous TiO 2 and TiO 2 /ZrO 2 films with developed surface area (400-800m 2 /g) show much higher activity in photoredox destruction of organic pollutants in comparison with their non-porous analogues (15-18). Aminoacridines, the representative acridine dyes, have ubiquitous use as colorant for synthetic fibers, tissue, leather etc (19-24), fluorophores with high fluorescente intensity on hydrophilic surfaces (20, 22, 23). At the same time this dyes represent some of the