Assessment Of Photocatalytic Activity Of Self-cleaning Materials

The photocatalytic activity of self-cleaning materials is mainly stributed to the TiO2 film coating on the surface, which has photohydrophlicity and photocatalysis. Such materials can be used for air purification, antisepticize, deodorization, antifouling, mist prevention and self-cleaning. At the present time, the production of self-cleaning glass and ceramics has been industrialized. However, there is not a unified standard for assessment of the quality of the self-cleaning materials. This thesis has prepared 8 kinds of self-cleaning materials with different photocatalytic activity through improved sol–gel methods. Using 7-hydroxycoumain as fluorescence probe, we established a method to rapid assessment of photocatalytic activity of self-cleaning materials with accuratissime. We also improvd the intelligent ink, which had no changed color on the ordinary materials. The main experimental results are described as follows.(1) Specified amounts of TiO2, PVA and distilled water were mixed well with ultrasonication, and the resultant mixture was heated up to result in the TiO2 sol. A layer of TiO2 film was coated on the substrates, followed by drying in the air, calcinating at 300℃for 2 hour to burn off PVA, which did not change crystallinity of TiO2, and hence the photocatalytic activity of the self-cleaning material. In the perparation, the type of TiO2 and substrate material were changed with the photocatalytic activity of the self-cleaning materials. It was found that these materials showed photocatalytic activity, and were stable to repeated washing with water, but not so stable to mechanical abrasion.(2) Under UV illumination, the hydroxyl radicals(·OH) produced on TiO2 film photocatalyst could quantitatively react with coumarin in aqueous solution, By measuring the increased fluorescence of the generated 7-hydroxycoumain during the UV illumination, the effect of·OH was investigated on the photocatalytic activity of the self-cleaning materials. The result was the same as that obtained with photochemical catalysis oxidative degradation of azo dyes. Moreover, the fluorescence method had a sensitivity which was 5000 times higher than the latter.Moreover, the examination time was only 40 min, being 1/6 of the latter. When inorganic ions, such as Cu2+ and F- existed, all the self-cleaning materials yielded higher photocatalytic activity. (3) A new method for the assessment of photocatalytic activity of self-cleaning materials was developed by using the dye Rz/glycerine/diluter A/hydroxyethyl cellulose mixtures. The examination time was shortened to 15 min, and the result was satisfactory. Compared with the fluorescence spectrophotometric method, the examination time is very short. thus it can be used in the fast on-site examination.