Photocatalytic decomposition of acetaldehyde with anatase nanocrystals-dispersed silica films prepared by the sol-gel process with hot water treatment

Anatase nanocrystals of 5 to 10 nm in diameter were formed in the silica-ti tanic films by treatment with hot water. The formation of nanocrystals with hot water treatment was a unique phenomenon to the silica-titanic system a nd the addition of organic polymers such as PEG was indispensable for the h igh dispersion of anatase nanocrystals in the films. The hydrolysis of Si-O -Ti bonds with hot water was considered to play an important role for the f ormation of anatase nanocrystals. The resultant films were transparent even after the formation of anatase nanocrystals. Acetaldehyde was photocatalyt ically decomposed into CO2 on. the films which were subjected to a hot wate r treatment. The amounts of generated CO2 were twice of that of introduced acetaldehyde, indicating that the total acetaldehyde was completely decompo sed to CO2. Anatase nanocrystals-dispersed films can be formed on various k inds of substrates including those with poor heat resistance such as organi c polymers and organisms by this process, so that the substrates coated wit h the films are expected to be widely used for photocatalytic applications.