Hot-water treatment of sol–gel derived SiO2–TiO2 microparticles and application to electrophoretic deposition for thick films

SiO2–TiO2 spherical microparticles of about 0.7 lm in diameter were prepared by the sol–gel method. Anatase nanocrystals were formed in the microparticles and their specific surface area was increased after a hot-water treatment at 90 C. From the changes in the concentration of I2 photocatalytically generated from KI aqueous solution, the activity of the SiO2–TiO2 microparticles was found to increase with increasing the hot-water treatment time. Particulate, thick films were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates using the anatase nanocrystal-precipitated SiO2–TiO2 microparticles. The thickness of the electrophoretically deposited particulate film increased to be approximately 10 lm with an increase in applied voltage. The resultant thick film showed a high photocatalytic activity.