Kazuhiro Doushita

Evaluation of Photocatalytic Activity by Dye Decomposition

A novel rapid evaluation method for the photocatalytic activity of TiO2 thin films was developed. An organic dye with a polyvinyl alcohol (PVA) binder was spin coated on the TiO2 thin film, and the decrease in the absorbance of the dyes absorption peak during UV light irradiation was measured. Acid Blue 9 (Brilliant Blue FCF; CI-42090) could be used as the probe, while Methylene Blue (CI-52015) was not applicable to this method because of the reversible color change after the UV irradiation was stopped. PVA has virtually no interaction with oxidizing radicals, therefore, it is regarded as a simple binder holding dye molecules in the coated dye-PVA film. It was found that the ambient humidity during the UV irradiation strongly accelerates the discoloration rate of the dye, probably due to the increase in the photogenerated oxidizing radicals on the TiO2 surface. This dye discoloration could be explainedby the one-dimensional diffusion model with a first order reaction.

A Large-Area Patterned TiO2/SnO2 Bilayer Type Photocatalyst Prepared by Gravure Printing

Anatase TiO2 films (thickness = 50 nm) were formed in shape of stripes (width = 1.6 mm, interval = 0.4 mm) by gravure printing on commercially available SnO2 coated soda-lime glass substrates (dimension = 300 × 300 mm). Its photocatalytic activity was examined for the gas-phase oxidation of CH3CHO in comparison with a simple TiO2 photocatalyst formed on a silica glass. The patterned TiO2/SnO2 bilayer type photocatalyst showed a high photocatalytic activity in an H2O bearing atmosphere. On the other hand, neither the patterning nor stacking effect was observed for the same reaction under dry conditions. These results could be explained in terms of the reducing potential of the electrons in the conduction band of the SnO2 layer.

Glass Flakes with Submicron Thickness Manufactured by the Sol-Gel Method

Glass flakes with submicron thickness were manufactured by the sol-gel process. The average thickness could be controlled from 0.15 to 1.2 microns by changing the concentration of oxides and the coating conditions. These glass flakes have sharp distribution in thickness and high stability compared with commercially available glass flakes.