抄録
Titanium oxide (TiO2) is popular material as a white pigment, an ultraviolet rays absorbent etc. and recently TiO2 has attracted attention as a photocatalyst. We prepared mono-dispersed needle-like TiO2 particles by hydrolysis and condensation polymerization of titanium alkoxides in methanol-rich alcohol solutions with mild conditions; at atmospheric pressure and at 20-50°C. In the case of using other alcohol rich solutions, spherical particles were obtained or any particle was not obtained. H2O concentrations in solutions also affected the shapes of the particles. Using the solvent containing ≥0.2vol% H2O, the shape of the particles obtained was not needle-like but spherical. The needle-like particles were obtained only within the case where particles were prepared in methanol-rich solutions containing ≤0.1vol% H2O. The length and the aspect ratio of the particles were increased with increasing reaction period and reaction temperature. All of the particles obtained were amorphous before heating treatment. The particles possessed anatase structure after being heat-treated at 500°C for 1h. After irradiation with UV-light to the aqueous solutions of methylene blue added with the TiO2 particles, the absorbance of methylene blue decreased. The particles after heating were active as photocatalysts for decomposition of methylene blue in aqueous solutions and photocatalytic activities were dependent on the reaction conditions.
