Activity of various vis-light-active titanium oxides, prepared by a plasma treatment and a wet process, was evaluated under irradiation of blue and green lights from light emitting diodes, which were two of the three primary colors of light. From this evaluation, the dependence of wavelength on the activity was obtained. The durability of the activity was examined by outdoor exposure test and load decomposition test. In the outdoor exposure : est, vis-light activity decreased with exposure time. The reason of the decrease was thought to be the adsorption of nitrate ion on titanium oxide that was formed by the oxidation of NO
x in the surroundings. After the removal of nitrate ion from the surface, SNH-Hy
cal, prepared from titanium (IV) sulfate in a wet process, recovered the activity, while PST-01, prepared by plasma treatment, was found to lose the activity during the cleaning process. In a durability test by load decomposition test, in which a mixture of UV and vis lights from xenon lamp was used, total UV-vis activity of both SNH-Hy
cai and PST-01 increased with increasing number of repeat tests. For SNH-Hy
cal, both UV and vis activities were found to increase. For PST-01, on the other hand, UV activity increased but vis activity decreased.
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