| dc.description.abstract | The absorption spectra of the transients formed in the reactions of titanium hydrous oxide with SO4•-, Tl2+, or OH* species in alkaline aqueous solution have been studied by using the pulse radiolysis technique. Direct hole capture via interfacial electron transfer from colloidal titanium hydrous oxide to SO4•- radicals leads to the formation of a product which has the broad absorption spectrum with an onset at about 480 nm rising steeply toward the UV region. A completely different absorption spectrum was found for the hydroxyl radical adduct formed by the reaction of OH* with titanium hydrous oxide that has a maximum at 620 nm. This maximum disappears in acidic solution at pH 3 with assistance of H+aq which transforms the OH adduct to the product the same as that formed in the reaction with SO4•-. The low-weight aggregates of titanium hydroxide also react with OH* radicals, and in the alkaline solution a similar transient spectrum with a maximum at 570 nm was obtained. In neutral and alkaline solutions the absorption spectra of transients formed in the reactions of OH*, Tl2+, or SO4•- with TiO2 do not appear to be dependent upon the mode of the colloid preparation. However, decay kinetics of these transients are very sensitive to surface chemistry. | en |
