Visible-light-induced activation of periodate that mimics dye-sensitization of TiO₂: Simultaneous decolorization of dyes and production of oxidizing radicals

Inspired by the mechanism behind self-sensitized destruction of dyes on semiconductor photocatalysts, we herein present the first instance of visible-light-induced activation of periodate (IO₄⁻) into reactive iodine radicals via sensitized electron transfer from an organic dye, Rhodamine B (RhB). The IO₄⁻ reduction not only leads to oxidative decolorization of RhB but also formation of reactive intermediates that degrade organic compounds. Electron transfer from the excited dye to IO₄⁻ was confirmed by detecting RhB radical cation (RhB[rad]⁺) and measuring its lifetime. The efficiency of organic compound degradation was found to significantly vary depending on the target substrate, i.e., phenol, bisphenol A, and 4-chlorophenol were rapidly decomposed, whereas benzoic acid, carbamazepine, 4-nitrophenol, and sulfamethoxazole exhibited moderate decomposition rate. Lines of evidence in addition to the substrate specificity, such as insignificant hydroxylation, non-stoichiometric dechlorination, and marginal quenching effects of organic/inorganic compounds (e.g., methanol, natural organic matters, and chloride ion), points toward the involvement of iodate radical (IO₃[rad]). The dye-sensitized IO₄⁻ activation process was also found to be highly effective in inactivation of MS2 bacteriophage.