Taken together, the decrease in the absorption features of the TiO2-RGO suspension upon irradiation with white light and the reaction between the OH• radicals and RGO observed in the flash photolysis experiments confirm the OH•-mediated RGO oxidation in the presence of UV-irradiated aqueous TiO2 suspensions. The fate of the oxidized RGO is highly relevant to the change in TOC concentration with the change in absorption during irradiation. One can observe the significant difference in the rate of the decrease in absorption as compared to the decrease in TOC concentration. The rapid decrease in the RGO visible absorbance during the initial 15 min of irradiation (c.a. 75% decrease, Figure 1A) from dark brown to essentially colorless contrasts the slower depletion of TOC in the same time frame.