Mechanistic Insights into RGO Degradation. The oxidation of RGO observed during irradiation of TiO2-RGO aqueous suspension can proceed through two distinct pathways: (1) oxidation of RGO with OH• radicals and (2) direct oxidation of RGO by TiO2 valence band holes. We employed nanosecond laser flash photolysis with 355 nm laser pulse excitation to verify contribution of OH• radicals to oxidation of RGO during irradiation of TiO2-RGO aqueous dispersion. The 355 nm laser pulse excites TiO2 at the band edge without photon depletion through the 1 cm path of the cuvette (abs @ 355 nm ∼0.75). This ensures excitation of the TiO2 colloids at the center of the cuvette where the probe light is used to monitor laser pulse-induced transient species.