Upon excitation of TiO2 colloids with 355 nm laser pulse, OH• radicals are generated at the TiO2 surface, which in turn react with SCN− to yield (SCN)2 −•, whose visible spectrum is
depicted in Figure 3A. With increasing concentration of RGO we observe a decrease in the transient absorbance of (SCN)2 −• radicals as reaction 5 competes with reaction 4. We used deaerated C60 solution as an actinometer to estimate the quantum yield of (SCN)2
−• radicals. The 355 nm laser pulse excitation of C60 exhibits triplet excited state with characteristic absorption maximum at 740 nm (ε = 16 000 M−1 cm−1). The quantum yield of thiocyanate radical decreases with each incremental addition of RGO as shown in Figure 3B confirming the competition between reactions 4 and 5.