Figure 5. Simultaneous photocatalytic degradation of naphthol blue black dye and RGO using UV/visible-irradiated TiO2 suspension. (A) Visual depiction of color changes (1) initial RGO suspension, (2) upon addition of naphthol blue black dye, (3) 10 min of UV irradiation, and (4) 100 min of UV irradiation, at which point the solution is completely colorless. (B) Comparison of absorbance changes at 600 nm following UV-irradiated (a) TiO2 and (b) TiO2/RGO suspensions containing naphthol blue black dye. The initial rapid change in absorption (zone I) is due to the breakdown of conjugation in dye and slower change in absorption in zone II is the degradation of residual dye and RGO. Spectra indicating depletion of dye after 20 min in dye/RGO sample can be found in Supporting Information Figure S4. The concentrations employed were [dye] = 45 μM, [TiO2] = 0.1 mM, [RGO] = 0.05 mg/mL.