Figure 3. Superoxide (O₂^•-) generation from irradiated TiO₂ in the presence of H₂O₂. (A) The time course of ESR spectrum during and after irradiation (365 nm) of TiO₂ measured by EPR spin-trapping following the addition of H₂O₂ at time 0 and with DMPO as a spin trap. (B) Monitoring of the spin concentration of the O₂^•- generated from irradiated TiO₂ (5 min) in the presence of H₂O₂. Each column represents the mean (n = 5). Experimental conditions are described in "MATERIALS & METHODS" and illustrated in Fig. 1.