Figure 6.

Fluorescence decay of BLG in the BLG/PPIX complexes (λ_ex = 280 nm and λ_em = 330 ± 4 nm). (A) pH 6. The decay of the complex before irradiation (black), the final nonirradiated complex (blue), and the complex irradiated with 23 J/cm² (red) are basically superimposed. (B) pH 9. The decay of the complex after irradiation with 23 J/cm² (red) is clearly longer lived than the decay of the complex before irradiation (blue) and the nonirradiated complex (black). (C) The values of ⟨τ⟩ calculated from eq 3 show that at pH 7 and below, the decay of BLG in the complex does not change when comparing irradiated samples [(○) pH 5 and (□) pH 7] and non irradiated samples that were left in the dark for the same amount of time as that required for irradiation [(●) pH 5 and (■) pH 7]. At pH 8 and above ⟨τ⟩, the irradiated complex (Δ) increases with the dose compared to the nonirradiated samples (▲). (Note: the error bars for the data at pH 7 and below appear larger because of the difference between the left-hand side scale and the right-hand side scale of the plot). (D) Comparison of the BLG decay in air and under N₂ saturation. The decay of the irradiated sample in air (blue) is longer than the decay of the nonirradiated sample in air (black). The decay of the nonirradiated sample under N₂ (red) is slower than the corresponding one in air. After irradiation (green), the decay lengthens even further. In A, B, and D, the prompt is represented by □.