Fig. 4. (a) The fluorescence spectra of PBT in the presence of different concentrations of F− [PBT is 10 μM], [Tris buffer is 20 mM] in a mixture of THF and Tris buffer solution (pH 8.0), (1 : 9, v/v), λex = 335 nm, λem = 470 nm. Inset: direct observation of the difference in fluorescence intensity of PBT under UV irradiation (365 nm) with various concentration F− (0–20 μM) after 10 min incubation time. (b) The linear relationship between fluorescence intensity and F− concentration (0.5–10 μM).
