The efficiency of the sensor in the absence and presence of Cr3+ was
tested by investigating the influence of pH on the fluorescence of PB in
THF–water (1:1, v/v, Fig. S1). The emission of blue fluorescence of PB
steadily decreasedwithout Cr3+when the solution becamemore acidic
(pH b 4.0) (λex = 343 nm). However, no significant variation of the
fluorescence intensity of PB + Cr3+ was observed in the 4–10 pH
range, indicating that the sensor can be applied over awide pHrange toward
Cr3+. Thus, further UV/Vis and fluorescence studies were carried
out under physiological conditions in a THF/H2O (1:1, v/v) system. In titration
experiments, the UV/Vis and fluorescence spectrawere recorded
at 2 h after the addition of Cr3+ based on the effect of time on the Cr3+
determination at room temperature (Fig. S2).
The changes in the fluorescence titration spectra of chemosensor PB
upon the addition of Cr3+ in a 1:1 THF:H2O buffered solution at pH =