In conclusion, we have developed a ratiometric and on–off fluorescent
chemosensor (PB) containing the pyrene moiety for the selective
detection of trivalent chromium ion over other common metal ions
based on an ICTmechanism. The fluorescence emission intensities demonstrated
a dramatic decrease at 425 nmand formation of a newband at
594 nm on increasing Cr3+ concentrations with an excitation wavelength
at 343 nm. A well-defined isoemissive point at 564 nm was observed.
The emission ratios (F425/F594) exhibited a significant decrease
of 14.7-fold, from 162.2 in the absence of Cr3+ to 11.0 in the presence
of Cr3+ (40 equiv.). More importantly, the good linearity between the
emission ratios (F425/F594) and the concentrations of Cr3+ allowed the
detection of Cr3+ by a ratiometric fluorescence method.