Pyrene-based ratiometric fluorescent chemosensor for sensitive detection of hypochlorite in a perfect aqueous solution

We synthesized a pyrene-based sensitive fluorescent chemosensor, TPA-Cl ((E)-N,N,N-trimethyl-2-oxo-2-(2-(pyren-1-ylmethylene)hydrazinyl)ethan-1-aminium chloride), to detect hypochlorite in a perfect aqueous solution. TPA-Cl showed high selectivity for hypochlorite through fluorescence color change from sky blue to blue. The detection limit for hypochlorite was calculated as 0.27 μM, which is a quite low value. Moreover, the presence of other anions or ROS hardly hindered the sensing of hypochlorite by TPA-Cl. Furthermore, TPA-Cl could be applied successfully as a test kit for the simple recognition of hypochlorite. Surprisingly, TPA-Cl is the first pyrene-based fluorescent chemosensor that can detect ClO⁻ by using the TPA-Cl-coated test kit. Moreover, TPA-Cl could achieve the quantification of ClO⁻ in various environmental water samples. The hydrolytic cleavage and oxidation mechanism of TPA-Cl by hypochlorite was elucidated through UV–vis and fluorescent spectroscopy, ¹H NMR titration, ESI-MS analysis and DFT calculation.