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, 1 H NMR titration, ESI‐MS analysis and DFT calculation.