A New, Highly Potent 1,8‐Naphthalimide‐based Fluorescence “Turn off” Chemosensor Capable of Cu 2+ Detection in China's Yellow River Water Samples

A new 1,8‐naphthalimide‐based fluorescence “turn off” chemosensor, N ‐phenyl‐4‐(3,3′‐((2‐aminoethyl)azanediyl)dipropanoic acid)‐1,8‐naphthalimide ( MAST ), for the detection of Cu 2+ was synthesized. Upon treatment with Cu 2+ , in coexistence with various competitive metal ions in HEPES‐buffered dimethylsulfoxide (DMSO) solution (v/v, 1:1; pH 7.4), MAST displayed a high selectivity toward Cu 2+ with a fluorescence quenching of 83.67%. Additionally, a good linear response of MAST for the detection of Cu 2+ was obtained in the concentration range of 10 × 10 −6 to 50 × 10 −6 M. A 1:1 stoichiometric interaction of MAST with Cu 2+ was observed, and the association constant and detection limit were calculated to be 1.37 × 10 6 and 0.69 × 10 −8 M, respectively. The sensing mechanism of the chemosensor toward Cu 2+ was proposed due to the effect of the paramagnetic nature of Cu 2+ and reverse‐photo‐induced electron transfer (PET) process. Ultimately, the proposed chemosensor was applied to quantify Cu 2+ in real‐world water samples, with excellent recovery rates of 98.00–109.80% observed.