A new, highly potent 1,8-naphthalimide-based fluorescence turn-off chemosensor capable of detecting Cu(II) ions in real-world water samples

The synthesis of a new 1,8-naphthalimide-based fluorescence turn-off chemosensor for the effective detection of Cu(II) ions is reported. The chemosensor MAST was characterised by mp, Fourier Transform-infrared (FTIR), ultraviolet-visible (UV-vis), fluorescence, H-1-NMR and C-13-NMR spectroscopy, and mass spectrometry. After treatment with Cu(II) ions in coexistence with various competitive metal ions in a dimethylsulphoxide (DMSO)/4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) buffer solution (v/v, 1:1; pH 7.4), the chemosensor demonstrated high selectivity towards Cu(II) ions and a fluorescence quenching of 83.67% was observed. In addition, a good linear response for the chemosensor detecting Cu(II) ions was obtained over the concentration range 0.2-1m. The combined results of UV-vis and fluorescence titrations with the Job plot yielded a 1:1 stoichiometric interaction of the chemosensor with Cu(II) ions. The association constant and detection limit were calculated as 1.37x10(6)m(-1) and 1.69x10(-8)m, respectively. Based on results, the quenching response of MAST towards Cu(II) ions could be ascribed to the reverse-photoinduced electron transfer (PET) mechanism. Finally, the proposed chemosensor was applied to quantify Cu(II) ions in real-world water samples and excellent recovery rates of 98-105.8% were obtained.