Highly selective and sensitive chemosensor for Hg2+ based on the naphthalimide fluorophore

A new OFF-ON fluorescent chemosensor (H1) composed of a naphthalimide fluorophore and a 6-[(quinolin-8-yloxy)methyl]pyridin-2-ylmethanamine receptor has been synthesized and characterized by infra-red, (1)H NMR, (13)C NMR and mass spectrometry. The developed chemosensor H1 exhibited good turn-on and reversible responses toward Hg(2+), with excellent selectivity and sensitivity, in a neutral buffered aqueous solution. Other common metal ions did not interfere with the fluorescence-enhancement response to Hg(2+). Furthermore, the chemosensor H1, at a concentration of 10 μM, showed a rapid and linear response toward Hg(2+) in the concentration range 0-10 μM. On addition of 10 μM Hg(2+), the fluorescence intensity of H1 was enhanced about 4-fold. The detection limit was calculated to be 63 nM. The association constant was 1.11 × 10(5) M(-1). The fluorescence quantum yield and lifetime of H1/Hg(2+) were 0.42 and 3.83 ns, respectively.