Highly selective fluorescent and colorimetric sensor for Hg2+ based on triazole-linked NBD

7-Nitrobenzo-2-oxa-1,3-diazole (NBD) derived compound 1 bearing triazole binding site was used as a selective fluorescent and colorimetric sensor for Hg2+ in aqueous solution. Among the metal ions examined, only Hg2+ caused significant fluorescence quenching in EtOH/HEPES (v/v = 9:1) at pH 7.4, along with a remarkable red shift in both absorption and fluorescence spectra which then facilitated naked-eye detection. 1H NMR titration and control experiments by using more rigid triazolyl NBD derivative 2 were carried out to illustrate the complexation mode and the importance of cooperation of amino acid moiety and triazole ring in improving the binding ability of 1 to Hg2+.

Research highlights
► NBD-linked triazolyl lysine derivative was used as a selective fluorescent and colorimetric sensor for Hg2+.
► In EtOH/HEPES at pH 7.4, only Hg2+ caused significant fluorescence quenching.
► A red shift was obtained both in fluorescence and absorption spectra, which was utilized for naked-eye detection of Hg2+.