Highly selective fluorescent and colorimetric sensor for Hg 2þ based on triazole-linked NBD Yi-Bin Ruan, Stéphane Maisonneuve, Juan Xie * PPSM, Institut d’Alembert, ENS Cachan, CNRS, 61 av President Wilson, F-94230 Cachan, France article info Article history: Received 25 October 2010 Received in revised form 4 November 2011 Accepted 5 November 2011 Available online 13 January 2011 Keywords: NBD Triazole Fluorescence Naked-eye detection Hg 2þ abstract 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 Hg 2þ in aqueous solution. Among the metal ions examined, only Hg 2þ caused significant fluorescence quenching in EtOH/HEPES (v/v ¼ 9:1) at pH 7.4, along with a remarkable red shift in both absorption and fluorescence spectra which then facilitated naked-eye detection. 1 H 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 Hg 2þ . Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Contamination of mercury is a worldwide concern for decades due to its extreme toxicity, causing adverse effects on human health. Accumulation of mercury in vital organs and tissues may cause serious damages to the central nervous and endocrine systems [1]. Therefore great efforts have been devoted to the design of highly selective and sensitive chemosensors for detection of Hg 2þ in recent years [2]. So far there have been several approaches based on organic fluorophores [3], DNAzyme [4], nanoparticles [5], protein [6] and conjugated polymers [7]. However, development of facile and practical chemosensors for Hg 2þ is still a great challenge. Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction between azide and alkyne is widely used as versatile tools in organic synthesis, medicinal chemistry, bioconjugated application and material chemistry [8]. Recently it was found that triazole could be a stabilizing ligand for coordination chemistry [9]. Incorporation with appropriate fluorophores, chemosensors based on triazole have been reported for various metal ions [10]. In our previous work, we have also reported selective detection of Zn 2þ , Ni 2þ and Cu 2þ through precise introduction of triazole into various fluorophores [10ner]. However, up to now there are still rare reports for the detection of mercury using triazole group as the binding sites, especially in aqueous solution [10aec]. NBD derivatives have been widely used as fluorescent labeling reagents for their good spectral properties and cell permeability [11]. Furthermore, chemosensors based on NBD have been reported for various transition metal ions by virtue of ICT (intramolecular charge transfer) and PET (photo- induced electron transfer) processes [12]. As a continuous work on development of chemosensors for metal ions based on triazole coordination chemistry, compounds 1 and 2 containing NBD as signaling moiety and triazole as recognition moiety were used as double-channel fluorescent and colorimetric sensors for metal ions (Fig. 1). Meanwhile amino acid groups were integrated to investi- gate structure-dependent sensitivity. 2. Experimental section 2.1. Reagents and instruments The tested metal salts included Cu(ClO 4 ) 2 , AgNO 3 , Ba(ClO 4 ) 2 , Mn (ClO 4 ) 2 , Co(ClO 4 ) 2 , Cd(ClO 4 ) 2 , Zn(ClO 4 ) 2 , Ni(ClO 4 ) 2 , Fe(ClO 4 ) 2 , Pb (ClO 4 ) 2 , Mg(ClO 4 ) 2 , Ca(ClO 4 ) 2 and Hg(ClO 4 ) 2 . Solvents of spectro- scopic grade are purchased from SDS/Carlo Erba. Absorption spectra were recorded on a Uvikon-940 KON-TRON spectrophotometer and corrected emission spectra were per- formed on a Jobin-Yvon Spex Fluorolog 1681 spectrofluorometer (1 cm quartz cell was used). The fluorescence quantum yield (F F ) * Corresponding author. Tel.: þ33 1 47405586; fax: þ33 1 47402454. E-mail address: joanne.xie@ppsm.ens-cachan.fr (J. Xie). Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig 0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.dyepig.2011.01.004 Dyes and Pigments 90 (2011) 239e244