Relay detection of Zn2+ and S2− by a quinoline-based fluorescent chemosensor in aqueous media and zebrafish.

Abstract A new quinoline-based fluorescent chemosensor MDCQA was designed and synthesized for the relay sensing of Zn2+ and S2−. MDCQA showed turn-on fluorescence toward Zn2+, and the resulting complex was able to detect S2− among the competitive anions by turn-off fluorescence. Detecting limits (0.06 μM and 2.33 μM) for zinc ion and sulfide were remarkably below WHO guidelines (76.0 μM for zinc ion and 14.7 μM for sulfide). In addition, sensor MDCQA successfully operated for imaging Zn2+ in live zebrafish larvae and quantifying it in real water samples. The detecting properties and mechanisms of MDCQA toward zinc ion and sulfide were demonstrated by UV–vis and fluorescence spectroscopy, NMR titration, DFT calculations and ESI-Mass. Graphical abstract Image 1 Highlights • A quinoline-based fluorescent sensor MDCQA was developed for the relay detection of Zn2+ and S2−. • MDCQA could detect Zn2+ by turn-on fluorescence and the resulting complex detected S2− by turn-off fluorescence. • MDCQA successfully detected Zn2+ in real water samples and in vivo. • Sensing mechanisms of MDCQA toward Zn2+ and S2− were demonstrated by the spectroscopic studies and DFT calculations. [ABSTRACT FROM AUTHOR]