Relay detection of Zn ²⁺ and S ²⁻ by a quinoline-based fluorescent chemosensor in aqueous media and zebrafish

A new quinoline-based fluorescent chemosensor MDCQA was designed and synthesized for the relay sensing of Zn ²⁺ and S ²⁻ . MDCQA showed turn-on fluorescence toward Zn ²⁺ , and the resulting complex was able to detect S ²⁻ 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 Zn ²⁺ 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.