A single fluorescent probe for multiple analyte sensing: efficient and selective detection of CN, HSO and extremely alkaline pH.

A simple tailor-made water-soluble broadly emitting (500-650 nm) fluorescent probe 3-methyl-2-(N-ethylcarbazole-3vinyl)-benzothiazolium iodide (IECBT) for the selective and sensitive detection of multiple analytes, including CN, HSO and extremely alkaline pH, is designed and synthesized via the ethylene bridging of 3-formyl-N-ethylcarbazole and 2,3-dimethyl benzothizolium iodide, which is a useful fluorescent probe for monitoring these analytes at extremely low concentrations quantitatively. CN and HSO are expected to undergo 1,4-addition reactions with the C-4 atom in the ethylene group of IECBT. This water-soluble fluorescent probe exhibits excellent sensitivity and selectivity toward CN in DMSO, which also results in a prominent fluorescence ratiometric change and a color change. The high selectivity and sensitivity of IECBT toward HSO and extremely alkaline pH over other coexisting species in water are also observed. The titration experiments show that it features a remarkably large Stokes shift and good stability towards CN, HSO or extremely alkaline pH with a significant fluorescence turn-off response. Importantly, we demonstrate that IECBT can be used for the real-time sensing and bioimaging of CN, HSO or extremely alkaline pH in living samples.