Highlights

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A ratiometric fluorescent probe (Probe) is facilely synthesized via the ethylene bridging of N-ethylcarbazole-3-formaldehyde and 1,1,2-trimethyl-3-ethyl-1H-benz[e]indolium iodide.

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It is a useful fluorescent probe for monitoring cyanide ion at very low concentrations (1–2 μM), quantitatively.

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The detection limit of probe for CN⁻ is found to be 0.23 μM.

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It exhibits a large Stokes shift, good selectivity, sensitivity and stability.

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Fluorescent CN⁻ imaging in living cells by this probe is further successfully applied.

Abstract

A ratiometric emission fluorescent probe 1,1-dimethyl-3-ethyl-2-(2-(N-ethyl-carbazol-3-yl)-vinyl)-1H-benzo[e]indolium iodide (Probe) is facilely synthesized via the ethylene bridging of N-ethylcarbazole-3-formaldehyde and 1,1,2-trimethyl-3-ethyl-1H-benz[e]indolium iodide, which is a useful fluorescent probe for monitoring cyanide ion at extremely low concentrations, quantitatively. The detection of cyanide is performed via the nucleophilic attack of cyanide toward the benzo[e]indolium group of the probe, resulting in a prominent fluorescence ratiometric change and a color change. The titration experiments for CN⁻ show that it exhibits a large Stokes shift (92 nm), high selectivity, excellent sensitivity and good stability for CN⁻ sensing in DMSO system. The detection limit of Probe for CN⁻ is found to be 0.23 μM. Furthermore, the probe has excellent cell membrane permeability and is applied successfully to rapidly detect CN⁻ in living cells.

Graphical abstract