A coumarin–indole based colorimetric and “turn on” fluorescent probe for cyanide

• A novel colorimetric and turn-on fluorescent probe for CN− has been developed.
• The probe has a low detection limit of 0.50 μM.
• The probe has been successfully applied in cyanide detection in tap water.

A novel coumarin–indole based chemodosimeter with a simple structure was designed and prepared via a condensation reaction in high yield. The probe exhibited very high selectivity towards cyanide on both fluorescence and UV–vis spectra, which allowed it to quantitatively detect and imaging cyanide ions in organic–aqueous solution by either fluorescence enhancement or colorimetric changes. Confirmed by 1H NMR and HRMS spectra, the detection mechanism was proved to be related with the Michael addition reaction induced by cyanide ions, which blocked the intramolecular charge transfer (ICT) of the probe. Moreover, the probe was able to be utilized efficiently in a wide pH range (7.5–10) with negligible interference from other anions and a low detection limit of 0.51 μM. Application in 5 kinds of natural water source and accurate detection of cyanide in tap water solvent system also indicated the high practical significance of the probe.

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