Indocyanine based dual optical probe for cyanide in HEPES buffer

•A dual optical probe for cyanide with a dramatic color and fluorescence change.•A water soluble probe with a hydroxyethylindolium unit of 1 and the adduct 1-CN.•Highly selective response to cyanide with a micromolar limit of detection (2.0 μM).•A reversible reaction-based probe in the presence of cyanide and Hg(II) ion.

A dual optical probe based on N-hydroxyethylindocyanine was prepared for the selective detection of cyanide in water. The probe exhibited a dramatic red-to-colorless optical change and a fluorescence on–off response in the visible region, displaying high selectivity toward cyanide over other various anions and Cys with a micromolar limit of detection (LOD = 2.0 μM) in an aqueous buffer. Furthermore, the probe underwent a reversible reaction with the probe-cyanide ion adduct in the presence of Hg(II), of which optical changes were easily detected by direct visualization.

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