Selective and Sensitive Detection of Cyanide Based on the Displacement Strategy Using a Water-Soluble Fluorescent Probe

A water-soluble fluorescent probe (C-GGH) was used for the highly sensitive and selective detection of cyanide (CN(−)) in aqueous media based on the displacement strategy. Due to the presence of the recognition unit GGH (Gly-Gly-His), the probe C-GGH can coordinate with Cu(2+) and consequently display ON-OFF type fluorescence response. Furthermore, the in situ formed nonfluorescent C-GGH-Cu(2+) complex can act as an effective OFF-ON type fluorescent probe for sensing CN(−) anion. Due to the strong binding affinity of CN(−) to Cu(2+), CN(−) can extract Cu(2+) from C-GGH-Cu(2+) complex, leading to the release of C-GGH and the recovery of fluorescent emission of the system. The probe C-GGH-Cu(2+) allowed detection of CN(−) in aqueous solution with a LOD (limit of detection) of 0.017 μmol/L which is much lower than the maximum contaminant level (1.9 μmol/L) for CN(−) in drinking water set by the WHO (World Health Organization). The probe also displayed excellent specificity for CN(−) towards other anions, including F(−), Cl(−), Br(−), I(−), SCN(−), PO(4) (3−), N(3) (−), NO(3) (−), AcO(−), SO(4) (2−), and CO(3) (2−).