Near-infrared chemodosimetric probes based on heptamethine cyanine dyes for the “naked-eye” detection of cyanide in aqueous media

Abstract

Two simple chemodosimetric probes (P1 and P2) based on heptamethine cyanine dyes have been synthesized for highly sensitive and selective detection of cyanide anions (CN−) in aqueous media. The probes with an immobilized indolium salt as the specifically nucleophilic addition reaction site for CN− exhibit absorption bands in the near-infrared (NIR) region (650–850nm). Upon the addition of CN−, the probes display a blue-shifted spectrum and result in apparent color change from green to brilliant yellow that can be easily observed by the naked eye even in the presence of other interfering anions such as F−, AcO−, Br−, NO2−, Cl−, SO42− and I−. There are good linear relationships between the fluorescence intensity of the probes and CN− concentrations, and the detection limits for P1 and P2 are estimated to be 0.017μM and 0.2μM, respectively. The sensing mechanism of the nucleophilic addition is confirmed by 1H NMR and mass spectroscopic analysis. In addition, the probe P2 is employed for cell imaging and the detection of CN− in living cells L929 is successfully realized.