A Quick, Highly Selective and Sensitive Colorimetric and Fluorimetric Sensor for Cyanide Ion

A newly developed diindolium moiety has been synthesized and structurally investigated by employing a number of spectroscopic methods like NMR and HRMS in order to serve as a cyanide sensor DI. The interaction between DI and the CN^- ion causes a noticeable color shift from pink to colorless, making it easy to detect CN^- ions with the naked eye. Besides, the sensor exhibited fluorescence color change from orange to light blue under UV lamp. Sensor DI has remarkable selectivity and sensitivity in distinguishing between CN^- and a wide range of interfering anions. The sensing mechanism of sensor DI towards CN^- ion involves the nucleophilic addition process of CN^- to the electron deficient indolium moiety. The detection limit of cyanide ion by sensor DI is calculated to be 1.4 × 10^- 7 M by UV-visible and 8.2 × 10^- 8 M by fluorescence technique which are lower than the limit set by WHO. The application of sensor DI for cyanide ion is utilized by making test kit and by taking different sources of water to test the presence of cyanide ion.