Cyanide ion colorimetric chemosensor based on protonated merocyanine in EtOH

This Letter aimed to develop an efficient method for the determination of cyanide ion (CN ⁻ ). A novel colorimetric chemosensor 4-[(1E)-2-(4-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (HPEAPB) was synthesized. HPEAPB displayed good selectivity toward CN ⁻ over other competing anions in ethanol. A color change from yellow to red was immediately observed upon the addition of CN ⁻ and the limit of detection (LOD) was 3.4×10 ⁻⁶ molL ⁻¹ . The sensing mechanism was discussed by UV–vis, ¹ H NMR titration, and a comparison study. Colorimetric test paper for CN ⁻ was prepared by attaching HPEAPB to a chromatography paper, which could be used to detect CN ⁻ in environmental samples as simply as a pH-indicator paper for pH value. The LOD of the test paper for CN ⁻ was 2.0×10 ⁻⁴ molL ⁻¹ . This detection method for CN ⁻ has potential applications in cyanide ion containing fields by combination of rapid and real-time advantages.