A Colorimetric and Fluorescent Probe Based on Quinoline‐Indolium for Detection of CN− in Aqueous Media

Abstract A new colorimetric and fluorescent probe (QI) based on quinoline‐indolium was developed for detection of CN − . In an aqueous solution, QI showed high selectivity and strong anti‐interruption for CN − . In addition, it was clearly visible to the naked eyes that the color and fluorescence changes induced by CN − exhibited sharp contrast. The research also found that QI could determine CN − in the range of pH 5–10. The spectral signal was linearly proportional to CN − concentration, and the detection limit was calculated to be low as 41.6 nM. The sensing mechanism of QI to CN − was accomplished via the attachment of CN − at the C atom of indolium salt C=N + group through the nucleophilic addition, which was confirmed by 1 H NMR studies. Notably, we could apply the designed probe for the cycle detection of CN − in a wide pH range, for practical purposes for a long duration. Furthermore, the TLC plates of QI were verified to detect CN − in a simple, rapid way in environmental systems.