A Carbazole Acrylonitrile Substituted Turn-On Fluorescence Chemosensors for Cyanide Ion and its Application to Real Sample Analysis 

Abstract An efficient probe (E)-2-(benzo[d]thiazol-2-yl)-3-(9-ethyl-9H-carbazol-3-yl)acrylonitrile (CZ-BTZ) for selective turn-on response with cyanide (CN−) ion sensor was developed by simple Knoevenagel condensation of 9-ethyl-9H carbazole-3-carbaldehyde with 2-(benzo[d]thiazol-2-yl) acetonitrile. The sensing ability of probe CZ-BTZ was tested with different inorganic anions through spectrophotometric and spectrofluorimetric methods. The UV-vis and fluorescence spectral studies show the formation of a new adduct between CZ-BTZ and CN− by appearing with a new absorbance band at 350 nm and turn-on fluorescence at 535 nm. The absorbance and fluorescence study reveals the formation of 1:1 (CZ-BTZ: CN−) stoichiometry adducts with an estimated association constant of 2.04 ×105 M− 1. The probe CZ-BTZ could detect CN− down to 1.48 nM without much interference, much lower than the WHO limit (1.9 µM) in drinking water. The sensing mechanism of CZ-BTZ with CN− ions was studied using FTIR, ESI mass analysis, and DFT calculation. Further, the probe was applied for the real-time food sample analysis of CN− ions.