A novel carbazole-benzothiazole-based chemodosimeter for the chromogenic and fluorogenic recognition of CN−

Abstract

A novel colorimetric and fluorescent sensing probe, (E)-3-(4-(9H-carbazol-9-yl)phenyl)-2-(benzo[d]thiazol-2-yl)acrylonitrile (CBTA), was synthesized and characterized by spectroscopic techniques. CBTA displayed “turn off” fluorescence in the presence of cyanide with a higher selectivity than that of others anions such as Br⁻, Cl⁻, I⁻, NO₃⁻, SO₄²⁻, SCN⁻, CO₃²⁻, N₃⁻, OH⁻, HCO₃⁻, H₂PO₄⁻, HPO₄²⁻, F⁻, ACO⁻, and PO₄³⁻ in a DMSO : H₂O medium (40 : 60, v/v, HEPES buffer, pH = 7.2). The “turn off” fluorescence response mechanism can be attributed to the intra-molecular charge transfer (ICT) process, which is blocked by the nucleophilic attack of cyanide ions at the cyano vinyl group of the probe. The LOD was found to be 3.57 × 10⁻⁸ M. The interaction involved behind the sensing of cyanide was investigated by Job's plot analysis, ¹H-NMR, and mass spectroscopic studies. DFT and TDDFT were also employed to verify the experimental outcomes. Moreover, the test strip experiment provides a wide application prospect of the receptor for detecting poisonous cyanide in the environment and biological system.