A new highly selective fluorescent sensor based on a novel fluorophore for cyanide and its applications in bioimaging

A novel highly active fluorescence chemical sensor (TBI) for CN− was synthesized based on triphenylamine–benzothiazole as a new fluorophore, and was used for the first time as a fluorophore for detection of CN−. Fluorescence quantum yield of the probe clearly increased when using triphenylamine–benzothiazole as the group. The probe possessed good selectivity towards CN− and had anti‐interference ability over common ions. After adding CN−, the UV–visible spectrum of TBI changed clearly and underwent a dramatic colour change from red to colourless, which could be observed clearly by the naked eye. The limit of detection for CN− was calculated to be 2.62 × 10−8 M, which was well below the WHO cut‐off point of 1.9 μM. The novel probe displayed fast sensing of CN−. The detection mechanism was a nucleophilic addition reaction between CN− and a carbon atom –C = N– in indole salt. The π‐conjugation and intramolecular charge transfer (ICT) transition in the TBI molecule were destroyed by this addition, which resulted in a change of fluorescence before and after the addition of CN−. The mechanism was verified using theoretical calculation, 1H NMR titration, and mass spectra. In addition, the probe showed low cytotoxicity and could be used for biological imaging in HeLa cells. Triphenylamine‐benzothiazole as novel fluorophore was firstly reported to detect CN−. The energy of the molecule is calculated by density functional theory (DFT) and time‐varying DFT.