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, 1 H NMR titration, and mass spectra. In addition, the probe showed low cytotoxicity and could be used for biological imaging in HeLa cells.