Cyanide detection using a highly selective fluorescent and colorimetrical double channel probe incorporating hybrid naphthopyran–benzothiazole in an aqueous solution

ABSTRACT A highly selective red-emitting fluorescent and colorimetric double-channel probe incorporating a conjugated benzopyran–benzothiazole system is proposed for the detection of cyanide (CN−) in water samples. Under the presence of CN−, the probe displays red fluorescence disappearance, having an immediate (<30 s) visible colour variation from red to colourless. Due to a blocking process where an intramolecular charge transfer occurs, the benzothiazole C = N bond of the probe is attacked by the CN− nucleophile; 1H NMR titration and DFT calculations for this occurrence varied. Results from this investigation enable feasible and simple test strips to be produced for detecting CN− in water samples. Graphical Abstract