A novel turn-on fluorescent probe for cyanide detection in aqueous media based on a BODIPY-hemicyanine conjugate

A novel BODIPY-hemicyanine based fluorescent probe 1 for cyanide (CN − ) detection was designed and synthesized. Among the tested anions, the probe showed high selectivity towards CN − . Only addition of CN − to probe 1 in aqueous solution (V H2O /V EtOH   =   1/1) could result in a remarkable blue shift of the absorption band from 385   nm to 265   nm and induce 20-fold fluorescence enhancement at 515   nm. The sensing mechanism was based on nucleophilic addition between CN − and indolium group, which was confirmed by 1 H NMR and mass spectrum analysis. Plot of fluorescence intensity as a function of CN − concentrations exhibited a good linear relationship in the range of 0–10   μM, with a detection limit to be 1.53   ppb. Moreover, the proposed sensing approach could work in a wide pH range from 5.0–9.0 and reach an equilibrium instantaneously. Finally, probe 1 was successfully applied in detection of CN − in natural water samples and on test paper strips with satisfactory results.