A simple colorimetric and fluorometric probe for rapid detection of CN- with large emission shift.

In this work, a novel probe R was synthesized via Knoevenagel reaction between 3H-benzo[f]chromium-2-formaldehyde and ethyl cyanoacetate for selective detection of CN- in both colorimetric and fluorescent signal channels. The recognition of CN- was through the nucleophilic reaction of CN- to C = C of probe R, which destroys π-conjugation and blocks the ICT effect of the probe, resulting in colorimetric and fluorometric responses. Probe R showed great sensitivity toward CN-, with large fluorescent emission (595 nm) and low detection limit (0.70 μM). Moreover, probe R can detect exogenous CN- in living cells.