Reaction-based colorimetric cyanide chemosensors: rapid naked-eye detection and high selectivity.

Taking advantages of both the well-known azobenzene structure and the special nucleophilicity of cyanide toward the acceptor moiety, a new ratiometric colorimetric chemodosimeter (Azo-1) toward cyanide anion was designed and synthesized by using intramolecular charge transfer (ICT) as a signaling mechanism. Upon the addition of CN(-) anion, the probe displayed apparent color changes from deep red to light yellow, which could be observed by naked eyes. With the aid of the UV-vis spectrometer, the detection limit could be as low as 1.1 μM. The probe possessed high selectivity for cyanide with respect to other common anions. In addition, Azo-1 could serve as practical colorimetric probe for "in-the-field" measurements that would not require any additional equipment by virtue of "dip-sticks" approach.