A highly selective and ratiometric molecular probe for cyanide sensing based on a phenothiazine-hemicyanine dye

Highlights: • A new ratiometric fluorescent probe was developed for CN^- detecting. • The probe showed excellent sensitivity with a low limit of detection to 20 nM. • The probe displayed high selectivity for CN^-. • A cell imaging experiment demonstrated the prospect for tracing cyanide anions. - Abstract: A new ratiometric fluorescent probe was designed based on hemicyanine moiety as a cyanide reaction site for nucleophilic addition. The titration experiment for CN^- showed this probe exhibits high selectivity, a low limit of detection to 20 nM and quick response for CN^- sensing. At the addition of CN^-, the colour of the solution changed from purple to colourless, accompanied by an increase in the fluorescence intensity. The sensing behavior was investigated by changes of UV–vis spectra, HRMS and ¹H NMR. Furthermore a HepG2 cell imaging experiment demonstrated the application prospect for tracing cyanide anions in biological systems.