A new chemodosimeter, Quino-P, recognizes the strongly nucleophilic cyanide by dual colorimetric and fluorescence 'off-on' signalling responses. Noteworthily, several other anions, even in significantly higher concentrations, induce no detectable photophysical perturbations. The chemodosimeter mechanism involves formation of a C4-cyano adduct, which exhibits an uncommon phenomenon of enhanced internal charge transfer interaction. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.