A new ‘‘naked-eye’’ ratiometric colorimetric and fluorometric chemodosimeter (PBF) was constructed to enable trace vapor detection of hydrazine. This probe utilizes an irreversible and fast hydrazine-promoted cleavage of the ester linkage in PBF. This probe was shown to be highly selective for hydrazine, and showed real time response as well as a positive linear relationship to hydrazine concentration. The probe also shows an excellent performance in the ‘‘dip stick’’ method.