A Highly Sensitive Naked-Eye Fluorescent Probe for Trace Hydrazine Based on ‘C-CN’ Bond Cleavage

In this work, a colorimetric and ratiometric fluorescent probe, 2,3-bis(((E)-4-(diethylamino)-2-hydroxybenzylidene)amino)maleonitrile (DHM), was developed based on N2H4-induced bond cleavage. Two cyanide groups of DHM were applied to sense hydrazine (N2H4) for the first time, which was demonstrated using 1H NMR and HRMS spectra. The specific 'C-CN' bond cleavage induced by N2H4 showed an excellent fluorescence ratiometric behavior and a visible colorimetric change from purple to yellow. Meanwhile, it showed a low detection limit of 58.1 nM (1.65 ppb), which is far below the safety level (10 ppb) set by the U.S. EPA. Moreover, the probe was successfully employed for the quantitative detection toward N2H4 in real water samples.