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.