A novel coumarin–naphthalimide-based ratiometric fluorescent probe for efficiently monitoring of hydrazine in environmental water

A novel coumarin–naphthalimide-based ratiometric fluorescent probe, called XPT, was synthesized with the aim of achieving high sensitivity and anti-interference for N₂H₄ detection. The probe XPT consists of coumarin species and naphthalimide species, which act as the energy donor and acceptor, respectively. The phthalimide group functions as the recognition unit for N₂H₄. Without the presence of hydrazine, the naphthalimide remains in a non-fluorogenic phthalimide mode, disrupting the FRET signal. However, the phthalimide group undergoes the Gabriel reaction to an amine, which induces FRET and consequently causes a shift in the emitted fluorescence from 468 to 528 nm when N₂H₄ was added. The results of the study demonstrated that XPT exhibits high sensitivity with a limit of detection 2.2 μM, as well as selectivity. Furthermore, it is remarkable that the distribution of N₂H₄ in real water samples can be monitored by XPT.