A fluorescent probe based on modulation of ESIPT signaling for the highly selective detection of N₂H₄ and...

The broad occurrence of the hydrazine (N₂H₄) residues in aqueousenvironment is a potential threat to human health. Currently, the mainstream strategy for designing N₂H₄-specific probes is to functionalize a fluorophore with nucleophilic sites for the reductionreaction with N₂H₄. In this work, we designed and synthesized an excited-state intermolecular proton transfer (inter-ESPT) fluorescent dye(2-amino-4-(4-methoxyphenyl)-7,8-dihydro-5H-spiro[quinoline-6,2'-[1,3]dioxolane]-3-carbonitrilem, DQN) and used it as a probe to sense N₂H₄. DQN exhibits blue fluorescence in conventional solvents, which is assigned to its normal emission. In the presence of N₂H₄, the probe DQN can anchor the N₂H₄ molecule via hydrogen binding, enabling DQN to undergo inter-ESPT process and light up its tautomeric fluorescence. From this basis, an inter-ESPT-based method for N₂H₄ detection was established, offering high selectivity and sensitivity (11.5 nM). Furthermore, we demonstrated that the probe DQN can recognize the proteins in living cells, affording cell-imaging. This research provides a promising sensing strategy for monitoring N₂H₄ in water environments and this inter-ESPT dye is a powerful tool for cell-imaging.