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

The broad occurrence of the hydrazine (N2H4) residues in aqueous environment 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 reduction reaction with N2H4. In this work, we designed and synthesized an excited-state intermolecular proton transfer (inter-ESPT) fluorescent dye(2-amino-4-(4-methoxyphenyl)-7,8dihydro-5H-spiro[quinoline-6,2 & PRIME;-[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.