Synthesis and Application of Specific N₂H₄ Fluorescent Probes with AIE Effect Based on Pyrazole Structure

Two fluorescent probes, Y_1-2 were synthesized from 2-acetonaphthone, 4-acetylbiphenyl, and phenyl hydrazine by Vilsmeier-Haack reaction and Knoevenagel condensation. Their recognition efficacies for N₂H₄ were tested by UV–visible absorption spectroscopy and fluorescence emission spectroscopy. The recognition mechanism were studies by density-functional theory calculations, and the effect of pH on N₂H₄ recognition was also studied. The results showed that the probe Y_1-2 has high selectivity and a low detection limit for N₂H₄, and the recognition of N₂H₄ can be accomplished at physiological pH. The probes have had obvious aggregation-induced luminescence effect, large Stokes shift, high sensitivity, and can be successfully applied to live cell imaging.