Colorimetric and ratiometric fluorescent probes for sensitive visualization of hydrazine in water and in living cells

Abstract

In view of the strong nucleophilicity of hydrazine, two fluorescent probes, DEA-A and Jul-B, were designed and synthesized. These probes employed 2,3,5,6-1H,4H-tetrahydroquinolo[9,9a,1-gh]coumarin (Jul-B) or N,N-diethyl-7-aminocoumarin (DEA-A) as the fluorophores, 2-benzothiazole acetonitrile serving as the recognition moiety for N2H4. The formation of hydrazones weakened the intramolecular charge transfer (ICT) process in both probes, leading to more than 100 nm blue-shifts in both absorption and emission. DEA-A and Jul-B demonstrated notable colorimetric and ratiometric fluorescence responses to N2H4, which enabled us to realize the identification of hydrazine by “naked-eye”. In the case of DEA-A, the ratio of I513/I616 is linear to N₂H₄ concentration in the range of 1.0-150 μM, and the detection limit for N₂H₄ was appraised to be 0.10 μM. With the assistance of smartphones, N2H4 concentrations in realistic samples were visualized via RGB image analysis. In addition, both probes were applied in ratiometric fluorescent imaging of N₂H₄ in living L929 cell line.