Dual-functional chemosensor with colorimetric/ratiometric response to Cu(II)/Zn(II) ions and its applications in bioimaging and molecular logic gates

Abstract

Rationally designed and synthesized Schiff base sensor CMTAH containing coumarin fluorophores by the coupling of coumarin aldehyde and thiophene-2-carbohydrazide and acts as differentially selective chemosensor via colorimetric/ratiometric responses to Cu(II)/Zn(II) ions with fluorescence switchable strategy in aqueous media. Variation in absorption and emission spectra of CMTAH with different metal cations in aqueous media reveal high-affinity binding to Cu(II)/Zn(II) ions over other coexisting cations. Moreover, the spectrometric titrations and Job's plot curves substantiated the stoichiometric ratio of 1:1 for Cu(II)/Zn(II) complexes formation with low detection limits of 141 nM and 72 nM, respectively. Particularly, the responding mechanism of CMTAH toward Cu(II)/Zn(II) ions was investigated by density functional theory calculations. Notably, the molecular logic gates were established with the combination of CMTAH for the intelligentialized recognition of Cu(II)/Zn(II) ions. Additionally, the compatibility and permeability of CMTAH were attributed to Schiff base group, which exhibited remarkable responding and bioimaging in living cells and zebrafish. Notably, CMTAH could be used to image in Drosophila larvae with a clearly visible profile of internal organs and effectively capture Cu(II) and Zn(II) ions in living Drosophila larvae, which lay the foundation of sensors in the field of Drosophila biological imaging research.