The turn-off fluorescent chemical sensor based on imidazole structure for highly selective and accurate detection of Cu2+ ion in living cells

The compounds with an imidazole structure, DHH and DHM, were synthesized using benzoyl, ammonium acetate, 2-hydroxy-5-methylisophthalaldehyde, and 2-(3-aldehyde-4-hydroxyphenyl)- 4-methylthiazole-5-carboxylate as raw materials. The structures of probes DHH and DHM were characterized by FT-IR, ¹H NMR, ¹³C NMR, and HR-MS. This study found that DHH and DHM can rapidly and highly selectively recognize Cu²⁺ in EtOH-H₂O (1:1 v/v). The spectral characteristics of DHH and DHM were studied using fluorescence spectroscopy and UV–vis spectroscopy. The results show that the combination of DHH and DHM with Cu²⁺ produces a significant fluorescence quenching effect, and the influence of other metal ions can be neglected. Subsequently, through Job’s plot analysis, ¹H NMR titration, and DFT calculations, the binding mechanisms of probes DHH and DHM with Cu²⁺ were explored, and it was found that they coordinate in a 2:1 ratio. The experimental study on standard addition recovery showed that probes DHH and DHM could be used for the quantitative detection of Cu²⁺ in actual water samples. The probes were also successfully applied to the monitoring of Cu²⁺ in living cells.

Graphical abstract

The compounds containing imidazole structures in probes DHH and DHM were successfully synthesized and characterized. Test strips made of DHH and DHM were used for rapid “naked-eye” detection of Cu2⁺ in an aqueous medium. The probes were successfully used to monitor Cu2⁺ in living cells and real water samples.