A visible dual-applicable imidazole-Schiff base fluorescent probe for precise determination of copper ions in actual aqueous solutions and living cells

A novel imidazole-based hydrazide fluorescent probe, ( E )- N' -((1 H -imidazol-2-yl)methylene)- 4-(4,5-diphenyl-1 H -imidazol-2-yl)benzohydrazide (HDB), was designed and synthesized. The chemical structure of HDB was fully characterized by FT-IR, 1 H NMR, 13 C NMR, and HR-MS, confirming the successful synthesis of the target product. Subsequently, the sensing performance of HDB was systematically investigated via fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy. The probe HDB exhibited naked-eye distinguishable recognition of Cu 2+ with high sensitivity and selectivity in the EtOH/H 2 O (1:1, v/v), where fluorescence quenching was triggered by the chelation between HDB and Cu 2+ . Performance evaluation results demonstrated that the detection limit of HDB for Cu 2+ was as low as 0.38 nM. Job’s plot analysis revealed a 1:1 binding stoichiometry between HDB and Cu 2+ , with a binding constant of 1.765×10 5 M −1 . Cyclic experiments involving the alternate addition of Cu 2+ and Na 2 EDTA verified the excellent reusability of HDB. The practical applicability of HDB was validated through quantitative detection of Cu 2+ in real water samples, where the obtained recoveries fell within an acceptable range, indicating its feasibility for trace Cu 2+ analysis in environmental water matrices. Furthermore, this study explored the potential application of HDB in fingerprint detection, providing a new avenue for the innovation of fingerprint identification and anti-counterfeiting technologies. Notably, HDB achieved visualized monitoring of Cu 2+ in living cells, which further expands its application prospects in the biomedical field.