A dual-response quinoline-based fluorescent sensor for the detection of Copper (II) and Iron(III) ions in aqueous medium

•A new and dual-response fluorescent probe for Cu2+ and Fe3+ detection is reported.•The probe has been used in 100% aqueous medium.•The probe exhibits a high selectivity for Cu2+ and Fe3+ over other metal ions.•It is firstly reported that the probe distinguished Cu2+ and Fe3+ by ascorbic acid.•The probe is used for tracking Cu2+ and Fe3+ in cell by fluorescence imaging.

A new and dual-response fluorescent probe (QLBM) based on quinoline and benzimidazole groups has been designed and developed for recognition of copper(II) ion (Cu2+) and iron(III) ion (Fe3+) simultaneously. This sensor displays a favorable selectivity for Cu2+ and Fe3+ ions over a range of other common metal cations in 100% aqueous medium (50 mM Tris buffer, pH 7.2), leading to prominent fluorescence on-off. The detection limits were 1.35 × 10−7 M for Cu2+ and 1.24 × 10−7 M for Fe3+ respectively. This dual-response fluorescent probe for Cu2+ and Fe3+ was distinguished by further reduction of the ascorbic acid. It is reported for the first time to use ascorbic acid to discriminate Cu2+ and Fe3+ by fluorescent probe technology. The recognizing mechanism of QLBM toward Cu2+ and Fe3+ has been investigated in detail by NMR, HR-MS and density functional theory (DFT) calculations. Moreover, further application of the sensor in fluorescence imaging was studied in HeLa cells due to the low cytotoxicity and good photophysical properties, suggesting that QLBM could be used as a fluorescent sensor for tracking Cu2+ and Fe3+ in cells.

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