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 (QLBM) based on quinoline and benzimidazole groups has been designed and developed for recognition of copper(II) ion (Cu 2+ ) and iron(III) ion (Fe 3+ ) simultaneously. This sensor displays a favorable selectivity for Cu 2+ and Fe 3+ 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 Cu 2+ and 1.24   ×   10 −7   M for Fe 3+ respectively. This dual-response fluorescent probe for Cu 2+ and Fe 3+ was distinguished by further reduction of the ascorbic acid. It is reported for the first time to use ascorbic acid to discriminate Cu 2+ and Fe 3+ by fluorescent probe technology. The recognizing mechanism of QLBM toward Cu 2+ and Fe 3+ 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 Cu 2+ and Fe 3+ in cells.