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An efficient fluorescein based probe (H 2 L) for the dual sensing of Al 3+ and Cu 2 + has been synthesized and characterized. H 2 L was highly selective toward these two ions with different fluorescence signals and binding modes in two different media. In EtOH-H 2 O (3:2, v/v; pH 4.0), H 2 L selectively binds Al 3+ to form a 1:1 ligand/metal complex, giving rise to a visible pale pink-to-yellow color change and fluorescence enhancement at 440 nm, while in CH 3 CN-H 2 O (2:3, v/v; pH 7.2), H 2 L and Cu 2+ form a 1:2 ratio complex, resulting in a color change from pink to orange-yellow and a significant fluorescence enhancement at 520 nm. The binding modes were confirmed by fluorescence, absorption, IR, ESI-MS and 1 H NMR titrations. The detection limits were calculated to be 7.32 × 10 −8 M and 1.47 × 10 −8 M for Al 3+ and Cu 2+ , respectively. Cell imaging studies demonstrate that this sensor is capable of sensing Al 3+ and Cu 2+ in living cells. [ABSTRACT FROM AUTHOR]

Based on fluorescein, a novel water-soluble and reversible fluorescent probe (Flu-Py) was designed and synthesized for the sequentially “ON–OFF–ON” fluorescent detection of Al 3+ and F − in concentration range of 0–10 μmol L −1 and 0–30 μmol L −1 , respectively, with high sensitivity and excellent selectivity. The detection limits for Al 3+ and F − were 0.092 μmol L −1 and 0.112 μmol L −1 , respectively. The binding mode and sensing mechanism of Flu-Py with Al 3+ was verified by density functional theory (DFT) and time dependent density functional theory (TDDFT) calculation. The “ON-OFF–ON” fluorescent property of Flu-Py upon the addition of Al 3+ and F − was utilized for the imaging of living cells. [ABSTRACT FROM AUTHOR]