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A rhodamine spirolactam derivative ( 1 ) bearing a hydrophilic carboxylic acid group is developed as a fluorescent chemodosimeter for bivalent mercury ions (Hg 2+ ) in 100% aqueous solution. It exhibits a highly sensitive “turn-on” fluorescent response toward Hg 2+ with a 42-fold fluorescence intensity enhancement under 1 equiv. of Hg 2+ added. The chemodosimeter can be applied to the quantification of Hg 2+ with a linear range covering from 3.0 × 10 −7 to 1.0 × 10 −5 M and a detection limit of 9.7 × 10 −8 M. Most importantly, the fluorescence changes of the chemodosimeter are remarkably specific for Hg 2+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Hg 2+ is pH independent in neutral condition (pH 5.0–8.0) and the response is fast (response time less than 3 min). Furthermore, the ring-opening mechanism of the rhodamine spirolactam induced by Hg 2+ was supported by NMR, MS, and DFT theoretical calculations. In addition, the proposed chemodosimeter has been used to detect Hg 2+ in water samples and image Hg 2+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]

A new colorimetric and fluorogenic probe ( RN 3 ) based on rhodamine-B has been successfully designed and synthesized. It displays a selective response to Hg 2+ in the aqueous buffer solution over the other competing metals. Upon addition of Hg 2+ , the solution of RN 3 exhibits a ‘naked eye’ observable color change from colorless to red and an intensive fluorescence with about 105-fold enhancement. The changes in the color and fluorescence are ascribed to the ring-opening of spirolactam in rhodamine fluorophore, which is induced by a binding of the constructed receptor to Hg 2+ with the association and dissociation constants of 0.22 × 10 5 M −1 and 25.2 μM, respectively. The Job's plot experiment determines a 1:1 binding stoichiometry between RN 3 and Hg 2+ . The resultant “turn-on” fluorescence in buffer solution, allows the application of a method to determine Hg 2+ levels in the range of 4.0–15.0 μM, with the limit of detection (LOD) calculated at 60.7 nM (3σ/slope). In addition, the fluorescence ‘turn-off’ and color ‘fading-out’ happen to the mixture of RN 3 -Hg 2+ by further addition of I − or S 2− . The reversible switching cycles of fluorescence intensity upon alternate additions of Hg 2+ and S 2− demonstrate that RN 3 can perform as an INHIBIT logic gate. Furthermore, the potential of RN 3 as a fluorescent probe has been demonstrated for cellular imaging. [ABSTRACT FROM AUTHOR]

A rhodamine spirolactam derivative ( 1 ) is developed as a colormetric and fluorescent probe for trivalent aluminum ions (Al 3+ ). It exhibits a highly sensitive “turn-on” fluorescent response toward Al 3+ with a 70-fold fluorescence intensity enhancement under 2 equiv. of Al 3+ added. The probe can be applied to the quantification of Al 3+ with a linear range covering from 5.0 × 10 −7 to 2.0 × 10 −5 M and a detection limit of 4.0 × 10 −8 M. Most importantly, the fluorescence changes of the probe are remarkably specific for Al 3+ in the presence of other metal ions, which meet the selective requirements for practical application. Moreover, the experiment results show that the response behavior of 1 towards Al 3+ is pH independent in neutral condition (pH 6.0–8.0) and the response of the probe is fast (response time less than 3 min). In addition, the proposed probe has been used to detect Al 3+ in water samples and image Al 3+ in living cells with satisfying results. [ABSTRACT FROM AUTHOR]