Near-infrared cell-permeable Hg2+-selective ratiometric fluorescent chemodosimeters and fast indicator paper for MeHg+ based on tricarbocyanines |
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Authors: | Guo Zhiqian Zhu Weihong Zhu Mingming Wu Xumeng Tian He |
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Institution: | Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, PR China. |
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Abstract: | Three tricarbocyanine dyes (IR‐897, IR‐877, and IR‐925) with different thiourea substituents that function as dosimeter units through specific Hg2+‐induced desulfurization have been demonstrated in a fast indicator paper for Hg2+ and MeHg+ ions. In comparison with available Hg2+‐selective chemodosimeters, IR‐897 and IR‐877 show several advantages, such as convenient synthesis, very long wavelengths falling in the near‐infrared (NIR) region (650–900 nm) with high molar extinction coefficients, a ratiometric response, and quite low disturbance with Ag+ and Cu2+ ions. They exhibit large redshifts, which result in a clear color change from deep blue to pea green that can be easily monitored by the naked eye for a convenient indicator paper. In emission spectra, they display a characteristic turn‐off mode at 780 nm and turn‐on mode at 830 nm with titration of Hg2+ ions. Remarkably, the signal/noise (S/N) ratio with other thiophilic metal ions (Ag+ and Cu2+) is greatly enhanced with ratiometric measurement of two channels: excitation spectra mode (I810 nm/I670 nm, monitored at 830 nm) and emission spectra mode (I830 nm/I780 nm, isosbestic absorption point at 730 nm as excitation). The distinct response is dependent upon the electron‐donating effect of the thiourea substituents; that is, the stronger the electron‐donating capability of the thiourea substituents, the faster the Hg2+‐promoted cyclization. Additionally, experiments with living SW1116 cells show that these three tricarbocyanine dyes with low toxicity can exhibit special characteristics that are favorable for visualizing intracellular Hg2+ and MeHg+ ions in biological systems, including excellent membrane permeability, minimal interfering absorption and fluorescence from biological samples, low scattering, and deep penetration into tissues. |
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Keywords: | chemodosimeters fluorescence mercury sensors tricarbocyanines |
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