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Near‐Infrared Cell‐Permeable Hg 2+ ‐Selective Ratiometric Fluorescent Chemodosimeters and Fast Indicator Paper for MeHg + Based on Tricarbocyanines
Author(s) -
Guo Zhiqian,
Zhu Weihong,
Zhu Mingming,
Wu Xumeng,
Tian He
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201001769
Subject(s) - fluorescence , infrared , chemistry , analytical chemistry (journal) , environmental chemistry , physics , optics
Three tricarbocyanine dyes (IR‐897, IR‐877, and IR‐925) with different thiourea substituents that function as dosimeter units through specific Hg 2+ ‐induced desulfurization have been demonstrated in a fast indicator paper for Hg 2+ and MeHg + ions. In comparison with available Hg 2+ ‐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 Cu 2+ 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 Hg 2+ ions. Remarkably, the signal/noise ( S / N ) ratio with other thiophilic metal ions (Ag + and Cu 2+ ) is greatly enhanced with ratiometric measurement of two channels: excitation spectra mode ( I 810 nm / I 670 nm , monitored at 830 nm) and emission spectra mode ( I 830 nm / I 780 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 Hg 2+ ‐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 Hg 2+ 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.