Mercury Probes Based On Optical Information Changes Of Hemicyanime And Rhodamine Deravitives

In recent years, environmental pollution caused by heavy metals is more and more serious. The development of highly selective fluorescent probes based on the theories of host-guest chemistry for metal ions detection is particularly important, since some metal ions can have extremely harmful effects on humans and the environment.This thesis developed a series of fluorescent probes (La-Lf) based on the fluorescent dyes of rhodamine 6G and hemicyanine as signal reporting groups. Their molecular recognition behaviours and molecular recognition mechanisms were evaluated detailly by UV-Vis absorption spectra and fluorescence spectra. The main contents are as follows:(a) Novel Hg²⁺-selective fluorescent probes (La-Ld) with hemicyanine as fluorescent reporting group and NSe2 chelating unit as ion binding site were synthesized and characterized. Fluorescent probes La and Lb show a specific Hg²⁺ selectivity to discriminate between Hg²⁺ and chemically close ions in junction with a visible colorimetric change from red to colorless, leading to potential production of both"naked-eye"and fluorometric detection of Hg²⁺ cations both in ethanol/water (v/v, 1:1) and water solutions. The detection limits are estimated to be l×10^-7 M for La and 5.0×10^-8 M for Lb, indicating that the limit of detection of Lb to Hg²⁺ met the discharge limit for industrial waste water according to China SA standard, or the U.S. EPA standard. Therefore, probe Lb can be used in practical waste water of industry to inspect and monitor mercury ions. Compared with probes La and Lb, only Ld has significant UV selectivity for Hg²⁺ in acetonitrile/water (v/v, 1:1) even though a slightly structural differences by replacement of the hydroxylethyl with phenyl in both Lc and Ld. In addition, in order to explore the possibility of compounds La-Ld as practical probes, the spectral changes of compounds L and L?Hg²⁺ are investigated at different pH value. The spectra of La?Hg²⁺, Lb?Hg²⁺ and Ld?Hg²⁺ are not sensitive within a wide range of pH value, indicating that these chemosensors can be used as colorimetric and fluorometric sensors in real samples.(b) Novel Hg²⁺-selective fluorescent probes (Le and Lf) with rhodamine 6G as fluorescent signal reporter were synthesized and characterized. Le and Lf have good selectivity and sensitivity for Hg²⁺ both in ethanol/water (v/v, 1:1) and water solutions. In the presence of Hg²⁺, the resulted Le solution exhibited an obvious and characteristic color change from colorless to rose, the color of Lf solution changed from colorless to light pink. The detection limits are estimated to be 5×10^-8 M for Le and 2.0×10^-8 M for Lf, indicating that the limits of detection of Le and Lf to Hg²⁺ met the discharge limit for industrial waste water. Therefore, probes Le and Lf can be used in practical waste water of industry to inspect and monitor mercury ions.