Preparation Of Specific Fluorescent Probes For Mercury Ions And Their Applicaitons In Environmental Analysis

Mercury,as a highly toxic non-essential element,does great harm to the environment and life.Mercury in the environment is widely distributed in water,atmosphere and soil.It can not be decomposed by microorganisms,but also can undergo various forms of migration and transformation.Mercury ions(Hg²⁺)in the environment can not only be transformed into more toxic organic mercury through the action of microorganisms,but also accumulate through the food chain and food web,which seriously endangers the health of animals,plants and human beings.When mercury enters the body,it can cause damage to the digestive system,respiratory system and nervous systems,which can lead to death.Therefore,it is of great significance to detect Hg²⁺in environment and living system.Fluorescence detection technology has become an important tool for real-time and on-site detection of environmental pollutants due to its advantages of high sensitivity,in situ analysis and simple operation.Therefore,the development of novel specific Hg²⁺fluorescent probes has important theoretical significance and practical application value.In this paper,we selected long wavelength fluorescent dyes with strong intramolecular charge transfer（ICT）mechanism.Based on the selective coordination between Hg²⁺and amino group and the strong sulfur affinity of Hg²⁺,three novel specific Hg²⁺fluorescent probes were constructed with diaminomaleonitrile,imide and thiocarbonate as Hg²⁺response groups,respectively.（1）Using benzimidazole dye as signal functional group and diaminomaleonitrile as recognition group,a novel Hg²⁺fluorescent probe TD-Hg was constructed.Probe TD-Hg has high specificity for Hg²⁺detection,and can quickly respond to Hg²⁺in the test system.In addition,the probe can not only be applied to the specific detection of Hg²⁺in environmental water samples,but also has low cytotoxicity and can monitor the level of Hg²⁺in cells and zebrafish.（2）In view of the characteristic of Hg²⁺coordinating with thymine（T）to form a stable"T-Hg²⁺-T"structure,a highly selective Hg²⁺fluorescence probe BC-Hg was constructed using barbituric acid as the coordination unit of Hg²⁺.Probe BC-Hg can not only rapidly respond to Hg²⁺,but also has good naked eye detection ability,and can also realize sensitive detection of Hg²⁺through Tyndall effect.More importantly,after identifying Hg²⁺,probe BC-Hg can form flocculated precipitates in pure water,which has the potential to remove Hg²⁺in the environment.In addition,probe BC-Hg can be applied to the detection of Hg²⁺in environmental water samples,cells and zebrafish.（3）Using 2-（2-hydroxyphenyl）benzothiazole as the electron donor group and dicyano isophorone as the electron withdrawing group,a novel near-infrared fluorescence dye with ICT-ESIPT structure was designed and synthesized.The dye was then modified with thiochlorobenzoate to form a thiocarbonate specific recognition receptor,and a ratio type Hg²⁺near-infrared fluorescence probe NIRPC-Hg was successfully constructed.Probe NIRPC-Hg has high selectivity and sensitivity for Hg²⁺detection,and the detection limit is as low as 9.21 n M.At the same time,the probe has the ratio detection performance with large emission wavelength shift,which can avoid signal crosstalk between two peaks,eliminate the influence of environmental factors,and achieve accurate analysis of Hg²⁺in environmental water samples.In addition,the near-infrared imaging characteristics of the probe enable it to have good biological penetration and low background fluorescence,which can sensitively trace the concentration levels of Hg²⁺in cells and zebrafish.In conclusion,three new specific Hg²⁺fluorescent probes were developed in this paper,which can not only be applied to the detection of Hg²⁺in environmental water samples,but also have low cytotoxicity,and can in-situ trace the concentration levels of Hg²⁺in cells and zebrafish.Therefore,the construction of probes in this article not only provides an effective tool for detecting Hg²⁺in the environment and life systems,but also provides new design strategies for researchers to develop other types of fluorescent probes.