Synthesis And Application Of Novel Ultra-sensitive Fluorescent Probes For Mercury Ions

Mercury,as a highly toxic metal element,can enter the human body through the bloodstream,respiratory and digestive systems.Instead of being digested,it accumulates in the body and is harmful to human health.Thus,mercury has become a closely watched environmental pollutant.Mercury ion(Hg²⁺)has a strong binding affinity for mercaptan.Once the mercury ions enter the body,they are easy to cause the dysfunction of proteins and enzymes,which will damage the human liver,kidney,brain,and even lead to death in severe cases.Therefore,the timely and effective detection of mercury in the environment is an important topic at yet.In recent years,fluorescent probes have become the focus among researchers due to its high sensitivity,strong selectivity and the ability to detect analyte in situ.At present,the reported mercury fluorescent probes have some disadvantages such as low sensitivity,poor selectivity and complex synthetic steps,which are difficult to meet requirements of the detection of Hg²⁺.Therefore,it is very important to develop a novel,sensitive,selective and simple fluorescent probe for Hg²⁺.In this paper,fluorescent dyes of Rhodol and coumarin were used as fluorophore,and dimethylthiocarbamate,1,4-dithiothreitol,mercaptoethanol and propanethiol were used as recognition receptors to construct four kinds of probes for mercury ions.（1）An ultra-sensitive fluorescent probe RH-Hg,using Rhodol dye as the signal functional group and dimethylthiocarbamate as the recognition group for Hg²⁺,was synthesized.The probe can realize the ultra-sensitive detection of Hg²⁺,the limit of detection is as low as 0.74 n M,and the detection process is accompanied by obvious color change,which can realize the recognition of Hg²⁺by naked eye.In addition,the probe has been successfully applied to the detection of Hg²⁺in actual water samples with a good recovery rate.（2）A ratiometric fluorescent probe CR-Hg for Hg²⁺with coumarin dye as the fluorophore and 1,4-dithiothritol as the recognition receptor was designed and synthesized.The accuracy of the detection for Hg²⁺is improved through the self-calibration of the probe.In addition,two hydroxyl groups were introduced into the probe,which enhanced the water solubility of CR-Hg,laying a good foundation for the application of the probe in living system.Experimental results show that the probe not only can detect Hg²⁺in environmental water samples,but also detect mercury ions in macrophages and zebrafish,which has a further practical application.（3）In order to obtain better ratiometric fluorescent probes with better performance,two novel ratiometric fluorescent probes,CMER and CP-Hg,were synthesized by introducing mercaptoethanol and propyl mercaptan as Hg²⁺recognition receptors in coumarin dyes.Spectral experiments show that CMER and CP-Hg have better selectivity and anti-interference for Hg²⁺,and these two probes can achieve the ultra-sensitive detection of Hg²⁺with detection limits of 7.6 n M and 0.5 n M,respectively.In addition,the probe CMER has also demonstrated good performance in the detection of Hg²⁺in environmental water samples,macrophages and zebrafish.In summary,we have successfully designed and synthesized four novel fluorescent probes for Hg²⁺,which not only have high sensitivity and good selectivity,but also realize the detection and high recovery of Hg²⁺in environmental water samples.And these probes react with Hg²⁺accompanied by color change,which can be used for the identification by naked eye and has important practical significance in field application.More importantly,the newly synthesized probes have low cytotoxicity and good permeability.Furthermore,CR-Hg and CMER have been successfully applied to the imaging analysis of Hg²⁺in cells and zebrafish,showing strong biological application ability,which can provide a theoretical foundation for the design and development of other fluorescent probes.