Synthesis And Properties Of Diarylethene Sensor Based On Rhodamine Derivatives

In recent years,due to the wanton discharge of industrial wastewater,domestic sewage and automobile exhaust,a large number of heavy metal ions have penetrated into the environment,water bodies and soil,which has caused varying degrees of damage to plant growth,animal development,soil composition and human health.Mercury is the most representative type of toxic heavy metal.It is extremely harmful due to its hysteresis,bioaccumulation and irreversibility.It can also contact the human body through the respiratory tract,digestive system,skin and mucous membranes,and cause a series of problems such as human physiological diseases and nervous system disorders.Therefore,the research on mercury has attracted wide attention from scientists.Among the many sensors that have been reported,the diarylethylene fluorescence sensors have attracted much attention because of its molecular switch function.Diarylenes are widely used in cell imaging,molecular switches and fluorescent sensors due to their photochromic properties,thermal stability and rapid response.Rhodamine derivatives have the advantages of high fluorescence quantum yield,good physical and chemical properties,etc.,and become one of the commonly used materials for the construction of fluorescence sensors.Therefore,how to design a convenient,highly selective and sensitive sensor to detect Hg²⁺is a very meaningful subject.In this paper,three diarylethene fluorescent sensors with excellent selectivity,simple operation,strong temporal and spatial resolution and low detection limit are developed for the detection of Hg²⁺and CH₃Hg⁺.The main contents of this subject are as follows:1)Summarized the types and research background of fluorescence sensors,the research progress of diarylethene and rhodamine sensors,and their applications in the fields of environment,biology and chemistry.2)A photo-tunable Hg²⁺fluorescence sensor（DT-1O）was synthesized based on piperazine-structured rhodamine and diarylene containing carboxylic acid functional group,and its structure was characterized by NMR and ESI-MS.In CH₃CN solution,the fluorescence and ultraviolet responses of DT-1O to various metal ions were tested.The results showed that only when Hg²⁺was added,the fluorescence intensity at 609nm was significantly increased,and the color of the solution changed from colorless to pink.In addition,the DT-1O not only has a naked eye recognition function,but also can be used to detect Hg²⁺in domestic water.3)A fluorescence sensor（DT-2O）that could specifically recognize Hg²⁺was synthesized based on the FRET mechanism,and its structure was characterized by NMR and ESI-MS.In methanol solution,the UV and fluorescence responses of DT-2O to various metal ions were studied.The test results showed that DT-2O could detect Hg²⁺with high sensitivity,selectivity,emits strong fluorescence,and the color of the solution changed from colorless to pink.Under alternating UV/Vis light irradiation,DT-2O exhibited excellent photochromic properties.Finally,DT-2O was successfully used to detect Hg²⁺in actual water samples.4)Based on diarylene-rhodamine spironylhydrazide and phenyl isothiocyanate,a reactive fluorescence sensor（DT-3O）that could recognize CH₃Hg⁺with high selectivity was synthesized,and its structure was analyzed by NMR and ESI-MS.In the DMSO/PBS（7/3,v/v）solution,the DT-3O reacted with CH₃Hg⁺for desulfurization and exhibited a fluorescence enhancement response.The detection limit was 4.24×10^-8 M.Under alternating UV/Vis irradiation,DT-3O showed excellent photochromic properties.In addition,the DT-3O can be used not only to detect CH₃Hg⁺in actual water samples,but also to detect CH₃Hg⁺in test paper experiments.