Preparation And Application Of Rhodamine Derivative PH Fluorescence Probe And Hg²⁺ Fluorescence Probe

pH is one of the important indicators of water quality parameters,indicating the acidity and alkalinity of water bodies.At low pH values,it increases the solubility of toxic pollutants in water,thereby increasing the risk of absorption by aquatic organisms,affecting the reproduction of bacteria and algae,and slowing down the degradation of organic matter in water.Mercury ion Hg²⁺is widely recognized as one of the most toxic pollutants in water bodies,causing serious harm to the ecological environment and human health.The World Health Organization stipulates that the maximum acceptable value of Hg²⁺in drinking water is 30.0 nM,which means that mercury ions can also pose a threat to human and animal health at very low concentrations.Due to the non degradation of Hg²⁺in organisms,it leads to various serious diseases,including Alzheimer’s disease,Minamata disease,kidney disease,liver disease,immune system diseases,etc.Given the many shortcomings of current methods for detecting pH,such as visual colorimetry and potentiometry,colorimetry relies too heavily on human judgment and lacks objectivity in the detection results.The potentiometric method is an electrochemical sensor detection method based on the combination of electrodes and reference electrodes.This method overly relies on electrode sensors,and commonly used glass sensors have shortcomings such as short lifespan and susceptibility to external interference in detection.The traditional detection methods of Hg²⁺,such as inductively coupled plasma detection method and enzyme-linked immunosorbent assay（ELISA）detection method,have many shortcomings,requiring a large number of sample pretreatment steps and cumbersome operation.Therefore,it is necessary to establish a strategy for rapid pH detection and a highly selective strategy for rapid detection of Hg²⁺.Fluorescent probes have attracted researchers’interest due to their simple operation and high sensitivity,and are widely used in environmental detection and other fields.Constructing pH fluorescent probes and Hg²⁺fluorescent probes for pH and Hg²⁺detection is an effective strategy.At present,most pH fluorescence probes can display strong fluorescence in dilute solutions,but in the aggregated state,the fluorescence intensity is significantly reduced due to the aggregation induced quenching effect（ACQ）,which limits their application.Currently,most mercury ion(Hg²⁺)probes have unsatisfactory specificity.Therefore,in this paper,Motofluor-2,a fluorescent probe that can be used for pH detection in strong acidic water,and MGHg,a fluorescent probe with high selectivity for rapid detection of Hg²⁺,were synthesized based on rhodamine derivatives,and the structures of related compounds have been verified by ¹H NMR,¹³C NMR or HRMS.In Chapter 3 of this article,the performance and application of pH fluorescence probes were studied.The results indicate that Motofluor-2 exhibits aggregation induced luminescence characteristics when the spironolactone is opened,which can prevent it from being troubled by the ACQ effect during application.Study the fluorescence spectra of Motofluor-2 in different pH solutions under viscosity environment.The results showed that the probe Motofluor-2 can achieve specific detection of pH in strong acid environments,and the response is most sensitive when the pH range is between 1.0-4.0.In addition,the response time of Motofluor-2 to pH was also studied,and the results showed that Motofluor-2’s response to pH was almost instantaneous.In Chapter 4 of this article,the performance of mercury ion fluorescence probes for detecting mercury ion Hg²⁺was studied.The results showed that MGHg has a specific response to Hg²⁺and is not affected by other metal cations.The study on the response of MGHg in Hg²⁺solutions with different pH indicates that the probe MGHg is suitable in the pH range of 3.0-11.0.In addition,the binding method between fluorescent probe MGHg and Hg²⁺was studied.The results showed that the coordination ratio betweenMGHg and Hg²⁺was 1:1 when detecting Hg²⁺,and the stability constant Ks=2.95 M^-1,indicating that MGHg has a strong interaction with Hg²⁺and the binding is relatively stable.The study on the response time of fluorescence probe MGHg and Hg²⁺shows that MGHg responds to Hg²⁺within 1 minute and can complete the response within 4 minutes.This indicates that the probe MGHg can achieve rapid detection of Hg²⁺.Finally,the detection limit and precision of fluorescence probe detection for Hg²⁺were studied,and the experimental results showed that the Hg²⁺concentration has a good linear relationship in the range of 0.1 to 0.6μM,with a detection limit of 1.12×10^-7 M,The method of detecting Hg²⁺with probe MGHg has a small error,with RSD=1.12%.