Construction Of A Ratiometric Fluorescence Sensor And Its Application In The Detection Of NO And Hg²⁺

Ratio fluorescence analysis usually uses two fluorescent materials with different emission wavelengths to construct a fluorescence sensor with dual emission peak characteristics.It is based on the relationship between the ratio change of the fluorescence intensity of the two emission peaks before and after the addition of the analyte and the concentration of the analyte,to quantitatively detect and analyze the target.To a certain extent,it can relatively reduce the interference of external factors on the analysis and improve the accuracy and reliability of the analysis results.Therefore,it is widely used in the fields of chemistry,biological analysis and environmental monitoring.In order to improve the detection ability of ratio fluorescent probes in the detection of small biological molecules and heavy metal ions,this thesis designed and synthesized two ratio fluorescent probes.The main content of this paper includes three chapters,each chapter is summarized as follows:Chapter 1:IntroductionIn this chapter,we mainly introduce five aspects.First of all,the fluorescent materials are classified and introduced,mainly divided into organic fluorescent materials and inorganic fluorescent materials,and the use of common materials is exemplified.Then the mechanism of the fluorescence sensing and construction of the ratio fluorescence sensor is introduced in detail.Next,the nitric oxide and mercury ion fluorescent probes are classified and introduced.And finally the basis of the thesis and the main research content are described.Chapter 2:A ratiometric fluorescence sensor based on UiO-66-CdTe@ZIF-8 core-shell nanocomposites for the highly selective detection of NONitric oxide(NO)is a signaling molecule in the organism,playing an important role in the regulation and control of the central nervous system,cardiovascular system and endocrine system,and maintains the normal operation of the body.Through the real-time detection of NO,exploring its important functions in the physiological activities of organisms has far-reaching significance for life science research and medical research.In this work,a ratiometric fluorescence sensor based on UiO-66-CdTe@ZIF-8 core-shell nanocomposites is developed for the highly selective detection of NO.Prior to coating with red-emitting CdTe quantum dots(QDs),the yellow-emitting Ui0-66-NH2 core was synthesised using the solvothermal method.The resulting core UiO-66-CdTe nanocomposite served as the signal-displaying unit(UiO-66-CdTe).Next,the UiO-66-CdTe nanocomposite was encapsulated in a zeolitic imidazolate framework(ZIF-8),forming a transition layer.This framework prevent the cores from being corroded and significantly reduced the interference impact of large molecules on the reaction matrix.A detectable signal was obtained by monitoring the NO quenching fluorescence of UiO-66-NH2,and the CdTe QDs embellished carboxylic acid served as the reference signal.There was a linear relation between the changes in the I442/I574 ratio and the NO concentration range from 0 to 0.10 nM.The results demonstrate the proposed UiO-66-CdTe@ZIF-8 CSNCPs-based sensor is suitable for quantitative purposes in various environmental and biological applications.Chapter 3:A ratiometric fluorescence sensor based on CD@QD nanocomposites for the highly selective detection of Hg2+In this work,a novel composite nanomaterial ratiometric fluorescence probe for detecting Hg2+ was designed and synthesized.By mixing a blue fluorescent carbon dot(CD)as an internal standard signal and a yellow luminescent CdTe QD as a detection fluorescent unit,a new color tunable strategy was developed to construct a ratio fluorescent probe for selective and sensitive determination of Hg2+.Under the excitation of 360 nm,the ratio of the emission intensity at 540 nm and 443 nm is defined as 4:1.Under optimal conditions,the response of the ratiomeric fluorescence probe to different concentrations of Hg2+ was monitored.The results showed that at pH 8.0,with the increase of Hg2+ concentration,the fluorescence intensity of QDs was significantly quenched,while the fluorescence intensity of CDs remained almost unchanged.According to the change of the ratio of the two peaks,quantitative detectio1 of Hg2+ can be achieved.According to the fluorescence response graph,the relationship between the relative fluorescence intensity and the concentration of Hg2+ is drawn.The linear relationship is between 0.2 ?M and 1.4 ?M.The linear regression equation obtained is Y=0.0523+0.4896X.