Preparation And Properties Of Graphene Quantum Dots Based Nano Fluorescent Material

Fluorescent probes are a common type of fluorescent materials which are used for detection.They can be specifically bound to the target analyte through coordination,hydrogen bonding,static electricity,or chemical reactions.The change of fluorescence emission spectrum before and after analysis of target will be obvious.Compared with other analytical methods such as chromatography and electrochemistry,fluorescent probe analysis method has the advantages of high sensitivity,rapid response,simple equipment and simple operation,it can also be used as various imaging tools to realize the cell in vivo.Therefore,fluorescent probes have become one of the best choices for researchers to study the impact of various small molecules,large molecules or the environment on biological systems.With the continuous advancement of science and technology,the research on fluorescent probes is also developing in the direction of making it have higher sensitivity and stronger anti-interference ability.Ratiometric fluorescent probes are a type of fluorescent probes that can utilize quantitative changes in the ratio of fluorescence intensities at different wavelengths before and after detection of the target and achieve quantitative analysis of the target.It can eliminate the influence of interference factors in the environment and avoid the generation of false positive results.However,limited by the detection mechanism of certain characteristic targets,it is difficult for traditional organic small molecule probes to design or synthesize related ratio probes for some analytes.In recent years,researchers have tried to solve such problems via nano-fluorescent materials.Graphene quantum dots are a new class of carbon nano fluorescent materials,which have the advantages of high chemical stability,relatively controllable size,and low cytotoxicity.More importantly,the ?-? conjugated system of graphene quantum dots and the surface functional groups make it easy to be functionalized.It can be modified with various organic,inorganic and biological materials as needed to prepare ratio-type fluorescent probes.In this thesis three of nanocomposites are prepared based on ?-? stacking action of graphene quantum dots and small organic fluorescent probes.They were tested for small molecules,biological macromolecules and cell microenvironments commonly found in biological systems.The details are as follows:(1)Graphite quantum dots with blue emission were obtained by pyrolysis of citric acid.Nanocomposite probe HVC-6 @GQDs was constructed by ?-? stacking action with the small molecule fluorescent probe HVC-6.The composite probe has low cytotoxicity,excellent selectivity.The fluorescence intensity ratio I610 / I470 shows a good linear relationship with the RNA concentration and can achieve the quantitative analysis of RNA.Meanwhile,the composite probe can also realize real-time detection and positioning of RNA in cells.(2)The nano-composite probe CP @ GQDs-OH was constructed by ?-? stacking action with the small molecule fluorescent probe CP.CP @ GQDs-OH showed two FRET processes between CP and GQDs-OH in the absent and present of SO2.Affected by the two FRET processes in the detection process,the composite probe can achieve multi-ratio detection of SO2.Several fluorescence intensity ratios have a good linear relationship with the concentration of SO2,and have lower detection limits.CP @ GQDs-OH can realize the quantitative detection of SO2 in vitro,cells and in vivo,and has the ability to locate the mitochondria of cells.(3)The nano-composite probe RV-1 @ GQDs-OH was constructed by the hydroxylated graphene quantum dots and the small molecule fluorescent probe RV-1 through ?-? stacking.The change of the fluorescence emission spectrum of the composite probe in different viscosity environments can achieve the measurement of the environmental viscosity,the fluorescence intensity ratio I635 / I530 show a good linear relationship with viscosity.After the cells are stimulated by stimulant,RV-1 @ GQDs-OH can also realize the visual imaging of viscosity change of cells with real-time measurement.