| In recent years,with the massive waste of electronic products and the overuse of pesticides,people have paid more and more attention to food safety and drinking water quality,and pay more attention to the detection of palladium ions and pesticides in the environment.Fluorescence detection technology stands out among various detection methods due to its outstanding advantages such as good selectivity,simple operation,high sensitivity and short response time.As a new type of carbon nanomaterials,carbon dots occupy an important position in fluorescence detection technology due to their unique optical properties and good biocompatibility.In recent years,carbon dots prepared from green and natural biomass raw materials not only have excellent fluorescence properties and biocompatibility,but also meet the requirements of green synthesis and two-carbon environmental protection.However,the emission wavelength of most of the carbon dots prepared based on biomass raw materials is in the blue-green light region,and there are disadvantages such as background interference in biological imaging,which affects the application of biomass carbon dots.The near-infrared emission wavelength has the advantages of strong penetration depth and little interference from the self background,and has incomparable advantages in the field of biological imaging.Therefore,in this paper,a variety of plant leaves are used as carbon sources,and a one-step solvothermal method is used to optimize the synthesis process to prepare nearinfrared carbon dots with excellent performance.On this basis,two kinds of fluorescent sensors are assembled and constructed by functional modification.The main research contents are as follows:1.The near-infrared fluorescent carbon dots with excellent performance were prepared by simple solvothermal method with five kinds of low-cost green plant leaves in Guangxi,acetone as solvent.The fluorescence intensity and quantum yield were used as inspection indexes,and the near-infrared carbon dots with better performance were selected.Through orthogonal design,the technological process of preparing carbon dots from Magnolia denudata leaves was optimized,and the best reaction conditions were selected by comparison: acetone as the reaction solvent,90 ℃ as the reaction temperature and 7 h as the reaction time.It is concluded that the reaction temperature and time indirectly affect the fluorescence performance by influencing the degree of carbonization.2.The near-infrared carbon dots prepared from Magnolia enudate leaves were deeply studied and functionalized to prepare water-soluble nano probes for palladium ion（II）biological imaging and sensitive detection.Through a static quenching mechanism,it is highly selectively quenched by palladium ions（II）in the range of 0～200 μM,with a detection limit as low as 85.3 n M.The probe exhibits high stability,long emission,and narrow half-peak width（FWHM）and other advantages,it can be applied to actual water sample detection.In addition,the probe exhibits excellent cytocompatibility and low cytotoxicity,and can be used to visualize palladium（II）ions in human hepatoma cells Li-7,providing a potential application for pathological studies in detecting palladium ion（II）-related diseases.3.Based on the oxidase-like activity of manganese dioxide nanosheets,it can effectively oxidize o-phenylenediamine to generate fluorescent substances,which were combined with near-infrared carbon dots to construct a ratiometric fluorescence sensor to realize the analysis and detection of organophosphorus pesticides.Based on the reference of near-infrared carbon dots,the fluorescence sensor can reduce background interference and experimental errors,and achieve high-selectivity and high-sensitivity detection with a detection limit as low as 4.3n M,which can be used for practical water sample analysis. |
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