Carbon Dots Prepared By Different Functionalization Methods And Their Applications In Environmental Analysis And Light-emitting Devices

Carbon dots(CDs)are a new type of carbon-based zero-dimensional nanomaterials with a size of less than 10 nm,which have excellent photoluminescence properties,low toxicity and rich surface functional groups.The research in this paper is mainly to realize the functionalization,multi-color emission and solid-state emission of CDs through different strategies.By studying the optical properties and luminescence mechanism of CDs,they are applied to the fields of analyte sensing and optical devices respectively.The thesis mainly includes the following parts:The research in this paper is mainly through surface modification,selection of suitable precursors and surface passivation strategies,amidation and solvothermal methods to prepare functionalized CDs,multicolor emission CDs and solid-state emission CDs,and analyzed its structure and mechanism through various techniques,and applied them to the preparation of fluorescence sensing and optical devices.The thesis mainly includes the following parts:1.Covalently link CDs with amino-rich surface to 3,4,9,10-tetracarboxylic dianhydride(PDT)through amidation reaction to synthesize PDT-functionalized CDs(CDs-PDT).Based on the mechanism of fluorescence resonance energy transfer,CDs-PTD shows specific fluorescence sensing ability for sunset yellow(FCF).At room temperature,the FCF concentration has a good linear relationship with CDs-PDT in the range of 0?180?M,and the detection limit is 106.8 n M.Therefore,we prepared a CDs-PDT/Sepharose sensor for FCF visual detection.In addition,CDs-PDT has also been successfully applied to the fluorescence sensing of FCF in actual beverage samples.2.Using isomers of diphenol as raw materials,concentrated sulfuric acid as catalyst,solvothermal method,controlled heating time to synthesize multicolor fluorescent carbon dots(M-CDs).The dehydration condensation process of CDs is affected by the solvothermal time and the position of the hydroxyl group on the raw material.The size of the conjugate area of CDs determines its fluorescence emission wavelength.Based on the static quenching mechanism,M-CDs shows excellent fluorescence sensing ability for Cl O~-.At room temperature,Cl O~-concentration in the range of 0?50?M and 4?44?M has a good linear relationship with green CDs and yellow CDs,respectively,and the detection limits are 31.1 n M and 56.5 n M,respectively.In addition,a high-transparency solid-state fluorescent film was prepared by mixing M-CDs with a solid-state substrate;and by adjusting the mass ratio of different CDs,and then encapsulating with epoxy resin,a white light-emitting diode was successfully prepared.3.Using maleic acid as the carbon source,(3-aminopropyl)triethoxysilane as the nitrogen source and surface passivator,by adjusting the ratio of the two,silicon-doped CDs with different solid-state emission were prepared(Si/CDs).The characterization results show that there are silicon chains(Si-C,Si-O and Si-N)on the surface of Si/CDs,forming a"protective shell"on the surface of CDs.The"protective shell"increases the Foster radius between adjacent Si/CDs in the solid state,avoids direct contact between the emission centers,and weakens the direct?-?interaction between them and excessive Foster Resonance energy transfers,thereby weakening their self-quenching effect,forming solid-state emission fluorescence.The fluorescence redshift of Si/CDs is related to their size radius and the degree of aggregation within the unit range.Based on the excellent solid-state emission performance of Si/CDs,it has been successfully applied to the preparation of color LEDs and fluorescent films.