Synthesis And Analytical Application Of Heteroatom-doped Fluorescent Carbon Dots

With the development of carbon-based nanomaterials,carbon dots(CDs),as a new zero-dimensional carbon nanomaterial,have a wide range of applications in fluorescence sensing,monitoring environment,cell imaging and others,due to their simple preparation and unique optical features,such as high quantum yield,adjustable emission wavelength,good light stability,as well as low toxicity and good biocompatibility.There are various synthesis methods for CDs,among which the hydrothermal method is simple and convenient to operate,and the product is easy to obtain,which has been interested by the majority of scientific researchers.Here,three kinds of doped-CDs with different fluorescence properties were prepared by the hydrothermal reaction with different carbon sources and other compounds,and they were successfully applied to the detection of VB₁₂,small biological molecules and metal ions.Chapter 1:There generalize many contents inconcluding composition and structure of CDs,synthesis methods,luminescence properties,applications and the trend of development.Moreover,describing the background information and the main content of the research.Chapter 2:N,P-CDs are obtained by a one-pot hydrothermal synthesis strategy using L-arginine and phosphoric acid as the raw materials.The resulting N,P-CDs have good water-solubility and luminescence properties,with a high fluorescence quantum yield(18.38%).The maximum emission intensity of CDs is obtained at 444 nm with an excitation of 340 nm.Based on the mechanism of inner filter effect(IFE),CDs are used as an efficient and selective fluorescence sensor for the detection of vitamin B₁₂(VB₁₂).The linear response of CDs towards VB₁₂ is obviously widened in the range of 1.99–98.6?M and 98.6–176?M with the LOD is 59 n M.This method is successfully applied to detect VB₁₂ in two types of vitamin pills and blood serums.In addition,it can be used to bioimaging He La cells.Chapter 3:Using 2-aminoterephthalic acid and concentrated sulfuric acid as the reaction precursors,green fluorescent N,S-codoped CDs are synthesized by a one-step hydrothermal method.The surface characteristics,chemical groups and optical characteristics of CDs are explored by transmission electron microscopy(TEM),infrared(IR),and X-ray photoelectron spectroscopy(XPS),fluorescence(FL)and other means.The CDs particles are spherical and dispersed uniformly and have a good water solubility,good photoluminescence and anti-photobleaching.The sensing platform for tetracycline(TC)and picric acid(PA)is established in a phosphate buffer solution with a p H of 7.4,and their detection limits are91.2 n M and 78.9 n M,respectively.In addition,the CDs have been successfully applied in Hela cell imaging,showing potential in bioimaging because of low toxicity and good biocompatibility.Chapter 4:Using o-phenylenediamine,arginine and concentrated sulfuric acid as the reaction precursors,dual-emission fluorescent N,S-codoped CDs are synthesized by a one-step hydrothermal method,and a visualization of Cr(VI)was established based on the internal filtration effect(IFE)ratiometric fluorescence detection platform.In the presence of Cr(VI),the CDs solution changes from light pink to orange under a UV lamp,realizing rapid and visual detection of Cr(VI).The linear range of this method for the detection of Cr(VI)is 3.83-18.87?M,and the detection limit is 47.2 n M.In addition,the CDs have also been successfully used in Hela cell imaging and the determination of Cr(VI)in actual water samples.The synthesis methods of the three kinds of carbon dots synthesized in this thesis are simple,and the CDs have excellent luminescence performance.They have been successfully used in the analysis and detection of small molecules or metal ions of actual samples,and cell imaging,which have certain theoretical and applied research values.