Preparation Of Fluorescence Carbon Quantum Dots And Detection Of Drugs

Carbon dots(CDs)have unique spectral properties such as tunable photoluminescence(PL)and excitation-dependent multicolor emission,as well as excellent water dispersibility,good photostability and biocompatibility,which have been used to detect analytes,drug release/transport and bioimaging.In this thesis,three different carbon dots were synthesized,and their structures and properties were characterized.The corresponding sensors were constructed for in vitro imaging.Chapter 1: Briefly introduces the structural composition,optical properties and biological properties of fluorescent carbon dots,and summarizes the synthesis methods of carbon dots and the application research progress in analytical detection,drug detection,drug delivery and bioimaging.Chapter 2: Nitrogen-doped carbon dots(CDs-Ws)were prepared by one-step hydrothermal method using biomass carbon source wheat straw and nitrogen source 1,2-ethylenediamine.The structure and optical properties were characterized by TEM,FTIR,XPS,UV-visible absorption spectroscopy and fluorescence spectroscopy.The average particle diameter of CDs-Ws was 4.97 nm.The prepared CDs-Ws showed excitation-dependent emission at 478 nm with excitation wavelength at 378 nm and the quantum yield was 0.42.Due to the internal filtration effect,the blue fluorescence of the CDs-Ws can be effectively quenched by curcum(Cur),and a fluorescence sensor for detecting Cur is constructed.The linear range is 3-10 ?mol/L,and the minimum detection limit is 55.17 nmol/L.CDs-Ws have low cytotoxicity and are also applied to multicolor imaging of SMMC 7721 cells.Chapter 3: The use of green organic carbon source flour and nitrogen dopant 1,2-ethylenediamine simple and rapid synthesis of nitrogen-doped carbon dots(CDs-F).CDs-F were characterized by modern analyticalmethods with an average particle size of 3.99 nm,In the case of the excitation wavelength at 381 nm,the maximum emission wavelength was observed at 467 nm with the fluorescence quantum yield of 0.87.It has been found that the fluorescence of CDs-F can be quenched by picric acid(PA),and the mechanism is studied as an internal filtration effect.The linear range is 0-30 ?mol/L,and the detection limit is 45 nmol/L.The fluorescence sensor for detecting PA is constructed and applied to the imaging of human hepatoma cells.Chapter 4: Nitrogen and sulfur co-doped carbon quantum dots(N,S-CDs)were prepared by a simple one-step acid-base neutralization exothermic carbonization method.It was characterized by a modern analytical method with an average particle size of 3.4 nm and an emission wavelength of 465 nm at an excitation wavelength of 372 nm.Based on the internal filtration effect(IFE),hexavalent chromium(Cr(?))can effectively quench the fluorescence of N,S-CDs,and ascorbic acid(AA)can recover N,S-CDs / Cr(?)due to weakened IFE Fluorescence.Therefore,an "on-off" nanoprobe for continuous determination of Cr(?)and AA was constructed.The nanoprobe system has good selectivity and sensitivity to Cr(?)and AA,and the linear ranges are 0.065~198?mol/L and 6.6~892?mol/L,respectively.At the same time,based on the significant response of N,S-CDs to Cr(?)and AA,a molecular level "AND" logic gate was constructed.More importantly,the prepared N,S-CDs have low toxicity and can be used for multicolor cell imaging in SMMC 7721 cells.