Separation And Characterization Of Fluorescent Carbon Quantum Dots And Their Application In Metal Ions Detections

Carbon quantum dots,a kind of carbon particles,also called carbon dots or carbon nanodots,is a class of new nanomaterials.The most prominent characteristic of carbon quantum dot is photoluminescence property,for the unseparated carbon quantum dots,the emission wavelength changed with the excitation wavelength and,for the purified carbon quantum dots,its emission wavelength is independent on the excitation wavelength.Now we get mixture of particles with different relative molecular mass by using present methods,which have strong ultraviolet absorption peak,the fluorescence spectrum is mostly wide,emission spectrum covers a visible wavelength region.Therefore,it is necessary to adopt effective methods to purify the carbon quantum dots in order to obtain the carbon quantum dots with relatively concentrated molecular weight.Chapter 1 mainly introduces the preparation methods of carbon quantum dots,common characterization methods and pufification methods of carbon quantum dots.The synthesis methods of carbon quantum dots are divided into top-down and from bottom to top.Characterization methods with mass spectrometry,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy,transmission electron microscopy?TEM?and nuclear magnetic resonance?NMR?.The purification methods of carbon quantum dots,including conventional physical and modern chromatography.Finally,the purpose of this research project is proposed.Chapter 2 introduces the synthesis and preliminary purification of fluorescent carbon quantum dots.The effects of reaction temperature and reaction time on the properties of the carbon quantum dots are investigated.The initial dialysis of fluorescent carbon quantum dots was studied.The conditions of preparation chromatography were introduced,including the flow rate and eluent.Carbon quantum dots were treated with methanol and water.Ultraviolet,infrared,fluorescence and mass spectra were performed on unseparated carbon quantum dots.The purification and properties of methanol as solvent and water as solvent were explored respectively.Chapter 3 introduces the application of fluorescent carbon quantum dots.The main content is the detection of Hg²⁺with unseparated fluorescent carbon quantum dots,detecting the linear range,the linear range is 0.01-100?M,the LOD value of Hg²⁺detected by the unseparated fluorescent carbon quantum dots.Investigates the stability of Hg²⁺detected by unseparated fluorescent carbon quantum dots.The detection of Hg²⁺with purified fluorescent carbon quantum dots.Including detects the linear range,the LOD value of Hg²⁺detected by the purified fluorescent carbon quantum dots,is 1nM.Investigates the stability of Hg²⁺with purified fluorescent carbon quantum dots.Chapter 4 mainly introduces the preliminary exploration of carbon quantum dots by capillary electrophoresis.The influence of buffer solution type and pH value on the carbon quantum dots of capillary electrophoresis was studied,capillary electrophoresis was used to separate the carbon quantum dots separated once by gel column,capillary electrophoresis was used to separate the carbon quantum dots separated twice by gel column.Chapter 5 includes the conclusion and outlook of the research content.