Study On Synthesis And Application Of Fluorescent Carbon Quantum Dots

Carbon quantum dots is a new type of nanomaterials,mainly composed of a carbon core and organic functional groups on the surface.The average grain size of carbon quantum dots is about 10 nm,and it has excellent photoluminescence properties and adjustable fluorescence properties.Due to their surfacial containing oxygen-based functional groups,excellent biocompatibility,chemical inertness and low cytotoxicity,carbon quantum dots have been applied in photocatalysis,ion sensing,biological imaging,heavy metal detection,adsorption treatment,supercapacitor,membrane preparation and water pollution treatment.In this paper,carbon quantum dots with blue,green and yellow emission wavelengths were synthesized using glucose and lignin as carbon sources,and their structures,compositions,optical properties and applications were studied.The specific research contents of this dissertation are as follows:Firstly,blue fluorescent carbon quantum dots(N-CQDs)were synthesized by hydrothermal method at 190? using glucose and m-phenylenediamine(1.5:1)as precursors in deionized water.The structure,morphology and fluorescence properties of N-CQDs were characterized by infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),transmission electron microscopy(TEM),X-ray diffraction(XRD),Raman spectroscopy(Raman),fluorescence spectrometer(FL)and ultraviolet-visible spectrophotometer(UV-Vis).The results showed that N-CQDs were rich in hydrophilic groups,and most of the carbon elements existed in the form of sp2 hybrid carbon.High-resolution TEM showed that the lattice spacing of N-CQDs was 0.212 nm,corresponding to the(100)crystal plane of graphite.N-CQDs had excitation wavelength dependence,the maximum excitation and emission wavelengths were 320 nm and 460 nm,respectively,and the relative fluorescence quantum yield was 17.5%;Fe3+and CrO42-can be selectively detected with detection limits of 9.11 and 8.34 ?M,respectively.It can be applied to multicolor HeLa cell imaging.Secondly,green fluorescent carbon quantum dots(G-CQDs)were synthesized by hydrothermal method after adding SmCl3 based on the preparation of N-CQDs.The morphology,elemental composition and optical properties of G-CQDs were analyzed by structure,composition and optical characterization.The results showed that the surface of G-CQDs contained amino,carboxyl and hydroxyl groups.Sm existed in the form of Sm(?).The maximum excitation and emission wavelengths of G-CQDs were 450 and 520 nm,and the quantum yield was 40.27%.The excitation wavelength of G-CQDs was independent.The acid precipitation method showed that G-CQDs could change the emission wavelength by reducing the content of samarium ions on the surface.The experimental data of ion selective expression showed that G-CQDs had high selectivity to Ag+and CrO42-ions with detection limits of 1.41?M and 4.52 ?M.It was used to culture HeLa cells and showed blue,green and red images under confocal microscope.Finally,yellow fluorescent carbon quantum dots(Y-CQDs)were obtained by using lignin,m-phenylenediamine and samarium trichloride as precursors and reacting at 130? for 3 h.The above analysis techniques were also used to systematically characterize Y-CQDs,and the results showed that the disordered carbon content of Y-CQDs was higher than that of graphite,and the average particle size was 4.2 nm.The maximum excitation and emission wavelengths are 400 and 550 nm,and the quantum yield is 15.4%.It has the independence of excitation wavelength and good fluorescence emission stability.It can be applied to the detection of Fe3+ions with the detection limit of 0.54 ?M;HeLa cells cultured in Y-CQDs solution show different color images by adjusting the excitation wavelength.