Study On Preparation Of Fluorescent Carbon Dots Of Ethylenediamine Passivated Dehydrorosin Acid

In this paper,the carbon dots were prepared by a one-pot hydrothermal method using dehydrorosin acid as the precursor and ethylenediamine as passivation reagent and reaction agent.The production was obtained by freeze drying.After dissolved in ethanol,water-soluble carbon dots were collected by filtration from the filter residue.Filtrate was evaporated and dried in vacuum oven and mixture was got.After the mixture was dissolved in ether and then filtered,ethanol-soluble carbon dots were got from filter residue and ether-soluble carbon dots was got from filtrate by vacuum drying.The main research content is as follows.(1)The micromorphology,particle size distribution,element composition and crystal structure of the prepared ethanol-soluble solid carbon dots was analyzed by TEM,FTIR,1H NMR,XPS and XRD.The result showed that tricyclic phenanthrene skeleton structure and amide functional group was retained on the surface of ethanol-soluble carbon dots with main element of C,N and O.The carbon dots are spherical nanoparticles with a particle size of 10 nm.The fluorescence performance of carbon dots in ethanol solution and solid state were analyzed.The result shows that with the increase of the solution concentration(1?25 mg,mL-1),these optimal excitation wavelength of solutions has a red-shifted from 370 nm to 450 nm and the corresponding emission also have a red-shifted from the blue region(447 nm)to the green region(516 nm)exhibiting a excitation-dependent and fluorescent tunable behaviors.The decay curve of ethanol-soluble carbon dots solution is perfectly fitted by a dual-exponential formula with a lifetime of 5.14 ns.The optimal excitation wavelength of the ethanol-soluble carbon dots in the solid state is 440 nm and the corresponding optimal emission wavelength is 510 nm,which is similar to the excitation and emission wavelength of carbon dots solution at high-concentration.The results further demonstrated that the ethanol-soluble carbon dots have fluorescence emission in both solution and solid state.The white light emitting diode(WLED)was successfully fabricated by using the ethanol-soluble carbon dots as the color conversion layer.(2)The micromorphology,particle size distribution,element composition and crystal structure of the prepared ether-soluble solid carbon dots was analyzed by TEM,FTIR,1H NMR,XPS and XRD.These result showed that tricyclic phenanthrene skeleton structure was retained on the surface of ether-soluble carbon dots.The carbon dots with main element of C,N and O has amino and amide functional groups.The carbon dots showed a spherical nanoparticle with a particle size from 2.1-4.2 nm.The lattice spacing was 0.21 nm corresponding to the(100)lattice plane of graphene.The fluorescence performance of carbon dots in ethanol solution and solid state were also analyzed.With the increase of solution concentration(1?30 mg·mL-1),the optimal excitation wavelength shifted from 370 nm to 480 nm,and the corresponding optimal emission peak has a red-shift from the blue region(438 nm)to the green region(548 nm),proving excitation dependence and fluorescence tunability.The decay curve of ether-soluble carbon dots solution is perfectly fitted by a dual-exponential formula with a lifetime of 1.47 ns.The optimal excitation wavelength of the carbon dots in the solid state is 480 nm and optimal emission wavelength is 544 nm,which is similar to the excitation and emission wavelength of carbon dots solution at high-concentration,which further demonstrated that the ether-soluble carbon dots has fluorescence emission in both solution and solid state.The white light emitting diode(WLED)was successfully fabricated by using the ether-soluble carbon dots as the color conversion layer material.The fabricated WLED has CIE coordinates of(0.3322,0.3383),color developing index of 81.8 and the color temperature of 5511 K.(3)The micromorphology and structure of the prepared water-soluble carbon dots was analyzed by FTIR,1H NMR and TEM.The results showed that there might be C=O?-NH2+-?-NH2 on the surface of the carbon core.The carbon dots agglomerated into large particles with a lattice spacing of 0.35 nm corresponding to the(002)lattice plane of graphene.The analyzed results of fluorescence performance of carbon dots water solution show that the the optimal excitation wavelength is 370 nm with emission peak of 470 nm in blue light region.The water-soluble carbon dots has excitation dependence,but no fluorescence color tunability.The decay curve to the solution of water-soluble carbon dots is perfectly fitted by a dual-exponential formula with a lifetime of 1.63 ns.Analysis of the cytotoxicity of water-soluble carbon dots showed that the carbon dots were non-toxic to human normal cells of HUVEC cells,while had lethality on cancer cells of MG-63 with increasing concentrations of water-soluble carbon dot.