Yellow double-excitation graphene quantum dot and preparation method thereof

Abstract

The invention discloses a yellow double-excitation graphene quantum dot and a preparation method thereof, and the preparation method comprises the following steps: 1, preparing a graphene quantum dot: at room temperature, dissolving graphene oxide and o-phenylenediamine in a dimethylformamide solution according to a mass ratio of 5: 1, transferring the solution into a hydrothermal reaction kettle, reacting at 180-220 DEG C for 8-12 hours, and filtering insoluble substances to obtain a bright yellow solution; step 2, dialyzing in a container containing a mixed solution of absolute ethyl alcohol and water in a volume ratio of 1: 1 for one week through a 1000Da dialysis bag, removing a residual solvent from the obtained dialysate by using a rotary evaporator to obtain a concentrated graphene quantum dot solution, and putting the solution into a vacuum freeze drying box to remove the residual solvent, thereby obtaining the graphene quantum dot. A powdery sample of the graphene quantum dots is obtained. The graphene quantum dot disclosed by the invention is high in luminous intensity, long in fluorescence average life, simple in preparation process, low in preparation condition requirement and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of nano-functional materials, and relates to a yellow dual-excitation graphene quantum dot and a preparation method thereof. Background Art

[0002] In recent years, more and more fluorescent nanomaterials, such as semiconductor quantum dots, nanocrystals, and fluorescent dyes, have attracted wide attention. Among them, graphene quantum dots, as an emerging fluorescent material, can be widely applied in the fields of biology, chemistry, physics, etc., such as biological detection, solar cells, light-emitting diodes, information encryption, etc., due to their good optical stability, biocompatibility, low toxicity, simple preparation, and high light resistance. The fluorescence intensity and average fluorescence lifetime of graphene quantum dots without any treatment are relatively low, the fluorescence color is single, and most are excited by a single-wavelength light source, which limits the expansion space of material performance. How to further enhance the fluorescence intensity and average fluorescence lifetime of graphene quantum dots and achieve dual excitation is one of the technical problems faced. Therefore, there is an urgent need to develop a graphene quantum dot with high fluorescence intensity, long average fluorescence lifetime, and dual-wavelength light source excitation at the same time, so as to provide excellent backup materials for applications in the field of information encryption. Summary of the Invention

[0003] Aiming at the problems of relatively low fluorescence intensity and average fluorescence lifetime of current graphene quantum dots, as well as achieving single fluorescence emission with dual excitation, the present invention provides a yellow dual-excitation graphene quantum dot.

[0004] The carbon source used in the synthesis process of the yellow dual-excitation graphene quantum dot is graphene oxide, and the doping source is o-phenylenediamine. Compared with the prior art, this doping source has a symmetrical structure, is alkaline and rich in amino groups, and can also provide a nitrogen source. It can realize the large-scale preparation of yellow graphene quantum dots and can achieve dual excitation with light sources of 360 nm to 380 nm and 430 nm to 450 nm.

[0005] The technical solution of the present invention is as follows:

[0006] (1) Using dimethylformamide solution as a solvent, reacting graphene oxide and o-phenylenediamine as precursors, and stirring thoroughly at a constant temperature of 35 °C for 30 minutes; transferring the mixed solution into a reaction kettle with a polytetrafluoroethylene inner liner, and keeping it at 180-220 °C for 8-12 hours, then naturally cooling to room temperature to obtain a crude product of yellow dual-excitation graphene quantum dots;

[0007] (2) Put the crude product of graphene quantum dots obtained in step (1) into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyze for one week, use a rotary evaporator to remove the residual solvent from the obtained dialysis solution to obtain a concentrated solution of yellow dual-excitation graphene quantum dots, and put the above solution into a vacuum freeze-drying oven to remove the residual solvent to obtain a powdery sample of yellow dual-excitation graphene quantum dots;

[0008] (3) Scanning electron microscope observation shows that the synthesized graphene quantum dots are spherical particles. Fourier transform infrared spectroscopy shows that there are a large number of functional groups on the surface of graphene quantum dots. Under the excitation of light sources at 360 nm - 380 nm and 430 nm - 450 nm, graphene quantum dots emit bright yellow light, and the central wavelength of its emission band is located at 560 nm - 570 nm.

[0009] Preferably, in step (1), the mass ratio of graphene oxide to o-phenylenediamine is 5:1.

[0010] Preferably, in step (1), transfer the mixed solution into a reaction kettle lined with polytetrafluoroethylene and keep it at 180 °C for 12 hours.

[0011] Preferably, the dialysis bag in step (2) contains a mixed solution with a volume ratio of absolute ethanol to water of 1:1.

[0012] Advantages of the present invention: The preparation technology is simple, the production is easy to scale up, the obtained product has good dispersibility, uniform shape, high graphitization degree, long average fluorescence lifetime, stable luminescence performance, and has the yellow light emission characteristics with different excitation wavelengths of 360 nm - 380 nm and 430 nm - 450 nm, providing more choices of excitation light sources, adapting to different experimental conditions, being compatible with a variety of fluorescence detection devices, and being convenient to be integrated into the existing system. Description of the Drawings

[0013] Figure 1 XRD pattern of the GQDs (o-phenylenediamine doped) prepared by the present invention.

[0014] Figure 2 Fluorescence emission spectrum of the GQDs (without o-phenylenediamine doping) prepared by the present invention. The abscissa is the wavelength and the ordinate is the fluorescence intensity.

[0015] Figure 3 Fluorescence excitation and emission spectra of the GQDs (o-phenylenediamine doped) prepared by the present invention.

[0016] Figure 4 Fluorescence excitation spectrum of the GQDs (o-phenylenediamine doped) prepared by the present invention.

[0017] Figure 5Comparison diagram of fluorescence emission spectra of GQDs (doped with o-phenylenediamine) prepared by the present invention at different excitation wavelengths.

[0018] Figure 6 Fluorescence average lifetime diagram of GQDs (doped with o-phenylenediamine) and GQDs (undoped with o-phenylenediamine) prepared by the present invention.

[0019] Figure 7 Comparison diagram of Fourier transform infrared spectra of GQDs (doped with o-phenylenediamine) and GQDs (undoped with o-phenylenediamine) prepared by the present invention.

[0020] Figure 8 UV-visible absorption diagram of ultrasmall-sized GQDs (doped with o-phenylenediamine) prepared by the present invention under 375 nm excitation, with the abscissa being the wavelength and the ordinate being the absorbance.

[0021] Figure 9 Scanning electron microscope diagram of GQDs (doped with o-phenylenediamine) prepared by the present invention. Detailed implementation manners

[0022] The following further analyzes the present invention in combination with specific embodiments.

[0023] Example 1

[0024] (1) Dissolve 25 mg of graphene oxide in 50 mL of dimethylformamide solution, stir well at a constant temperature of 35 °C for 30 minutes, transfer the mixed solution into a reaction kettle with a polytetrafluoroethylene inner liner, keep it at 180 °C for 12 hours, and then naturally cool it to room temperature to obtain a crude product of graphene quantum dots.

[0025] (2) Put the crude product of graphene quantum dots obtained in step (1) into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyze it in a container filled with a mixed solution of anhydrous ethanol and water with a volume ratio of 1:1 for one week, use a rotary evaporator to remove the residual solvent from the obtained dialysate to obtain a concentrated solution of graphene quantum dots, and put the above solution into a vacuum freeze-drying oven to remove the residual solvent to obtain a powdery sample of graphene quantum dots;

[0026] Example 2

[0027] (1) Dissolve 25 mg of graphene oxide and 5 mg of o-phenylenediamine in 50 mL of dimethylformamide solution, stir well at a constant temperature of 35 °C for 30 minutes, transfer the mixed solution into a reaction kettle with a polytetrafluoroethylene inner liner, keep it at 180 °C for 12 hours, and then naturally cool it to room temperature to obtain a crude product of yellow dual-excitation graphene quantum dots.

[0028] (2) Put the crude product of graphene quantum dots obtained in step (1) into a dialysis bag with a molecular weight cut-off of 1000 Da, and dialyze it in a container filled with a mixed solution of anhydrous ethanol and water with a volume ratio of 1:1 for one week. Use a rotary evaporator to remove the residual solvent from the obtained dialysate to obtain a concentrated solution of yellow dual-excitation graphene quantum dots. Put the above solution into a vacuum freeze-drying oven to remove the residual solvent to obtain a powdery sample of yellow dual-excitation graphene quantum dots;

[0029] Effect verification

[0030] As Figure 1 shown is the XRD pattern of the yellow dual-excitation graphene quantum dots. It can be seen that the prepared graphene quantum dots (doped with o-phenylenediamine) have the sp2 structure of graphene.

[0031] As Figure 2 shown is the fluorescence emission spectrum of the sample prepared in Example 1 excited by a light source with a wavelength of 375 nm, and its emission wavelength is 420 nm - 440 nm.

[0032] As Figures 3-4 shown is the fluorescence excitation and emission spectrum of graphene quantum dots (doped with o-phenylenediamine), and its fluorescence excitation spectrum shows two excitation peaks with different wavelengths.

[0033] As Figure 5 shown is the comparison diagram of the fluorescence emission spectra of graphene quantum dots (doped with o-phenylenediamine) excited at 380 nm and 430 nm. It can be seen that at different excitation wavelengths, its emission wavelength does not change significantly, and it has stable luminescence performance.

[0034] As Figure 6 shown is the fluorescence average lifetime fitting diagram of graphene quantum dots (doped with o-phenylenediamine) and graphene quantum dots (undoped with o-phenylenediamine), which shows that the fluorescence average lifetime after doping is significantly improved.

[0035] As Figure 7 shown is the Fourier transform infrared diagram of graphene quantum dots (doped with o-phenylenediamine) and graphene quantum dots (undoped with o-phenylenediamine). By comparison, it can be seen that the surface functional groups increase after doping with o-phenylenediamine.

[0036] As Figure 8 shown is the ultraviolet-visible absorption diagram of graphene quantum dots (doped with o-phenylenediamine). The abscissa is the wavelength and the ordinate is the absorbance. Among them, graphene quantum dots have obvious absorption at 375 nm, indicating that it is suitable for applications such as ultraviolet light detection, photocatalysis, and fluorescence labeling.

[0037] As Figure 9The scanning electron microscope image of graphene quantum dots (doped with o-phenylenediamine) shows that the graphene quantum dots have a spherical particle shape, indicating uniform dispersion.

[0038] This specific embodiment is only an explanation of the present invention and does not limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A preparation method of yellow double-excitation graphene quantum dots, characterized in that, It includes the following steps: (1) Preparation of yellow dual-excitation graphene quantum dots: Using dimethylformamide solution as the solvent, graphene oxide and o-phenylenediamine as the reaction precursors, stirring vigorously at a constant temperature of 35 °C for 30 minutes; transferring the mixed solution into a reaction kettle lined with polytetrafluoroethylene, keeping it at 180-220 °C for 8-12 hours, and then naturally cooling to room temperature to obtain the crude product of yellow dual-excitation graphene quantum dots; (2) Purification of yellow dual-excitation graphene quantum dots: Putting the crude product of graphene quantum dots obtained in step (1) into a dialysis bag with a molecular weight cut-off of 1000 Da, dialyzing for one week, using a rotary evaporator to remove the residual solvent from the obtained dialysate to obtain a concentrated solution of yellow dual-excitation graphene quantum dots, and putting the above solution into a vacuum freeze-drying oven to remove the residual solvent to obtain a powdery sample of yellow dual-excitation graphene quantum dots; (3) Observing the powder of yellow dual-excitation graphene quantum dots obtained in step (2) by scanning electron microscopy, which are spherical particles, and the luminescent carbon quantum dot material can emit bright yellow light under the excitation of light sources at 360 nm - 380 nm and 430 nm - 450 nm.

2. The preparation method of the yellow dual-excitation graphene quantum dots according to claim 1, characterized in that, In step (1), the mass ratio of graphene oxide to o-phenylenediamine is 5:

1.

3. The preparation method of the yellow dual-excitation graphene quantum dots according to claim 1, wherein, In step (1), the mixed solution is transferred into a reaction kettle lined with polytetrafluoroethylene and kept at 180 °C for 12 hours.

4. The preparation method of the yellow dual-excitation graphene quantum dots according to claim 1, wherein The dialysis bag in step (2) contains a mixed solution with a volume ratio of absolute ethanol to water of 1:

1.

5. The preparation method of the yellow dual-excitation graphene quantum dots according to claim 1, wherein, The central wavelength of the yellow light emission band in step (3) is located at 560 nm - 570 nm.

6. A yellow dual-excitation graphene quantum dot prepared by using the preparation method according to any one of claims 1-5.

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