Yellow double-excitation graphene quantum dots and a preparation method thereof

Abstract

The application discloses a kind of yellow double excitation graphene quantum dots and preparation method, including step one: graphene quantum dot preparation step, at room temperature, according to mass ratio 5:1, graphene oxide and o-phenylenediamine are dissolved in dimethylformamide solution, solution is transferred to hydrothermal reactor, 180~220 ℃ is reacted for 8~12 hours, after filtering insoluble material, bright yellow solution is obtained;Step two: by 1000Da dialysis bag, in the container that mixed solution of volume ratio of anhydrous ethanol and water is 1:1 is dialyzed for a week, the dialysate obtained is removed residual solvent using rotary evaporator, and concentrated graphene quantum dot solution is obtained, the above-mentioned solution is placed into vacuum freeze-drying box to remove residual solvent, and powder sample of graphene quantum dot is obtained.The graphene quantum dot of the application has high luminous intensity, long fluorescent average life, simple preparation process, low preparation condition requirement and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology and relates to a yellow dual-excited graphene quantum dot and its preparation method. Background Technology

[0002] In recent years, an increasing number of fluorescent nanomaterials, such as semiconductor quantum dots, nanocrystals, and fluorescent dyes, have attracted widespread attention. Among them, graphene quantum dots, as an emerging fluorescent material, have the potential for wide application in biology, chemistry, and physics due to their excellent photostability, biocompatibility, low toxicity, simple preparation, and high photostability. Applications include biosensoring, solar cells, light-emitting diodes, and information encryption. However, untreated graphene quantum dots exhibit low fluorescence intensity and average fluorescence lifetime, a single fluorescence color, and are mostly excited by a single wavelength light source, limiting the potential for further performance enhancement. One of the key technical challenges is how to further enhance the fluorescence intensity and average fluorescence lifetime of graphene quantum dots and achieve dual excitation. Therefore, there is an urgent need to develop graphene quantum dots with high fluorescence intensity, long average fluorescence lifetime, and the ability to be excited by dual wavelength light sources, providing a high-performance backup material for applications in information encryption. Summary of the Invention

[0003] To address the current problems of low fluorescence intensity and average fluorescence lifetime of graphene quantum dots, as well as the difficulty in achieving dual excitation and single fluorescence emission, this invention provides a yellow dual-excitation graphene quantum dot.

[0004] The carbon source used in the synthesis of the yellow dual-excited graphene quantum dots 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, which can realize the large-scale preparation of yellow graphene quantum dots and achieve dual excitation of 360nm-380nm and 430nm-450nm light sources.

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

[0006] (1) Using dimethylformamide solution as solvent, graphene oxide and o-phenylenediamine reaction precursors were stirred at a constant temperature of 35°C for 30 minutes. The mixed solution was transferred into a reaction vessel lined with polytetrafluoroethylene and kept at 180-220°C for 8-12 hours. After cooling naturally to room temperature, the crude product of yellow double-excited graphene quantum dots was obtained.

[0007] (2) The crude graphene quantum dot product obtained in step (1) is placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed for one week. The obtained dialysate is removed by a rotary evaporator to remove the residual solvent and obtain a concentrated solution of yellow double-excited graphene quantum dots. The above solution is placed in a vacuum freeze dryer to remove the residual solvent and obtain a powder sample of yellow double-excited graphene quantum dots.

[0008] (3) Scanning electron microscopy showed that the synthesized graphene quantum dots were spherical particles. Fourier transform infrared spectroscopy showed that there were a large number of functional groups on the surface of the graphene quantum dots. Under the excitation of light sources at 360nm~380nm and 430nm~450nm, the graphene quantum dots emitted bright yellow light, and the center wavelength of their emission band was located at 560nm~570nm.

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

[0010] Preferably, in step (1), the mixed solution is transferred into a polytetrafluoroethylene-lined reactor and kept at 180°C for 12 hours.

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

[0012] The advantages of this invention are: simple preparation technology, easy production scale-up, good product dispersion, uniform shape, high degree of graphitization, long average fluorescence lifetime, stable luminescence performance, and yellow light emission characteristics with different excitation wavelengths of 360nm~380nm and 430nm~450nm, providing more excitation source options, adapting to different experimental conditions, compatible with various fluorescence detection devices, and easy to integrate into existing systems. Attached Figure Description

[0013] Figure 1 XRD pattern of GQDs (o-phenylenediamine doped) prepared in this invention.

[0014] Figure 2 The fluorescence emission spectrum of the GQDs (without o-phenylenediamine doping) prepared in this invention has wavelength on the horizontal axis and fluorescence intensity on the vertical axis.

[0015] Figure 3 The fluorescence excitation and emission spectra of the GQDs (o-phenylenediamine doped) prepared in this invention.

[0016] Figure 4 The fluorescence excitation spectrum of the GQDs (o-phenylenediamine doped) prepared in this invention.

[0017] Figure 5Comparison of fluorescence emission spectra of GQDs (o-phenylenediamine doped) prepared in this invention at different excitation wavelengths.

[0018] Figure 6 The average fluorescence lifetime of GQDs (doped with o-phenylenediamine) and GQDs (without o-phenylenediamine doping) prepared in this invention.

[0019] Figure 7 A comparison of Fourier transform infrared spectra of GQDs (doped with o-phenylenediamine) and GQDs (without o-phenylenediamine doping) prepared in this invention.

[0020] Figure 8 The ultraviolet-visible absorption spectrum of the ultra-small GQDs (o-phenylenediamine doped) prepared in this invention under 375 nm excitation is shown, with wavelength on the horizontal axis and absorbance on the vertical axis.

[0021] Figure 9 Scanning electron microscope image of the GQDs (o-phenylenediamine doped) prepared in this invention. Detailed Implementation

[0022] The present invention will be further analyzed below with reference to specific embodiments.

[0023] Example 1

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

[0025] (2) The crude graphene quantum dots obtained in step (1) are placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in a container containing a mixed solution of anhydrous ethanol and water in a volume ratio of 1:1 for one week. The obtained dialysate is used to remove the residual solvent using a rotary evaporator to obtain a concentrated graphene quantum dot solution. The above solution is placed in a vacuum freeze dryer to remove the residual solvent and obtain a powdered 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 thoroughly at 35 °C for 30 minutes, transfer the mixed solution into a reaction vessel lined with polytetrafluoroethylene, keep warm at 180 °C for 12 hours, and then cool naturally to room temperature to obtain the crude product of yellow double-excited graphene quantum dots.

[0028] (2) The crude graphene quantum dots obtained in step (1) are placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed for one week in a container containing a mixed solution of anhydrous ethanol and water in a volume ratio of 1:1. The obtained dialysate is used to remove the residual solvent using a rotary evaporator to obtain a concentrated solution of yellow double-excited graphene quantum dots. The above solution is placed in a vacuum freeze dryer to remove the residual solvent and obtain a powder sample of yellow double-excited graphene quantum dots.

[0029] Effect verification

[0030] like Figure 1 The image shows the XRD pattern of the yellow double-excited graphene quantum dots. It can be seen that the prepared graphene quantum dots (doped with o-phenylenediamine) possess the sp2 structure of graphene.

[0031] like Figure 2 The image shows the fluorescence emission spectrum of the sample prepared in Example 1 when excited by a light source with a wavelength of 375 nm. The emission wavelength is 420 nm to 440 nm.

[0032] like Figure 3-4 The image shows the fluorescence excitation and emission spectra of graphene quantum dots (doped with o-phenylenediamine). The fluorescence excitation spectrum shows two excitation peaks with different wavelengths.

[0033] like Figure 5 The image shows a comparison 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 the emission wavelength does not change significantly under different excitation wavelengths, indicating stable luminescence performance.

[0034] like Figure 6 The figure shows the fluorescence average lifetime fitting plots of graphene quantum dots (doped with o-phenylenediamine) and graphene quantum dots (without o-phenylenediamine doping), which shows that the fluorescence average lifetime is significantly improved after doping.

[0035] like Figure 7 The image shows Fourier transform infrared (FTIR) images of graphene quantum dots (doped with o-phenylenediamine) and graphene quantum dots (without o-phenylenediamine doping). The comparison shows that the surface functional groups increase after o-phenylenediamine doping.

[0036] like Figure 8 The image shows the UV-Vis absorption spectrum of graphene quantum dots (doped with o-phenylenediamine), with the horizontal axis representing wavelength and the vertical axis representing absorbance. The graphene quantum dots exhibit significant absorption at 375 nm, indicating their suitability for applications such as UV detection, photocatalysis, and fluorescent labeling.

[0037] like Figure 9The image shown is a scanning electron microscope image of graphene quantum dots (doped with o-phenylenediamine). It can be seen that the graphene quantum dots have a spherical particle shape, indicating that they are uniformly dispersed.

[0038] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing yellow dual-excited graphene quantum dots, characterized in that, Includes the following steps: (1) Preparation of yellow dual-excited graphene quantum dots: using dimethylformamide as solvent, graphene oxide and o-phenylenediamine as reaction precursors, the mixture was stirred at a constant temperature of 35°C for 30 minutes; the mixed solution was transferred into a reaction vessel lined with polytetrafluoroethylene, and kept at 180-220°C for 8-12 hours, and then naturally cooled to room temperature to obtain the crude product of yellow dual-excited graphene quantum dots; (2) Purification of yellow double-excited graphene quantum dots: The crude graphene quantum dots obtained in step (1) were placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed for one week. The obtained dialysate was removed by a rotary evaporator to remove the residual solvent and obtain a concentrated solution of yellow double-excited graphene quantum dots. The above solution was placed in a vacuum freeze dryer to remove the residual solvent and obtain a powder sample of yellow double-excited graphene quantum dots. (3) Observe the yellow double-excited graphene quantum dot powder obtained in step (2) using a scanning electron microscope. It is a spherical particle. The luminescent carbon quantum dot material can emit bright yellow light when excited by light sources of 360nm~380nm and 430nm~450nm.

2. The method for preparing yellow dual-excited 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 method for preparing yellow dual-excited graphene quantum dots according to claim 1, characterized in that, In step (1), the mixed solution is transferred into a polytetrafluoroethylene-lined reactor and kept at 180°C for 12 hours.

4. The method for preparing yellow dual-excited graphene quantum dots according to claim 1, characterized in that, The dialysis bag in step (2) contains a mixed solution of anhydrous ethanol and water in a volume ratio of 1:

1.

5. The method for preparing yellow dual-excited graphene quantum dots according to claim 1, characterized in that, The center wavelength of the yellow light emitted in step (3) is between 560nm and 570nm.

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

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