A method for rapidly and greenly preparing graphene oxide quantum dots

Abstract

The application provides a method for rapidly and greenly preparing graphene oxide quantum dots, which comprises the following steps: A) mixing a high iodate with a strong acid, then adding carbon material to mix and stir, and heating to react; B) adding the reaction liquid obtained in step A) into deionized water, and centrifuging to obtain a centrifugal liquid; C) dialyzing and purifying the centrifugal liquid to obtain a graphene oxide quantum dot dispersion liquid; and D) freeze-drying the graphene oxide quantum dot dispersion liquid to obtain graphene oxide quantum dot powder. The method for preparing graphene oxide quantum dots is simple, safe and controllable, the graphene oxide quantum dots have high yield, the carbon material is converted into graphene oxide quantum dots in one step, and the graphene oxide quantum dots do not need to be dispersed by strong mechanical crushing such as ultrasonic, so that the method is suitable for laboratory preparation and industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial preparation, and particularly relates to a method for rapidly and greenly preparing graphene oxide quantum dots. BACKGROUND

[0002] Graphene quantum dots have significant quantum confinement effect, boundary effect, biological low toxicity, good biocompatibility and other characteristics, and have broad application prospects in optoelectronic devices, biological imaging, fluorescent probes, drug delivery, photocatalysis and the like. Graphene oxide quantum dots are graphene quantum dots with a large number of oxygen-containing functional groups. As a new type of quantum dot, graphene oxide quantum dots have excellent properties of both graphene oxide and quantum dots. Graphene oxide quantum dots have rich oxygen-containing functional groups on the surface, and have size adjustability, surface effect, edge effect, excellent water solubility, excellent surface modifiability and heteroatom doping characteristics, so that the luminescent properties of graphene oxide quantum dots are effectively realized, and graphene oxide quantum dots have important application prospects in medicine, optoelectronics, energy, biosensors, catalysis and the like.

[0003] The preparation methods of graphene oxide quantum dots mainly include a bottom-up method and a top-down method. The bottom-up method is to use an organic small molecule as a precursor, and to obtain graphene oxide quantum dots through a series of chemical reactions. The size and morphology of graphene quantum dots can be controlled by controlling the synthesis conditions, but the steps are relatively complex, the conditions are harsh, and the yield is low, which limits the large-scale development. The top-down method is to oxidize and cut carbon materials (graphene, carbon nanotubes, graphite) into small-size graphene oxide quantum dots by a chemical method. The top-down method mainly includes an acid medium oxidation cutting method, a solvothermal method and an electrochemical exfoliation method. The top-down method for preparing graphene oxide quantum dots is currently a research hotspot and focus. However, at present, the yield of graphene oxide quantum dots obtained by the top-down method is low, the reaction period is long, a complex separation and purification process is needed, the realization process of quantum dots usually needs to rely on strong mechanical crushing such as ultrasonic dispersion, and the size distribution of the prepared graphene oxide quantum dots is uneven. It is still a key and difficult point to rapidly, greenly and efficiently prepare graphene oxide quantum dots with uniform size. SUMMARY

[0004] Therefore, the technical problem to be solved by the application is to provide a method for rapidly and greenly preparing graphene oxide quantum dots. The graphene oxide quantum dots provided by the application have rich oxygen-containing functional groups and uniform size distribution, do not contain heavy metal ions, and the reaction process is safe and controllable.

[0005] The application provides a method for rapidly and greenly preparing graphene oxide quantum dots, which comprises the following steps:

[0006] A) mixing a high iodate salt and a strong acid, adding a carbon material, stirring, and heating to react;

[0007] B) adding the reaction solution obtained in step A) into deionized water, and centrifuging to obtain a centrifugal solution;

[0008] C) purifying the centrifugal solution by dialysis to obtain a graphene oxide quantum dot dispersion solution;

[0009] D) freeze-drying the graphene oxide quantum dot dispersion solution to obtain graphene oxide quantum dot powder.

[0010] Preferably, the periodate is one or more of potassium periodate, sodium periodate, ammonium periodate, magnesium periodate, calcium periodate, and strontium periodate.

[0011] Preferably, the strong acid is one or more of sulfuric acid, phosphoric acid, fuming sulfuric acid, concentrated nitric acid, fluorosulfonic acid, and trifluoromethanesulfonic acid.

[0012] Preferably, the carbon material is one or more of graphite, carbon black, and carbon nanotubes.

[0013] Preferably, the mass ratio of the carbon material, the acid, and the oxidizing agent is 1:(50-200):(25-50).

[0014] Preferably, in step A), the temperature for mixing the periodate and the strong acid is 0-40℃, and the time is 5-30 min.

[0015] Preferably, in step A), the temperature for heating to perform the reaction is 70-140℃, and the time is 30 s-24 h.

[0016] Preferably, the rotation speed for centrifugation is 300 rpm.

[0017] The application also provides a graphene oxide quantum dot prepared by the above method, wherein the graphene oxide quantum dot is a single-layer structure.

[0018] Preferably, the planar size of the graphene oxide quantum dot is ≤5 nm.

[0019] Compared with existing technologies, this invention provides a rapid and green method for preparing graphene oxide quantum dots, comprising the following steps: A) mixing periodate with a strong acid, adding carbon material, stirring, and heating to react; B) adding the reaction solution obtained in step A) to deionized water and centrifuging to obtain a centrifuged liquid; C) dialysis purification of the centrifuged liquid to obtain a graphene oxide quantum dot dispersion; D) freeze-drying the graphene oxide dispersion quantum dots to obtain graphene oxide quantum dot powder. This invention provides a simple, safe, and controllable process for preparing graphene oxide quantum dots, achieving a high yield. Carbon material is converted into graphene oxide quantum dots in one step, eliminating the need for strong mechanical crushing and dispersion such as ultrasound, making it suitable for laboratory preparation and industrial production. Attached Figure Description

[0020] Figure 1 The image shown is a transmission electron microscope image of graphene oxide quantum dots obtained in Example 1 of this invention.

[0021] Figure 2 Here is a high-resolution transmission electron microscope image of the graphene oxide quantum dots obtained in Example 1 of this invention;

[0022] Figure 3 The X-ray photoelectron spectrum of the graphene oxide quantum dots obtained in Example 1 of this invention is shown below.

[0023] Figure 4 An atomic force microscope image of the graphene oxide quantum dots obtained in Example 1 of this invention.

[0024] Figure 5 High-resolution transmission electron microscope images of graphene oxide quantum dots obtained in Example 1 are provided for comparison.

[0025] Figure 6 High-resolution transmission electron microscope images of graphene oxide quantum dots obtained in Example 2 are provided for comparison.

[0026] Figure 7 For comparison, a scanning electron microscope image of the graphene oxide obtained in Example 3;

[0027] Figure 8 For comparison, see the atomic force microscope image of the graphene oxide obtained in Example 3;

[0028] Figure 9 An atomic force microscope image of the graphene oxide obtained in Example 4 is shown for comparison. Detailed Implementation

[0029] This invention provides a rapid and green method for preparing graphene oxide quantum dots, comprising the following steps:

[0030] A) mixing the periodate with a strong acid, then adding carbon material, mixing and stirring, and heating to react;

[0031] B) adding the reaction solution obtained in step A) into deionized water, and centrifuging to obtain a centrifugal solution;

[0032] C) dialyzing and purifying the centrifugal solution to obtain an oxidized graphene quantum dot dispersion;

[0033] D) freeze-drying the oxidized graphene quantum dot dispersion to obtain an oxidized graphene quantum dot powder.

[0034] The periodate is mixed with a strong acid, wherein the mixing temperature is 0-40°C, which can be 0, 10, 20, 30, 40, or any value between 0-40°C, and the mixing time is 5-30 min, which can be 5, 10, 15, 20, 25, 30, or any value between 5-30 min.

[0035] The periodate is potassium periodate, sodium periodate, ammonium periodate, magnesium periodate, calcium periodate, or strontium periodate.

[0036] The strong acid is sulfuric acid, phosphoric acid, oleum, concentrated nitric acid, fluorosulfonic acid, or trifluoromethanesulfonic acid. In some embodiments of the present application, the strong acid is selected from concentrated sulfuric acid, a mixture of concentrated sulfuric acid and concentrated phosphoric acid, a mixture of concentrated sulfuric acid and concentrated nitric acid, a mixture of concentrated sulfuric acid and fluorosulfonic acid, trifluoromethanesulfonic acid, or fluorosulfonic acid.

[0037] Then, carbon material is added to the mixture of periodate and strong acid, mixed and stirred, and heated to react.

[0038] The carbon material is a mixture of one or more of graphite, carbon black, and carbon nanotubes. The present application does not have special restrictions on the types of graphite, carbon black, and carbon nanotubes. The graphite can be natural graphite, expanded graphite, or artificial graphite. In the present application, the particle size of the graphite is 0.5-500 μm, which can be 0.5, 1, 2, 10, 45, 50, 100, 300, 500, or 0.5-500 μm. The carbon black can be acetylene black, Ketjen black, or other conductive carbon black. The carbon nanotube can be multi-walled carbon nanotube or single-walled carbon nanotube. The present application does not have special restrictions on the source of the carbon material, and any of the above types of carbon material known to those skilled in the art can be used, such as those available on the market.

[0039] In the present application, the mass ratio of the carbon material, the acid and the oxidizing agent is 1:(50-200):(25-50), which can be 1:100:40, 1:200:50, 1:90:25, 1:100:40, 1:150:40, 1:80:25, 1:100:30, 1:200:40, 1:50:25, 1:100:30, 1:120:30, or any value between 1:(50-200):(25-50).

[0040] The temperature for the reaction is 70-140℃, which can be 70, 80, 90, 100, 110, 120, 130, 140, or any value between 70-140℃, and the time is 30s-24h, which can be 30s, 1min, 5min, 10min, 30min, 1h, 2h, 3h, 5h, 6h, 8h, 10h, 12h, 24h, or any value between 30s-24h.

[0041] Then, the reaction solution obtained by the above reaction is added into deionized water, and centrifugation is performed to obtain a centrifugal solution. The centrifugal speed is 300rpm.

[0042] Then, the centrifugal solution is purified by dialysis to obtain a graphene oxide quantum dot dispersion. The specific method for the dialysis is not particularly limited in the present application, and the dialysis is used to remove the salt in the system. The dialysis membrane used has no particular requirement, and the method known to those skilled in the art can be used.

[0043] Finally, the graphene oxide quantum dot dispersion is freeze-dried to obtain graphene oxide quantum dot powder.

[0044] The present application also provides a graphene oxide quantum dot prepared by the above method, and the graphene oxide quantum dot is a single-layer structure.

[0045] The planar size of the graphene oxide quantum dot is ≤5nm.

[0046] The process for preparing the graphene oxide quantum dot is simple, safe and controllable, and has low energy consumption and time consumption. The graphene oxide quantum dot has high yield, and the carbon material is converted into graphene oxide quantum dot in one step without the need for strong mechanical crushing and dispersion such as ultrasonic.

[0047] In order to further understand the present application, the method for rapidly and greenly preparing graphene oxide quantum dots provided by the present application is described below in combination with examples, and the protection scope of the present application is not limited by the following examples.

[0048] Example 1

[0049] Potassium periodate and concentrated sulfuric acid are stirred and mixed at 25℃ for 15 minutes, then 45um graphite is added, the temperature is raised to 100℃, and stirring is continued for 15 minutes; after the reaction is completed, the reaction solution is added to deionized water, centrifuged at 300rpm, no solid precipitate, the centrifugate is purified by dialysis to obtain an oxidized graphene quantum dot dispersion, and the oxidized graphene quantum dot dispersion is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the ratio of strong acid to graphite is 100g:1g, and the ratio of potassium periodate to graphite is 40g:1g. The yield of the oxidized graphene quantum dots is as high as 135%.

[0050] The oxidized graphene quantum dots obtained in Example 1 are subjected to transmission electron microscope analysis, and the results are shown in Table 1. Figure 1 Figure 1 The transmission electron microscope picture of the oxidized graphene quantum dots obtained in Example 1 is shown in Figure 1. Figure 1 As can be seen from Figure 1, the oxidized graphene quantum dots obtained in Example 1 are uniform in size, and the planar size of the oxidized graphene quantum dots is basically within 5nm.

[0051] The oxidized graphene quantum dots obtained in Example 1 are subjected to high-resolution transmission electron microscope analysis, and the results are shown in Table 2. Figure 2 Figure 2 The high-resolution transmission electron microscope image of the oxidized graphene quantum dots obtained in Example 1 is shown in Figure 2. Figure 2 As can be seen from Figure 2, the oxidized graphene quantum dots obtained in Example 1 have a typical microstructure of carbon quantum dots.

[0052] The oxidized graphene quantum dots obtained in Example 1 are subjected to X-ray photoelectron spectroscopy analysis, and the results are shown in Table 3. Figure 3 Figure 3 The X-ray photoelectron spectrogram of the oxidized graphene quantum dots obtained in Example 1 is shown in Figure 3. Figure 3 As can be seen from Figure 3, the oxidized graphene quantum dots obtained in Example 1 are rich in oxygen-containing functional groups.

[0053] The oxidized graphene quantum dots obtained in Example 1 are subjected to atomic force microscope analysis, and the results are shown in Table 4. Figure 4 Figure 4 The atomic force microscope analysis picture of the oxidized graphene quantum dots obtained in Example 1 is shown in Figure 4. Figure 4 As can be seen from Figure 4, the thickness of the oxidized graphene quantum dots obtained in Example 1 is about 1nm, indicating that the obtained oxidized graphene quantum dots are single-layered. In combination with Figure 1 , Figure 2 , Figure 3 and Figure 4 ​​​​And the analysis of the yield of graphene oxide quantum dots can know that the graphene oxide quantum dots obtained by the embodiment 1 of the application have uniform size distribution, rich oxygen-containing functional groups, high single-layer rate of the obtained graphene oxide quantum dots and high yield of the graphene oxide quantum dots.

[0054] Embodiment 2

[0055] The sodium periodate and concentrated sulfuric acid are stirred and mixed at 40 DEG C for 5 min, 2 um graphite is added, the temperature is raised to 140 DEG C, and stirring is carried out for 30 s; after the reaction is completed, the reaction liquid is poured into deionized water, 300 rpm centrifugation is carried out, the centrifugal liquid is purified by dialysis to obtain a graphene oxide quantum dot dispersion liquid, and the graphene oxide quantum dot dispersion liquid is freeze-dried to obtain graphene oxide quantum dot powder. In the reaction process, the ratio of strong acid to graphite is 200 g:1 g, and the ratio of potassium periodate to graphite is 50 g:1 g. The yield of graphene oxide quantum dots is as high as 80%.

[0056] Embodiment 3

[0057] The sodium periodate and concentrated sulfuric acid are stirred and mixed at 40 DEG C for 5 min, 2 um graphite is added, the temperature is raised to 140 DEG C, and stirring is carried out for 30 s; after the reaction is completed, the reaction liquid is poured into deionized water, 300 rpm centrifugation is carried out, the centrifugal liquid is purified by dialysis to obtain a graphene oxide quantum dot dispersion liquid, and the graphene oxide quantum dot dispersion liquid is freeze-dried to obtain graphene oxide quantum dot powder. In the reaction process, the ratio of strong acid to graphite is 200 g:1 g, and the ratio of potassium periodate to graphite is 50 g:1 g. The yield of graphene oxide quantum dots is as high as 80%.

[0058] Embodiment 4

[0059] The mixed acid of sodium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 10 DEG C for 10 min, stirred and mixed at 40 DEG C for 5 min, 300 um graphite is added, the temperature is raised to 120 DEG C, and stirring is carried out for 30 s; after the reaction is completed, the reaction liquid is poured into deionized water, 300 rpm centrifugation is carried out, the centrifugal liquid is purified by dialysis to obtain a graphene oxide quantum dot dispersion liquid, and the graphene oxide quantum dot dispersion liquid is freeze-dried to obtain graphene oxide quantum dot powder. In the reaction process, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of mixed strong acid to graphite is 90 g:1 g, and the ratio of potassium periodate to graphite is 25 g:1 g. The yield of graphene oxide quantum dots is as high as 45%.

[0060] Embodiment 5

[0061] The mixed acid of sodium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 10°C for 10 min, stirred and mixed at 0°C for 5 min, 2 um graphite is added, the temperature is raised to 120°C, and the reaction is stirred for 30 s; after the reaction is completed, the reaction liquid is poured into deionized water, centrifuged at 300 rpm, and the centrifugal liquid is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of mixed strong acid to graphite is 100 g:1 g, and the ratio of potassium periodate to graphite is 40 g:1 g. The yield of the oxidized graphene quantum dot is as high as 33%.

[0062] Example 6

[0063] The mixed acid of sodium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 10°C for 10 min, stirred and mixed at 0°C for 5 min, 2 um graphite is added, the temperature is raised to 120°C, and the reaction is stirred for 30 s; after the reaction is completed, the reaction liquid is poured into deionized water, centrifuged at 300 rpm, and the centrifugal liquid is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of mixed strong acid to graphite is 100 g:1 g, and the ratio of potassium periodate to graphite is 40 g:1 g. The yield of the oxidized graphene quantum dot is as high as 33%.

[0064] Example 7

[0065] The mixed acid of potassium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 10°C for 15 min, 0.5 um graphite is added, the temperature is raised to 120°C, and the reaction is stirred for 30 min; after the reaction is completed, the reaction liquid is poured into deionized water, centrifuged at 300 rpm, and the centrifugal liquid is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of mixed strong acid to graphite is 80 g:1 g, and the ratio of potassium periodate to graphite is 25 g:1 g. The yield of the oxidized graphene quantum dot is as high as 65%.

[0066] Example 8

[0067] The mixed acid of potassium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 10°C for 15 min, 0.5 um graphite is added, the temperature is raised to 120°C, and stirring is performed for 1 h; after the reaction is completed, the reaction solution is poured into deionized water, centrifuged at 300 rpm, and the centrifuged solution is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of the mixed strong acid to graphite is 80 g:1 g, and the ratio of potassium periodate to graphite is 25 g:1 g. The yield of the oxidized graphene quantum dots is as high as 88%.

[0068] Example 9

[0069] The mixed acid of ammonium periodate, concentrated sulfuric acid and concentrated phosphoric acid is stirred and mixed at 0°C for 15 min, conductive carbon black SP is added, the temperature is raised to 90°C, and stirring is performed for 0.5 h; after the reaction is completed, the reaction solution is poured into deionized water, centrifuged at 300 rpm, and the centrifuged solution is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated phosphoric acid is 9:1, the ratio of the mixed strong acid formed by concentrated sulfuric acid and concentrated phosphoric acid to conductive carbon black SP is 100 g:1 g, and the ratio of ammonium periodate to conductive carbon black SP is 30 g:1 g. The yield of the oxidized graphene quantum dots is as high as 78%.

[0070] Example 10

[0071] The mixed acid of magnesium periodate, concentrated sulfuric acid and concentrated nitric acid is stirred and mixed at 0°C for 30 min, multi-walled carbon nanotubes are added, the temperature is raised to 70°C, and stirring is performed for 0.5 h; after the reaction is completed, the reaction solution is poured into deionized water, centrifuged at 300 rpm, and the centrifuged solution is purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which is freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated nitric acid is 10:1, the ratio of the mixed strong acid formed by concentrated sulfuric acid and concentrated nitric acid to multi-walled carbon nanotubes is 200 g:1 g, and the ratio of magnesium periodate to multi-walled carbon nanotubes is 40 g:1 g. The yield of the oxidized graphene quantum dots is as high as 90%.

[0072] Example 11

[0073] Mixing potassium periodate, concentrated sulfuric acid and fluorosulfonic acid mixed acid at 0℃ for 30min, add the particle size of 100um graphite, increase the temperature to 80℃, continue to stir for 24h; after the reaction is completed, the reaction liquid is poured into deionized water, 300rpm centrifugal, the centrifugal liquid is purified by dialysis, and the graphene oxide quantum dot dispersion liquid is obtained. The graphene oxide quantum dot dispersion liquid is freeze-dried to obtain graphene oxide quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to fluorosulfonic acid is 2:1, the ratio of the mixed strong acid formed by concentrated sulfuric acid and fluorosulfonic acid to graphite is 100g:1g, and the ratio of potassium periodate to graphite is 40g:1g. The yield of graphene oxide quantum dots is as high as 85%.

[0074] Example 12

[0075] Mixing potassium periodate and trifluoromethanesulfonic acid at 0℃ for 15min, add single-walled carbon nanotubes, increase the temperature to 75℃, continue to stir for 24h; after the reaction is completed, the reaction liquid is poured into deionized water, 300rpm centrifugal, the centrifugal liquid is purified by dialysis, and the graphene oxide quantum dot dispersion liquid is obtained. The graphene oxide quantum dot dispersion liquid is freeze-dried to obtain graphene oxide quantum dot powder. During the reaction, the ratio of trifluoromethanesulfonic acid to single-walled carbon nanotubes is 200g:1g, and the ratio of potassium periodate to single-walled carbon nanotubes is 50g:1g. The yield of graphene oxide quantum dots is as high as 93%.

[0076] Example 13

[0077] Mixing calcium periodate and concentrated sulfuric acid at 50℃ for 20min, add the particle size of 2um graphite, increase the temperature to 100℃, continue to stir for 2h; after the reaction is completed, the reaction liquid is poured into deionized water, and purified by dialysis, 300rpm centrifugal, the centrifugal liquid is obtained. The graphene oxide quantum dot dispersion liquid is obtained by freeze-drying graphene oxide quantum dot dispersion liquid to obtain graphene oxide quantum dot powder. During the reaction, the ratio of strong acid to graphite is 50g:1g, and the ratio of calcium periodate to graphite is 25g:1g. The yield of graphene oxide quantum dots is as high as 35%.

[0078] Example 14

[0079] Strontium periodate, concentrated sulfuric acid and concentrated nitric acid mixed acid was stirred at 0 ℃ for 30 min, multi-walled carbon nanotubes were added, the temperature was raised to 75 ℃, and stirring was continued for 12 h; after the reaction was completed, the reaction liquid was poured into deionized water, centrifuged at 300 rpm, and the centrifugate was purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which was freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the mass ratio of concentrated sulfuric acid to concentrated nitric acid was 5:1, the ratio of the mixed strong acid formed by concentrated sulfuric acid and concentrated nitric acid to graphite was 100 g:1 g, and the ratio of calcium periodate to multi-walled carbon nanotubes was 30 g:1 g. The yield of oxidized graphene quantum dots was as high as 78%.

[0080] Example 15

[0081] Potassium periodate and fluorosulfonic acid were stirred and mixed at 0 ℃ for 30 min, 2-μm graphite was added, the temperature was raised to 75 ℃, and stirring was continued for 8 h; after the reaction was completed, the reaction liquid was poured into deionized water, centrifuged at 300 rpm, and the centrifugate was purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which was freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the ratio of strong acid to graphite was 120 g:1 g, and the ratio of potassium periodate to graphite was 30 g:1 g. The yield of oxidized graphene quantum dots was as high as 85%.

[0082] Example 16

[0083] Potassium periodate and concentrated sulfuric acid were stirred and mixed at 20 ℃ for 5 min, Ketjen black was added, the reaction temperature was raised to 80 ℃, and stirring was continued for 8 h; after the reaction was completed, the reaction liquid was slowly poured into deionized water, centrifuged at 300 rpm, and the centrifugate was purified by dialysis to obtain an oxidized graphene quantum dot dispersion liquid, which was freeze-dried to obtain an oxidized graphene quantum dot powder. During the reaction, the ratio of concentrated sulfuric acid to Ketjen black was 100 g:1 g, and the ratio of potassium periodate to Ketjen black was 30 g:1 g. The yield of oxidized graphene quantum dots was 75%.

[0084] Comparative Example 1

[0085] Potassium periodate and concentrated sulfuric acid were stirred and mixed at 10 ℃ for 15 min, 2-μm graphite was added, and stirring was continued for 15 min; the temperature was raised to 90 ℃, and stirring was continued for 24 h; during the reaction, the ratio of strong acid to graphite was 100 g:1 g, and the ratio of potassium periodate to graphite was 20 g:1 g. After the reaction was completed, the reaction liquid was poured into deionized water, centrifuged at 300 rpm, and the centrifugate was purified by dialysis to obtain the target product.

[0086] The target product obtained in Comparative Example 1 was subjected to transmission electron microscope analysis, and the results are shown in Figure 5 . Figure 5The transmission electron microscope picture of the target product obtained in Example 1 of the present application is shown in Figure 1. Figure 5 It can be seen that the product obtained in Example 1 of the present application has a wide size distribution, and the product size mainly distributes in the range of 10-60 nm, and part of it is above 100 nm.

[0087] Comparative Example 2

[0088] Potassium periodate and concentrated sulfuric acid were stirred and mixed at 40℃ for 15 min, and then 2um graphite was added and stirred and mixed for 15 min, and then the temperature was raised to 70℃, and the stirring was continued for 24 h; during the reaction, the ratio of strong acid to graphite was 100g:1g, and the ratio of potassium periodate to graphite was 20g:1g. After the reaction was completed, the reaction liquid was poured into deionized water, and centrifuged at 300 rpm, and the centrifuged liquid was purified by dialysis to obtain the target product.

[0089] The target product obtained in Comparative Example 2 was analyzed by transmission electron microscope, and the results are shown in Figures 2 and 3. Figure 6 Figure 6 The transmission electron microscope picture of the product obtained in Example 2 of the present application is shown in Figure 4. Figure 6 It can be seen that the target product obtained in Example 2 of the present application has a wide size distribution, and the product size mainly distributes in the range of 20-120 nm, and part of it is above 140 nm.

[0090] Comparative Example 3

[0091] Potassium periodate and concentrated sulfuric acid were stirred and mixed at 40℃ for 15 min, and then 2um graphite was added and stirred and mixed for 15 min, and then the temperature was raised to 70℃, and the stirring was continued for 24 h; during the reaction, the ratio of strong acid to graphite was 100g:1g, and the ratio of potassium periodate to graphite was 20g:1g. After the reaction was completed, the reaction liquid was poured into deionized water, and centrifuged at 300 rpm, and the centrifuged liquid was purified by dialysis to obtain the target product.

[0092] The target product obtained in Comparative Example 3 was analyzed by transmission electron microscope, and the results are shown in Figures 2 and 3. Figure 7 and Figure 8 Figure 7 The scanning electron microscope picture of the target product obtained in Comparative Example 3 is shown in Figure 6. Figure 7 It can be seen that the target product obtained in Comparative Example 3 has a microscale size; Figure 8 The atomic force microscope picture of the target product obtained in Comparative Example 3 is shown in Figure 7. Figure 8 It can be seen that the target product prepared in Comparative Example 3 has a multi-layer structure, and the sheet thickness is 3-4 nm. Figure 7 and Figure 8 It can be seen that the product obtained in Comparative Example 3 is mainly multi-layer graphene oxide sheets.

[0093] ​​Comparative Example 4

[0094] Potassium periodate and concentrated sulfuric acid were stirred and mixed at 40°C for 15 min, 45-μm graphite was added, the reaction temperature was maintained at 40°C, and stirring was continued for 6 h; during the reaction, the ratio of strong acid to graphite was 100 g:1 g, and the ratio of potassium periodate to graphite was 40 g:1 g. After the reaction was completed, the reaction solution was poured into deionized water, centrifuged at 12000 rpm, and the target product was collected; the target product was diluted and dispersed and then subjected to ultrasonic exfoliation.

[0095] The target product obtained in Comparative Example 4 after ultrasonic exfoliation was subjected to atomic force microscope analysis, and the results are shown in FIG. 2. Figure 9 Figure 9 FIG. 2 is an atomic force microscope analysis image of the target product obtained in Comparative Example 4. Figure 9 As can be seen from FIG. 2, the target product obtained in Comparative Example 4 is a single-layer graphene oxide sheet with a planar size of several hundred nanometers to 1 μm and a thickness of about 1 nm.

[0096] The above description is merely preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the scope of the present application.​

Claims

1. A method for rapid and green preparation of graphene oxide quantum dots, characterized in that, Includes the following steps: A) After mixing periodate with a strong acid, carbon material is added and stirred, and the mixture is heated to carry out the reaction. The mass ratio of the carbon material, strong acid and periodate is 1:(50~200):(25~50). The temperature for heating the reaction is 70~90℃ and the time is 30s~30min. B) Add the reaction solution obtained in step A) to deionized water and centrifuge to obtain the centrifuged liquid; C) The centrifuged liquid was purified by dialysis to obtain a graphene oxide quantum dot dispersion; D) Graphene oxide quantum dot powder was obtained by freeze-drying the graphene oxide dispersion quantum dots.

2. The method according to claim 1, characterized in that, The periodate is one or more of potassium periodate, sodium periodate, ammonium periodate, magnesium periodate, calcium periodate, and strontium periodate.

3. The method according to claim 1, characterized in that, The strong acid is one or a mixture of several of the following: sulfuric acid, phosphoric acid, fuming sulfuric acid, concentrated nitric acid, fluorosulfonic acid, and trifluoromethanesulfonic acid.

4. The method according to claim 1, characterized in that, The carbon material is one or a mixture of graphite, carbon black, and carbon nanotubes.

5. The method according to claim 1, characterized in that, In step A), the temperature for mixing periodate and strong acid is 0~40℃, and the time is 5~30min.

6. The method according to claim 1, characterized in that, The centrifuge speed is 300 rpm.

7. A graphene oxide quantum dot prepared by the method according to any one of claims 1 to 6, characterized in that, The graphene oxide quantum dots have a single-layer structure.

8. The graphene oxide quantum dot according to claim 7, characterized in that, The planar size of the graphene oxide quantum dots is ≤5nm.

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