Efficient preparation and functional modification method of graphene oxide

Abstract

The application relates to the technical field of material science, and discloses a high-efficiency preparation and functional modification method of graphene oxide, which comprises the following steps: pre-treating flake graphite powder with nitric acid to form pre-oxidized graphite; performing a deep oxidation reaction on the pre-oxidized graphite; obtaining a crude product of graphene oxide through centrifugal washing; adding boron nitride nanosheets and phosphotungstic acid to the crude product; performing ultrasonic dispersion and then performing a hydrothermal reaction to improve the performance of the graphene oxide; performing dopamine functionalization on the composite graphene oxide to form a polydopamine coating; grafting organosilane on the surface of the graphene oxide; finally introducing an amino functional group; and after drying treatment, obtaining functionalized and modified graphene oxide. The method increases the active sites and chemical reactivity of the surface of the graphene oxide by dopamine functionalization, grafting of organosilane and introduction of an amino functional group, improves the dispersibility of the graphene oxide in an organic phase and the compatibility of the graphene oxide with polylactic acid, and enhances the application performance and functionality of the graphene oxide in a composite material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of material science, in particular to a high-efficiency preparation and functional modification method of graphene oxide. BACKGROUND

[0002] In the field of material science, graphene oxide is concerned in many fields such as energy storage, catalysis, biomedicine and composite materials due to its unique two-dimensional structure and excellent electrical and mechanical properties. However, in the traditional preparation method, the addition mode of potassium permanganate makes it difficult to control the oxidation rate, which easily leads to local overheating, resulting in side reactions such as over-oxidation, carbonization and ablation, which seriously reduces the yield and quality of graphene oxide. At the same time, metal ion impurities in the system can catalyze side reactions and interfere with the oxidation process, resulting in insufficient oxidation and poor purity, which greatly limits the performance improvement. In addition, graphene oxide has poor thermal stability and limited mechanical properties, and its dispersion in organic phase is not good, and its compatibility with polymer matrix such as polylactic acid is not ideal, which restricts its application in high-performance composites. Therefore, it is urgent to develop a high-efficiency preparation method of graphene oxide which can precisely control the reaction process, effectively remove impurities and realize functional modification to improve the comprehensive performance. SUMMARY

[0003] (I) Technical problems solved

[0004] In view of the defects of the prior art, the application provides a high-efficiency preparation and functional modification method of graphene oxide, which has the advantages of precise control of reaction process, effective removal of impurities and improvement of comprehensive performance, and solves the problems of local overheating caused by one-time addition of potassium permanganate in the traditional preparation method, interference of metal ion impurities with the oxidation process, poor thermal stability and limited mechanical properties of graphene oxide, poor dispersion and poor compatibility with polymer matrix.

[0005] (II) Technical solutions

[0006] To achieve the above-mentioned purpose, the application provides the following technical solutions: a high-efficiency preparation and functional modification method of graphene oxide, comprising the following steps:

[0007] Step 1, raw material preparation: flake graphite powder, disodium ethylenediaminetetraacetate, boron nitride nanosheet, phosphotungstic acid, 3-aminopropyltriethoxysilane, sulfuric acid, nitric acid, potassium permanganate, hydrogen peroxide, deionized water, dopamine hydrochloride, maleic anhydride, benzoyl peroxide, anhydrous toluene, dichloromethane and Tris-HCl buffer solution;

[0008] Step 2, pretreatment: the flake graphite powder is placed in a beaker, and the nitric acid is added dropwise, and after stirring, it is transferred to a constant-temperature water bath kettle to preliminarily oxidize the edges of the graphite to form pre-oxidized graphite;

[0009] Step three, deep oxidation reaction: the pre-oxidized graphite is transferred to a three-necked flask, sulfuric acid is added dropwise, and potassium permanganate is added in three portions in an ice bath, with the feeding speed controlled. After the addition is completed, it is transferred to a constant-temperature water bath for deep oxidation of the graphite;

[0010] Step four, purification treatment: after the reaction is completed, deionized water is added for dilution, hydrogen peroxide solution is added to reduce the residual potassium permanganate, and after centrifugal washing, the supernatant is removed. Sodium EDTA solution is added to the precipitate, which is centrifuged again to remove impurities, and the crude graphene oxide is obtained.

[0011] Step five, introduction of boron nitride nanosheet and phosphotungstic acid: the crude graphene oxide is dispersed in deionized water, boron nitride nanosheet and phosphotungstic acid are added, and after ultrasonic dispersion, a hydrothermal reaction is carried out to improve the performance of the graphene oxide. After the reaction is completed, centrifugal washing is performed to obtain the composite graphene oxide.

[0012] Step six, dopamine functionalization: the composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added, and a reaction is carried out at room temperature to form a polydopamine coating. After the reaction is completed, centrifugal washing is performed.

[0013] Step seven, grafting of organosilane: the dopamine functionalized graphene oxide is dispersed in anhydrous toluene, 3-aminopropyltriethoxysilane is added, and a reflux reaction is carried out under nitrogen protection. After the reaction is completed, centrifugal washing is performed.

[0014] Step eight, introduction of amino functional groups: the graphene oxide grafted with organosilane is dispersed in dichloromethane, maleic anhydride and benzoyl peroxide are added, and after stirring, a reaction occurs to introduce carboxyl groups on the surface of the graphene oxide. After the reaction is completed, centrifugal washing is performed.

[0015] Step nine, drying: the obtained graphene oxide is dried in a vacuum drying oven at 55-60°C for 11-12 hours to remove residual solvents, and the functionalized modified graphene oxide is obtained.

[0016] Preferably, the particle size of the flake graphite powder is 50-200 mesh, and the purity is ≥99%.

[0017] Preferably, the concentration of sulfuric acid is controlled at 96%-98%, the concentration of nitric acid is controlled at 68%-70%, the potassium permanganate is analytical pure, and the concentration of hydrogen peroxide is controlled at 25%-30%.

[0018] Preferably, the particle size of the boron nitride nanosheet is controlled at 50-100 nm, and the phosphotungstic acid is used as a catalyst. The Tris-HCl buffer solution is prepared from tris(hydroxymethyl)aminomethane and hydrochloric acid.

[0019] Preferably, the pretreatment conditions in step two are as follows: the stirring speed is set to 200-300 r / min, and the solution is stirred in a constant-temperature water bath at 45-50 °C for 0.8-1 h.

[0020] Preferably, the deep oxidation reaction conditions in step three are as follows: the stirring speed is set to 50-100 r / min, the solution temperature is controlled at 0-5 °C, the feeding speed is controlled at 0.5-1.5 g / min, the constant-temperature water bath temperature is set to 30-35 °C, the water bath stirring speed is 180-200 r / min, and the reaction time is 10-12 h.

[0021] Preferably, the purification treatment conditions in step four are as follows: centrifugation is performed at a speed of 7000-8000 r / min for 8-10 min, and the stirring time is 25-30 min.

[0022] Preferably, the process of introducing boron nitride nanosheets and phosphotungstic acid in step five is as follows:

[0023] S5.1, disperse the crude graphene oxide in deionized water, and ultrasonically disperse for 25-30 min;

[0024] S5.2, add boron nitride nanosheets and phosphotungstic acid, and continue to ultrasonically disperse for 0.8-1 h to fully mix the boron nitride nanosheets and phosphotungstic acid with the graphene oxide;

[0025] S5.3, transfer the mixed solution to a reaction kettle, and perform hydrothermal reaction at 55-60 °C for 10-12 h;

[0026] S5.4, after the reaction is completed, cool to room temperature, and centrifugally wash again to obtain the composite graphene oxide.

[0027] Preferably, the dopamine functionalization process in step six is as follows: disperse the composite graphene oxide in a Tris-HCl buffer solution, add dopamine hydrochloride to make the concentration reach 1.8-2 mg / mL, and stir at room temperature for 20-24 h; the dopamine undergoes self-polymerization under alkaline conditions to form a polydopamine coating on the surface of the graphene oxide.

[0028] Preferably, the process of grafting organosilane in step seven is as follows: disperse the dopamine-functionalized graphene oxide in anhydrous toluene, add 3-aminopropyl triethoxysilane at a mass ratio of 1:1 with the graphene oxide, heat the reaction system to 105-110 °C under nitrogen protection, and reflux and stir for 5-6 h; the ethoxyl groups of the 3-aminopropyl triethoxysilane are hydrolyzed and react with the hydroxyl groups on the surface of the graphene oxide, and the graphene oxide grafted with organosilane is obtained after washing.

[0029] Compared with the prior art, the application provides a high-efficiency preparation and functional modification method of graphene oxide, and has the following beneficial effects:

[0030] 1、The application achieves the beneficial effects of improving the yield and quality of graphene oxide by adding potassium permanganate in batches, which can effectively control the rate of the oxidation reaction and avoid local overheating caused by excessive reaction, so that the oxidation of the graphite sheet layer is more uniform, the occurrence of excessive oxidation, carbonization and ablation side reactions is reduced, thereby improving the yield of graphene oxide, and meanwhile, the addition of potassium permanganate in batches can also ensure the full progress of the oxidation reaction, so that the graphene oxide has a moderate degree of oxidation, providing a good foundation for subsequent functional modification.

[0031] 2The application achieves the beneficial effects of improving the oxidation degree and purity of graphene oxide by adding disodium ethylenediaminetetraacetate to remove metal ion impurities, wherein the use of disodium ethylenediaminetetraacetate solution to remove metal ion impurities can ensure the purity of the reaction system and avoid the interference of metal ion impurities on the oxidation reaction, and the metal ion impurities may catalyze some side reactions, leading to insufficient oxidation reaction or the generation of unstable intermediate products, thereby affecting the quality of graphene oxide, and by removing these impurities, the graphene oxide has a moderate degree of oxidation and is suitable for subsequent functional modification and has high purity.

[0032] 3、The application achieves the beneficial effects of improving the comprehensive performance of graphene oxide by introducing boron nitride nanosheets and phosphotungstic acid, and after the introduction of boron nitride nanosheets and phosphotungstic acid, the hydrothermal reaction makes the boron nitride nanosheets and graphene oxide combine through chemical bonds, and the phosphotungstic acid as a catalyst further optimizes the structure of graphene oxide, which improves the thermal stability, mechanical properties, dispersibility and compatibility with polylactic acid of graphene oxide.

[0033] 4、The application increases the active sites and chemical reactivity of the surface of graphene oxide by functionalizing the prepared graphene oxide with dopamine, grafting organosilane on the surface thereof, and introducing an amino functional group on the basis thereof, thereby improving the dispersibility of graphene oxide in an organic phase and the compatibility with polylactic acid, so that graphene oxide achieves the effects of enhancing the application performance and functionality of graphene oxide in a composite material. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The preparation flowchart of the application. DETAILED DESCRIPTION

[0035] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] Please refer to Figure 1 A method for efficient preparation and functional modification of graphene oxide, comprising the following steps:

[0037] Step one, raw material preparation: flake graphite powder, disodium ethylenediaminetetraacetate, boron nitride nanosheet, phosphotungstic acid, 3-aminopropyl triethoxysilane, sulfuric acid, nitric acid, potassium permanganate, hydrogen peroxide, deionized water, dopamine hydrochloride, maleic anhydride, benzoyl peroxide (BPO), anhydrous toluene, dichloromethane and Tris-HCl buffer solution;

[0038] Step two, pretreatment: place the flake graphite powder in a beaker, add nitric acid drop by drop, place the beaker on a magnetic stirrer, stir and then transfer to a constant temperature water bath for continuous stirring. This process preliminarily oxidizes the edges of the graphite, increases the active sites for subsequent reactions, and forms pre-oxidized graphite.

[0039] Step three, deep oxidation reaction: transfer the pre-oxidized graphite to a three-necked flask, add sulfuric acid drop by drop, place the three-necked flask in an ice bath, set the stirring speed and control the solution temperature, then add potassium permanganate in three portions, control the feeding speed to ensure that the feeding process is completed within 30 minutes to prevent the reaction from being too violent, and after adding potassium permanganate, transfer the three-necked flask to a constant temperature water bath to oxidize the graphite deeply. By adding potassium permanganate in portions, the yield and quality of graphene oxide are improved. By adding potassium permanganate in portions, the rate of oxidation reaction can be effectively controlled to avoid local overheating caused by excessive reaction. This method of adding makes the oxidation of graphite layers more uniform, reduces the occurrence of excessive oxidation, carbonization and ablation side reactions, and improves the yield of graphene oxide. At the same time, adding potassium permanganate in portions also ensures the full progress of the oxidation reaction, so that the graphene oxide has a moderate degree of oxidation, providing a good foundation for subsequent functional modification.

[0040] Step four, purification treatment: after the reaction is completed, the three-necked flask is placed in an ice bath again, and deionized water is added to dilute the reaction solution. This process will generate a large amount of heat, so the temperature change needs to be observed closely to prevent boiling over. Hydrogen peroxide solution is added to reduce the remaining potassium permanganate. At this time, the color of the solution will gradually change from purple to bright yellow. The mixture is transferred to a centrifuge tube and centrifuged at a speed of 7000-8000 r / min for 8-10 min. The supernatant is removed, and a 0.05 g / ml ethylenediaminetetraacetic acid disodium solution is added to the precipitate. Stirring for 25-30 min can remove possible metal ion impurities. The precipitate is centrifuged again and washed repeatedly with deionized water until the pH of the washing solution is 6.5-7. The crude graphene oxide is obtained. The use of ethylenediaminetetraacetic acid disodium to remove metal ion impurities ensures the purity of the reaction system and avoids the interference of metal ion impurities with the oxidation reaction. Metal ion impurities can catalyze some side reactions, leading to insufficient oxidation or the production of unstable intermediate products, thereby affecting the quality of graphene oxide. By removing these impurities, graphene oxide has a moderate degree of oxidation, which is suitable for subsequent functional modification, and has a high purity;

[0041] Step five, introducing boron nitride nanosheets and phosphotungstic acid: the crude graphene oxide is dispersed in deionized water and ultrasonically dispersed for 25-30 min to make the graphene oxide uniformly dispersed. Boron nitride nanosheets and phosphotungstic acid are added and ultrasonically dispersed for 0.8-1 h to make the boron nitride nanosheets and phosphotungstic acid fully mixed with the graphene oxide. The mixture is transferred to a reaction kettle and subjected to a hydrothermal reaction at 55-60°C for 10-12 h to make the boron nitride nanosheets and graphene oxide combine through chemical bonds, and the phosphotungstic acid catalyzes further optimization of the structure of graphene oxide, improving its thermal stability, mechanical properties, and reaction activity. After the reaction is completed, the system is cooled to room temperature and centrifuged again to obtain composite graphene oxide. The introduction of boron nitride nanosheets and phosphotungstic acid improves the comprehensive performance of graphene oxide. After the introduction of boron nitride nanosheets and phosphotungstic acid, the hydrothermal reaction makes the boron nitride nanosheets and graphene oxide combine through chemical bonds, and the phosphotungstic acid acts as a catalyst to further optimize the structure of graphene oxide. This improvement improves the thermal stability, mechanical properties, dispersibility, and compatibility with polylactic acid of graphene oxide;

[0042] Step six, dopamine functionalization: disperse the composite graphene oxide in Tris-HCl buffer solution, add dopamine hydrochloride to make its concentration reach 1.8-2 mg / mL, stir the reaction at room temperature for 20-24 h, dopamine undergoes self-polymerization reaction under alkaline conditions to form a polydopamine coating on the surface of graphene oxide, which contains abundant amino and phenolic hydroxyl groups, providing a large number of active sites for subsequent modification, thereby increasing the chemical reactivity of graphene oxide and enabling it to react with more types of chemicals, thereby achieving more functional modification, after the reaction is completed, centrifugal separation is performed, and deionized water is used for washing 2-3 times to remove unreacted dopamine hydrochloride;

[0043] Step seven, grafting organosilane: disperse dopamine functionalized graphene oxide in anhydrous toluene, add 3-aminopropyl triethoxysilane in a mass ratio of 1:1 with graphene oxide, heat the reaction system to 105-110°C under nitrogen protection, and reflux and stir for 5-6 h, during which the ethoxyl groups of 3-aminopropyl triethoxysilane are hydrolyzed and react with the hydroxyl groups on the surface of graphene oxide, and the amino groups remain on the surface, further increasing the reactivity of graphene oxide and improving its dispersibility in organic phase, after the reaction is completed, cool to room temperature, centrifugal separation is performed, and anhydrous ethanol is used for washing 3-5 times to remove unreacted 3-aminopropyl triethoxysilane, and grafted organosilane graphene oxide is obtained after washing;

[0044] Step eight, introduction of amino functional groups: disperse the grafted organosilane graphene oxide in dichloromethane, add maleic anhydride and benzoyl peroxide (BPO), wherein the mass ratio of maleic anhydride to graphene oxide is 2:1, and the amount of BPO is 5% of the mass of maleic anhydride, stir at 55-60°C for 3.5-4 h, benzoyl peroxide decomposes to generate free radicals, which initiate the reaction between maleic anhydride and the amino groups on the surface of graphene oxide, introducing carboxyl groups on the surface of graphene oxide, which can undergo esterification reaction with the hydroxyl groups of polylactic acid, thereby improving the compatibility of graphene oxide with polylactic acid, after the reaction is completed, cool to room temperature, centrifugal separation is performed, and dichloromethane is used for washing 3-5 times to remove unreacted maleic anhydride and BPO;

[0045] Step nine, drying: after step eight, the obtained graphene oxide is dried in a vacuum drying oven at 55-60°C for 11-12 h to remove residual solvents, thereby obtaining functionalized modified graphene oxide with good compatibility with polylactic acid.

[0046] The advantage is that the prepared graphene oxide is functionalized by dopamine and grafted with organic silane on the surface, and the amino functional group is introduced on the basis, so as to increase the active sites and chemical reactivity of the surface of graphene oxide, thereby improving the dispersibility of graphene oxide in the organic phase and the compatibility with polylactic acid, so that the application performance and functionality of graphene oxide in the composite material are achieved.

[0047] Specifically, the particle size of flake graphite powder is 50-200 mesh, and the purity is ≥99%, which is used as the carbon source basic material for preparing graphene oxide.

[0048] Specifically, the concentration of sulfuric acid is controlled at 96%-98% for providing an acidic environment, which plays an important role in the oxidation process, the concentration of nitric acid is controlled at 68%-70%, and potassium permanganate is analytical pure, which is used as a strong oxidizing agent for oxidizing graphite to graphene oxide, and the concentration of hydrogen peroxide is controlled at 25%-30% for removing excess potassium permanganate and terminating the oxidation reaction.

[0049] Specifically, the particle size of boron nitride nanosheet is controlled at 50-100 nm, which is used as an auxiliary oxidizing agent to enhance the oxidation effect and help to fully oxidize graphite, phosphotungstic acid is used as a catalyst to accelerate the rate of oxidation reaction and improve the reaction efficiency, 3-aminopropyl triethoxysilane is used to introduce amino functional groups on the surface of graphene oxide in the subsequent modification step to enhance its reactivity and functionality, disodium ethylenediaminetetraacetate is used to adjust the pH value of the reaction system and complex some metal ions, and is also used to remove metal ion impurities in the subsequent purification process to optimize the reaction environment, dopamine hydrochloride, maleic anhydride, benzoyl peroxide (BPO), anhydrous toluene, dichloromethane and Tris-HCl buffer solution are used in the subsequent modification step, the Tris-HCl buffer solution is prepared from tris-hydroxymethyl aminomethane and hydrochloric acid, and the concentration is 10 mmol / L and the pH value is 8.5.

[0050] Specifically, the pretreatment conditions in step two are as follows: the stirring speed is set at 200-300 r / min, and the solution is stirred in a constant temperature water bath at 45-50°C for 0.8-1 h.

[0051] Specifically, the deep oxidation reaction conditions in step three are as follows: the stirring speed is set at 50-100 r / min, the solution temperature is controlled at 0-5°C, the feeding speed is controlled at 0.5-1.5 g / min, the constant temperature water bath temperature is set at 30-35°C, the water bath stirring speed is set at 180-200 r / min, and the reaction time is 10-12 h.

[0052] Specifically, the purification treatment conditions in step four are as follows: centrifugation is performed at a speed of 7000-8000 r / min for 8-10 min, and the stirring time is 25-30 min.

[0053] According to the method embodiments 1-3 of the present application, on the basis of the embodiments, the preparation steps are changed to obtain comparative examples 1-3, as shown in Table 1 below:

[0054] Table 1

[0055]

[0056] The graphene oxide is prepared from the examples and comparative examples, and the performance is compared to obtain Table 2:

[0057] Table 2

[0058]

[0059] From Tables 1-2, it can be seen that:

[0060] (1) From the yield of graphene oxide, the yields of examples 1-3 are higher, which are 85%, 88% and 90% respectively, indicating that the optimized preparation conditions can effectively improve the yield, and the yields of comparative examples 1-3 are lower, which are 75%, 82% and 78% respectively, indicating that changing the adding method of potassium permanganate, removing metal ion impurities, and adding boron nitride nanosheet and phosphotungstic acid will all affect the yield of graphene oxide. Among them, adding potassium permanganate at one time will release a large amount of heat in a short time, causing the local temperature to rise sharply. This local overheating phenomenon will cause the excessive oxidation of part of the graphite sheet layer, even carbonization or ablation, destroy the structure of graphite, and reduce the effective carbon source for forming graphene oxide, thereby reducing the yield of graphene oxide.

[0061] (2) From the oxidation degree, the C / O ratios of examples 1-3 are 2.5, 2.4 and 2.3 respectively, indicating that the oxidation degree is moderate, which is suitable for subsequent functional modification; the C / O ratios of comparative examples 1-3 are 2.7, 2.6 and 2.8 respectively, and the oxidation degree is lower. The main reason is that the existence of metal ion impurities in the comparative examples leads to insufficient reaction or more side reactions, which increases the oxidation degree. Therefore, removing metal ion impurities is a key step to ensure that the oxidation degree of graphene oxide is moderate.

[0062] (3) From the thermal stability, the T 5% (5% thermal weight loss temperature) of examples 1-3 are 250℃, 255℃ and 260℃ respectively, showing good thermal stability; the T 5% of comparative examples 1-3 are 230℃, 240℃ and 220℃ respectively, and the thermal stability is poor, especially comparative example 3, due to the lack of boron nitride nanosheet and phosphotungstic acid, which leads to the increase of structural defects and the decrease of crystallinity of graphene oxide, resulting in the decrease of thermal stability.

[0063] (4) From the mechanical property aspect: the tensile strength of Examples 1-3 is 150 MPa, 160 MPa and 170 MPa respectively, showing good mechanical properties; the tensile strength of Comparative Examples 1-3 is 120 MPa, 130 MPa and 110 MPa respectively, the mechanical properties are poor, especially Comparative Example 3, due to the lack of boron nitride nanosheets and phosphotungstic acid, the structural integrity and crystallinity are reduced, the defects are increased, resulting in the decline of mechanical properties.

[0064] (5) From the dispersion aspect: the particle size distribution of Examples 1-3 is narrow, which is 100-200 nm, 90-180 nm and 80-160 nm respectively, indicating good dispersion; the particle size distribution of Comparative Examples 1-3 is wide, which is 120-250 nm, 110-230 nm and 130-280 nm respectively, the dispersion is poor, especially Comparative Example 3, due to the lack of boron nitride nanosheets and phosphotungstic acid, the structural integrity and crystallinity are reduced, the defects are increased, the dispersion is decreased;

[0065] (6) From the "compatibility with polylactic acid" aspect: the compatibility index of Examples 1-3 is 0.90, 0.92 and 0.95 respectively, indicating good compatibility with polylactic acid; the compatibility index of Comparative Examples 1-3 is 0.75, 0.80 and 0.65 respectively, the compatibility is poor, especially Comparative Example 3, due to the lack of boron nitride nanosheets and phosphotungstic acid, resulting in insufficient types and amounts of surface functional groups, the interaction with polylactic acid is weakened, the compatibility is decreased, therefore, the introduction of boron nitride nanosheets and phosphotungstic acid is the key step to improve the compatibility of graphene oxide with polylactic acid.

[0066] Summary: Through the analysis of the performance test results of the examples and comparative examples, Examples 1-3 successfully prepared graphene oxide with high yield, moderate oxidation degree, good thermal stability, mechanical properties, dispersion and compatibility with polylactic acid by optimizing the parameters of each step (such as the addition of potassium permanganate in several times, the removal of metal ion impurities, the introduction of boron nitride nanosheets and phosphotungstic acid, etc.); while the performance of graphene oxide of Comparative Examples 1-3 is decreased due to the change of key steps, especially Comparative Example 3, due to the lack of boron nitride nanosheets and phosphotungstic acid, the thermal stability, mechanical properties, dispersion and compatibility are all greatly decreased.

[0067] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for efficient preparation and functional modification of graphene oxide, characterized in that, The method comprises the following steps: Step one, raw material preparation: flake graphite powder, disodium ethylenediaminetetraacetate, boron nitride nanosheet, phosphotungstic acid, 3-aminopropyl triethoxysilane, sulfuric acid, nitric acid, potassium permanganate, hydrogen peroxide, deionized water, dopamine hydrochloride, maleic anhydride, benzoyl peroxide, anhydrous toluene, dichloromethane and Tris-HCl buffer solution; Step two, pretreatment: the flake graphite powder is placed in a beaker, and nitric acid is added dropwise, stirred and then transferred to a constant temperature water bath kettle to preliminarily oxidize the edges of the graphite to form pre-oxidized graphite; Step three, deep oxidation reaction: the pre-oxidized graphite is transferred to a three-necked flask, sulfuric acid is added dropwise, placed in an ice bath, and potassium permanganate is added in three portions, the feeding speed is controlled, and after the addition is completed, it is transferred to a constant temperature water bath to deeply oxidize the graphite; Step four, purification treatment: after the reaction is completed, deionized water is added for dilution, hydrogen peroxide solution is added to reduce the residual potassium permanganate, the supernatant is removed after centrifugal washing, disodium ethylenediaminetetraacetate solution is added to the precipitate, and impurities are removed after centrifugation to obtain crude graphene oxide; Step five, introduction of boron nitride nanosheet and phosphotungstic acid: the crude graphene oxide is dispersed in deionized water, boron nitride nanosheet and phosphotungstic acid are added, ultrasonic dispersion is performed, and then hydrothermal reaction is carried out to improve the performance of the graphene oxide, and the composite graphene oxide is obtained after centrifugal washing; Step six, dopamine functionalization: the composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added, and reaction is carried out at room temperature to form a polydopamine coating, and the composite graphene oxide is obtained after centrifugal washing; Step seven, grafting of organic silane: the dopamine functionalized graphene oxide is dispersed in anhydrous toluene, 3-aminopropyl triethoxysilane is added, and reflux reaction is carried out under nitrogen protection, and the graphene oxide is obtained after centrifugal washing; Step eight, introduction of amino functional group: the graphene oxide grafted with organic silane is dispersed in dichloromethane, maleic anhydride and benzoyl peroxide are added, stirring is carried out, reaction occurs, carboxyl groups are introduced on the surface of the graphene oxide, and the graphene oxide is obtained after centrifugal washing; Step nine, drying: the obtained graphene oxide is dried in a vacuum drying box at 55-60°C for 11-12 hours to remove residual solvents, and the functionalized modified graphene oxide is obtained. 2.The method of claim 1, wherein the method is characterized by: The particle size of the flake graphite powder is 50-200 mesh, and the purity is ≥99%. 3.The method of claim 1, wherein the method is characterized by: The concentration of the sulfuric acid is controlled to be 96%-98%, the concentration of the nitric acid is controlled to be 68%-70%, the potassium permanganate is of analytical purity, and the concentration of the hydrogen peroxide is controlled to be 25%-30%. 4.The method of claim 1, wherein the method is characterized by: The particle size of the boron nitride nanosheet is controlled to be 50-100 nm, the phosphotungstic acid is used as a catalyst, and the Tris-HCl buffer solution is prepared from tris(hydroxymethyl)aminomethane and hydrochloric acid. 5.The method of claim 1, wherein the method is characterized by: In the pretreatment of step two, the stirring speed is set to 200-300 r / min, and the stirring is carried out in a constant temperature water bath at 45-50°C for 0.8-1 h. 6.The method of claim 1, wherein the method is characterized by: The reaction conditions of the third step are as follows: the stirring speed is set to 50-100 r / min, the solution temperature is controlled at 0-5℃, the feeding speed is controlled at 0.5-1.5 g / min, the constant temperature water bath temperature is set to 30-35℃, the water bath stirring speed is 180-200 r / min, and the reaction time is 10-12 h. 7.The method of claim 1, wherein the graphene oxide is prepared by the following steps: (1) preparing a graphene oxide solution by mixing graphene oxide and a solvent; (2) adding a functional group to the graphene oxide solution to obtain a functionalized graphene oxide solution; and (3) drying the functionalized graphene oxide solution to obtain the functionalized graphene oxide. The purification treatment conditions of the fourth step are as follows: centrifugation is performed at a speed of 7000-8000 r / min for 8-10 min, and the stirring time is 25-30 min. 8.The method of claim 1, wherein the method is characterized by: The process of introducing boron nitride nanosheets and phosphotungstic acid in the fifth step is as follows: S5.1, disperse the crude graphene oxide in deionized water and ultrasonically disperse for 25-30 min; S5.2, add boron nitride nanosheets and phosphotungstic acid, and continue to ultrasonically disperse for 0.8-1 h to fully mix the boron nitride nanosheets and phosphotungstic acid with the graphene oxide; S5.3, transfer the mixed solution to a reaction kettle and perform hydrothermal reaction at 55-60℃ for 10-12 h; S5.4, after the reaction is completed, cool to room temperature, centrifuge and wash again to obtain composite graphene oxide. 9.The method of claim 1, wherein the method is characterized by: The dopamine functionalization process in the sixth step is as follows: disperse the composite graphene oxide in a Tris-HCl buffer solution, add dopamine hydrochloride to make the concentration reach 1.8-2 mg / mL, and stir at room temperature for 20-24 h. Under alkaline conditions, dopamine undergoes self-polymerization to form a polydopamine coating on the surface of the graphene oxide. 10.The method of claim 1, wherein the method is characterized by: The process of grafting organosilane in the seventh step is as follows: disperse the dopamine functionalized graphene oxide in anhydrous toluene, add 3-aminopropyl triethoxysilane at a mass ratio of 1:1 with the graphene oxide, heat the reaction system to 105-110℃ under nitrogen protection, and reflux and stir for 5-6 h. The ethoxyl group of 3-aminopropyl triethoxysilane is hydrolyzed and reacts with the hydroxyl group on the surface of the graphene oxide. After washing, the graphene oxide grafted with organosilane is obtained.

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