Efficient preparation and functional modification method of graphene oxide

Abstract

The invention relates to the technical field of material science, and discloses an efficient preparation and functional modification method of graphene oxide, which comprises the following steps: carrying out nitric acid pretreatment on crystalline flake graphite powder to form pre-oxidized graphite, carrying out deep oxidation reaction on the pre-oxidized graphite, and carrying out centrifugal washing to obtain a graphene oxide crude product; the preparation method comprises the following steps: adding a crude product into boron nitride nanosheets and phosphotungstic acid, carrying out ultrasonic dispersion, carrying out a hydrothermal reaction to improve the performance of graphene oxide, carrying out dopamine functionalization on composite graphene oxide to form a polydopamine coating, grafting organosilane on the surface of the polydopamine coating, introducing an amino functional group, and carrying out drying treatment to obtain functionalized modified graphene oxide. According to the method, through dopamine functionalization, organosilane grafting and amino functional group introduction, active sites and chemical reactivity on the surface of the graphene oxide are increased, the dispersity of the graphene oxide in an organic phase and the compatibility of the graphene oxide with polylactic acid are improved, and the application performance and functionality of the graphene oxide in a composite material are enhanced.

Description

Technical Field

[0001] The present invention relates to the field of material science and technology, and in particular to a method for efficiently preparing and functionalizing graphene oxide. Background Art

[0002] In the field of materials science, graphene oxide has attracted much attention 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 traditional preparation methods, the addition of potassium permanganate makes it difficult to control the oxidation reaction rate, which can easily cause local overheating, leading to side reactions such as excessive oxidation, carbonization and ablation, seriously reducing the yield and quality of graphene oxide; at the same time, metal ion impurities in the system will catalyze side reactions and interfere with the oxidation process, resulting in insufficient oxidation and poor purity, greatly limiting its performance improvement. In addition, graphene oxide itself has poor thermal stability and limited mechanical properties, poor dispersibility in organic phases, and unsatisfactory compatibility with polymer matrices such as polylactic acid, making it difficult to fully exert its reinforcing effect, which restricts its application in high-performance composite materials. Therefore, there is an urgent need to develop an efficient preparation method for graphene oxide that can accurately control the reaction process, effectively remove impurities, and achieve functional modification to improve comprehensive performance. Summary of the Invention

[0003] (1) Technical problems solved In response to the shortcomings of the existing technology, the present invention provides an efficient preparation and functional modification method for graphene oxide, which has the advantages of precisely controlling the reaction process, effectively removing impurities, and improving comprehensive performance. It solves the problems of local overheating caused by the one-time addition of potassium permanganate in traditional preparation methods, interference of metal ion impurities in the oxidation process, poor thermal stability of graphene oxide, limited mechanical properties, poor dispersibility, and unsatisfactory compatibility with the polymer matrix.

[0004] (2) Technical solution To achieve the above objectives, the present invention provides the following technical solution: a method for efficiently preparing and functionalizing graphene oxide, comprising the following steps: Step 1. Prepare raw materials: flake graphite powder, disodium ethylenediaminetetraacetic acid, boron nitride nanosheets, 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; Step 2: Pretreatment: Place the flake graphite powder in a beaker, add nitric acid dropwise, stir, and transfer to a constant temperature water bath to preliminarily oxidize the edges of the graphite to form pre-oxidized graphite; Step 3, deep oxidation reaction: transfer the pre-oxidized graphite to a three-necked flask, add sulfuric acid dropwise, place in an ice bath, add potassium permanganate three times, control the addition rate, and after addition, transfer to a constant temperature water bath to deeply oxidize the graphite; Step 4: Purification: After the reaction is completed, deionized water is added to dilute it, and hydrogen peroxide solution is added to reduce the remaining potassium permanganate. The product is centrifuged and washed to remove impurities to obtain crude graphene oxide; Step 5: Introducing boron nitride nanosheets and phosphotungstic acid: Dispersing crude graphene oxide in deionized water, adding boron nitride nanosheets and phosphotungstic acid, and performing a hydrothermal reaction after ultrasonic dispersion to improve the performance of graphene oxide. After the reaction, centrifugation and washing are performed to obtain composite graphene oxide; Step 6: Dopamine functionalization: The composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added, and the mixture is reacted at room temperature to form a polydopamine coating. After the reaction, the mixture is centrifuged and washed; Step 7: Grafting organosilane: disperse the dopamine-functionalized graphene oxide in anhydrous toluene, add 3-aminopropyltriethoxysilane, and reflux under nitrogen protection. After the reaction, centrifuge and wash; Step 8: Introducing amino functional groups: dispersing the organosilane-grafted graphene oxide in dichloromethane, adding maleic anhydride and benzoyl peroxide, stirring and reacting to introduce carboxyl groups on the surface of the graphene oxide, and centrifuging and washing after the reaction is completed; Step 9: Drying: Dry the obtained graphene oxide in a vacuum drying oven at 55-60° C. for 11-12 hours to remove the residual solvent and obtain functionalized modified graphene oxide.

[0005] Preferably, the flake graphite powder has a particle size of 50-200 mesh and a purity of ≥99%.

[0006] Preferably, the concentration of the sulfuric acid is controlled at 96% to 98%, the concentration of the nitric acid is controlled at 68% to 70%, the potassium permanganate is analytical grade, and the concentration of the hydrogen peroxide is controlled at 25% to 30%.

[0007] Preferably, the particle size of the boron nitride nanosheets is controlled at 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.

[0008] Preferably, the pretreatment conditions in step 2 are: setting the stirring speed to 200-300 r / min, and stirring in a constant temperature water bath at 45-50° C. for 0.8-1 h.

[0009] Preferably, the deep oxidation reaction conditions in step three are: setting the stirring speed to 50-100 r / min, controlling the solution temperature at 0-5°C, controlling the feeding rate between 0.5-1.5 g / min, setting the constant temperature water bath temperature to 30-35°C, the water bath stirring speed to 180-200 r / min, and the reaction time to 10-12 h.

[0010] Preferably, the purification treatment conditions in step 4 are: centrifugation at a speed of 7000-8000 r / min for 8-10 min and stirring for 25-30 min.

[0011] Preferably, the process of introducing boron nitride nanosheets and phosphotungstic acid in step five is: S5.1. Disperse the crude graphene oxide in deionized water and ultrasonically disperse for 25-30 minutes; S5.2. Add boron nitride nanosheets and phosphotungstic acid, and continue ultrasonic dispersion for 0.8-1 h to fully mix the boron nitride nanosheets, phosphotungstic acid, and graphene oxide; S5.3. Transfer the mixed solution to a reactor and perform a hydrothermal reaction at 55-60°C for 10-12 hours; S5.4. After the reaction is completed, cool to room temperature and centrifuge and wash again to obtain composite graphene oxide.

[0012] Preferably, the dopamine functionalization process in step six is ​​as follows: the composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added to a concentration of 1.8-2 mg / mL, and the reaction is stirred at room temperature for 20-24 hours. Dopamine undergoes self-polymerization under alkaline conditions to form a polydopamine coating on the surface of the graphene oxide.

[0013] Preferably, the process of grafting organosilane in step seven is as follows: dopamine-functionalized graphene oxide is dispersed in anhydrous toluene, 3-aminopropyltriethoxysilane is added at a mass ratio of 1:1 to graphene oxide, and under nitrogen protection, the reaction system is heated to 105-110°C, refluxed and stirred for 5-6 hours, the ethoxy group of 3-aminopropyltriethoxysilane is hydrolyzed and reacts with the hydroxyl group on the surface of the graphene oxide, and the graphene oxide grafted with organosilane is obtained after washing.

[0014] Compared with the prior art, the present invention provides a method for the efficient preparation and functionalization modification of graphene oxide, which has the following beneficial effects: 1. The present invention achieves the beneficial effect of improving the yield and quality of graphene oxide by adding potassium permanganate in batches. The addition of potassium permanganate in batches can effectively control the rate of the oxidation reaction and avoid local overheating caused by excessive reaction. This addition method makes the oxidation of graphite sheets more uniform, thereby reducing the occurrence of excessive oxidation, carbonization and ablation side reactions, thereby improving the yield of graphene oxide. At the same time, the addition of potassium permanganate in batches can also ensure that the oxidation reaction is fully carried out, so that the graphene oxide has a moderate degree of oxidation, providing a good foundation for subsequent functional modification.

[0015] 2 The present invention achieves the beneficial effect of improving the oxidation degree and purity of graphene oxide by adding disodium ethylenediaminetetraacetic acid to remove metal ion impurities. Among them, the use of disodium ethylenediaminetetraacetic acid 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. Metal ion impurities may catalyze some side reactions, resulting in insufficient oxidation reaction or the production of unstable intermediates, thereby affecting the quality of graphene oxide. By removing these impurities, the graphene oxide has a moderate oxidation degree, is suitable for subsequent functional modification, and has a high purity.

[0016] 3. The present invention achieves the beneficial effect of improving the comprehensive performance of graphene oxide by introducing boron nitride nanosheets and phosphotungstic acid. After the introduction of boron nitride nanosheets and phosphotungstic acid, the hydrothermal reaction causes the boron nitride nanosheets to be chemically bonded to graphene oxide. At the same time, 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 of graphene oxide with polylactic acid.

[0017] 4. The present invention functionalizes the prepared graphene oxide with dopamine, grafts organic silane on its surface, and introduces amino functional groups on its basis to increase the active sites and chemical reactivity on 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 composite materials are enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart was prepared for the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] See also Figure 1 , a method for efficiently preparing and functionalizing graphene oxide, comprising the following steps: Step 1. Prepare raw materials: flake graphite powder, disodium ethylenediaminetetraacetic acid, boron nitride nanosheets, phosphotungstic acid, 3-aminopropyltriethoxysilane, 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; Step 2: Pretreatment: Place the flake graphite powder in a beaker, add nitric acid dropwise, place the beaker on a magnetic stirrer, stir, and then transfer to a constant temperature water bath and continue stirring. This process causes the graphite edge to initially oxidize, increasing the active sites for subsequent reactions and forming pre-oxidized graphite. Step 3, deep oxidation reaction: the pre-oxidized graphite is transferred to a three-necked flask, sulfuric acid is added dropwise, the three-necked flask is placed in an ice bath, the stirring speed is set, and after controlling the solution temperature, potassium permanganate is added three times, the feeding rate is controlled, and the feeding process is completed within 30 minutes to prevent the reaction from being too violent. After adding potassium permanganate, the three-necked flask is transferred to a constant temperature water bath to deeply oxidize the graphite. The beneficial effect of improving the yield and quality of graphene oxide is achieved by adding potassium permanganate in batches. The rate of the oxidation reaction can be effectively controlled by adding potassium permanganate in batches to avoid local overheating caused by excessive reaction. This addition method makes the oxidation of the graphite flakes more uniform, so as to reduce the occurrence of excessive oxidation, carbonization and ablation side reactions, thereby improving the yield of graphene oxide. At the same time, the addition of potassium permanganate in batches can also ensure that the oxidation reaction is fully carried out, so that the graphene oxide has a moderate degree of oxidation, providing a good foundation for subsequent functional modification. Step 4: Purification: After the reaction is completed, place the three-necked flask back in an ice bath and add deionized water to dilute the reaction solution. This process will generate a lot of heat, so the temperature change must be closely observed to prevent boiling. Add hydrogen peroxide solution to reduce the remaining potassium permanganate. At this time, the color of the solution will gradually change from purple to bright yellow. Transfer the mixed solution to a centrifuge tube and centrifuge at a speed of 7000-8000r / min for 8-10min. Remove the supernatant and add 0.05g / ml disodium ethylenediaminetetraacetic acid solution to the precipitate. Stir for 25-30min to remove possible metal ion impurities. Centrifuge again and rinse repeatedly with deionized water. The precipitate is washed until the pH value of the washing solution is 6.5-7 to obtain a crude graphene oxide. Disodium ethylenediaminetetraacetic acid is added to remove metal ion impurities, thereby achieving the beneficial effect of improving the oxidation degree and purity of the graphene oxide. The use of a disodium ethylenediaminetetraacetic acid solution to remove metal ion impurities can ensure the purity of the reaction system and avoid interference of metal ion impurities with the oxidation reaction. Metal ion impurities may catalyze some side reactions, resulting in incomplete oxidation reaction or the production of unstable intermediates, thereby affecting the quality of the graphene oxide. By removing these impurities, the graphene oxide has a moderate oxidation degree, is suitable for subsequent functional modification, and has a high purity. Step 5: Introducing boron nitride nanosheets and phosphotungstic acid: Disperse the crude graphene oxide in deionized water, ultrasonically disperse for 25-30 minutes to uniformly disperse the graphene oxide, add boron nitride nanosheets and phosphotungstic acid, and continue ultrasonic dispersion for 0.8-1 hour to fully mix the boron nitride nanosheets, phosphotungstic acid and graphene oxide. Transfer the mixed solution to a reactor and perform a hydrothermal reaction at 55-60°C for 10-12 hours to chemically bond the boron nitride nanosheets to the graphene oxide. At the same time, the phosphotungstic acid catalyzes the further optimization of the structure of the graphene oxide. Improve its thermal stability, mechanical properties and reaction activity. After the reaction is completed, cool to room temperature and centrifuge and wash again to obtain composite graphene oxide. The introduction of boron nitride nanosheets and phosphotungstic acid has achieved the beneficial effect of improving the comprehensive performance of graphene oxide. After the introduction of boron nitride nanosheets and phosphotungstic acid, the hydrothermal reaction causes the boron nitride nanosheets to be chemically bonded to the graphene oxide. At the same time, 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 of graphene oxide with polylactic acid. Step 6: Dopamine functionalization: The composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added to a concentration of 1.8-2 mg / mL, and the reaction is stirred at room temperature for 20-24 hours. Dopamine undergoes self-polymerization under alkaline conditions to form a polydopamine coating on the surface of the graphene oxide. The coating contains rich amino and phenolic hydroxyl groups, providing a large number of active sites for subsequent modification, thereby increasing the chemical reactivity of the graphene oxide, enabling it to react with a wider variety of chemical substances, thereby achieving more functional modifications. After the reaction is completed, centrifugation is performed and the graphene oxide is washed with deionized water 2-3 times to remove unreacted dopamine hydrochloride. Step 7: Grafting organic silane: disperse the dopamine-functionalized graphene oxide in anhydrous toluene, add 3-aminopropyltriethoxysilane at a mass ratio of 1:1 to graphene oxide, and under nitrogen protection, heat the reaction system to 105-110°C and reflux with stirring for 5-6 hours. During this period, the ethoxy group of 3-aminopropyltriethoxysilane is hydrolyzed and reacts with the hydroxyl group on the surface of graphene oxide, while the amino group remains on the surface, further increasing the reactivity of graphene oxide and improving its dispersibility in the organic phase. After the reaction is completed, cool to room temperature, centrifuge, and wash with anhydrous ethanol 3-5 times to remove unreacted 3-aminopropyltriethoxysilane. After washing, obtain graphene oxide grafted with organic silane; Step 8: Introducing amino functional groups: dispersing the organosilane-grafted graphene oxide in dichloromethane, adding 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. Stirring and reacting at 55-60°C for 3.5-4h, benzoyl peroxide decomposes to produce free radicals, which trigger the reaction of maleic anhydride with the amino groups on the surface of graphene oxide, and introduce carboxyl groups on the surface of graphene oxide. The carboxyl groups will undergo esterification reaction with the hydroxyl groups of polylactic acid, thereby improving the compatibility of graphene oxide and polylactic acid. After the reaction is completed, cooling to room temperature, centrifuging, and washing with dichloromethane 3-5 times to remove unreacted maleic anhydride and BPO; Step nine: Drying: After the treatment in step eight, the obtained graphene oxide is dried in a vacuum drying oven at 55-60° C. for 11-12 hours to remove the residual solvent, thereby obtaining functionalized modified graphene oxide having good compatibility with polylactic acid.

[0021] The advantages are: by functionalizing the prepared graphene oxide with dopamine, grafting organic silane on its surface, and introducing amino functional groups on its basis, the active sites and chemical reactivity on the surface of the graphene oxide are increased, thereby improving the dispersibility of the graphene oxide in the organic phase and the compatibility with polylactic acid, so that the graphene oxide can achieve the effect of enhancing the application performance and functionality of the graphene oxide in composite materials.

[0022] Specifically, the flake graphite powder has a particle size of 50-200 mesh and a purity of ≥99%, and is used as a carbon source basic material for preparing graphene oxide.

[0023] Specifically, the concentration of sulfuric acid is controlled at 96% to 98% to provide an acidic environment, which plays an important role in the oxidation process. The concentration of nitric acid is controlled at 68% to 70%. Potassium permanganate is of analytical grade and is used as a strong oxidant to oxidize graphite and convert it into graphite oxide. The concentration of hydrogen peroxide is controlled at 25% to 30% to remove excess potassium permanganate and terminate the oxidation reaction.

[0024] Specifically, the particle size of boron nitride nanosheets is controlled at 50-100 nm, and they serve as an auxiliary oxidant to enhance the oxidation effect and help to more fully oxidize graphite. Phosphotungstic acid serves as a catalyst to accelerate the rate of the oxidation reaction and improve the reaction efficiency. 3-Aminopropyltriethoxysilane is used to subsequently introduce amino functional groups on the surface of graphene oxide to enhance its reactivity and functionality. Disodium ethylenediaminetetraacetic acid is used to adjust the pH of the reaction system and complex some metal ions. It is also used to remove metal ion impurities in subsequent purification treatments and optimize the reaction environment. Dopamine hydrochloride, maleic anhydride, benzoyl peroxide (BPO), anhydrous toluene, dichloromethane and Tris-HCl buffer solution are used for subsequent modification steps. The Tris-HCl buffer solution is prepared from trishydroxymethylaminomethane and hydrochloric acid, and has a concentration of 10 mmol / L and a pH of 8.5.

[0025] Specifically, the pretreatment conditions in step 2 are: setting the stirring speed to 200-300 r / min, and stirring in a constant temperature water bath at 45-50° C. for 0.8-1 h.

[0026] Specifically, the deep oxidation reaction conditions in step 3 are: setting the stirring speed to 50-100 r / min, controlling the solution temperature at 0-5°C, controlling the feeding rate between 0.5-1.5 g / min, setting the constant temperature water bath temperature to 30-35°C, the water bath stirring speed to 180-200 r / min, and the reaction time to 10-12 h.

[0027] Specifically, the purification treatment conditions in step 4 are: centrifugation at a speed of 7000-8000 r / min for 8-10 minutes and stirring for 25-30 minutes.

[0028] According to Examples 1-3 of the present invention, the preparation steps were changed on the basis of the examples to obtain Comparative Examples 1-3, as shown in Table 1 below: Table 1

[0029] Graphene oxide was prepared by the embodiment and the comparative example, and the performance was compared, as shown in Table 2: Table 2

[0030] From Table 1-2 we can get: (1) From the perspective of graphene oxide yield: Examples 1-3 have relatively high yields, namely 85%, 88% and 90%, respectively, indicating that the optimized preparation conditions can effectively improve the yield, while Comparative Examples 1-3 have relatively low yields, namely 75%, 82% and 78%, respectively, indicating that changing the addition method of potassium permanganate, whether metal ion impurities are removed, and whether boron nitride nanosheets and phosphotungstic acid are added will all affect the reduction of graphene oxide yield. Among them, the one-time addition of potassium permanganate will cause the reaction system to release a large amount of heat in a short period of time, resulting in a sharp increase in local temperature. This local overheating phenomenon will cause partial areas of the graphite sheet to be over-oxidized, and even carbonized or ablated, destroying the structure of graphite, reducing the effective carbon source that can be used to form graphene oxide, and thus reducing the graphene oxide yield.

[0031] (2) From the perspective of 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 and 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 relatively low. This is mainly due to the presence of metal ion impurities in the comparative examples, which leads to insufficient reaction or more side reactions, thereby increasing the oxidation degree. Therefore, removing metal ion impurities is a key step to ensure that the oxidation degree of graphene oxide is moderate.

[0032] (3) From the perspective of thermal stability: T 5% (5% thermal weight loss temperature) were 250℃, 255℃ and 260℃, respectively, showing good thermal stability; T 5% The temperatures are 230°C, 240°C and 220°C respectively, and the thermal stability is poor, especially in Comparative Example 3. Due to the lack of boron nitride nanosheets and phosphotungstic acid, the structural defects of graphene oxide increase and the crystallinity decreases, which reduces its thermal stability.

[0033] (4) From the perspective of mechanical properties: the tensile strengths of Examples 1-3 were 150 MPa, 160 MPa, and 170 MPa, respectively, showing good mechanical properties; the tensile strengths of Comparative Examples 1-3 were 120 MPa, 130 MPa, and 110 MPa, respectively, showing poor mechanical properties, especially Comparative Example 3, which lacked boron nitride nanosheets and phosphotungstic acid, resulting in reduced structural integrity and crystallinity, increased defects, and decreased mechanical properties.

[0034] (5) From the perspective of dispersibility: Examples 1-3 have narrow particle size distributions of 100-200 nm, 90-180 nm, and 80-160 nm, respectively, indicating good dispersibility; Comparative Examples 1-3 have wide particle size distributions of 120-250 nm, 110-230 nm, and 130-280 nm, respectively, indicating poor dispersibility. In particular, Comparative Example 3 has poor structural integrity and crystallinity due to the lack of boron nitride nanosheets and phosphotungstic acid, resulting in increased defects and decreased dispersibility. (6) From the perspective of “compatibility with polylactic acid”: the compatibility indexes of Examples 1-3 are 0.90, 0.92 and 0.95, respectively, indicating good compatibility with polylactic acid; the compatibility indexes of Comparative Examples 1-3 are 0.75, 0.80 and 0.65, respectively, indicating poor compatibility, especially in Comparative Example 3. Due to the lack of boron nitride nanosheets and phosphotungstic acid, the types and quantities of surface functional groups are insufficient, the interaction with polylactic acid is weakened, and the compatibility decreases. Therefore, the introduction of boron nitride nanosheets and phosphotungstic acid is a key step in improving the compatibility of graphene oxide with polylactic acid.

[0035] Summary: By analyzing the performance test results of the embodiments and comparative examples, Examples 1-3 successfully prepared graphene oxide with high yield, moderate oxidation degree, good thermal stability, mechanical properties, dispersibility and compatibility with polylactic acid by optimizing the parameters of each step (such as the gradual addition of potassium permanganate, the removal of metal ion impurities, the introduction of boron nitride nanosheets and phosphotungstic acid, etc.); However, due to the changes in key steps in Comparative Examples 1-3, the performance of graphene oxide decreased, especially in Comparative Example 3, due to the lack of boron nitride nanosheets and phosphotungstic acid, the thermal stability, mechanical properties, dispersibility and compatibility were greatly reduced.

[0036] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for efficiently preparing and functionalizing graphene oxide, characterized in that: The following steps are involved: Step 1. Prepare raw materials: flake graphite powder, disodium ethylenediaminetetraacetic acid, boron nitride nanosheets, 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; Step 2: Pretreatment: Place the flake graphite powder in a beaker, add nitric acid dropwise, stir, and transfer to a constant temperature water bath to preliminarily oxidize the edges of the graphite to form pre-oxidized graphite; Step 3, deep oxidation reaction: transfer the pre-oxidized graphite to a three-necked flask, add sulfuric acid dropwise, place in an ice bath, add potassium permanganate three times, control the addition rate, and after addition, transfer to a constant temperature water bath to deeply oxidize the graphite; Step 4: Purification: After the reaction is completed, deionized water is added to dilute it, and hydrogen peroxide solution is added to reduce the remaining potassium permanganate. The product is centrifuged and washed to remove impurities to obtain crude graphene oxide; Step 5: Introducing boron nitride nanosheets and phosphotungstic acid: Dispersing crude graphene oxide in deionized water, adding boron nitride nanosheets and phosphotungstic acid, and performing a hydrothermal reaction after ultrasonic dispersion to improve the performance of graphene oxide. After the reaction, centrifugation and washing are performed to obtain composite graphene oxide; Step 6: Dopamine functionalization: The composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added, and the mixture is reacted at room temperature to form a polydopamine coating. After the reaction, the mixture is centrifuged and washed; Step 7: Grafting organosilane: disperse the dopamine-functionalized graphene oxide in anhydrous toluene, add 3-aminopropyltriethoxysilane, and reflux under nitrogen protection. After the reaction, centrifuge and wash; Step 8: Introducing amino functional groups: dispersing the organosilane-grafted graphene oxide in dichloromethane, adding maleic anhydride and benzoyl peroxide, stirring and reacting to introduce carboxyl groups on the surface of the graphene oxide, and centrifuging and washing after the reaction is completed; Step 9: Drying: Dry the obtained graphene oxide in a vacuum drying oven at 55-60° C. for 11-12 hours to remove the residual solvent and obtain functionalized modified graphene oxide.

2. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The flake graphite powder has a particle size of 50-200 meshes and a purity of ≥99%.

3. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The concentration of the sulfuric acid is controlled at 96% to 98%, the concentration of the nitric acid is controlled at 68% to 70%, the potassium permanganate is analytical grade, and the concentration of the hydrogen peroxide is controlled at 25% to 30%.

4. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The particle size of the boron nitride nanosheets is controlled at 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 for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The pretreatment conditions in step 2 are: setting the stirring speed to 200-300 r / min, and stirring in a constant temperature water bath at 45-50° C. for 0.8-1 h.

6. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The deep oxidation reaction conditions in step 3 are as follows: setting the stirring speed to 50-100 r / min, controlling the solution temperature at 0-5°C, controlling the feeding rate to between 0.5-1.5 g / min, setting the constant temperature water bath temperature to 30-35°C, the water bath stirring speed to 180-200 r / min, and the reaction time to 10-12 h.

7. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The purification treatment conditions in step 4 are: centrifugation at a speed of 7000-8000 r / min for 8-10 minutes and stirring for 25-30 minutes.

8. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The process of introducing boron nitride nanosheets and phosphotungstic acid in step 5: S5.

1. Disperse the crude graphene oxide in deionized water and ultrasonically disperse for 25-30 minutes; S5.

2. Add boron nitride nanosheets and phosphotungstic acid, and continue ultrasonic dispersion for 0.8-1 h to fully mix the boron nitride nanosheets, phosphotungstic acid, and graphene oxide; S5.

3. Transfer the mixed solution to a reactor and perform a hydrothermal reaction at 55-60°C for 10-12 hours; S5.

4. After the reaction is completed, cool to room temperature and centrifuge and wash again to obtain composite graphene oxide.

9. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: The dopamine functionalization process in step six is ​​as follows: the composite graphene oxide is dispersed in a Tris-HCl buffer solution, dopamine hydrochloride is added to a concentration of 1.8-2 mg / mL, and the reaction is stirred at room temperature for 20-24 hours. Dopamine undergoes self-polymerization under alkaline conditions to form a polydopamine coating on the surface of the graphene oxide.

10. The method for efficiently preparing and functionalizing graphene oxide according to claim 1, wherein: In the step seven, the organosilane grafting process is as follows: the dopamine-functionalized graphene oxide is dispersed in anhydrous toluene, 3-aminopropyltriethoxysilane is added at a mass ratio of 1:1 to the graphene oxide, and under nitrogen protection, the reaction system is heated to 105-110° C., refluxed and stirred for 5-6 hours, and the ethoxy group of the 3-aminopropyltriethoxysilane is hydrolyzed and reacts with the hydroxyl group on the surface of the graphene oxide, and the graphene oxide grafted with the organosilane is obtained after washing.

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