Preparation method and application of amino acid covalent functionalized graphene

Abstract

The invention discloses a preparation method and application of amino acid covalent functionalized graphene, and belongs to the technical field of graphene composite materials. According to the preparation method, a high-energy solid-state ball milling mode is adopted, amino acid with an amphoteric function is grafted on graphene, strong acid, strong alkali or organic solvents are not needed in the whole process, environmental pollution is avoided, and the sustainable development requirement is met; only ball milling equipment and amino acid raw materials are needed, equipment investment is low, the method is suitable for large-scale production, amino acid covalent bonding is directly achieved through ball milling shearing force, and side reactions of a traditional chemical method are avoided; after the amphoteric amino acid is grafted, the dispersion stability of the graphene in water or a polymer matrix is obviously improved, and the graphene is suitable for the fields of coatings, composite materials and the like; different amino acids are selected to adapt to specific application scenes such as water-based nanofluid and oil paint; in conclusion, the method has important application value in the fields of water-based nanofluids, coatings and polymer modification.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of graphene composite materials, and particularly relates to a preparation method of amino acid covalent functionalized graphene and application thereof. BACKGROUND

[0002] As a new material, graphene has a broad application prospect in many fields due to its excellent physical and mechanical properties, electrical conductivity, heat resistance and chemical stability. However, the surface of the complete graphene is inert, has a high specific surface area, and there is a strong van der Waals force between the graphene layers, which leads to irreversible aggregation of the graphene in the preparation and application process, and the compatibility of the graphene with polymers is poor, which seriously restricts the full play of the performance and industrial application of the graphene. Chemical or physical modification of the graphene can improve the dispersibility of the graphene in the polymer matrix and improve the performance of the polymer material.

[0003] In recent years, researchers have done a lot of work to effectively prepare functionalized graphene to improve its dispersibility and compatibility with media or matrix. Common methods include chemical oxidation-reduction method, liquid phase exfoliation method and plasma treatment method, wherein the chemical oxidation-reduction method usually needs to use strong oxidizing agents (such as concentrated sulfuric acid and potassium permanganate) or strong reducing agents (such as hydrazine hydrate), which not only has a complex process, but also introduces environmental pollutants. In addition, the liquid phase exfoliation method depends on a large amount of organic solvents or surfactants, which not only increases the difficulty of the subsequent purification process, but also may affect the intrinsic properties of the graphene; finally, the plasma treatment method needs to be carried out in a high vacuum environment, which has large equipment investment, high energy consumption, and uneven functionalization degree, and can only realize the modification of a limited area on the surface, and is not suitable for large-scale industrial application.

[0004] In summary, the existing functionalization methods have certain disadvantages, such as high cost, use of corrosive chemicals or volatile organic compounds, complex post-treatment, complex multi-step experimental process, need for high temperature conditions, and difficulty in large-scale preparation. Therefore, it is urgent to solve the above problems and meet the higher demands of the graphene composite material technical field. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a preparation method of amino acid covalent functionalized graphene and application thereof.

[0006] The purpose of the present application can be achieved by the following technical solutions.

[0007] A preparation method of amino acid covalent functionalized graphene, comprising the following steps:

[0008] S1, the graphene powder, amino acid powder and zirconium oxide beads are weighed according to the proportion, added into a ball mill tank, pre-milled at room temperature, and the raw materials are uniformly mixed and the graphene layers are initially peeled off;

[0009] S2, after pre-milling, the ball mill tank is placed in a temperature control device, and secondary ball milling is carried out at 50-80℃;

[0010] S3, after the completion of secondary ball milling, the ball mill tank is thoroughly washed with deionized water, filtered to obtain the ball milling product, dispersed in deionized water for washing and suction filtration, repeated three times, and then dried to obtain the amino acid covalently functionalized graphene.

[0011] As a further technical solution, the raw material of the graphene powder in step S1 is one of gas phase synthesis graphene, chemical vapor deposition graphene, reduced graphene oxide and mechanical exfoliation graphene.

[0012] As a further technical solution, the amino acid in step S1 is one or more of serine, threonine, glutamic acid, alanine, lysine, arginine, glycine, phenylalanine, proline, methionine, aspartic acid.

[0013] As a further technical solution, the diameter of the zirconium oxide beads in step S1 is 0.1-5mm.

[0014] As a further technical solution, the mass ratio of the graphene powder and the amino acid powder in step S1 is 50:1-5; the ball material ratio is 100:1.

[0015] As a further technical solution, the rotation speed of pre-milling in step S1 is 200-300rpm, and the time is 2-4h.

[0016] As a further technical solution, the rotation speed of secondary ball milling in step S2 is 400-600rpm, and the time is 6-36h.

[0017] As a further technical solution, the drying condition in step S3 is drying in a vacuum drying oven at 60-80℃ for 12-24h.

[0018] The amino acid modification of graphene is carried out by using a ball milling method, which effectively improves the dispersibility of graphene and the compatibility with other polymer matrices, the amino acid is an amphoteric small molecule with amino and carboxyl functional groups, and the high-energy ball milling is a simple and efficient dispersion method widely used in composite materials, the forced action (shear force and impact force) in the ball milling process enables the graphene to be in close contact or adsorption with the amino acid powder to react, the graphene material grafted with amino acid is obtained, and the heating in the secondary ball milling process can promote the covalent reaction efficiency of the active functional groups (amino and carboxyl) of the amino acid molecules and the surface defects of graphene, compared with other chemical methods for modifying graphene, the method is simple, efficient and environmentally friendly, and is more conducive to realizing large-scale production.

[0019] The beneficial effects of the present application are:

[0020] 1. The present application does not require strong acid, strong base or organic solvent throughout, avoids environmental pollution and meets the requirements of sustainable development;

[0021] 2. The present application only needs ball milling equipment and amino acid raw materials, the equipment investment is low, it is suitable for large-scale production, and the covalent bonding of amino acid is directly realized by ball milling shear force, avoiding the side reactions of traditional chemical methods;

[0022] 3. After the amphoteric amino acid grafting, the dispersion stability of graphene in water or polymer matrix is significantly improved, and it is suitable for the fields of coatings and composite materials;

[0023] 4. By selecting different amino acids (such as hydrophilic serine and hydrophobic phenylalanine), specific application scenarios such as water-based nanofluid and oil-based coating can be adapted;

[0024] In summary, the present application grafts the amphoteric amino acid on graphene by using high-energy solid-state ball milling, improves the dispersibility of graphene and the compatibility of polymer matrix, avoids the use of other chemical reagents, has the advantages of environmental protection, low cost, high feasibility, simple preparation, excellent effect, and has important application value in the fields of water-based nanofluid, coating and high polymer modification. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present application will be further described below in combination with the drawings.

[0026] Figure 1 The picture of the graphene dispersion liquid prepared by the embodiment 1 of the present application after standing at room temperature for 3 days.

[0027] Figure 2 The picture of the graphene dispersion liquid prepared by the embodiment 1 of the present application after standing at room temperature for 3 days.

[0028] Figure 3A photograph of a graphene dispersion liquid prepared from Comparative Example 1 of the present application, as a raw material, added to a conventional anticorrosive coating, after a salt water immersion test for 144 hours. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0030] Embodiment 1

[0031] A method for preparing amino acid covalently functionalized graphene comprises the following steps:

[0032] S1, 5 g of graphene powder prepared by a gas phase synthesis method, 0.1 g of serine powder and 510 g of zirconium oxide beads (with a diameter of 0.1-5 mm) are added together into a ball mill tank, pre-ball milling is performed at a rotation speed of 200 rpm at room temperature, and the time is 2 h, so as to uniformly mix the raw materials and initially peel the graphene layers;

[0033] S2, after the pre-ball milling, the ball mill tank is placed in a temperature control device, secondary ball milling is performed at a rotation speed of 400 rpm at 50℃, and the time is 6 h;

[0034] S3, after the secondary ball milling, the ball mill tank is thoroughly washed with deionized water, filtration is performed, a ball milling product is obtained, washing and suction filtration are performed again in deionized water, the washing and suction filtration are repeated three times, then drying is performed in a vacuum drying box at 60℃ for 12 h, and amino acid covalently functionalized graphene is obtained.

[0035] Embodiment 2

[0036] A method for preparing amino acid covalently functionalized graphene comprises the following steps:

[0037] S1, 5 g of reduced graphene oxide powder, 0.5 g of glutamic acid powder and 550 g of zirconium oxide beads (with a diameter of 0.1-5 mm) are added together into a ball mill tank, pre-ball milling is performed at a rotation speed of 300 rpm at room temperature, and the time is 4 h, so as to uniformly mix the raw materials and initially peel the graphene layers;

[0038] S2, after the pre-ball milling, the ball mill tank is placed in a temperature control device, secondary ball milling is performed at a rotation speed of 600 rpm at 80℃, and the time is 36 h;

[0039] S3, after the completion of secondary ball milling, the ball milling tank is washed thoroughly with deionized water, filtered to obtain the ball milling product, which is dispersed in deionized water again, washed, and suction-filtered, and the above steps are repeated three times, and then dried in a vacuum drying box at 80°C for 24h to obtain the amino acid covalently functionalized graphene.

[0040] Comparative Example 1

[0041] The graphene powder prepared by the gas phase synthesis method without modification is used.

[0042] The graphene dispersion liquid is prepared by dispersing Example 1, 2 and Comparative Example 1 with water as the solvent, wherein the graphene dispersion liquid prepared in Example 1 is left to stand at room temperature for 3 days, and the results are shown in Table 1. Figure 1 Figure 1 It can be seen that the dispersion liquid does not have the stratification phenomenon after standing for 3 days, which indicates that the amino acid covalently functionalized graphene has good dispersibility.

[0043] The above dispersion liquid is added as a raw material into a traditional anticorrosive coating (polyurethane system), and the anticorrosive performance and thermal conductivity of the coating are measured, and the measured results are shown in Table 1.

[0044] Table 1

[0045] Test item Salt water immersion resistance time / h Thermal conductivity / W / (m K) Example 1 2000 5 Example 2 1700 4.5 Comparative Example 1 144 1.7

[0046] Figure 2 and 3 are respectively the coating surface photos of Example 1 and Comparative Example 1 after being soaked in salt water for 144h, and Figure 3 It can be seen that the coating surface of Comparative Example 1 is seriously foamed after being soaked in salt water for 144h, while Figure 2 It can be seen that the coating surface of Example 1 has no change after being soaked in salt water for 144h, and the anticorrosive performance is good; in addition, it can be seen from Table 1 that the thermal conductivity of Example 1 and 2 is better, so it can be inferred that the dispersibility of the amino acid covalently functionalized graphene in the coating of Example 1 and 2 is better.

[0047] The amino acid covalently functionalized graphene powder prepared in Example 1 is dispersed again with water as the solvent to prepare graphene water-based nanofluids with the graphene content of 1%, 0.5% and 0.1% respectively, and the thermal conductivity thereof is tested, and the measured results are shown in Table 2.

[0048] Table 2

[0049]

[0050] It can be seen from Table 2 that the thermal conductivity of the amino acid covalently functionalized graphene prepared in Example 1 of the present application is significantly improved with the increase of the content.

[0051] ​In the description, references to "one embodiment," "an example," "certain examples" etc. mean that the particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of an item in various examples or embodiments is not necessarily indicative of a frequency of occurrence in the various examples or embodiments. Moreover, descriptions of well-known methods associated are omitted so as not to obscure the disclosure.

[0052] The foregoing merely illustrates the principles of the application. Various modifications and adaptations will occur to those skilled in the art after consideration of the preceding description. All such modifications and adaptations employing the principles of the application are intended to be within the scope of the claims.

Claims

1. A method for preparing amino acid covalently functionalized graphene, characterized in that, Includes the following steps: S1. Add graphene powder, amino acid powder and zirconium oxide beads together into a ball mill jar and pre-mill at room temperature; S2. After pre-ball milling, place the ball milling jar in a temperature control device and perform secondary ball milling at 50-80℃; S3. After the second ball milling is completed, the ball mill jar is thoroughly cleaned with deionized water, filtered, and the ball milling product is obtained. It is then dispersed again in deionized water for washing and filtration, repeated three times, and then dried to obtain amino acid covalently functionalized graphene.

2. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, The raw material for the graphene powder in step S1 is one of the following: graphene synthesized by vapor phase, graphene produced by chemical vapor deposition, graphene reduced oxide, and graphene produced by mechanical exfoliation.

3. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, The amino acid in step S1 is one or more of the following: serine, threonine, glutamic acid, alanine, lysine, arginine, glycine, phenylalanine, proline, methionine, and aspartic acid.

4. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, In step S1, the diameter of the zirconia beads is 0.1-5 mm.

5. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, In step S1, the mass ratio of graphene powder to amino acid powder is 50:1-5; the ball-to-powder ratio is 100:

1.

6. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, In step S1, the pre-ball milling speed is 200-300 rpm and the time is 2-4 hours.

7. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, In step S2, the secondary ball milling speed is 400-600 rpm, and the time is 6-36 h.

8. The method for preparing amino acid covalently functionalized graphene according to claim 1, characterized in that, The drying conditions in step S3 are drying in a vacuum drying oven at 60-80℃ for 12-24 hours.

9. The application of amino acid covalently functionalized graphene prepared by the method according to claim 1 in the fields of water-based nanofluids, coatings and polymer modification.

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