Preparation method of oil-soluble three-dimensional graphene

Abstract

This application relates to the technical field of nanomaterials, and specifically discloses a preparation method of oil-soluble three-dimensional graphene. The preparation method of the oil-soluble three-dimensional nanographene provided by this application includes the following steps: pretreatment of the metal substrate, chemical vapor deposition, chemical vapor growth, oxidation, and alkylation treatment; the specific steps of chemical vapor deposition are: placing the pretreated metal substrate in a tubular furnace, introducing a gaseous carbon source and hydrogen for chemical vapor deposition to obtain two-dimensional graphene; the specific steps of chemical vapor growth are: introducing a gaseous carbon source and hydrogen into the tubular furnace for chemical vapor growth to obtain three-dimensional graphene; the specific steps of oxidation are: oxidizing the graphene to obtain graphene oxide. The preparation method of the oil-soluble three-dimensional nanographene provided by this application can greatly improve the solubility and dispersibility of graphene in non-polar solvents, making it easy to be compounded with other materials, thereby expanding its application scope.

Description

Technical Field

[0001] This application relates to the technical field of nanomaterials, and specifically relates to a preparation method of oil-soluble three-dimensional graphene. Background Art

[0002] In recent years, with the in-depth research of nanomaterials, due to its unique physical and chemical properties, graphene has shown broad application prospects in many fields. Graphene has excellent electrical conductivity, thermal conductivity and mechanical strength, making it have great potential in the fields of electronic devices, energy storage, composite materials, etc. However, in practical applications, the solubility and dispersibility of traditional two-dimensional graphene are poor, which greatly limits its application in many liquid media.

[0003] In order to improve the solubility and dispersibility of graphene, researchers have developed a series of methods. Common methods include chemical modification and surface modification. For example, various functional groups are introduced onto the graphene surface through chemical reduction methods, thereby enhancing its hydrophilicity or lipophilicity. In addition, there are also physical methods such as ultrasonic treatment and microemulsion method to improve the dispersibility of graphene. Although these methods can improve the solubility and dispersibility of graphene to a certain extent, they usually sacrifice some physical and chemical properties of graphene, especially its structural integrity and electrical conductivity.

[0004] Therefore, how to further improve its oil solubility and dispersion stability while maintaining the original excellent properties of graphene has become a technical problem to be solved urgently. Summary of the Invention

[0005] In order to improve the oil solubility and dispersion stability of graphene, this application provides a preparation method of oil-soluble three-dimensional graphene.

[0006] In the first aspect, this application provides a preparation method of oil-soluble three-dimensional graphene, adopting the following technical solution:

[0007] A preparation method of oil-soluble three-dimensional graphene includes the following steps: pretreatment of the metal substrate, chemical vapor deposition, chemical vapor growth, oxidation and alkylation treatment;

[0008] Chemical vapor deposition: Place the pretreated metal substrate in a tube furnace, and introduce a gaseous carbon source and hydrogen for chemical vapor deposition to obtain two-dimensional graphene; the gas volume flow rate of the gaseous carbon source is 5 - 10 sccm, and the gas volume flow rate of hydrogen is 40 - 50 sccm;

[0009] Chemical vapor growth: Introduce a gaseous carbon source and hydrogen into the tube furnace for chemical vapor growth to obtain three-dimensional graphene; the gas volume flow rate of the gaseous carbon source is 10 - 15 sccm, and the gas volume flow rate of hydrogen is 50 - 100 sccm;

[0010] Oxidation: The graphene is oxidized to obtain graphene oxide.

[0011] This application provides a preparation method of oil-soluble three-dimensional graphene. First, the metal substrate is pretreated to remove the oxide layer on the surface of the metal matrix, ensuring its surface cleanliness and flatness, which is beneficial to the uniform growth of graphene during the subsequent chemical vapor deposition process. Then, by controlling the volume flow rates of specific gaseous carbon sources and hydrogen, two-dimensional graphene is successfully grown. Subsequently, gaseous carbon sources and hydrogen are introduced for chemical vapor growth, enabling the two-dimensional graphene to grow three-dimensionally on the basis of functional groups to form a three-dimensional graphene structure. Then, a strong oxidant is used to oxidize the three-dimensional graphene, effectively destroying its planar structure and forming abundant functional groups such as carboxyl, hydroxyl, and epoxy groups on the surface of the graphene. Finally, the graphene oxide is alkylated, and long-chain alkyl groups are introduced onto the surface of the three-dimensional graphene through covalent bond connection, thereby significantly improving the oil solubility and dispersion stability of the three-dimensional graphene. The preparation method provided by this application not only ensures the structural integrity and high quality of the three-dimensional graphene but also improves its solubility and dispersion stability in non-polar solvents, laying a solid foundation for the application of graphene in a wider range of fields.

[0012] Optionally, the oxidizing reagent used in the oxidation treatment is potassium permanganate and hydrogen peroxide.

[0013] Optionally, the oxidizing reagent is potassium permanganate and hydrogen peroxide with a volume ratio of 1:(2 - 4).

[0014] In this application, by treating the three-dimensional graphene with an oxidizing reagent, abundant functional groups such as carboxyl, hydroxyl, and epoxy groups can be formed on the surface of the graphene, facilitating subsequent alkylation treatment. Specifically, potassium permanganate mainly acts on the edges of the graphene, facilitating the start of the oxidation reaction; while hydrogen peroxide reacts with the carbon in the central part of the graphene sheets. Through experimental exploration in this application, it is found that further using potassium permanganate and hydrogen peroxide with the above ratio as the oxidizing reagent results in more and more fully exposed functional groups such as carboxyl, hydroxyl, and epoxy groups on the surface of the prepared graphene oxide, and better dispersion stability of the three-dimensional graphene in non-polar solvents.

[0015] In some embodiments, the volume ratio of potassium permanganate to hydrogen peroxide can be 1:(1 - 1.5), 1:(1 - 2), 1:(1 - 2.5), 1:(1 - 3), 1:(1 - 3.5), 1:(1 - 4), 1:(1.5 - 2), 1:(1.5 - 2.5), 1:(1.5 - 3), 1:(1.5 - 3.5), 1:(1.5 - 4), 1:(2 - 2.5), 1:(2 - 3), 1:(2 - 3.5), 1:(2 - 4), 1:(2.5 - 3), 1:(2.5 - 3.5), 1:(2.5 - 4), 1:(3 - 3.5), 1:(3 - 4), or 1:(3.5 - 4).

[0016] In a specific embodiment, the volume ratio of potassium permanganate to hydrogen peroxide can also be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4.

[0017] Optionally, the temperature of the chemical vapor deposition and chemical vapor growth is 1000 - 1200 °C.

[0018] Optionally, the gaseous carbon source is selected from one or more of methane, ethylene, and acetylene.

[0019] Optionally, the alkylating agent used for the alkylation treatment is a long-chain thiol compound.

[0020] Optionally, the long-chain thiol compound is selected from one or more of docosyl mercaptan, octadecyl mercaptan, hexadecyl mercaptan, tetradecyl mercaptan, and dodecyl mercaptan.

[0021] Optionally, the specific steps of the alkylation treatment are as follows: dissolve a dispersant and an alkylating agent in an organic solvent, then add graphene oxide, and stir and react at a rotation speed of 4000 - 6000 rpm for 10 - 12 h, and obtain oil-soluble three-dimensional graphene through suction filtration, washing, and drying.

[0022] In the present application, alkylating graphene oxide can introduce long-chain alkyl groups on the surface of graphene, greatly improving the solubility and dispersibility of graphene in non-polar solvents. Through experimental exploration, it is found in the present application that the rotation speed and time in the alkylation treatment step will affect the effect of the alkylation treatment. By controlling the rotation speed and time of the alkylation treatment within the above ranges, the obtained three-dimensional graphene has good solubility and excellent dispersion stability in non-polar solvents.

[0023] In some embodiments, the stirring speed can be 4000 - 4500 rpm, 4000 - 5000 rpm, 4000 - 5500 rpm, 4000 - 6000 rpm, 4500 - 5000 rpm, 4500 - 5500 rpm, 4500 - 6000 rpm, 5000 - 5500 rpm, 5000 - 6000 rpm or 5500 - 6000 rpm.

[0024] In some specific embodiments, the stirring speed can also be 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm or 6000 rpm.

[0025] In some specific embodiments, the stirring time can be 10 h or 12 h.

[0026] Optionally, the specific steps of the pretreatment of the metal substrate are: immersing the metal substrate in glacial acetic acid for 20 - 30 min to obtain the pretreated metal substrate.

[0027] In a second aspect, the present application provides an oil-soluble three-dimensional graphene prepared by the preparation method of oil-soluble three-dimensional graphene.

[0028] In summary, the present application has the following beneficial effects:

[0029] 1. The present application provides a preparation method of oil-soluble three-dimensional graphene. This preparation method not only ensures the structural integrity and high quality of the three-dimensional graphene, but also can greatly improve the solubility and dispersibility of graphene in non-polar solvents, laying a solid foundation for the application of graphene in a wider range of fields.

[0030] 2. The present application further uses potassium permanganate and hydrogen peroxide with a volume ratio of 1:(2 - 4) as oxidation reagents, which can expose more and more fully the functional groups such as carboxyl, hydroxyl and epoxy groups on the surface of graphene, and the dispersion stability of the three-dimensional graphene in non-polar solvents is better.

[0031] 3. In the present application, by controlling the rotation speed of the alkylation treatment within the range of 4000 - 6000 rpm and the stirring time within the range of 10 - 12 h, the obtained three-dimensional graphene has good solubility and excellent dispersion stability in non-polar solvents. Specific Embodiments

[0032] A preparation method of oil-soluble three-dimensional graphene includes the following steps:

[0033] (1) Pretreatment of the metal substrate: Immerse the metal substrate in glacial acetic acid for 20 - 30 min to remove the oxide film on the surface;

[0034] (2) Chemical vapor deposition: Place the pretreated metal substrate in a tube furnace, heat it up to 700 - 900 °C, then introduce hydrogen and methane. The volumetric flow rate of hydrogen is 200 - 230 sccm, the volumetric flow rate of methane is 50 - 60 sccm, and the gas introduction time is 10 - 20 min. Then heat it up to 1000 - 1200 °C and introduce a gaseous carbon source and hydrogen. The volumetric flow rate of the gaseous carbon source is 5 - 10 sccm, and the volumetric flow rate of hydrogen is 40 - 50 sccm. At this time, graphene begins to grow on the surface of the metal substrate until the graphene grows to 3 - 5 layers. The gaseous carbon source is selected from one or more of methane, ethylene, and acetylene.

[0035] (3) Chemical vapor growth: Then heat the tube furnace to 1000 - 1200 °C and introduce a gaseous carbon source and hydrogen. The volumetric flow rate of the gaseous carbon source is 10 - 15 sccm, and the volumetric flow rate of hydrogen is 50 - 100 sccm. At this time, three-dimensional graphene begins to deposit and grow. When the thickness reaches 8 - 10 nm, cool it down to room temperature, take out the metal substrate, and obtain three-dimensional graphene. The gaseous carbon source is selected from one or more of methane, ethylene, and acetylene.

[0036] (4) Oxidation: Assemble a 250 mL reaction flask in an ice-water bath, add 20 mL of concentrated sulfuric acid, add a solid mixture of 2 g of the three-dimensional graphene obtained in step (3) and 1 g of sodium nitrate under stirring, and then add 6 g of the oxidation reagent in batches. Control the reaction temperature not to exceed 20 °C and stir the reaction for 30 min. Then heat it up to 35 °C and continue stirring for 30 min. Then slowly add 20 mL of deionized water, continue stirring for 20 min, and then add 2 g of sodium sulfite. Filter while it is hot, and wash it with 5% HCl solution and deionized water until no sulfate is detected in the filtrate. Finally, place the filter cake in a vacuum drying oven at 60 °C and dry it thoroughly to obtain graphene oxide. The oxidation reagent is potassium permanganate and hydrogen peroxide.

[0037] (5) Alkylation treatment: Dissolve the SDS dispersant and the alkylation reagent in an organic solvent, then add it to the graphene oxide obtained in step (4), and stir and react at a rotation speed of 4000 - 6000 rpm for 10 - 12 h. After suction filtration, washing, and drying, oil-soluble three-dimensional graphene is obtained. The alkylation reagent is a long-chain thiol compound, and the organic solvent is 75% ethanol. Further, the alkylation reagent is selected from one or more of docosyl mercaptan, octadecyl mercaptan, hexadecyl mercaptan, tetradecyl mercaptan, and dodecyl mercaptan.

[0038] The raw materials, reagents, solvents, etc. used in this application can all be obtained through commercial purchase.

[0039] The following further elaborates on this application in combination with examples and performance detection tests. Example 1

[0040] Example 1 provides a method for preparing oil-soluble three-dimensional graphene, comprising the following steps:

[0041] (1) Pretreatment of the metal substrate: Immerse the copper substrate in glacial acetic acid for 30 min to remove the surface oxide film.

[0042] (2) Chemical vapor deposition: Place the pretreated metal substrate in a tubular furnace, heat it to 800 °C, then introduce hydrogen and methane. The gas flow rate of hydrogen is 220 sccm, the volume flow rate of methane is 50 sccm, and the gas introduction time is 15 min; then heat it to 1100 °C and introduce methane and hydrogen. The volume flow rate of methane is 5 sccm, and the gas flow rate of hydrogen is 40 sccm. At this time, graphene begins to grow on the surface of the metal substrate until three layers of graphene are grown.

[0043] (3) Chemical vapor growth: Then heat the tubular furnace to 1100 °C and introduce methane and hydrogen. The volume flow rate of methane is 10 sccm, and the gas flow rate of hydrogen is 80 sccm; at this time, three-dimensional graphene begins to deposit and grow. When the thickness reaches 10 nm, cool it to room temperature, take out the metal substrate, and obtain three-dimensional graphene.

[0044] (4) Oxidation: Assemble a 250 mL reaction flask in an ice-water bath, add 20 mL of concentrated sulfuric acid, add a solid mixture of 2 g of the three-dimensional graphene obtained in step (3) and 1 g of sodium nitrate under stirring, and then add 6 g of an oxidation reagent (a 1:1 volume ratio of potassium permanganate and hydrogen peroxide) in 3 batches; control the reaction temperature not to exceed 20 °C and stir for 30 min; then heat it to 35 °C and continue stirring for 30 min; then slowly add 20 mL of deionized water, continue stirring for 20 min, and then add 2 g of sodium sulfite; filter while it is hot, and wash with 5% HCl solution and deionized water until no sulfate is detected in the filtrate; finally, place the filter cake in a vacuum drying oven at 60 °C for sufficient drying to obtain oxidized graphene oxide.

[0045] (5) Alkylation treatment: Mix SDS, dodecyl mercaptan, and 75% ethanol in a weight ratio of 1:1:20. Take 20 mL of the above mixture and add it to 1 g of the graphene oxide obtained in step (4). Stir and react at a rotation speed of 5000 rpm for 12 h. After suction filtration, washing, and drying, oil-soluble three-dimensional graphene is obtained.

[0046] Examples 2-7

[0047] Examples 2-7 respectively provide a method for preparing oil-soluble three-dimensional graphene

[0048] The differences between the above embodiments and Embodiment 1 are as follows: the type and ratio of the oxidation reagent used in the oxidation step are shown in Table 1 below.

[0049] Table 1 Types and ratios of oxidants used in the preparation methods provided in Embodiments 2-7

[0050]

[0051] Embodiments 8-12

[0052] Embodiments 8-12 respectively provide a preparation method of oil-soluble three-dimensional graphene.

[0053] The differences between the above embodiments and Embodiment 5 are as follows: the stirring speed and time in the alkylation treatment step are shown in Table 2 below.

[0054] Table 2 Stirring speed and time in the alkylation treatment step in Embodiments 5, 8-12

[0055] Comparative Example 1

[0056] Comparative Example 1 provides a preparation method of oil-soluble graphene oxide, including the following steps:

[0057] Add 3.00 g of graphene oxide and 210 mL of N,N-dimethylformamide to a 1000 mL fluorination bottle. First, stir and disperse for dissolution on a high-speed stirrer (rotation speed is 8000 rpm), and then break it in an ultrasonic crusher for 3 h (ultrasonic power is 350 W); then transfer the solution into a 1000 mL four-necked flask, add 1.00 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 8.00 g of dicyclohexylcarbodiimide, and 9.00 g of octadecylamine, and stir and react at 25 °C for 24 h. Stop stirring, centrifuge the reaction solution, wash it several times with deionized water, and freeze-dry to obtain modified oil-soluble graphene oxide. Comparative Example 2

[0058] Comparative Example 2 provides a preparation method of three-dimensional graphene, including the following steps:

[0059] (1) Preparation of three-dimensional graphene: Immerse the copper foil substrate in glacial acetic acid for 30 min to remove the surface oxide film; place the copper foil substrate in a tube furnace for reaction. First, raise the temperature to 1000 °C and then introduce Ar and H2, with the gas flow rates being 30 sccm and 50 sccm respectively, and the time being 40 min; then introduce CH4 and H2 into the reaction furnace, with the gas flow rates both being 15 sccm, and the reaction temperature being 1000 °C; then introduce Ar and H2 into the reaction furnace again and gradually cool down to room temperature, with the gas flow rates both being 30 sccm;

[0060] (2)Transfer of three-dimensional graphene: Take out the copper foil substrate with three-dimensional graphene on its surface prepared in step (2) from the reaction furnace, spin-coat a layer of PMMA on the surface of the three-dimensional graphene, and cure it on a hot plate at 150 °C for 1 h; Immerse the copper foil substrate with PMMA and three-dimensional graphene in a 1 mol / L ferric chloride solution for 1 h to completely etch the copper foil substrate. After etching, the three-dimensional graphene with PMMA floats in the solution. Take out the etched three-dimensional graphene with PMMA and soak and wash it repeatedly in deionized water, with each soaking time being 20 min, to remove the remaining etching agent. Take out the three-dimensional graphene with PMMA, dry the surface moisture with nitrogen, and dry it at room temperature.

[0061] (3)Removal of the PMMA layer: Under the condition of vacuum heat treatment at 350 °C, remove the PMMA layer compounded on the surface of the three-dimensional graphene by thermal degradation to obtain three-dimensional graphene.

[0062] Performance detection test

[0063] Test the dispersibility of the oil-soluble three-dimensional graphene obtained in Examples 1-12, the oil-soluble graphene oxide obtained in Comparative Example 1, and the three-dimensional graphene obtained in Comparative Example 2 in non-polar solvents. The results are shown in Table 3 below.

[0064] Test method: Prepare graphene dispersions with a concentration of 0.2 mg / mL using non-polar solvents (ethyl acetate, toluene, chloroform) respectively. Ultrasonically disperse the graphene dispersions for 1 h and then let them stand. Observe the sedimentation of the graphene dispersions at 10 min after ultrasonication, 1 day of standing, 7 days of standing, and 14 days of standing respectively. Classify the sedimentation degree of the graphene dispersions as follows:

[0065] A—Indicates uniform dispersion and no sedimentation;

[0066] B—Indicates a small amount of sedimentation, with a turbid upper layer and a large amount of graphene;

[0067] C—Indicates most of the sedimentation, with a relatively turbid upper layer and a small amount of graphene;

[0068] D—Indicates nearly complete sedimentation, with a clear upper layer and basically no graphene;

[0069] E—Indicates complete sedimentation, with a clear upper layer and no graphene.

[0070] Table 3 Detection results of the dispersion performance of graphene obtained in Examples 1-12 and Comparative Examples 1-2

[0071]

[0072] According to the detection results in Table 3, the oil-soluble three-dimensional graphene provided in Examples 1-12 can be dissolved in non-polar solvents such as ethyl acetate, toluene, and chloroform, and still maintain excellent dispersion performance after standing for 1 day, and the dispersion performance is good after standing for 14 days. However, for the oil-soluble graphene oxide provided in Comparative Example 1, after being dissolved in non-polar solvents such as ethyl acetate, toluene, and chloroform and standing for 7 days, its dispersion performance began to decrease significantly, and the graphene was close to complete sedimentation or completely sedimented; for the three-dimensional graphene provided in Comparative Example 2, after being dissolved in toluene and standing for 1 day, and being dissolved in ethyl acetate and chloroform and standing for 7 days, it was already close to complete sedimentation. Therefore, it shows that the preparation method of the oil-soluble three-dimensional graphene provided in this application can obtain oil-soluble three-dimensional graphene with good solubility and excellent dispersion stability, and it can be stably dispersed in non-polar solvents for at least 7 days.

[0073] From the detection results of Examples 1-7, it can be seen that the oil-soluble three-dimensional graphene obtained in Example 1 was dissolved in three non-polar solvents, and the sedimentation situation within 7 days was A-B, but the sedimentation situation at 14 days reached C; the oil-soluble three-dimensional graphene obtained in Example 2 had sedimentation situations of A-B after being dissolved in ethyl acetate and chloroform for 14 days, but the sedimentation situation was C when dissolved in toluene for 14 days; while the oil-soluble three-dimensional graphene obtained in Examples 3-7 had sedimentation situations of A-B within 14 days after being dissolved in three non-polar solvents. Therefore, it shows that by further using potassium permanganate and hydrogen peroxide with a volume ratio of 1:(2-4) as oxidation reagents in this application, the prepared oil-soluble three-dimensional graphene has excellent dispersion stability in various polar solvents.

[0074] From the detection results of Example 5 and Examples 8-12, it can be seen that the oil-soluble three-dimensional graphene obtained in Example 5 and Examples 9-10 was uniformly dispersed and had no sedimentation after being dissolved in ethyl acetate and chloroform for 14 days, and there was a small amount of sedimentation when dissolved in toluene for 14 days. Therefore, it shows that by further controlling the stirring speed in the alkylation treatment step within the range of 4500-5500 rpm in this application, the prepared oil-soluble three-dimensional graphene has better solubility and better dispersion stability.

[0075] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for preparing oil-soluble three-dimensional graphene, characterized in that: The following steps are involved: Metal substrate pretreatment, chemical vapor deposition, chemical vapor growth, oxidation and alkylation treatment; Chemical vapor deposition: placing the pretreated metal substrate in a tube furnace, introducing a gaseous carbon source and hydrogen for chemical vapor deposition to obtain two-dimensional graphene; the gaseous carbon source has a ventilation volume flow rate of 5-10 sccm, and the hydrogen has a ventilation volume flow rate of 40-50 sccm; Chemical vapor growth: introducing a gaseous carbon source and hydrogen into a tubular furnace for chemical vapor growth to obtain three-dimensional graphene; the gaseous carbon source has a ventilation volume flow rate of 10-15 sccm, and the hydrogen has a ventilation volume flow rate of 50-100 sccm; Oxidation: oxidizing the graphene to obtain graphene oxide; Alkylation treatment: dissolve the dispersant and the alkylating agent in an organic solvent, then add graphene oxide, stir and react at a speed of 4000-6000 rpm for 10-12 hours, and obtain oil-soluble three-dimensional graphene through suction filtration, washing and drying.

2. The method for preparing oil-soluble three-dimensional graphene according to claim 1, characterized in that: The oxidizing agents used in the oxidation treatment are potassium permanganate and hydrogen peroxide.

3. The method for preparing oil-soluble three-dimensional graphene according to claim 2, characterized in that: The oxidizing agent is potassium permanganate and hydrogen peroxide in a volume ratio of 1:(2-4).

4. The method for preparing oil-soluble three-dimensional graphene according to claim 1, characterized in that: The temperature of the chemical vapor deposition and chemical vapor growth is 1000-1200°C.

5. The method for preparing oil-soluble three-dimensional graphene according to claim 1, characterized in that: The gaseous carbon source is selected from one or more of methane, ethylene and acetylene.

6. The method for preparing oil-soluble three-dimensional graphene according to claim 1, characterized in that: The alkylating agent is selected from one or more of docosyl mercaptan, octadecyl mercaptan, hexadecyl mercaptan, tetradecyl mercaptan and dodecyl mercaptan.

7. The method for preparing oil-soluble three-dimensional graphene according to claim 1, characterized in that: The specific steps of the metal substrate pretreatment are: soaking the metal substrate in glacial acetic acid for 20-30 minutes to obtain a pretreated metal substrate.

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