A method for exfoliating two-dimensional layered nanomaterials

Abstract

This invention belongs to the field of nanomaterials, specifically relating to a method for exfoliating two-dimensional layered nanomaterials. The method involves ultrasonically dispersing layered nanomaterial powder in a precursor solution, controlling the solution pH, allowing it to stand, filtering, and collecting the filtrate. The precursor-two-dimensional layered nanomaterial mixture is then heated in a water bath, the solution pH is adjusted, stirred, centrifuged at high speed, and the filtrate is discarded. Following vacuum distillation, washing, and drying, the two-dimensional layered nanomaterials are obtained. The layered nanomaterials refer to graphitic carbon nitride nanosheets. The precursor is prepared by the following steps: a 1 mol / L solution of tert-butanol and tert-butylamine is prepared as a carrier; N,N-dimethylformamide and dimethyl sulfoxide are mixed uniformly; benzoyl peroxide is added slowly while stirring to the carrier prepared in step A1 to obtain the precursor. The two-dimensional graphitic carbon nitride nanosheets obtained by this invention have the characteristics of high yield and large specific surface area.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials, and specifically relates to a method for exfoliating two-dimensional layered nanomaterials. Background Technology

[0002] Graphitic carbon nitride nanosheets are materials composed of carbon and nitrogen, possessing a unique layered structure. Their molecular structure is similar to graphene, making them nanomaterials with photocatalytic and electrocatalytic properties. Two-dimensional graphitic carbon nitride nanosheets exhibit several unique properties, such as short charge / mass transfer pathways, abundant reaction sites, and ease of functionalization. Graphitic carbon nitride nanosheets are widely used in energy conversion and storage applications.

[0003] Common exfoliation methods in existing technologies include chemical vapor deposition (CVD), mechanical exfoliation, and liquid phase exfoliation. CVD typically requires high temperatures, which can lead to thermal expansion and lattice defects in the material. Furthermore, CVD requires precise gas control and reaction conditions, including control of parameters such as gas flow rate, temperature, and pressure. The presence of impurity gases during CVD can also contaminate the material, affecting its performance and quality. Mechanical exfoliation usually uses mechanical force to peel graphitic carbon nitride nanosheets from their substrate; this process is time-consuming, labor-intensive, and has relatively low yields, resulting in uneven thickness of the obtained graphitic carbon nitride nanosheets. Liquid phase exfoliation, compared to other methods, is relatively simple and easy to operate, requiring no high temperatures or complex equipment. However, traditional liquid phase exfoliation techniques suffer from incomplete exfoliation, low yields, and the adhesion of the exfoliating agent to the surface of the graphitic carbon nitride nanosheets. Summary of the Invention

[0004] The purpose of this invention is to provide a method for exfoliating two-dimensional layered nanomaterials. The method involves ultrasonically dispersing layered nanomaterial powder in a precursor solution, controlling the pH value of the solution, allowing it to stand, filtering it, and keeping the filtrate for later use. The precursor-two-dimensional layered nanomaterial is then heated in a water bath, the pH value of the solution is adjusted, stirred, centrifuged at high speed, the filtrate is discarded, and the material is post-processed by vacuum distillation, washing, drying, etc., to obtain the two-dimensional layered nanomaterials.

[0005] The technical problem to be solved by this invention is: incomplete stripping, low yield, and the stripping agent adhering to the surface of graphitic carbon nitride nanosheets.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for exfoliating two-dimensional layered nanomaterials includes the following steps:

[0008] S1. The layered nanomaterial powder is ultrasonically dispersed in the precursor solution, the pH value of the solution is controlled at 11-12, the solution is allowed to stand for 20-30 minutes, filtered, and the filtrate is used for later use to obtain the precursor-two-dimensional layered nanomaterial.

[0009] S2. Heat the precursor-two-dimensional layered nanomaterial in a water bath to 40℃-45℃, adjust the pH of the solution to 3-4, stir for 40min-60min, centrifuge at high speed, discard the filtrate, and then perform post-treatment such as vacuum distillation, washing, and drying to obtain the two-dimensional layered nanomaterial.

[0010] In step S1, the layered nanomaterials refer to graphitic carbon nitride nanosheets.

[0011] In step S1, the precursor refers to a solvent using a mixed solution of tert-butanol and tert-butamine as a carrier and N,N-dimethylformamide-dimethyl sulfoxide as a stripping agent.

[0012] Furthermore, the precursor in step S1 is obtained through the following steps:

[0013] A1. Prepare a 1 mol / L solution of tert-butanol and tert-butamine as a carrier;

[0014] A2. Mix N,N-dimethylformamide and dimethyl sulfoxide evenly, add benzoyl peroxide, control the temperature at 50℃-55℃, and react under nitrogen protection in the dark for 30min-40min. Remove impurities by vacuum distillation to obtain the N,N-dimethylformamide-dimethyl sulfoxide complex system.

[0015] A3. The N,N-dimethylformamide-dimethyl sulfoxide complex system is slowly added to the carrier prepared in step A1 while stirring, and stored at low temperature in the dark to obtain the precursor.

[0016] In step S1, the high-speed centrifugation speed is 4000rpm-5000rpm and the centrifugation time is 30min-40min.

[0017] In step A1, the mass ratio of tert-butanol to tert-butamine is (1-2):(3-6).

[0018] In step A2, the ratio of N,N-dimethylformamide, dimethyl sulfoxide, and benzoyl peroxide is (10-15) mL: (10-15) mL: (2-4) g.

[0019] In step A3, the ratio of the N,N-dimethylformamide-dimethyl sulfoxide complex system to the carrier is (8-10):(15-20).

[0020] The beneficial effects of this invention are:

[0021] 1. In the technical solution of the present invention, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are oxidized to N,N-dimethylformamide-N-oxide (DMF-N-oxide) and dimethyl sulfoxide-oxide (DMSO-N-oxide) respectively under the action of an oxidant, forming a DMF-DMSO complex. The oxygen atoms in the DMF-DMSO complex will undergo nucleophilic substitution reaction with the carbon atoms on the surface of the graphitic carbon nitride nanosheets to form carbon-oxygen bonds. In the form of covalent bonds, the graphitic carbon nitride nanosheets overcome the van der Waals forces between layers, thereby achieving the effect of complete exfoliation.

[0022] 2. In the technical solution of the present invention, the surface of the exfoliated graphitic carbon nitride nanosheets is attached with a precursor. Under acidic conditions, heating causes the carbon-oxygen bonds to break, and at the same time, the DMF-DMSO complex disintegrates and decomposes into small molecule impurities such as methyl mercaptan, formaldehyde, dimethyl sulfide and methanesulfonic acid. After purification treatment such as vacuum distillation and centrifugal filtration, high-purity graphitic carbon nitride nanosheets are obtained. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] The precursor is prepared by the following steps:

[0026] A1. Prepare a 1 mol / L solution of tert-butanol and tert-butylamine in a mass ratio of 1:3 as a carrier;

[0027] A2. Mix 10 mL of N,N-dimethylformamide and 10 mL of dimethyl sulfoxide evenly, add 2 g of benzoyl peroxide, control the temperature at 55℃, react under nitrogen protection and in the dark for 35 min, remove impurities by vacuum distillation to obtain the N,N-dimethylformamide-dimethyl sulfoxide complex system.

[0028] A3. Add 8 mL of the N,N-dimethylformamide-dimethyl sulfoxide complex system slowly to the 15 mL of the carrier prepared in step A1 while stirring, and store at low temperature in the dark to obtain the precursor.

[0029] Example 2

[0030] The precursor is prepared by the following steps:

[0031] A1. Prepare a 1 mol / L solution of tert-butanol and tert-butylamine in a mass ratio of 1:3 as a carrier;

[0032] A2. Mix 12.5 mL of N,N-dimethylformamide and 12.5 mL of dimethyl sulfoxide evenly, add 3 g of benzoyl peroxide, control the temperature at 55℃, and react in the dark for 35 min under nitrogen protection. Remove impurities by vacuum distillation to obtain the N,N-dimethylformamide-dimethyl sulfoxide complex system.

[0033] A3. While stirring, slowly add 9 mL of the N,N-dimethylformamide-dimethyl sulfoxide complex system to the 17.5 mL of the carrier prepared in step A1, and store it at low temperature in the dark to obtain the precursor.

[0034] Example 3

[0035] The precursor is prepared by the following steps:

[0036] A1. Prepare a 1 mol / L solution of tert-butanol and tert-butylamine in a mass ratio of 1:3 as a carrier;

[0037] A2. Mix 15 mL of N,N-dimethylformamide and 15 mL of dimethyl sulfoxide evenly, add 4 g of benzoyl peroxide, control the temperature at 55℃, react under nitrogen protection and in the dark for 35 min, remove impurities by vacuum distillation to obtain the N,N-dimethylformamide-dimethyl sulfoxide complex system.

[0038] A3. Add 10 mL of the N,N-dimethylformamide-dimethyl sulfoxide complex system slowly to the 20 mL of the carrier prepared in step A1 while stirring, and store at low temperature in the dark to obtain the precursor.

[0039] Example 4

[0040] S1. The layered nanomaterial powder was ultrasonically dispersed in the precursor solution prepared in Example 1. The pH value of the solution was controlled at 12. After standing for 25 minutes, the solution was filtered and the filtrate was used for later use to obtain the precursor-two-dimensional layered nanomaterial.

[0041] S2. The precursor-two-dimensional layered nanomaterials were heated to 40°C in a water bath, the pH of the solution was adjusted to 3, stirred for 50 min, the centrifugation rate was controlled at 4500 rpm, and the centrifugation time was 35 min. The filtrate was discarded, and the two-dimensional layered nanomaterials were obtained after post-treatment such as vacuum distillation, washing, and drying.

[0042] Example 5

[0043] S1. The layered nanomaterial powder was ultrasonically dispersed in the precursor solution prepared in Example 2. The pH value of the solution was controlled at 12. After standing for 25 minutes, the solution was filtered and the filtrate was used for later use to obtain the precursor-two-dimensional layered nanomaterial.

[0044] S2. The precursor-two-dimensional layered nanomaterials were heated to 40°C in a water bath, the pH of the solution was adjusted to 3, stirred for 50 min, the centrifugation rate was controlled at 4500 rpm, and the centrifugation time was 35 min. The filtrate was discarded, and the two-dimensional layered nanomaterials were obtained after post-treatment such as vacuum distillation, washing, and drying.

[0045] Example 6

[0046] S1. The layered nanomaterial powder was ultrasonically dispersed in the precursor solution prepared in Example 3. The pH value of the solution was controlled at 12. After standing for 25 minutes, the solution was filtered and the filtrate was used for later use to obtain the precursor-two-dimensional layered nanomaterial.

[0047] S2. The precursor-two-dimensional layered nanomaterials were heated to 40°C in a water bath, the pH of the solution was adjusted to 3, stirred for 50 min, the centrifugation rate was controlled at 4500 rpm, and the centrifugation time was 35 min. The filtrate was discarded, and the two-dimensional layered nanomaterials were obtained after post-treatment such as vacuum distillation, washing, and drying.

[0048] Comparative Example 1

[0049] Two-dimensional layered nanomaterials were prepared by chemical vapor deposition (CVD).

[0050] Comparative Example 2

[0051] Two-dimensional layered nanomaterials were prepared by mechanical exfoliation.

[0052] The yields (within 1 hour) of Examples 4-6 and Comparative Examples 1-2 were calculated, and the results are shown in Table 1:

[0053] Table 1. Yields of Examples 4-6 and Comparative Examples 1-2

[0054] project Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Yield / % 41％ 44％ 42％ 25％ 18％

[0055] Examples 4-6 and Comparative Examples 1-2 were used to determine the specific surface area of ​​graphene materials using the methylene blue adsorption method in GB / Z 38062-2019 "Determination of Specific Surface Area of ​​Graphene Materials in Nanotechnology - Methylene Blue Adsorption Method". The results are shown in Table 2.

[0056] Table 2. Specific surface area of ​​Examples 4-6 and Comparative Examples 1-2

[0057]

[0058] As shown in Tables 1 and 2, the specific surface area of ​​Examples 4-6 is higher than that of the graphitic carbon nitride nanosheets prepared by mechanical exfoliation in Comparative Example 2. The specific surface area of ​​Examples 4-6 is close to that of Comparative Example 1. However, the yield of Examples 4-6 is higher than that of Comparative Examples 1-2 per unit time. This indicates that by ultrasonically dispersing the layered nanomaterial powder in the precursor solution, controlling the pH value of the solution, allowing it to stand, filtering it, and keeping the filtrate for later use, heating the precursor-two-dimensional layered nanomaterial in a water bath, adjusting the pH value of the solution, stirring, centrifuging at high speed, discarding the filtrate, and then performing post-treatment such as vacuum distillation, washing, and drying, two-dimensional layered nanomaterials with high yield and specific surface area can be obtained.

[0059] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0060] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for exfoliating a two-dimensional layered nanomaterial, characterized by, Comprising the following steps: S1, ultrasonic dispersion of layered nanometer material powder in precursor solution, control the pH value of the solution at 11-12, stand for 20-30 min, filter, take the filtrate for standby, get the precursor-two-dimensional layered nanometer material; S2, heating the precursor-two-dimensional layered nanometer material to 40-45℃ in water bath, adjusting the pH value of the solution to 3-4, stirring for 40-60 min, high-speed centrifugation, discarding the filtrate, drying after vacuum distillation, washing and drying to get two-dimensional layered nanometer material; The precursor in step S1 Comprising the following steps: A1, prepare a 1 mol / L solution of tert-butyl alcohol and tert-butylamine as a carrier; A2, mix N,N-dimethylformamide and dimethyl sulfoxide uniformly, add diphenyl peroxide, control the temperature at 50-55℃, react for 30-40 min under nitrogen protection and light protection, remove impurities by vacuum distillation to get N,N-dimethylformamide-dimethyl sulfoxide complex system; A3, slowly add N,N-dimethylformamide-dimethyl sulfoxide complex system to the carrier prepared in step A1 while stirring, store at low temperature and light protection to get the precursor; The centrifugal rate of high-speed centrifugation in step S1 is 4000-5000 rpm, and the centrifugation time is 30-40 min; The mass ratio of tert-butyl alcohol to tert-butylamine in step A1 is (1-2):(3-6); The amount ratio of N,N-dimethylformamide, dimethyl sulfoxide and diphenyl peroxide in step A2 is (10-15) mL:(10-15) mL:(2-4) g; The amount ratio of N,N-dimethylformamide-dimethyl sulfoxide complex system to carrier in step A3 is (8-10):(15-20). 2.The method according to claim 1, wherein The layered nanometer material in step S1 refers to graphite phase carbon nitride nanosheet. 3.The method according to claim 1, wherein The precursor in step S1 refers to a solvent with tert-butyl alcohol and tert-butylamine mixed solution as a carrier and N,N-dimethylformamide-dimethyl sulfoxide as a stripping agent.

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