A method for preparing MXene films using biological macromolecules as dispersants

Abstract

The present invention provides a method for preparing MXene films using biological macromolecules as dispersants, which relates to the technical field of film preparation. Specifically, it includes the following steps: Step 1: Add DNA to deionized water and dissolve it, then add MXene powder, and place it in an ice-water bath for ultrasonic treatment to obtain a uniformly dispersed MXene filtrate; Step 2: Dissolve anhydrous calcium chloride in the deionized water, then add ethanol, and stir evenly to obtain a coagulating liquid; Step 3: After vacuum filtration of the MXene filtrate until the filtration is complete, add the coagulating liquid, perform secondary vacuum filtration until it is complete, and then place it in a vacuum condition for drying at room temperature to obtain an MXene film. The MXene film prepared by the present invention has uniform and consistent lamellar orientation, few defects, and excellent mechanical, electrical, and flexible properties.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film preparation, and in particular, to a method for preparing MXene thin films using biopolymers as dispersants. Background Art

[0002] With the continuous increase in the demand for flexible electronic products, flexible conductive materials have attracted more and more attention. Studying a material with flexibility and conductive properties has become the primary task. The two main forms of flexible materials are fibers and thin films. In recent years, thin films composed of two-dimensional nanosheet materials have been a new type of membrane material that has received much attention. They have unique physical and chemical properties and show broad application prospects in the field of flexible conductive materials.

[0003] Among them, MXene, as a new type of two-dimensional nanosheet material, has received extensive attention. It shows great application potential in energy storage, water treatment, catalysis, and sensing. MXene has diverse chemical and structural characteristics compared to other two-dimensional materials (such as graphene, black phosphorus, silicene, etc.), and at the same time has higher stability and conductivity. And because compared with graphene materials, MXene has better electrical properties and a larger specific surface area, and its components can be appropriately adjusted, so it is more suitable for use as a flexible electrode material. Assembling MXene materials with microscale into macroscopic materials with high performance has far-reaching significance in applications, so it has attracted extensive research. The main macroscopic forms are powders and self-supporting MXene thin films, and among them, thin films are more suitable for application in the field of flexible electrodes. However, it has been found that the performance of preparing self-supporting thin films by traditional direct vacuum filtration of MXene liquid does not reach the ideal effect. This is because similar to other two-dimensional materials, due to the combined action of hydrogen bonds and van der Waals forces between adjacent nanosheets of MXene, it is very easy for the sheets to stack together again, resulting in uneven dispersion in the system. As a result, the self-supporting MXene membranes prepared by direct vacuum filtration have a large number of defects such as folding and even cracking. Especially when preparing MXene powder into a filtrate and filtering it into a film, this method will result in uneven dispersion of MXene, leading to stacking of MXene sheets, and the MXene sheet orientations are different, so that the prepared thin films are uneven, have many defects, and have poor flexibility and other related properties. Summary of the Invention

[0004] The problem solved by the present invention is how to improve the problems of unevenness, many defects, poor flexibility and other related properties of self-supporting thin films prepared by traditional direct vacuum filtration of MXene liquid.

[0005] To solve the above problems, the present invention provides a method for preparing MXene thin films using biopolymers as dispersants, including the following steps:

[0006] Step 1: After dissolving the DNA in deionized water, add MXene powder and place it in an ice-water bath for ultrasonic treatment to obtain a uniformly dispersed MXene filtrate.

[0007] Step 2: Dissolve anhydrous calcium chloride in the deionized water, then add ethanol and stir evenly to obtain a coagulating liquid.

[0008] Step 3: After vacuum filtering the MXene filtrate until the filtration is complete, add the coagulating liquid, perform secondary vacuum filtration until complete, and then place it in a vacuum condition for drying at room temperature to obtain a MXene film.

[0009] Further, in Step 1, the mass ratio of the DNA to the MXene powder is 1:(1.5 - 3).

[0010] Further, in Step 1, the ultrasonic frequency is 20 - 25 KHz, and the ultrasonic time is 30 - 60 min.

[0011] Further, in Step 1, the dissolution method is static dissolution, and the dissolution time is 1 - 2 h.

[0012] Further, in Step 1, the mass ratio of the DNA to the deionized water is (2 - 3):(250 - 500).

[0013] Further, in Step 2, the mass ratio of the anhydrous calcium chloride to the deionized water is 1:(4.6 - 6).

[0014] Further, in Step 2, the volume ratio of the deionized water to the ethanol is 1:(2 - 3).

[0015] Further, in Step 3, the filter membrane for vacuum filtration is a polytetrafluoroethylene filter membrane, and the pore size of the polytetrafluoroethylene filter membrane is 22 - 45 μm.

[0016] Further, in Step 3, it also includes: after the secondary vacuum filtration is completed, remove the polytetrafluoroethylene filter membrane with the MXene film attached, place it in a vacuum condition for drying at room temperature, and then separate the polytetrafluoroethylene filter membrane to obtain the MXene film.

[0017] Further, in Step 3, the room temperature drying time is 10 - 24 h.

[0018] The beneficial effects of the method for preparing MXene films using biopolymers as dispersants according to the present invention compared with the prior art are as follows. By using biopolymer DNA as the raw material for the dispersant, compared with the traditional surfactant as the raw material for the dispersant, the proportion of the dispersant in the MXene filtrate system is reduced, and the concentration of nanomaterials in the MXene filtrate system is relatively increased, improving the performance of the prepared MXene films. In particular, a small amount of DNA can uniformly disperse MXene in the system. By introducing the coagulation liquid CaCl2 solution for wet spinning, the negatively charged phosphate groups in DNA in the system can combine with the positively charged calcium ions in the coagulation liquid CaCl2 through electrostatic interaction to form calcium bridges, fixing the MXene lamellae, and then promoting the formation of MXene films, resulting in a self-supporting MXene film with uniform and consistent lamellar orientation, few defects, and excellent mechanical, electrical, and flexible properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a micrograph of the MXene filtrate using biopolymer DNA as a dispersant in the examples of the present invention;

[0020] Figure 2 It is a micrograph of the MXene filtrate using a surfactant as a dispersant in the examples of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings.

[0022] The embodiments of the present invention provide a method for preparing MXene films using biopolymers as dispersants, including the following steps:

[0023] Step 1: Add DNA to deionized water and dissolve it, then add MXene powder, and place it in an ice-water bath for ultrasonic treatment to obtain a uniformly dispersed MXene filtrate;

[0024] Step 2: Dissolve anhydrous calcium chloride in deionized water, then add ethanol, and stir evenly to obtain a coagulation liquid;

[0025] Step 3: Vacuum filter the MXene filtrate until the filtration is complete, then add the coagulation liquid, perform secondary vacuum filtration until complete, and place it in a vacuum condition for room temperature drying to obtain MXene films.

[0026] In the embodiments of the present invention, by using biological macromolecule DNA as the raw material of the dispersant, compared with the traditional surfactant as the raw material of the dispersant, the proportion of the dispersant in the MXene filtrate system is reduced, and the concentration of the nanomaterials in the MXene filtrate system is relatively increased, so that the performance of the prepared MXene self-supporting film is improved; more importantly, a small amount of DNA can make MXene evenly dispersed in the system, and the coagulating liquid CaCl2 solution for wet spinning is introduced. The negatively charged phosphate groups in the DNA in the system can combine with the positively charged calcium ions in the coagulating liquid CaCl2 through electrostatic interaction to form a calcium bridge, fixing the MXene lamellae, and then promoting the formation of the MXene film, so that the prepared self-supporting MXene film has uniform and consistent layer orientation, few defects, and excellent mechanical, electrical and flexible properties.

[0027] In some specific embodiments, in step 1, the mass ratio of DNA to MXene powder is 1:(1.5 - 3). Thereby, the sufficient dispersion of MXene powder in deionized water is effectively realized, and the proportion is lower than that of the dispersant in the prior art, improving the performance of the prepared MXene film.

[0028] In some specific embodiments, in step 1, the ultrasonic frequency is 20 - 25KHz and the ultrasonic time is 30 - 60min. Thereby, the dispersion of MXene powder in the MXene filtrate is fully realized. Preferably, the interval time of ultrasonic is 1 second, which is beneficial to improving the uniform dispersion effect.

[0029] In some specific embodiments, in step 1, the dissolution method is static dissolution and the dissolution time is 1 - 2h. Thereby, on the premise of not destroying the biological macromolecule DNA, its full dissolution is realized, which is beneficial to ensuring the subsequent dispersion effect.

[0030] In some specific embodiments, in step 1, the mass ratio of DNA to deionized water is (2 - 3):(250 - 500). Thereby, the full dissolution of DNA is realized, ensuring the dissolution quality.

[0031] In some specific embodiments, in step 2, the mass ratio of anhydrous calcium chloride to deionized water is 1:(4.6 - 6). Thereby, the full dissolution of anhydrous calcium chloride in deionized water is realized.

[0032] In some specific embodiments, in step 2, the volume ratio of deionized water to ethanol is 1:(2 - 3).

[0033] In some specific embodiments, in step 3, the filter membrane for vacuum filtration is a polytetrafluoroethylene filter membrane, and the pore diameter of the polytetrafluoroethylene filter membrane is 22 - 45μm. Thereby, by using the hydrophilic polytetrafluoroethylene filter membrane, it is beneficial to improve the effect of vacuum filtration and the vacuum filtration efficiency.

[0034] In some specific embodiments, in step 3, it further includes: after the secondary vacuum filtration is completed, the polytetrafluoroethylene filter membrane with the MXene film attached is removed, placed in a vacuum condition and dried at room temperature. After drying is completed, the polytetrafluoroethylene filter membrane is separated to obtain the MXene film. Thus, after drying, the polytetrafluoroethylene filter membrane is separated and removed to prevent it from affecting the MXene film and improve the quality of the MXene film.

[0035] In some specific embodiments, in step 3, the room temperature drying time is 10 - 24 h. Thus, sufficient and gentle drying of the MXene film is achieved, ensuring the quality and mechanical properties of the MXene film. Specific Example 1

[0037] The embodiment of the present invention provides a method for preparing an MXene film using a biological macromolecule as a dispersant, including the following steps:

[0038] Step 1: Dissolve 40 - 60 mg of DNA stored at low temperature in 5 - 10 mL of deionized water and let it stand for 1 - 2 h to completely dissolve to obtain a DAN solution. Then add 80 - 120 mg of MXene powder, place it in an ice - water bath and ultrasonicate it. Under the condition of an ultrasonic frequency of 20 - 25 KHz, ultrasonicate for 30 - 60 min to obtain a uniformly dispersed MXene filtrate;

[0039] Step 2: Dissolve 25 g of anhydrous calcium chloride in 150 mL of deionized water, shake it to completely dissolve, and then add 350 mL of ethanol and stir until it is evenly mixed to obtain a coagulating liquid;

[0040] Step 3: Transfer the MXene filtrate into a vacuum filtration device lined with a polytetrafluoroethylene filter membrane for vacuum filtration. After the liquid filtration is completed, add the coagulating liquid to the funnel of the vacuum filtration device for secondary vacuum filtration until the liquid filtration is completed; remove the polytetrafluoroethylene filter membrane with the MXene film attached after the filtration is completed, place it in a vacuum condition and let it stand at room temperature for 10 - 24 h until it is completely dry, and separate the polytetrafluoroethylene filter membrane to obtain the MXene film.

[0041] After testing, the MXene film prepared in the embodiment of the present invention has excellent electrical properties, and the resistivity is measured and calculated to be 14.06 ± 1.47 Ω·m; the MXene film prepared in the embodiment of the present invention has excellent mechanical properties, and the fracture strength is calculated to be 80.42 ± 1.32 MPa and the modulus is 2.24 ± 0.29 GPa through a tensile experiment.

[0042] Comparative Example 1

[0043] This comparative example is used to compare the dispersibility of MXene filtrates obtained with different dispersants, specifically as follows:

[0044] Add DAN to deionized water and dissolve for 1 - 2 h. Then add MXene powder to the DAN solution at a mass ratio of MXene to DAN of 2:1, and ultrasonicate for 30 - 60 min to obtain the MXene filtrate. Prepare the MXene filtrate with p-toluenesulfonate surfactant as the dispersant raw material in the same method and at the same mass ratio, and compare the dispersing abilities of the two. Take photos of the two filtrates under a microscope, as Figure 1 and Figure 2 shown. Figure 2 is the MXene filtrate prepared with the surfactant as the dispersant, Figure 1 is the MXene filtrate prepared with DAN as the dispersant. It can be observed that under the condition of the same dosage of the dispersant, DNA can better disperse the MXene material.

[0045] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A method for preparing MXene films using biopolymers as dispersants, characterized in that, It includes the following steps: Step 1: After adding DNA to deionized water and dissolving it, add MXene powder, place it in an ice-water bath and ultrasonicate to obtain a uniformly dispersed MXene filtrate; Step 2: Dissolve anhydrous calcium chloride in the deionized water, then add ethanol and stir evenly to obtain a coagulating liquid; Step 3: After vacuum filtering the MXene filtrate until the filtration is complete, add the coagulating liquid, conduct secondary vacuum filtration until complete, and place it in a vacuum condition for drying at room temperature to obtain a MXene film.

2. The method for preparing an MXene film using a biopolymer as a dispersant according to claim 1, characterized in that, In Step 1, the mass ratio of the DNA to the MXene powder is 1:(1.5 - 3).

3. The method for preparing MXene film using a biological macromolecule as a dispersant according to claim 1, characterized in that, In Step 1, the ultrasonic frequency is 20 - 25 KHz, and the ultrasonic time is 30 - 60 min.

4. The method for preparing an MXene film using a biopolymer as a dispersant according to claim 1, wherein In Step 1, the dissolution method is static dissolution, and the dissolution time is 1 - 2 h.

5. The method for preparing MXene film using biopolymer as dispersant according to claim 1, wherein In Step 1, the mass ratio of the DNA to the deionized water is (2 - 3):(250 - 500).

6. The method for preparing MXene thin films using biomacromolecules as dispersants according to claim 1, characterized in that, In Step 2, the mass ratio of the anhydrous calcium chloride to the deionized water is 1:(4.6 - 6).

7. The method for preparing MXene thin films using biopolymers as dispersants according to claim 1, characterized in that, In Step 2, the volume ratio of the deionized water to the ethanol is 1:(2 - 3).

8. The method for preparing MXene thin films using biopolymers as dispersants according to claim 1, characterized in that, In Step 3, the filter membrane for vacuum filtration is a polytetrafluoroethylene filter membrane, and the pore size of the polytetrafluoroethylene filter membrane is 22 - 45 μm.

9. The method for preparing MXene film using a biological macromolecule as a dispersant according to claim 8, wherein, In Step 3, it also includes: after the secondary vacuum filtration is completed, remove the polytetrafluoroethylene filter membrane with the MXene film attached, place it in a vacuum condition for drying at room temperature until completion, and separate the polytetrafluoroethylene filter membrane to obtain the MXene film.

10. The method for preparing MXene thin films using biological macromolecules as dispersants according to claim 1, characterized in that, In Step 3, the room temperature drying time is 10 - 24 h.

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