A method for preparing MXene microcapsules

Abstract

The application discloses a preparation method of MXene microcapsules, and MXene hollow flower-shaped microcapsules are synthesized by using a surfactant-assisted hydrothermal method. The method promotes the polymerization of nanosheets in a hydrothermal process by using a cationic surfactant and a long-chain neutral polymer, improves the stability of MXene, and promotes the generation and formation of rich internal cavities in the microcapsules. The microcapsules can greatly improve the specific surface area of MXene and fully utilize the advantages of MXene. The prepared microcapsules can prevent macromolecular substances from entering and slowly release small-size molecules. The application has simple process and easy-to-control flow, and provides a new way for comprehensive utilization of MXene.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and relates to a general synthesis method based on three-dimensional MXene. Background Technology

[0002] Nanomaterials are inorganic solid-state materials with dimensions ranging from 1 to 100 nm. They possess unique physical, chemical, and biological properties and are widely used in electronics, energy, environment, and medicine. MXene is a novel type of two-dimensional nanomaterial, a graphene-like structure obtained by processing the MAX phase. The MAX phase is a layered ternary transition metal carbide or nitride with the molecular formula Mn+1AXn (n = 1, 2, or 3), where M is a transition metal, A is a main group element, and X is C or N. MXene can be obtained by selectively removing the A layer, and its surface is typically capped with groups such as OH, O, or F. MXene exhibits excellent electrical conductivity, mechanical properties, and surface activity, showing potential applications in catalysis, molecular sieving, and electromagnetic shielding.

[0003] The strong van der Waals forces and hydrogen bonds between MXene layers cause MXene to tend to stack during assembly, significantly reducing its chemically active surface area. This loss of surface active sites severely hinders electron transport and limits the effective loading of other functional materials on its surface, further affecting the performance of the composite material. To address the stacking problem of 2D materials and achieve high surface utilization, researchers have made significant efforts in surface modification and heteroatom doping to obtain MXene composites with excellent properties. Three-dimensional MXene structures can not only effectively suppress self-stacking of layers and increase interlayer spacing, but also provide more active sites and stronger charge transfer capabilities, thus significantly improving their performance. Summary of the Invention

[0004] To address the challenge of small interlayer spacing and limited utilization caused by the stacking of MXene nanosheets, this invention provides a method for preparing three-dimensional flower-like microcapsules. This method employs a hydrothermal synthesis with two surfactants under acidic conditions, offering simple operation and stable synthesized structures. Adjusting the pH with an acidic solution lowers the zeta potential of the MXene solution, causing the monolayer MXene dispersion to aggregate. Due to the high electronegativity of MXene, and the amphoteric affinity of cationic surfactant molecules (one end being hydrophilic and the other hydrophobic), the surfactants, when dissolved in water, align at the MXene interface, forming monolayers or bilayers. The positively charged head of the surfactant attracts the negatively charged MXene nanosheets, forming an electrostatic complex. The hydrophobic tail of the surfactant extends into the solution, forming a hydrophobic layer that guides the formation of the hollow microcapsule structure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing MXene microcapsules, the method comprising:

[0007] A cationic surfactant, a long-chain polymeric surfactant, and phosphoric acid were added to an aqueous dispersion of monolayer MXene to construct a reaction system. Hydrothermal synthesis was carried out at 100-160℃ (preferably 120℃-140℃) for 7-18 hours (preferably 7-12 hours). The resulting reaction solution was post-treated to obtain the MXene microcapsules. The cationic surfactant was C... 12-36 Ammonium salt type surfactant with carbon chain; the long carbon chain polymer type surfactant is one or more of polyvinylpyrrolidone, sodium polyacrylate, polyacrylate, and polyethylene glycol (preferably polyvinylpyrrolidone);

[0008] In the reaction system, the final concentration of monolayer MXene is 0.5-2 mg / mL, the final concentration of the cationic surfactant is 2-16 g / L (preferably 2 g / L), the final concentration of the long carbon chain polymer surfactant is 1-2 g / L (preferably 1.5 g / L), and the final concentration of phosphoric acid is 0.8-1.5 M (preferably 1 M).

[0009] The main function of inorganic acids is to regulate the zeta potential, causing monolayer MXene tablets to aggregate and promote capsule formation. Sulfuric acid and hydrochloric acid can also work, but they are too strong and their performance is not as good as phosphoric acid.

[0010] Furthermore, the cationic surfactant is cocamidopropyl betaine, hexadecyltrimethylammonium bromide, dodecyl dimethyl benzyl ammonium chloride, or dimethyl dioctadecyl ammonium chloride, preferably hexadecyltrimethylammonium bromide.

[0011] In an embodiment of the present invention, the monolayer MXene is Ti3C2T. X MXene, Ti2C1 MXene, V2C MXene, or Mo2C MXene, preferably Ti3C2T X MXene.

[0012] This invention provides a single-layer MXene dispersion (Ti3C2T) X A method for preparing MXene, wherein the method is as follows:

[0013] (1) Dissolve LiF in 9M HCl, slowly add Ti3AlC2 under stirring in an argon atmosphere, stir vigorously in a polytetrafluoroethylene bottle for one day at 30℃-40℃, centrifuge and wash with deionized water until the pH of the supernatant is 6, dry the precipitate to obtain the stripping powder.

[0014] (2) Disperse the stripped powder obtained in step (1) evenly in deionized water, sonicate for 1-3 hours, centrifuge, and the resulting supernatant is the monolayer MXene dispersion. Dilute to 0.5-2 mg / ml before use.

[0015] In one embodiment of the present invention, the post-processing is as follows: the reaction solution is naturally cooled to room temperature, centrifuged, the resulting precipitate is washed with deionized water by centrifugation, and freeze-dried to obtain the MXene microcapsules.

[0016] The present invention particularly recommends the following method: adding a cationic surfactant, a long-chain polymeric surfactant, and phosphoric acid to an aqueous dispersion of monolayer MXene to construct a reaction system, performing hydrothermal synthesis at 120°C for 12 hours, and then post-processing the resulting reaction solution to obtain the MXene microcapsules; wherein the cationic surfactant is hexadecyltrimethylammonium bromide; and the long-chain polymeric surfactant is polyvinylpyrrolidone.

[0017] In the reaction system, the monolayer MXene is Ti3C2 Mxene with a final concentration of 1 mg / mL; the final concentration of the cationic surfactant is 2 g / L; the final concentration of the long-chain polymeric surfactant is 1.5 g / L; and the final concentration of the phosphoric acid is 1 M.

[0018] Compared with existing technologies, the advantages of this invention are as follows: Firstly, a cationic surfactant is used for the first time to hydrothermally synthesize a three-dimensional MXene structure with a long-chain neutral polymer surfactant. The synthesis process is simple, the structure exhibits good stability, and it has a certain degree of versatility. This invention synthesizes MXene hollow flower-shaped microcapsules using a surfactant-assisted hydrothermal method. This method utilizes the cationic surfactant and long-chain neutral polymer to promote the polymerization of nanosheets during hydrothermal processing, improving the stability of MXene and promoting the formation of abundant internal cavities within the microcapsules. These microcapsules can significantly increase the specific surface area of ​​MXene, fully utilizing its advantages. The prepared microcapsules can prevent the entry of large molecules and slowly release small molecules. This invention features a simple process and easy-to-control procedures, providing a new approach for the comprehensive utilization of MXene. Attached Figure Description

[0019] Figure 1 Example 1: Scanning electron microscope three-dimensional structure of Ti3C2 MXene

[0020] Figure 2 Example 1: Transmission Electron Microscopy Three-Dimensional Structure

[0021] Figure 3 Example 1 Ti3C2T X EDX spectrum of hollow flower-shaped microcapsules.

[0022] Figure 4 Pore ​​size distribution of Ti3C2 MXene microcapsules in Example 1

[0023] Figure 5 Nitrogen adsorption-desorption curves of Ti3C2 MXene microcapsules in Example 1

[0024] Figure 6 Scanning electron microscope structure of Comparative Example 1

[0025] Figure 7 Scanning electron microscope image of the three-dimensional structure of Ti2C1 in Comparative Example 2

[0026] Figure 8 Comparative Example 4: Ti3C2T X Three-dimensional transmission electron microscope image Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Any variations or implementations that do not depart from the content and scope of the present invention should be included within the technical scope of the present invention.

[0028] Example 1: Preparation of Ti3C2 MXene microcapsules

[0029] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and washed repeatedly by centrifugation with deionized water until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The precipitate was dried in a vacuum oven at 60 °C, and the concentration of the supernatant was calculated by weighing. The monolayer MXene in the supernatant was diluted to 1 mg / mL with deionized water.

[0030] Preparation of MXene microcapsules: 0.1 g of cetyltrimethylammonium bromide and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added and the final concentration of phosphoric acid was adjusted to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 12 hours. After naturally cooling to room temperature, the microcapsules were washed five times with deionized water at 3500 rpm and then freeze-dried to obtain Ti3C2 MXene microcapsules.

[0031] Hollow flower-like microcapsules with an average diameter of 3 μm were observed in the scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the above-mentioned Ti3C2 MXene microcapsules. Figure 1 , Figure 2 Interleaved Ti3C2T X Nanosheets facilitated the formation of numerous internal vacancies. In the tests, methyl orange (MO, 1.2 nm), methylene blue (MB, 1.4 nm), and reactive red (X-3B, 1.6 nm) were used as probe molecules. For the sustained release effect test using methyl orange (MO), the prepared microcapsules were immersed in a 1 g / L dye solution for 24 h to reach saturation. After centrifugation and drying, the prepared MXene microcapsules were placed in deionized water and continuously released in a shaker at 100 rpm. A rapid release of 39.12% occurred within 1 hour, followed by 53.02% after 3 hours. The release rate gradually slowed, reaching 62.02% after 5 hours, and finally 82.59% after 16 hours. Further ultrasonic treatment resulted in a more pronounced release process, indicating that some dye molecules remained within the internal structure of MHM. In sustained-release tests using methylene blue (MB, 1.4 nm) as the raw material, MB released more slowly than MO, achieving only 18.42% release within 1 hour, and ultimately releasing 60.20% of the MB molecules after 16 hours. Because MB has a larger kinetic diameter than MO, it is closer to the limiting nanochannels of MXene microcapsules, allowing dye molecules to pass through more slowly, thus exhibiting a longer sustained-release performance. When X-3B was used as the raw material, sustained-release tests showed that MXene microcapsules exhibited almost no sustained-release performance, indicating that X-3B exceeds the pore size of most MXene microcapsules. BET performance tests also showed that the nanochannels in MXene microcapsules are mostly in the 1.2-1.6 nm range.

[0032] Example 2: Preparation of Ti3C2 MXene microcapsules

[0033] Ti3C2T XPreparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 8 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0034] Preparation of MXene microcapsules: 0.1 g of dodecyl dimethyl benzyl ammonium chloride and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added to adjust the final concentration of phosphoric acid to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 12 hours. After naturally cooling to room temperature, the microcapsules were washed five times by centrifugation with deionized water at 3500 rpm, and then freeze-dried to obtain hollow microcapsules.

[0035] In the test, methyl orange (MO) was used as the probe molecule. The prepared MXene microcapsules were placed in 100 ml of deionized water according to the method in Example 1 and continuously released in a shaker at 100 rpm. 43.87% was released rapidly within 1 hour, 56.95% after 3 hours, and the release rate gradually slowed down. 66.73% was released after 5 hours, and finally 85.18% was released after 16 hours. A more obvious release process was observed after further sonication, indicating that dye molecules still remained in the internal structure of MHM.

[0036] Example 3: Preparation of Ti3C2 MXene microcapsules

[0037] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and then centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0038] Preparation of MXene microcapsules: 0.1 g of cocamidopropyl betaine, an amphoteric surfactant, and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added to adjust the final phosphoric acid concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 12 hours. After naturally cooling to room temperature, the microcapsules were washed five times with deionized water at 3500 rpm and then freeze-dried.

[0039] In the test, methyl orange (MO) was used as the probe molecule. The prepared MXene microcapsules were placed in 100 ml of deionized water according to the method in Example 1 and continuously released in a shaker at 100 rpm. 56.13% was released rapidly in 1 hour, 76.56% was released after 3 hours, the release rate gradually slowed down, 87.34% was released after 5 hours, and finally 93.85% was released after 16 hours. After ultrasonic treatment, complete release was achieved, indicating that the performance of amphoteric surfactants on MXene microcapsules is slightly worse than that of cationic surfactants.

[0040] Example 4

[0041] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and then centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0042] Preparation of MXene microcapsules: 0.1 g of dimethyl dioctadecyl ammonium chloride and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added to adjust the final phosphoric acid concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 12 hours. After naturally cooling to room temperature, the microcapsules were washed five times with deionized water at 3500 rpm and then freeze-dried.

[0043] In the test, methyl orange (MO) was used as the probe molecule. The prepared MXene microcapsules were placed in 100 ml of deionized water according to the method in Example 1 and continuously released in a shaker at 100 rpm. 53.26% was released rapidly within 1 hour, 71.92% was released after 3 hours, the release rate gradually slowed down, 82.63% was released after 5 hours, and finally 89.93% was released after 16 hours. After ultrasonic treatment, all the microcapsules were released.

[0044] Example 5

[0045] The other operations were the same as in Example 1, the only difference being that the hydrothermal synthesis time for the MXene microcapsules was 18 hours. When testing the sustained release effect using methyl orange (MO) as the raw material, the prepared microcapsules were immersed in a 1 g / L dye solution for 24 hours to reach saturation. After centrifugation and drying, the prepared MXene microcapsules were placed in deionized water and continuously released in a shaker at 100 rpm. 45.63% was released rapidly within 1 hour, 62.28% after 3 hours, the release rate gradually slowed, reaching 76.59% after 5 hours, and finally 91.22% after 16 hours. Further ultrasonic treatment revealed a more pronounced release process, indicating that some dye molecules remained within the internal structure of MHM. The longer hydrothermal synthesis time actually weakened the hollow structure of the microcapsules.

[0046] Example 6

[0047] The other operations were the same as in Example 1, the only difference being that the hydrothermal synthesis temperature was adjusted to 140℃. When testing the sustained release effect using methyl orange (MO) as the raw material, the prepared microcapsules were continuously immersed in a 1 g / L dye solution for 24 hours to reach saturation. After centrifugation and drying, the prepared MXene microcapsules were placed in deionized water and continuously released in a shaker at 100 rpm. 56.15% was released rapidly within 1 hour, 73.89% after 3 hours, the release rate gradually slowed down, reaching 82.49% after 5 hours, and finally 95.22% after 16 hours. Further ultrasonic treatment revealed a more pronounced release process, indicating that some dye molecules remained within the internal structure of MHM. Higher hydrothermal synthesis temperatures did not promote the formation of more hollow microcapsule structures.

[0048] Example 7: Preparation of Ti2C1 three-dimensional MXene structure

[0049] Ti2C1T XPreparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti₂AlC was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer Ti₂Cl-MXene in the supernatant was diluted to 1 mg / mL.

[0050] Preparation of MXene microcapsules: 0.1 g of cetyltrimethylammonium bromide and 0.15 g of polyvinylpyrrolidone were added to 30 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added to adjust the phosphoric acid concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 140 °C for 7 hours. After naturally cooling to room temperature, the microcapsules were washed five times with deionized water at 3500 rpm and then freeze-dried.

[0051] In the test, using methyl orange (MO) as the probe molecule according to the method in Example 1, the prepared MXene microcapsules rapidly released 63.53% within 1 hour, 82.65% within 3 hours, and 92.76% within 5 hours. After ultrasonic treatment, complete release was achieved, indicating that the MXene microcapsules prepared using Ti2C1 also possess sustained-release properties. SEM images show that the Ti2C1 MXene nanosheets also assembled into a three-dimensional flower-like structure, demonstrating the general applicability of this preparation method.

[0052] Comparative Example 1: Preparation of 3D MXene Structures Without PVP

[0053] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and then centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0054] Preparation of MXene microcapsules: 0.1 g of hexadecyltrimethylammonium bromide was added to 50 mL of MXene solution with a concentration of 1 mg / mL, and phosphoric acid was added to adjust the phosphoric acid concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 12 hours. After naturally cooling to room temperature, the microcapsules were washed 5 times by centrifugation at 3500 rpm and then freeze-dried.

[0055] Ti3C2T without PVP X Nanosheets synthesized via hydrothermal processes can only form solid, fan-shaped structures. In the test, methyl orange (MO) was used as a probe molecule to test the sustained-release performance according to the method in Example 1. The prepared MXene microcapsules rapidly released 87.96% of their contents within 15 minutes, exhibiting almost no sustained-release performance. This indicates that the sample without added PVP did not have an internal hollow structure and only relied on electrostatic and van der Waals forces to adsorb some dye molecules.

[0056] Comparative Example 2: Preparation of Ti3C2 MXene microcapsules using short-chain cationic surfactant

[0057] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and then centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0058] Preparation of MXene microcapsules: 0.1 g of tetrapropylammonium bromide cationic surfactant and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Phosphoric acid was added to adjust the final phosphoric acid concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 140 °C for 7 hours. After naturally cooling to room temperature, the microcapsules were washed five times with deionized water at 3500 rpm and then freeze-dried.

[0059] In the test, methyl orange (MO) was used as the probe molecule according to the method in Example 1. The prepared MXene microcapsules were placed in 100 ml of deionized water and continuously released in a shaker at 100 rpm. 73.62% was released rapidly within 1 hour, 86.76% after 3 hours, and the release rate gradually slowed down, reaching 91.33% after 5 hours, and finally 96.53% after 16 hours. After ultrasonic treatment, complete release was achieved. Overall, the effect was worse than that of long-chain surfactants. This indicates that although short-chain cationic surfactants can also show effects, the long carbon chain of the surfactant plays an important role.

[0060] Comparative Example 3: Preparation of three-dimensional MXene structures under alkaline conditions

[0061] Ti3C2T X Preparation of nanosheets: 1 g LiF was dissolved in 9 M HCl, and 1 g Ti3AlC2 was slowly added to the solution under an argon atmosphere. The sample was stirred vigorously at 35 °C for 24 hours, and then centrifuged and washed multiple times until the pH of the supernatant was approximately 6. The precipitate was dried in a vacuum oven at 60 °C for 12 hours. 0.2 g of the exfoliated powder was dissolved in 50 mL of deionized water, sonicated for 2 hours, and centrifuged at 3500 rpm for 2 hours to obtain the supernatant. The monolayer MXene in the supernatant was diluted with deionized water to 1 mg / mL.

[0062] Preparation of MXene microcapsules: 0.1 g of cetyltrimethylammonium bromide and 0.15 g of polyvinylpyrrolidone were added to 50 mL of MXene solution with a concentration of 1 mg / mL. Sodium hydroxide was added to adjust the sodium hydroxide concentration to 1 mol / L. The mixture was transferred to a reaction vessel and hydrothermally synthesized at 120 °C for 18 hours. After naturally cooling to room temperature, the capsules were washed five times by centrifugation at 3500 rpm and then freeze-dried.

[0063] Using the alkali Ti3C2T X Nanosheets synthesized via hydrothermal processes can only form solid structures. In testing, methyl orange (MO) was used as a probe molecule according to the method in Example 1 for sustained-release performance testing. The prepared MXene microcapsules rapidly released 81.56% within 15 minutes, exhibiting almost no sustained-release performance. This indicates that the sample without added PVP did not have an internal hollow structure, relying solely on electrostatic and van der Waals forces to adsorb some dye molecules. TEM images showed a solid structure.

[0064] Comparative Example 4

[0065] The other operations were the same as in Example 1, except that hydrochloric acid was used instead of phosphoric acid. In the test, methyl orange (MO) was used as a probe molecule according to the method in Example 1. The prepared MXene microcapsules were placed in 100 ml of deionized water and continuously released in a shaker at 100 rpm. 71.82% was released rapidly within 1 hour, 84.36% was released after 3 hours, the release rate gradually slowed down, and 91.33% was released after 5 hours. Finally, after ultrasonic treatment, all the MXene was released. The overall effect was worse than that of phosphoric acid.

[0066] Comparative Example 5

[0067] The other operations were the same as in Example 1, except that sulfuric acid was used instead of phosphoric acid. In the test, methyl orange (MO) was used as a probe molecule according to the method in Example 1. The prepared MXene microcapsules were placed in 100 ml of deionized water and continuously released in a shaker at 100 rpm. 76.18% was released rapidly within 1 hour, 88.45% was released after 3 hours, the release rate gradually slowed down, and 95.64% was released after 5 hours. Finally, after ultrasonic treatment, all the microcapsules were released. The overall effect was worse than that of phosphoric acid and hydrochloric acid.

Claims

1. A method for preparing MXene microcapsules, characterized by The method is: The cationic surfactant, long carbon chain polymer surfactant and phosphoric acid are added into a water dispersion of monolayer MXene to construct a reaction system, and hydrothermal synthesis is carried out at 100-160 DEG C for 7-18 hours, and the obtained reaction liquid is treated to obtain the MXene microcapsule; the cationic surfactant is C 12-36 ammonium salt type surfactant with long carbon chain; the long carbon chain polymer surfactant is one or two or more of polyvinylpyrrolidone, polyacrylic acid sodium, polyacrylic acid ester and polyethylene glycol. In the reaction system, the final concentration of the single-layer MXene is 0.5-2 mg / mL, the final concentration of the cationic surfactant is 2-16 g / L, the final concentration of the long carbon chain polymer surfactant is 1-2 g / L, and the final concentration of the phosphoric acid is 0.8-1.5 M.

2. The method of claim 1, wherein: The cationic surfactant is cocamidopropyl betaine, hexadecyl trimethyl ammonium bromide, dodecyl dimethyl benzyl ammonium chloride or dimethyl dioctadecyl ammonium chloride.

3. The method of claim 2, wherein: The cationic surfactant is hexadecyl trimethyl ammonium bromide.

4. The method of claim 1, wherein: The single-layer MXene contained in the aqueous dispersion of the single-layer MXene is Ti3C2T X MXene, Ti2C MXene, V2C MXene, or Mo2C MXene.

5. The method of claim 4, wherein: The single layer MXene is Ti3C2T X MXene.

6. The method of claim 2, wherein: The preparation method of the single-layer MXene dispersion liquid is as follows: (1) LiF is dissolved in 9M HCl, Ti3AlC2 is added under stirring in an argon environment, and the mixture is stirred vigorously in a polytetrafluoroethylene bottle at 30-40 DEG C for one day, then centrifuged and washed with deionized water until the pH value of the supernatant is 6, and the obtained precipitate is dried to obtain a peeled powder; (2) The peeled powder obtained in step (1) is uniformly dispersed in deionized water, and ultrasonic treatment is performed for 1-3 hours, and then centrifuged, and the obtained supernatant is the single-layer MXene dispersion liquid.

7. The method of claim 1, wherein: The long carbon chain polymer surfactant is polyvinylpyrrolidone.

8. The method of claim 1, wherein: The final concentration of the long carbon chain polymer surfactant is 1.5 g / L.

9. The method of claim 1, wherein: The post-treatment is as follows: the reaction liquid is naturally cooled to room temperature, centrifuged, the obtained precipitate is washed with deionized water by centrifugation, and freeze-dried to obtain the MXene microcapsule. 10.The method of claim 1, wherein The method is: cationic surfactant, long carbon chain polymer surfactant and phosphoric acid are added to the aqueous dispersion liquid of single-layer MXene to construct a reaction system, and hydrothermal synthesis is performed at 120 DEG C for 12 hours, and the obtained reaction liquid is post-treated to obtain the MXene microcapsule; the cationic surfactant is hexadecyl trimethyl ammonium bromide; the long carbon chain polymer surfactant is polyvinylpyrrolidone; In the reaction system, the single-layer MXene is Ti3C2 MXene, and the final concentration is 1 mg / mL; the final concentration of the cationic surfactant is 2 g / L, the final concentration of the long carbon chain polymer surfactant is 1.5 g / L, and the final concentration of the phosphoric acid is 1 M.

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