A method for improving the stability of MXene dispersions using amino acids

Abstract

This invention discloses a method for improving the stability of MXene dispersions using amino acids. Adding amino acids to MXene dispersions significantly improves MXene stability, maintaining good physical dispersibility and chemical stability, and effectively addresses the fundamental problem of easy oxidation of MXene dispersions during storage. This method significantly improves the stability of MXene dispersions by adding a small amount of amino acids, and is characterized by being environmentally friendly, simple, and controllable.

Description

Technical Field

[0001] This invention belongs to the field of materials technology and relates to a method for improving the stability of MXene dispersions using amino acids. Background Technology

[0002] Two-dimensional nanomaterials, with their atomic-level thickness and unique layered structure, are currently a hot research topic in materials science. They mainly include transition metal dichalcogenides, borophenes, silicenes, and black phosphorus (phosphene), whose excellent catalytic, electronic, and optoelectronic properties continuously drive research and technological innovation in various fields. In 2011, Yury Gogotsi's research group first prepared a novel class of two-dimensional layered materials, MXenes, namely two-dimensional transition metal carbides, nitrides, and carbonitrides. These materials possess high electrical conductivity, large specific surface area, tunable surface end groups, and good biocompatibility, and can be uniformly dispersed in water and various polar organic solvents. Therefore, they have attracted widespread attention in multiple fields such as energy storage, catalysis, environmental protection, electronics, and biomedicine.

[0003] However, during the synthesis, storage, and practical application of MXene materials, the surface and edge active sites are highly susceptible to irreversible oxidation reactions with water molecules and dissolved oxygen in the environment, leading to the destruction of their layered structure. This irreversible oxidation reaction causes MXene to lose its original excellent properties and significantly shortens its effective lifespan. The susceptibility of MXene to oxidation has become one of the key factors restricting its large-scale application and industrial development. Therefore, exploring efficient anti-oxidation strategies for MXene has significant practical implications and research value for its practical application.

[0004] Maintaining the stability of MXene is a crucial prerequisite for its practical application. In recent years, extensive research has been conducted on protection strategies to improve the stability of MXene materials. These protection methods can be broadly categorized into two main technical routes: pretreatment optimization and post-treatment modification. In the pretreatment synthesis stage, the focus is primarily on obtaining more stable MXene materials with lower defect densities by controlling the etching process. More research has been done on protection measures for the post-treatment stage. Using common etching methods to obtain MXene nanosheets, the stability of MXene can be improved through methods such as moderate high-temperature annealing to reshape the surface end-group distribution, improving the physical storage environment of the dispersion, surface modification, and adding antioxidants. Among these methods, directly adding antioxidants to the dispersion is favored due to its simplicity and ease of scalability. An ideal liquid-phase antioxidant should provide long-term protection without affecting the subsequent application performance of MXene. Summary of the Invention

[0005] This invention provides a method for improving the stability of MXene dispersions using amino acids. By coordinating heteroatoms in the amino acids with the active sites of MXene, the stability and storage time of MXene in the aqueous phase are improved, extending the shelf life of MXene aqueous solutions to 40-200 days. This invention not only improves the chemical stability of MXene in the aqueous phase but also maintains the dispersion stability of MXene, providing a green and convenient method to solve the problems of easy oxidation during long-term storage, transportation, and practical applications of MXene dispersions.

[0006] The specific technical solution adopted in this invention is as follows: A method for improving the stability of MXene dispersions using amino acids involves dispersing amino acids in water by stirring and sonication, followed by adding the MXene dispersion. The amino acids adsorb onto the MXene, and the heteroatoms on the functional groups of the amino acids coordinate with the active sites, thereby improving the stability of the MXene dispersion, maintaining good dispersibility, and extending storage life.

[0007] The amino acids mentioned include one or more of histidine, tryptophan, tyrosine, theanine, and serine. The concentration range of the amino acids is 0.01 mmol / L. -1 -3 mmol L -1 ; The general formula of the MXene structure is M n+1 X n T x Where M represents one or more transition metals such as Ti, V, Zr, Nb, Mo, W, and Ta, X represents one or two of C or N, n = 1 or 2, T represents a surface end group -OH, -O, or -F, and the MXene is Ti3C2T. x Ti2CT x V2CT x Nb2CT x Mo2CT x Ti3N2T x At least one of them.

[0008] This invention solves the problem of easy oxidation of MXene during long-term storage, transportation, and practical applications using a green and convenient method. Specific benefits are as follows: This invention provides a method for improving the stability of MXene dispersions using amino acids, which enables stable storage of MXene dispersions at room temperature for up to 200 days, maintaining the chemical and dispersion stability of MXene dispersions and solving the problem of easy oxidation of MXene during long-term storage, transportation, and practical applications. Attached Figure Description

[0009] Figure 1Histidine-protected Ti3C2T in Example 1 of this invention x Dispersion and unprotected Ti3C2T x Photographs of the dispersion after 56 days of storage at room temperature; where (a) is unprotected Ti3C2T x (b) Histidine-protected Ti3C2T x ; Figure 2 For unprotected Ti3C2T x XPS spectra of the dispersion after 35 days of storage; Figure 3 The histidine-protected Ti3C2T in Example 1 x XPS spectra of the dispersion after 35 days of storage; Figure 4 The tryptophan-protected Ti3C2T in Example 2 x Photographs of the dispersion after 35 days of storage; Figure 5 The tyrosine-protected Ti3C2T in Example 3 x Photographs of the dispersion after 35 days of storage; Detailed Implementation This invention proposes a method for improving the stability of MXene dispersions using amino acids. Amino acid molecules contain heteroatoms with lone pairs of electrons in their functional groups such as carboxyl, amino, and imidazole groups, while MXene contains empty orbitals in its transition metals. Therefore, the N and O heteroatoms in amino acids interact with MXene and coordinate with the active sites of the transition metals, thereby enhancing the stability of MXene.

[0010] The embodiments of the present invention are described below.

[0011] Example 1: (1) Ti3C2T x Preparation of the dispersion: 1.98 g LiF and 20 mL hydrochloric acid (12M) were added to a polytetrafluoroethylene (PTFE) bottle to prepare the etching solution. 2 g Ti3AlC2 precursor powder was slowly added under stirring. The mixture was placed in a 35 ℃ water bath and reacted at 900 r / min for 24 hours. After the reaction, the etched mixture was centrifuged and washed until the pH reached approximately 6. The precipitate was collected and ultrasonically exfoliated at 360 W for 1 hour, followed by centrifugation at 5000 r / min for 1 hour to obtain Ti3C2T. x Dispersion.

[0012] (2) Add 50 mg of histidine to the stirred deionized water and mix thoroughly, then add Ti3C2T xThe dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and histidine. The total solution volume was 500 mL, and the molar concentration of histidine was 0.1 mg / mL. -1 Ti3C2T x The dispersion concentration was 0.05 mg / mL. -1 .

[0013] The above Example 1 and the unprotected Ti3C2T x The resulting dispersion was sealed and stored, and its state was recorded by optical photography. It was then filtered to form a film, and the changes in its surface chemical state were measured. Figure 1 As shown, after 56 days of storage, the addition of histidine-protected Ti3C2T x The dispersion still maintains a good dark green colloidal state, and the unprotected Ti3C2T x It has been completely oxidized and turned into a white, flocculent substance. For example... Figure 2 and Figure 3 As shown, unprotected Ti3C2T x The proportion of TiO2 in the XPS dispersion increased significantly after 35 days of storage, indicating severe oxidative degradation. The histidine-protected Ti3C2T in Example 1... x The proportion of TiO2 in the XPS dispersion did not change significantly after 35 days of storage, indicating that the addition of histidine improved the stability of the MXene dispersion.

[0014] Example 2: (1) Ti3C2T x The preparation of the dispersion is the same as in Example 1.

[0015] (2) Add 200 mg of tryptophan to the stirred deionized water and mix thoroughly, then add Ti3C2T x The dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and tryptophan. The total solution volume was 500 mL, and the molar concentration of tryptophan was 0.4 mg / mL. -1 Ti3C2T x The dispersion concentration was 0.05 mg / mL. -1 .

[0016] The dispersion obtained in Example 2 above was sealed and stored, and the state of the dispersion was recorded by optical photography. For example... Figure 4 As shown, after 35 days of storage, the tryptophan-protected Ti3C2T x The dispersion remains a dark green dispersion.

[0017] Example 3: (1) Ti3C2T x The preparation of the dispersion is the same as in Example 1.

[0018] (2) Add 250 mg of tyrosine to the stirred deionized water and mix thoroughly, then add Ti3C2T x The dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and tyrosine. The total solution volume was 500 mL, and the molar concentration of tyrosine was 0.5 mg / mL. -1 Ti3C2T x The dispersion concentration was 0.05 mg / mL. -1 .

[0019] The dispersion obtained in Example 3 above was sealed and stored, and the state of the dispersion was recorded by optical photography. Figure 5 As shown, after 35 days of storage, the tyrosine-protected Ti3C2T x The dispersion remains a dark green dispersion.

[0020] Example 4: (1) Ti3C2T x The preparation of the dispersion is the same as in Example 1.

[0021] (2) Add 50 mg of theanine to the stirred deionized water and mix thoroughly, then add Ti3C2T x The dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and theanine. The total solution volume was 500 mL, and the molar concentration of theanine was 0.1 mg / mL. -1 Ti3C2T x The dispersion concentration was 0.05 mg / mL. -1 .

[0022] Example 5: (1)Ti3C2T x The preparation of the dispersion is the same as in Example 1.

[0023] (2) Add 300 mg of serine to the stirred deionized water and mix thoroughly, then add Ti3C2T x The dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and serine. The total solution volume was 500 mL, and the molar concentration of serine was 0.6 mg / mL. -1 Ti3C2T x The dispersion concentration was 0.05 mg / mL. -1 .

[0024] Example 6: (1) Ti2CT xPreparation of the dispersion: 0.99 g LiF and 10 mL hydrochloric acid (12M) were added to a polytetrafluoroethylene bottle to prepare the etching solution. 1 g Ti₂AlC precursor powder was slowly added while stirring. The mixture was placed in a 35 ℃ water bath and reacted at 900 r / min for 24 hours. After the reaction, the resulting mixture was centrifuged and washed until the pH reached approximately 6. The precipitate was collected and ultrasonically exfoliated at 360 W for 1 hour, followed by centrifugation at 5000 r / min for 1 hour to obtain Ti₂CT. x Dispersion.

[0025] (2) Add 100 mg of histidine to the stirred deionized water and mix thoroughly, then add Ti3C2T x The dispersion was sonicated for 5 minutes to ensure uniform dispersion of MXene and histidine. The total solution volume was 500 mL, and the molar concentration of histidine was 0.2 mg / mL. -1 Ti2CT x The dispersion concentration was 0.05 mg / mL. -1 .

Claims

1. A method for improving the stability of MXene dispersions using amino acids, characterized in that, At room temperature, amino acids are dispersed in an aqueous medium to prepare an MXene protective agent solution. The amino acid solution is then mixed with the MXene dispersion to ensure that the amino acids are adsorbed on the MXene surface to provide protection.

2. The method for improving the stability of MXene dispersion using amino acids according to claim 1, characterized in that, The amino acids mentioned include one or more of histidine, tryptophan, tyrosine, theanine, and serine.

3. The method for improving the stability of MXene dispersion using amino acids according to claim 1, characterized in that, The concentration range of the amino acids is 0.01 mg / mL. -1 -3 mmol L -1 .

4. The method for improving the stability of MXene dispersion using amino acids according to claim 1, characterized in that, The MXene mentioned is Ti3C2T x Ti2CT x V2CT x Nb2CT x Mo2CT x Ti3N2T x .

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