Two-dimensional particle, two-dimensional particle-containing dispersion liquid, two-dimensional particle-containing composite, two-dimensional particle-containing film, and two-dimensional particle production method

Abstract

Two-dimensional particles according to the present invention each include one or more layers. Each of the layers includes: a layer body represented by formula MmXn (in the formula, M represents at least one group 3, 4, 5, 6, or 7 metal, X represents a carbon atom, a nitrogen atom, or a combination thereof, n represents 1-4, and m is greater than n but not greater than 5); and modifications or terminals T existing on the surface of the layer body. Each of said T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom. A structure exists in which an ionic bond or a covalent bond is formed, via an oxygen atom derived from a hydroxyl group of the layer body, between the M atom of the layer body and a heteroatom of a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group. The rate of substitution, to the structure, of hydroxyl groups existing on the surface of the layer body is 37.5% or more.

Description

Two-dimensional particles, two-dimensional particle-containing dispersion, two-dimensional particle-containing composite, two-dimensional particle-containing film, and method for producing two-dimensional particles

[0001] The present disclosure relates to two-dimensional particles, two-dimensional particle-containing dispersions, two-dimensional particle-containing composites, two-dimensional particle-containing films, and methods for making two-dimensional particles.

[0002] In recent years, MXene has been attracting attention as a new material. MXene is a type of so-called two-dimensional material, and is a layered material having the form of one or more layers. ｍ X ｎ T s It is a layered compound represented by the following composition, and is obtained by etching the precursor MAX. Due to the etching of the MAX, modifications or terminations such as -OH, =O, and -F are generated on the surface of MXene. These modifications or terminations impart hydrophilic properties to MXene. Therefore, MXene has excellent water dispersion properties. MXene also exhibits excellent electrical conductivity.

[0003] However, MXene dispersed in water is easily oxidized by water molecules and dissolved oxygen to form a metal oxide (titanium oxide), resulting in the loss of its inherently excellent properties. Furthermore, because MXene has a hydrophilic surface, it has low attraction to hydrophobic materials (polymers, organic solvents, etc.), making it difficult to mix with hydrophobic materials to form homogeneous composite materials. Furthermore, forming an MXene film using a liquid process such as spray coating requires high energy consumption to remove water.

[0004] In response to the above-mentioned problems, Patent Document 1 discloses passivated 2D MXene particles, which include 2D MXene particles surface-modified with functional groups containing saturated or unsaturated hydrocarbons, and an organic protective film formed on the surface of the surface-modified 2D MXene particles, the functional groups being selected from the group consisting of phosphonates and amines, and the 2D MXene particles surface-modified with functional groups containing saturated or unsaturated hydrocarbons are dispersed in an organic solvent that forms the protective film. Patent Document 1 also discloses that the 2D MXene particles are easily dispersible in organic solvents, making it easy to manufacture polymer composites containing the particles, as well as having advantageous properties for application in films and coating products with various performances.

[0005] In addition, Non-Patent Document 1 discloses that, for example, in order to realize a stretchable electrode, Ti is mixed with a non-polar polymer matrix that is soluble in an organic medium, and is therefore stable in an organic solvent. ３ C ２ T ｘ It is shown that a dispersion containing MXene particles can be prepared. Specifically, alkylphosphonic acid (R-P(=O)(OH) ２ Ti adsorbed on the surface ３ C ２ T ｘ The Ti flake is shown. ３ C ２ T ｘ The flakes were etched using an etching solution of LiF dissolved in HCl. ３ AlC ２ It is made by etching Ti ３ C ２ On the surface of the silicon dioxide, -F, -Cl, -O, and -OH are present.

[0006] Japanese Patent Application Laid-Open No. 2020-93971

[0007] Nonpolar Organic Dispersion of 2D Ti3C2Tx MXene Flakes via Simultaneous Interfacial Chemical Grafting and Phase Transfer Method. ACS Nano 2019, 13, 12, 13818-13828

[0008] The MXene particles of Patent Document 1 and Non-Patent Document 1 could only be dispersed in organic dispersion media that were immiscible with water (solubility in water <10% w / w), and were limited in the organic dispersion media in which they could be dispersed. Furthermore, the MXene particles of Patent Document 1 and Non-Patent Document 1 had the problem of low dispersion stability in organic dispersion media. The present disclosure has been made in light of the above circumstances, and its purpose is to provide two-dimensional particles that are dispersible in various organic dispersion media and have high dispersion stability in dispersions, two-dimensional particle-containing dispersions, two-dimensional particle-containing composites, and two-dimensional particle-containing films that contain the two-dimensional particles, and methods for producing the two-dimensional particles.

[0009] According to one aspect of the present disclosure, there is provided a two-dimensional particle comprising one or more layers, wherein said layers are of the following formula: M ｍ X ｎ (wherein M is at least one Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and modified or terminated T present on the surface of the layer body, wherein T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and the M atom of the layer body and a heteroatom of a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group have a structure in which they are covalently or ionically bonded via an oxygen atom derived from the hydroxyl group of the layer body, and the substitution rate of the hydroxyl groups present on the surface of the layer body with the structure is 37.5% or more.

[0010] According to the present disclosure, it is possible to provide two-dimensional particles that can be dispersed in various organic dispersion media and have high dispersion stability in dispersions, two-dimensional particle-containing dispersions, two-dimensional particle-containing composites, and two-dimensional particle-containing films that contain the two-dimensional particles, and methods for producing the two-dimensional particles.

[0011] 6A and 6B are schematic cross-sectional views illustrating MXene constituting the two-dimensional particles of this embodiment (or precursor particles used in producing the two-dimensional particles of this embodiment), where (a) shows single-layer MXene and (b) shows multi-layer (exemplarily two-layer) MXene.

[0023] FIG. 1 is a diagram showing weight changes by differential thermal analysis of ligand-substituted MXene particles in Example 1-1.

[0024] FIG. 2 is a diagram explaining the prerequisites for calculating the ligand coverage.

[0025] FIG. 3 is a diagram showing the results of ultraviolet-visible spectrophotometric measurement (ultraviolet-visible absorption spectrum) in Example 1-1.

[0026] FIG. 4 is a diagram showing the results of ultraviolet-visible spectrophotometric measurement (ultraviolet-visible absorption spectrum) by standing time in Example 1-1.

[0027] FIG. 5 is a diagram showing the relationship between standing time and the ratio of absorbance to initial absorbance (indicated as "absorbance (normalized)" in FIG. 6).

[0028] FIG. 6B is a diagram showing the relationship between ligand coverage and dispersion stability in Example 1.

[0029] FIG. 7 is a diagram showing the relationship between ligand coverage and conductivity of the ligand-substituted MXene film in Example 2.

[0012] There is a demand for two-dimensional particles containing MXene that are dispersible in various organic dispersion media. However, as mentioned above, the MXene particles described in Patent Document 1 and Non-Patent Document 1 have limitations on the organic dispersion media in which they can be dispersed and suffer from poor dispersion stability in organic dispersion media. The present inventors investigated these issues and first discovered that the causes of these problems lie in the manufacturing methods of MXene particles described in Patent Document 1 and Non-Patent Document 1. The manufacturing methods described in Patent Document 1 and Non-Patent Document 1 require the addition of hydrochloric acid to the aqueous dispersion containing the MXene particles to lower the pH (to approximately 2.5) prior to the substitution reaction. This is intended to protonate the hydroxyl groups on MXene and accelerate the reaction rate of the phase-separation interfacial reaction. However, under strong acid conditions of approximately pH 2.5, MXene aggregates, forming MXene aggregates. This is thought to be because the zeta potential of MXene changes from negative to near zero, eliminating electrostatic repulsion between flakes. If MXene aggregates are formed before the substitution reaction, the substitution reaction will involve the replacement of hydroxyl groups present on the surface of the MXene layer itself with heteroatom-containing compounds (hereinafter referred to as "ligands") having saturated or unsaturated hydrocarbon groups only around the MXene aggregates (hereinafter referred to as "ligand substitution"). This is thought to result in a decrease in the degree of substitution of hydroxyl groups present on the surface of the layer itself with the heteroatom-containing compounds (hereinafter referred to as "ligand coverage"). A low ligand coverage indicates insufficient hydrophobicity due to surface modification of MXene, which is thought to result in poor dispersion stability in organic dispersion media.

[0013] Therefore, after extensive research, the present inventors have found that in order to solve the above-mentioned problems, in the MXene particle manufacturing process, ligand substitution can be performed on each MXene particle (e.g., single-layer or few-layer MXene flakes) without causing agglomerations of the MXene particles, thereby improving the ligand coverage rate, and that to do this, it is necessary to perform ligand substitution without acidifying the aqueous dispersion in which the MXene particles are dispersed at a stage prior to the substitution reaction.

[0014] Hereinafter, the two-dimensional particles, the two-dimensional particle-containing dispersion, the two-dimensional particle-containing composite, the two-dimensional particle-containing film, and the method for producing the two-dimensional particles according to the present disclosure will be described.

[0015] (Embodiment 1: Two-dimensional particles) Hereinafter, two-dimensional particles according to one embodiment of the present invention will be described in detail, but the present disclosure is not limited to such an embodiment.

[0016] The two-dimensional particle in this embodiment is a two-dimensional particle comprising one or more layers, wherein said layers have the following formula: M ｍ X ｎ (wherein M is at least one metal of Group 3, 4, 5, 6 or 7; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and modified or terminated T present on the surface of the layer body, wherein T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and the layer body has a structure in which M atoms of the layer body and heteroatoms of a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups of the layer body, and the substitution rate of hydroxyl groups present on the surface of the layer body with said structure is 37.5% or more. The two-dimensional particles of this embodiment have a high substitution rate of the phosphate compound for the multiple hydroxyl groups present on the surface of the layer body, i.e., many M atoms in the layer body and heteroatoms of the heteroatom-containing compound having a saturated or unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups in the layer body, thereby providing the two-dimensional particles with excellent dispersion stability in organic dispersion media.

[0017] In this specification, when an "atom" refers to a certain element, the oxidation number of the element is not limited to 0, but may be any number within the range of oxidation numbers that the element can have.

[0018] First, MXene, which constitutes the two-dimensional particles of this embodiment (or precursor particles used to produce the two-dimensional particles of this embodiment), will be described.

[0019] The one or more layers may be understood as a layered compound and referred to as "M ｍ X ｎ T ｓ ", where s is any number, and conventionally, x or z may be used instead of s. Typically, n can be 1, 2, 3, or 4, but is not limited thereto.

[0020] In the above formula for MXene, M is preferably at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn, more preferably at least one selected from the group consisting of Ti, V, Cr, and Mo. Most preferably, M contains Ti. M may be only Ti.

[0021] MXene is a compound represented by the formula: M ｍ X ｎ However, it is known that it can be expressed as follows: Sc ２ C, Ti ２ C, Ti ２ N, Zr ２ C, Zr ２ N, Hf ２ C, Hf ２ N.V. ２ C.V. ２ N, Nb ２ C, Ta ２ C, Cr ２ C, Cr ２ N, Mo ２ C, Mo １．３ C, Cr １．３ C, (Ti, V) ２ C, (Ti, Nb) ２ C.W. ２ C.W. １．３ C, Mo ２ N, Nb １．３ C, Mo １．３ Y ０．６ C (in the above formula, "1.3" and "0.6" mean approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3), respectively), Ti ３ C ２ , Ti ３ N ２ , Ti ３ (CN), Zr３ C ２ 、(Ti,V) ３ C ２ 、(Ti ２ Nb)C ２ 、(Ti ２ Ta)C ２ 、(Ti ２ Mn)C ２ 、Hf ３ C ２ 、(Hf ２ V)C ２ 、(Hf ２ Mn)C ２ 、(V ２ Ti)C ２ 、(Cr ２ Ti)C ２ 、(Cr ２ V)C ２ 、(Cr ２ Nb)C ２ 、(Cr ２ Ta)C ２ 、(Mo ２ Sc)C ２ 、(Mo ２ Ti)C ２ 、(Mo ２ Zr)C ２ 、(Mo ２ Hf)C ２ 、(Mo ２ V)C ２ 、(Mo ２ Nb)C ２ 、(Mo ２ Ta)C ２ 、(W ２ Ti)C ２ 、(W ２ Zr)C ２ 、(W ２ Hf)C ２ 、 Ti ４ N ３ 、V ４ C ３ 、Nb ４ C ３ 、Ta ４ C ３ 、(Ti,Nb) ４ C ３ 、(Nb,Zr) ４ C ３ 、(Ti ２ Nb ２ )C ３, (Ti ２ Ta ２ ) C ３ , (V ２ Ti ２ ) C ３ , (V ２ Nb ２ ) C ３ , (V ２ Ta ２ ) C ３ , (Nb ２ Ta ２ ) C ３ , (Cr ２ Ti ２ ) C ３ , (Cr ２ V ２ ) C ３ , (Cr ２ Nb ２ ) C ３ , (Cr ２ Ta ２ ) C ３ , (Mo ２ Ti ２ ) C ３ , (Mo ２ Zr ２ ) C ３ , (Mo ２ Hf ２ ) C ３ , (Mo ２ V ２ ) C ３ , (Mo ２ Nb ２ ) C ３ , (Mo ２ Ta ２ ) C ３ , (W ２ Ti ２ ) C ３ , (W ２ Zr ２ ) C ３ , (W ２ Hf ２ ) C ３ , (Mo ２．７ V １．３ ) C ３ (In the above formula, "2.7" and "1.3" mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3), respectively.)

[0022] Typically, in the above formula, M can be titanium or vanadium, and X can be a carbon atom or a nitrogen atom. For example, the MAX phase can be Ti ３ AlC ２ and MXene is Ti ３ C ２ T ｓ (In other words, the layer body can be Ti ３ C ２ wherein M is Ti, X is C, n is 2, and m is 3. ３ C ２ In this case, two-dimensional particles with a high ligand coverage can be provided. ３ C ２ Two-dimensional particles in which the surface of the layer body is substituted with a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group, preferably with an alkylphosphonic acid, are preferred because they have extremely high dispersion stability in organic dispersion media.

[0023] In this embodiment, MXene may contain a relatively small amount of A atoms derived from the precursor MAX phase, for example, 10% by mass or less of the original A atoms. The residual amount of A atoms is preferably 8% by mass or less, more preferably 6% by mass or less. However, even if the residual amount of A atoms exceeds 10% by mass, this may not be a problem depending on the application and use conditions of the two-dimensional particles.

[0024] MXene, which constitutes the two-dimensional particles of this embodiment (or precursor particles used to produce the two-dimensional particles of this embodiment), will be described below with reference to Figure 1. Note that Figures 1(a) and 1(b) below do not show the substituents on the surface of the layer body, which are derived from the heteroatom-containing compound having a saturated or unsaturated hydrocarbon group.

[0025] The MXene constituting the two-dimensional particles of this embodiment is an aggregate including one layer of MXene particles (hereinafter simply referred to as "MXene particles") 10a (single-layer MXene particles) as illustrated in Fig. 1(a). More specifically, the MXene particles 10a are ｍ X ｎ The layer body (M ｍX ｎ The MXene layer 7a has a main layer 1a and modifications or terminations T3a, 5a present on the surface of the main layer 1a (more specifically, on at least one of the two opposing surfaces of each layer). ｍ X ｎ T ｓ ", where s is an arbitrary number.

[0026] The two-dimensional particles of this embodiment may contain one or more layers. Examples of MXene particles with multiple layers (multilayer MXene particles) include, but are not limited to, two-layer MXene particles 10b, as shown schematically in FIG. 1(b). 1b, 3b, 5b, and 7b in FIG. 1(b) are the same as 1a, 3a, 5a, and 7a in FIG. 1(a). Two adjacent MXene layers (e.g., 7a and 7b) in a multilayer MXene particle do not necessarily need to be completely separated and may be partially in contact. The MXene particle 10a may be a mixture of the single-layer MXene particle 10a and the multilayer MXene particle 10b, with the multilayer MXene particles 10b remaining unseparated.

[0027] Although this embodiment is not limited thereto, the thickness of each layer (corresponding to the above-described MXene layers 7a and 7b) contained in the MXene particle is, for example, 0.8 nm to 5 nm, particularly 0.8 nm to 3 nm (this thickness may vary mainly depending on the number of M atomic layers contained in each layer). The interlayer distance (or gap dimension, shown as Δd in FIG. 1(b)) of each stack of the multilayer MXene particle that may be contained may be, for example, 0.8 nm to 10 nm, particularly 0.8 nm to 5 nm, more particularly about 1 nm, and the total number of layers may be 2 to 20,000.

[0028] The MXene constituting the two-dimensional particles of this embodiment is preferably a multilayer MXene particle with a small number of layers obtained by a delamination process. The term "small number of layers" refers to, for example, six or fewer MXene layers. Furthermore, the thickness of the multilayer MXene particle with a small number of layers in the stacking direction is preferably 15 nm or less, and more preferably 10 nm or less. Hereinafter, these "multilayer MXene particles with a small number of layers" may be referred to as "small-layer MXene particles." Furthermore, single-layer MXene particles and small-layer MXene particles may be collectively referred to as "single-layer / small-layer MXene particles."

[0029] The MXene constituting the two-dimensional particles of this embodiment preferably contains a large amount of single-layered and few-layered MXene. By including a large amount of single-layered and few-layered MXene, the specific surface area of ​​MXene can be made larger than that of multi-layered MXene, which is thought to result in a larger contact area with the ligand during the substitution reaction and a higher ligand coverage. For example, the layered material particles of this embodiment have 10 or fewer MXene stacks and a thickness of 15 nm or less, preferably 10 nm or less, and the single-layered and few-layered MXene preferably accounts for 80 vol% or more, more preferably 90 vol% or more, and even more preferably 95 vol% or more of the total MXene. Furthermore, it is more preferable that the volume of single-layered MXene is greater than the volume of few-layered MXene. Because the true density of these MXenes does not vary significantly depending on their form, it can also be said that it is more preferable that the mass of single-layered MXene is greater than the mass of few-layered MXene. When these relationships are satisfied, the specific surface area can be further increased, resulting in, for example, improved dispersion stability and, for example, sufficient suppression of deterioration of electrical conductivity over time when the two-dimensional particles of this embodiment are used in electrodes. Most preferably, the MXene constituting the two-dimensional particles of this embodiment is formed solely of a single layer of MXene.

[0030] In the manufacturing process of the two-dimensional particles according to this embodiment, at least some of the hydroxyl groups of the modified or terminated T present on the surface of the layer body are replaced with a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group, and the substitution rate (ligand coverage rate) of the hydroxyl groups present on the surface of the layer body with the heteroatom-containing compound is 37.5% or more.

[0031] In the process for producing two-dimensional particles according to this embodiment, a dehydration condensation reaction occurs between hydroxyl groups present on the surface of the MXene particle (precursor particle) layer and a heteroatom-containing compound having a saturated or unsaturated hydrocarbon group, which serves as a ligand. This reaction can also be described as a reaction in which the hydroxyl groups (particularly hydrogen atoms) present on the surface of the MXene particle (precursor particle) layer are replaced with a heteroatom-containing compound having a saturated or unsaturated hydrocarbon group (preferably an alkylphosphonic acid). This reaction is sometimes referred to as "ligand substitution" below.

[0032] The two-dimensional particles according to this embodiment have a structure in which the M atom (preferably a titanium atom) of the layer body and the heteroatom (preferably one or more atoms selected from the group consisting of phosphorus, nitrogen, sulfur, and silicon, more preferably a phosphorus atom) of the heteroatom-containing compound are covalently or ionically bonded via an oxygen atom (M-O-heteroatom covalent or ionic bond, preferably Ti-O-heteroatom covalent or ionic bond, more preferably Ti-O-P covalent bond). A hydrophobic ligand is connected to MXene via this structure. The M-O-heteroatom covalent or ionic bond can be confirmed by, for example, EDX, NMR, or the like.

[0033] During the manufacturing process of the two-dimensional particles of this embodiment, a substitution reaction of multiple hydroxyl groups present on the surface of the layer body of the MXene particles (precursor particles) with the above-mentioned compound progresses, increasing the covalent or ionic bonds of the above-mentioned M-O-heteroatom and the amount of ligand present on the MXene, i.e., increasing the ligand coverage rate, and introducing many hydrophobic functional groups onto the MXene surface. As a result, the hydrophobicity of the MXene surface is increased, and two-dimensional particles that can be easily dispersed in organic dispersion media can be obtained.

[0034] Examples of the heteroatom-containing compound include phosphoric acid compounds, nitrogen-containing compounds such as amines, silicon-containing compounds such as silanes, and sulfur-containing compounds. Phosphate compounds are preferred. The phosphoric acid compound is preferably a phosphonic acid having a saturated hydrocarbon group or an unsaturated hydrocarbon group. The saturated hydrocarbon group or unsaturated hydrocarbon group may be an aliphatic hydrocarbon, an aliphatic cyclic hydrocarbon, or an aromatic hydrocarbon having 1 or more, further 2 or more, or even 3 or more carbon atoms and, for example, 25 or less, further 20 or less carbon atoms. In some cases, hydrogen atoms in the hydrocarbon may be -OH, NH ２ The phosphonic acid may be substituted with a functional group such as -COOH, -CH=CH-, or the like. Examples of the phosphonic acid having a saturated hydrocarbon group or an unsaturated hydrocarbon group include alkylphosphonic acids. There are no restrictions on the alkyl chain length of the alkylphosphonic acid, and examples include alkylphosphonic acids having alkyl chains of C1 to C15, or even C1 to C12. Examples include methylphosphonic acid (C1), propylphosphonic acid (C3), hexylphosphonic acid (C6), octylphosphonic acid (C8), decylphosphonic acid (C10), and dodecylphosphonic acid (C12).

[0035] The ligand coverage is 37.5% or more, preferably 50% or more. Increasing the ligand coverage dramatically improves dispersion stability when dispersed in an organic dispersion medium. One possible mechanism is that the hydrophobic ligands bound to MXene make the surface hydrophobic, and the degree of hydrophobicity increases. Furthermore, the particles can now be dispersed in organic dispersion media that are compatible with water (solubility in water > 10% w / w), which previously could not be dispersed. One possible reason for this is that the two-dimensional particles according to this embodiment exist in the form of a single layer or a few layers, rather than as aggregates.

[0036] The higher the ligand coverage, the more preferable it is from the viewpoint of improving dispersion stability when dispersed in an organic dispersion medium. The upper limit of the ligand coverage may be, for example, preferably 95%, more preferably about 90%, from the viewpoint of ensuring dispersion stability. The ligand coverage may be calculated as shown in Example 1-1 (Calculation of Ligand Coverage) in the Examples described below.

[0037] The two-dimensional particles can be obtained by, for example, producing them by the recommended production method described below.

[0038] (Embodiment 2: Two-dimensional particle-containing dispersion) The two-dimensional particle-containing dispersion according to this embodiment contains the two-dimensional particles and an organic dispersion medium. The two-dimensional particle-containing dispersion according to this embodiment has a high ligand coverage of the contained two-dimensional particles and many hydrophobic functional groups introduced onto the MXene surface, resulting in excellent dispersion stability. Furthermore, the two-dimensional particle-containing dispersion according to this embodiment uses an organic dispersion medium, which reduces contact with water and oxygen and inhibits oxidation of MXene, and also reduces energy consumption for removing the dispersion medium during film formation.

[0039] The two-dimensional particles contained in the two-dimensional particle-containing dispersion are as described above (Embodiment 1: Two-dimensional particles). The organic dispersion medium is not limited. As the organic dispersion medium, an organic dispersion medium compatible with water (solubility in water > 10% w / w) may be used, or an organic dispersion medium incompatible with water may be used. Unlike Patent Document 1 and the like, this embodiment allows dispersion in an organic dispersion medium compatible with water (solubility in water > 10% w / w), thereby providing a wider selection of organic dispersion media than conventional methods. As the organic dispersion medium, for example, one or more selected from the group consisting of ethanol, 2-propanol, ethylene glycol, methanol, acetone, acetonitrile, DMF, NMF, DMSO, and NMP may be used. Examples of organic dispersion media incompatible with water include 1-hexanol, chloroform, and toluene. The organic dispersion medium is preferably one or more selected from the group consisting of ethanol, 2-propanol, and 1-hexanol. Two-dimensional particle-containing dispersions using these organic dispersion media can achieve a dispersion stability of 50 hours or more (the time it takes for the absorbance in the ultraviolet-visible absorption spectrum to decrease by half from the initial absorbance) in the examples described below.

[0040] (Embodiment 3: Two-Dimensional Particle-Containing Composite) The two-dimensional particle-containing composite according to this embodiment includes the two-dimensional particle-containing dispersion and a polymeric material. The polymeric material may be a solid such as particles, for example, a particulate material that can be dispersed together with the two-dimensional particles in the two-dimensional particle-containing dispersion, or a water-soluble polymer that can be dissolved in the dispersion, i.e., a material dissolved in the dispersion. In the case of a solid such as particles, examples include particles of one or more of polystyrene, polyurethane, and nylon. Examples of water-soluble polymers include water-soluble urethane, acrylic polymer, polyethylene glycol, carboxymethyl cellulose (CMC), alginate polymer, polyether, polyvinyl alcohol, water-soluble polyester, dicarboxylated polysaccharide, etc. One or more of these can be used. The polymeric material preferably includes one or more selected from the group consisting of urethane, nylon, and carboxymethyl cellulose (CMC). When a polymeric material is included, the proportion of the polymeric material in the two-dimensional particle-containing composite may be, for example, 0.01% by mass or more and 50% by mass or less.

[0041] The two-dimensional particle-containing dispersion liquid contained in the two-dimensional particle-containing composite and the two-dimensional particles contained in the dispersion liquid are as described above in (Embodiment 1: Two-dimensional particles) and (Embodiment 2: Two-dimensional particle-containing dispersion liquid).

[0042] The two-dimensional particle-containing composite according to this embodiment is preferably composed of the two-dimensional particle-containing dispersion and a polymer material, and may be, for example, a two-dimensional particle-containing dispersion in which particles composed of a polymer material are dispersed together with the two-dimensional particles according to this embodiment.

[0043] The MXene particles described in Patent Document 1 and Non-Patent Document 1 can only be dispersed in water-immiscible organic dispersion media (solubility in water <10% w / w), which poses a problem of limitations on the resins that can be used when preparing composites of MXene particles and resins. In contrast, the two-dimensional particle-containing composite of the present embodiment contains two-dimensional particles that can be dispersed in a variety of organic dispersion media, which broadens the range of resins that can be used, making it possible to produce composites of the two-dimensional particles of the present embodiment with a variety of resins.

[0044] (Embodiment 4: Two-dimensional particle-containing film) The two-dimensional particle-containing film according to this embodiment contains, among the two-dimensional particles described above (Embodiment 1: Two-dimensional particles), two-dimensional particles having a substitution rate (ligand coverage) of hydroxyl groups present on the surface of the layer body of 75.4% or more. A two-dimensional particle-containing film containing two-dimensional particles with a high ligand coverage, preferably a two-dimensional particle-containing film substantially composed of the above-mentioned two-dimensional particles with a high ligand coverage (unavoidable impurities such as residual dispersion medium are acceptable), exhibits high conductivity, as will be shown in the examples described below.

[0045] The ligand coverage of the two-dimensional particles contained in the two-dimensional particle-containing film can even be greater than 75.4%, even 78% or more, even 80% or more, and even 83% or more. The MXene particles described in Patent Document 1 and Non-Patent Document 1 have low dispersion stability in organic dispersion media, which causes filter membranes and spray films produced using the MXene particles to have poor film quality and fail to exhibit the excellent conductivity that is one of MXene's characteristics. In contrast, the two-dimensional particle-containing film according to this embodiment has a high ligand coverage of the contained two-dimensional particles, further improving dispersion stability in organic dispersion media. As a result, the film quality of two-dimensional particle-containing films, such as filter membranes and spray films, obtained using the two-dimensional particle-containing dispersion liquid is improved. As a result, the conductivity is dramatically increased. For example, the two-dimensional particle-containing film can achieve a conductivity of preferably 10 S / cm or more and 20,000 S / cm or less, measured by the method described in the Examples below. The two-dimensional particle-containing film according to this embodiment has such high conductivity and is suitable for use as, for example, an electrode.

[0046] Next, a method for producing a two-dimensional particle-containing film will be described. For example, two-dimensional particles with a ligand coverage of 75.4% or more can be applied to a substrate to form a film containing the two-dimensional particles on the substrate surface. The two-dimensional particles can be applied to a substrate using, for example, the aforementioned two-dimensional particle-containing dispersion. The two-dimensional particle-containing dispersion may be a suspension. The method for forming a two-dimensional particle-containing film using the two-dimensional particle-containing dispersion is not particularly limited. The two-dimensional particle-containing dispersion may be applied to a substrate either directly or after appropriate adjustment (e.g., dilution with a medium liquid or addition of a binder). Examples of application methods include spray coating using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush; slit coating using a table coater, comma coater, or bar coater; screen printing; metal mask printing; spin coating; dip coating; and dripping. The dispersion medium constituting the dispersion can be an organic dispersion medium. The organic dispersion medium is not particularly limited. According to this embodiment, as the organic dispersion medium, an organic dispersion medium that is compatible with water (solubility in water > 10% w / w) as described above (Embodiment 2: two-dimensional particle-containing dispersion liquid) may be used, or an organic dispersion medium that is not compatible with water may be used.

[0047] When a two-dimensional particle-containing film is obtained by spraying, a slurry containing two-dimensional particles in an organic dispersion medium is first prepared. The thus-prepared slurry is then sprayed to produce a two-dimensional particle-containing film. The two-dimensional particle-containing film may contain, or may not substantially contain, residual liquid components derived from the organic dispersion medium of the slurry. The two-dimensional particle-containing film may not contain a so-called binder.

[0048] The substrate is not particularly limited and can be made of any appropriate material. The substrate may be, for example, a resin film, a metal foil, a printed wiring board, a mounted electronic component, a metal pin, a metal wiring, a metal wire, or the like. For example, a substrate formed of a metal material suitable for an electrode, a resin, or the like can be appropriately employed. A two-dimensional particle-containing film can be formed on any appropriate substrate (which may constitute a predetermined component together with the two-dimensional particle-containing film or may ultimately be separated from the two-dimensional particle-containing film) by coating the two-dimensional particle-containing film on the substrate.

[0049] Instead of the coating method, suction filtration can be used to form a two-dimensional particle-containing film without a binder. Furthermore, a two-dimensional particle-containing film can be formed without using a substrate. Even in the case of suction filtration, the two-dimensional particle-containing film may contain or may be substantially free of liquid components derived from the liquid medium of the slurry.

[0050] Drying may be performed under mild conditions such as natural drying (typically, placing the film in an air atmosphere at room temperature and pressure) or air drying (blowing air), or under relatively active conditions such as hot air drying (blowing heated air), heat drying, and / or vacuum drying. In this embodiment, "drying" refers to removing an organic dispersion medium that may be present in the film. The drying may be performed, for example, at a temperature of 400°C or less using a normal pressure oven or a vacuum oven.

[0051] The formation and drying of the two-dimensional particle-containing film may be appropriately repeated until a desired thickness of the two-dimensional particle-containing film is obtained. For example, a combination of spraying and drying may be repeated multiple times.

[0052] (Embodiment 5: Method for Producing Two-Dimensional Particles) Hereinafter, a method for producing two-dimensional particles according to one embodiment of the present invention will be described in detail, but the present disclosure is not limited to this embodiment.

[0053] The method for producing two-dimensional particles according to this embodiment comprises: (a) a precursor particle comprising one or more layers, wherein the layers are represented by the following formula: M ｍ X ｎ(wherein M is at least one Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and a modified or terminated T present on the surface of the layer body (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and includes at least a hydroxyl group); (b) preparing an aqueous dispersion containing the precursor particles and a compound-containing organic solution in which a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is dissolved in an organic solvent that is compatible with the aqueous dispersion; and (c) mixing and stirring the aqueous dispersion containing the precursor particles and the compound-containing organic solution to obtain a structure in which M atoms of the layer body and heteroatoms of the heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups of the layer body. According to this method, aggregation of precursor particles (MXene particles) is suppressed, and two-dimensional particles with a high ligand coverage can be obtained.

[0054] Each step of the above-mentioned production method will be described in detail below. Step (a) Preparing predetermined MXene particles (precursor particles). The production of the MXene particles (precursor particles) is not limited, and they can be produced, for example, by the following method.

[0055] Etching of MAX Phases Particles of a given layered material (MXene particles, precursor particles) can be synthesized by selectively etching (removing and optionally layer-separating) A atoms (and optionally some of the M atoms) from a MAX phase. The MAX phase has the following formula: ｍ AX ｎ (wherein M, X, n and m are as defined above, A is at least one element of Groups 12, 13, 14, 15 and 16, and is usually an element of Group A, typically Group IIIA and Group IVA, and more particularly may contain at least one element selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S and Cd, and is preferably Al), and Mｍ X ｎ (each X may have a crystal lattice in which it is located in an octahedral array of M) and a layer composed of A atoms is located between them. In the MAX phase, typically when m=n+1, one layer of X atoms is arranged between each of the n+1 layers of M atoms (these are collectively referred to as "M ｍ X ｎ The repeating unit has a layer of A atoms (also referred to as an "A atom layer") arranged as the next layer after the n+1th layer of M atoms, but is not limited thereto.

[0056] Etching is performed to remove at least some of the A atoms from the precursor using an etching solution. The etching solution is HF, H ３ P.O. ４ , HCl, HI and H ２ SO ４ The etching solution preferably contains at least one of HF (hydrofluoric acid) and H ３ P.O. ４ It is more preferable that the etching solution contains at least one of the following: (phosphoric acid). For example, etching can be performed by the so-called MILD method, in which HCl and LiF contained in the etching solution are reacted in the system to generate HF; however, it is preferable to perform etching using an etching solution containing HF (hydrofluoric acid), the so-called ACID method, or an etching solution containing phosphoric acid. These methods are preferable because they make it easier to obtain flake-shaped layered material particles (MXene particles) with a large planar area than the MILD method. Other etching conditions are not particularly limited, and known conditions can be adopted. As the etching solution, a mixture of the above acid and, for example, pure water as a solvent can be used. As the etching solution, a solution with an HF concentration of 1.5M or more and 14M or less, and H ３ P.O. ４ concentration of 5.5M or more, HCl concentration of 6.0M or more, HI concentration of 5.0M or more, and H ２ SO ４An etching solution having a concentration of at least one selected from the group consisting of 5.0 M or more can be used. In the etching of the A atoms, in addition to the A atoms, some of the M atoms may also be selectively etched in some cases. An example of the etched product obtained by the above etching is a slurry.

[0057] The MAX phase can be produced by a known method. For example, TiC powder, Ti powder, and Al powder are mixed in a ball mill, and the resulting mixed powder is sintered in an Ar atmosphere to obtain a sintered body (a block of the MAX phase). The sintered body is then pulverized with an end mill to obtain the powdered MAX phase for the next step.

[0058] The A atoms (and possibly some of the M atoms) are selectively etched (removed and possibly layer separated) from the MAX phase, thereby removing the A atom layer (and possibly some of the M atoms) to expose the M ｍ X ｎ The surface of the layer is modified with at least one selected from the group consisting of hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms and hydrogen atoms (including at least hydroxyl groups) present in the etching solution (usually, an aqueous solution of fluorine-containing acid is used, but this is not limited to this), thereby terminating the surface.

[0059] The etching solution may contain a metal compound containing a monovalent metal ion, and an intercalation treatment of the monovalent metal ion may be carried out simultaneously with the etching. Examples of metal compounds containing monovalent metal ions include those used in the intercalation treatment described below. The content of the metal compound containing monovalent metal ions in the etching solution is preferably 0.001% by mass or more. The content is more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more. On the other hand, from the viewpoint of dispersibility in the solution, the content of the metal compound containing monovalent metal ions in the etching solution is preferably 10% by mass or less, more preferably 1% by mass or less.

[0060] (Water Washing) The etched product obtained by the etching is washed with water. By washing with water, the acid used in the etching can be sufficiently removed. The amount of water to be mixed with the etched product and the washing method are not particularly limited. For example, water may be added and the mixture may be stirred or centrifuged. Stirring methods include stirring using a hand shake, an automatic shaker, a shear mixer, a pot mill, or the like. The degree of stirring, such as the stirring speed and stirring time, may be adjusted depending on the amount and concentration of the material to be treated. The water washing may be performed one or more times. Preferably, the water washing is performed multiple times. For example, steps (i) to (iv) of (i) adding water (to the etched product or the remaining precipitate obtained in (iv) below), (ii) stirring, (iii) centrifuging the stirred product, and (iv) discarding the supernatant after centrifugation and recovering the remaining precipitate may be performed two or more times, for example, 15 or less times.

[0061] [MXene Layer Separation] The treated product (water-washed product) obtained by the water washing may be used to promote layer separation of MXene (delamination, separating multilayer MXene into single-layer MXene) by any appropriate post-treatment (e.g., ultrasonic treatment, hand shaking, automatic shaker, etc.). Since ultrasonic treatment can destroy MXene due to excessive shear force, if it is desired to obtain two-dimensional MXene particles with a larger aspect ratio (preferably single-layer MXene), it is preferable to apply an appropriate shear force using a hand shake or automatic shaker, etc. The intercalation treatment and delamination are described below.

[0062] (Intercalation Treatment) For example, a monovalent metal ion intercalation treatment may be performed, which includes a step of mixing the etched product obtained by the etching treatment with a metal compound containing a monovalent metal ion. Examples of the monovalent metal ion constituting the metal compound containing a monovalent metal ion include alkali metal ions such as lithium ions, sodium ions, and potassium ions, copper ions, silver ions, and gold ions. Examples of the metal compound containing a monovalent metal ion include ionic compounds in which the above metal ions are bonded to cations. Examples include iodides, phosphates, sulfide salts including sulfates, nitrates, acetates, and carboxylates of the above metal ions. As described above, lithium ions are preferred as the monovalent metal ion, and metal compounds containing lithium ions are preferred as metal compounds containing lithium ions, more preferably ionic compounds of lithium ions, and even more preferably one or more of iodides, phosphates, and sulfide salts of lithium ions. If lithium ions are used as the metal ion, it is thought that water hydrated with lithium ions has the most negative dielectric constant, making it easier to form a monolayer.

[0063] The content of the metal compound containing a monovalent metal ion in the formulation for intercalation treatment of a monovalent metal ion is preferably 0.001% by mass or more. The content is more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more. On the other hand, from the viewpoint of dispersibility in the solution, the content of the metal compound containing a monovalent metal ion is preferably 10% by mass or less, more preferably 1% by mass or less.

[0064] The specific method of intercalation is not particularly limited. For example, a metal compound containing a monovalent metal ion may be mixed with the MXene water medium clay, and the mixture may be stirred or left to stand. For example, stirring at room temperature may be used. Examples of the stirring method include a method using a stirring bar such as a stirrer, a method using a stirring blade, a method using a mixer, and a method using a centrifugal device. The stirring time can be set depending on the production scale of the two-dimensional particles, and may be set, for example, between 12 and 24 hours.

[0065] (Delamination) Delamination may be performed using the intercalation-treated product obtained by intercalation. For example, delamination may involve centrifuging the intercalation-treated product, discarding the supernatant, and then washing the remaining precipitate with water. The conditions for the delamination treatment are not particularly limited. The dispersion medium used for delamination is also not particularly limited, and examples include using one or more polar organic dispersion mediums and aqueous dispersion mediums. This process may be repeated at least once, preferably at least twice, but not more than 10 times, to obtain a supernatant containing single-layered and / or few-layered MXene as the delamination-treated product. Alternatively, the supernatant may be centrifuged, and the resulting supernatant may be discarded to obtain a single-layered and / or few-layered MXene-containing clay as the delamination-treated product. The resulting delamination-treated product may be used as an aqueous dispersion containing precursor particles.

[0066] The delamination-treated product, which is the supernatant containing the single-layer / few-layer MXene or the single-layer / few-layer MXene-containing clay, may be subjected to removal of the dispersion medium to obtain a dried precursor particle.

[0067] Step (b) preparing an aqueous dispersion containing the precursor particles; and a compound-containing organic solution in which a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is dissolved in an organic solvent that is compatible with the aqueous dispersion.

[0068] The aqueous dispersion containing the precursor particles may be the single-layered or few-layered MXene-containing clay obtained by the delamination process, or the aqueous dispersion may have an adjusted water content. Alternatively, the aqueous dispersion may be prepared by dispersing the precursor particles (dried product) obtained by the above method in water. The proportion of the precursor particles contained in the aqueous dispersion containing the precursor particles may be, for example, in the range of 0.01% by mass to 1% by mass (solid content).

[0069] Unlike Patent Document 1 and the like, the aqueous dispersion containing the precursor particles is not acidic but neutral when mixed with the compound-containing organic solution. The aqueous dispersion containing the precursor particles preferably has a pH in the range of 6 to 8. In other words, this invention differs from Patent Document 1 and Non-Patent Document 1 in that no acid such as hydrochloric acid is added to the aqueous dispersion containing precursor particles (MXene particles) before mixing with the compound-containing organic solution.

[0070] A compound-containing organic solution is prepared by dissolving a heteroatom-containing compound having a saturated or unsaturated hydrocarbon group in an organic solvent compatible with the aqueous dispersion. The compounds described above can be used as the heteroatom-containing compound having a saturated or unsaturated hydrocarbon group. The organic solvent used to prepare the compound-containing organic solution is not particularly limited as long as it is compatible with the aqueous dispersion (solubility in water > 10% w / w). Examples of organic solvents that are compatible with water (solubility in water > 10% w / w) include one or more selected from the group consisting of ethanol, 2-propanol, ethylene glycol, methanol, acetone, acetonitrile, DMF, NMF, DMSO, and NMP.

[0071] The ratio of the heteroatom-containing compound having a saturated or unsaturated hydrocarbon group contained in the compound-containing organic solution may be, for example, in the range of 0.01 mol / L to 1 mol / L.

[0072] Step (c) The aqueous dispersion containing the precursor particles and the compound-containing organic solution are mixed and stirred to obtain a structure in which the M atoms of the layer body and the heteroatoms of the heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups of the layer body.

[0073] The method for mixing and stirring the aqueous dispersion containing precursor particles and the compound-containing organic solution is not particularly limited. The stirring can be performed, for example, for a period of 6 hours or more and 24 hours or less. According to this embodiment, the aqueous dispersion containing precursor particles is mixed with a compound dissolved in an organic solvent compatible with the aqueous dispersion and stirred. This results in a reaction mode in which the precursor particles (MXene particles) and the ligand are contained in the same system, rather than a phase-separation type interfacial reaction as in Patent Document 1. Therefore, the contact frequency between the hydroxyl groups on MXene and the ligand is increased compared to the phase-separation type interfacial reaction described above, thereby facilitating the substitution reaction without the addition of hydrochloric acid as in Patent Document 1. As a result, the substitution rate (ligand coverage) of the ligand on the surface of the precursor particles (MXene particles) can be improved.

[0074] The ratio of the heteroatom-containing compound to the precursor particles is preferably as high as possible, and the ratio of the precursor particles to the heteroatom-containing compound may be 1:(3 or more). For example, when the precursor particles are Ti ３ C ２ (OH) ２ When the heteroatom-containing compound is dodecylphosphonic acid, the blending ratio may be precursor particles:heteroatom-containing compound (molar ratio)=1:(3 to 20), and may further be precursor particles:heteroatom-containing compound (molar ratio)=1:(6 to 10).

[0075] The method for producing two-dimensional particles according to this embodiment may include at least the above steps (a) to (c) in this order, and other steps are not limited. For example, after step (c), a step of washing the ligand-substituted MXene particles obtained by the reaction may be included.

[0076] The present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples, and can be implemented by making appropriate modifications within the scope of the above-mentioned and below-mentioned aims, and all such modifications are included in the technical scope of the present disclosure.

[0077] Example 1-1 In this example, dodecylphosphonic acid (phosphonic acid with an alkyl chain length of 12 (C12)) was used as the ligand (heteroatom-containing compound, surface modifier), and alkylphosphonic acid-substituted MXene particles were produced as two-dimensional particles (ligand-substituted MXene particles). However, the type of alkylphosphonic acid is not limited, and various alkylphosphonic acids can be used. Note that when the raw materials, such as alkylphosphonic acid, are changed, the weight added may change, taking into account the molecular weight of each.

[0078] (Preparation of MXene particles (precursor particles)) First, the following steps were carried out in order: (1) preparation of precursor (MAX), (2) etching of precursor, (3) cleaning after etching, (4) Li intercalation, and (5) delamination, as detailed below, to obtain precursor particles (single-layer / few-layer MXene-containing samples, MXene particles) to be subjected to treatments such as ligand substitution.

[0079] [1] Preparation of Precursor (MAX) TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were mixed in a molar ratio of 2:1:1 in a ball mill containing zirconia balls for 24 hours. The resulting mixed powder was fired at 1350°C for 2 hours in an Ar atmosphere. The fired body (block-shaped MAX) was then crushed with an end mill to a maximum size of 40 μm or less. This resulted in the preparation of TiC powder as a precursor (powdered MAX). ３ AlC ２ particles were obtained.

[0080] [2] Etching of precursor (MAX) Ti prepared by the above method ３ AlC ２ Etching was carried out using particles (powder) under the following etching conditions to remove Ti. ３ AlC ２ A solid-liquid mixture (slurry) containing solid components derived from the powder was obtained. (Etching conditions) Precursor: Ti ３ AlC ２ (Sieved through a 45 μm mesh) Etching solution composition: 49% HF 6 mL H ２O 18 mL HCl (12 M) 36 mL Precursor input amount: 3.0 g Etching container: 100 mL Eye Boy Etching temperature: 35°C Etching time: 24 h Stirrer rotation speed: 400 rpm

[0081] [3] Post-etching cleaning The above slurry was divided into two parts and placed in two 50 mL centrifuge tubes. Then, after centrifuging at 3500 G for 5 minutes using a centrifuge, the supernatant was discarded. Thereafter, (i) 40 mL of pure water was added to the remaining precipitate in each centrifuge tube, (ii) centrifugation was again performed at 3500 G for 5 minutes, and (iii) the supernatant was separated and removed. This procedure from (i) to (iii) was repeated 11 times. After the final centrifugation, the supernatant was discarded, and Ti ３ AlC ２ T ｘ - Water medium clay was obtained.

[0082] [4] Li intercalation Ti prepared by the above method ３ AlC ２ T ｘ The clay was subjected to Li intercalation using LiCl as a Li-containing compound under the following conditions: the clay was stirred at 20°C to 25°C for 12 hours. (Li intercalation conditions) ３ AlC ２ T ｘ - Water medium clay (MXene after washing): solid content 0.75 g LiCl: 0.75 g Intercalation container: 100 mL Eye Boy Temperature: 20 ° C or higher and 25 ° C or lower (room temperature) Time: 12 hours Stirrer rotation speed: 800 rpm

[0083] [5] Delamination The slurry obtained by Li intercalation was placed in a 50 mL centrifuge tube and centrifuged at 3500 G using a centrifuge. The supernatant was then discarded. Next, (i) 40 mL of pure water was added to the remaining precipitate, followed by stirring for 15 minutes on a shaker. (ii) The mixture was centrifuged at 3500 G. (iii) The supernatant was recovered as a single-layer / sparse-layer MXene-containing solution. These steps (i) to (iii) were repeated four times to obtain a single-layer / sparse-layer MXene-containing supernatant. Furthermore, this supernatant was centrifuged at 4300 G for 2 hours using a centrifuge. The supernatant was then discarded, and the remaining precipitate, a single-layer / sparse-layer MXene-containing clay (hereinafter simply referred to as MXene clay), was obtained as a clay containing MXene particles (precursor particles).

[0084] In this example, the clay (MXene clay) containing MXene particles (precursor particles) obtained in the preparation of the MXene particles (precursor particles) described above was used to obtain a ligand-substituted MXene particle-containing dispersion by carrying out the following steps in order: (1) synthesis of ligand-substituted MXene particles, (2) washing of the ligand-substituted MXene particles, and (3) preparation of a ligand-substituted MXene particle-containing dispersion, as described in detail below. The ligand-substituted MXene particle-containing dispersion was then used to evaluate the ligand coverage by TG-DTA and (5) dispersion stability.

[0085] (1) Synthesis of Ligand-Substituted MXene Particles MXene clay was dispersed in pure water to prepare an aqueous dispersion containing MXene particles at a solids concentration of 1 mg / mL. 20 mL of this aqueous dispersion containing MXene particles was prepared and transferred to a 50 mL vial containing a stirrer. 165.2 mg (0.660 mmol) of dodecylphosphonic acid (Tokyo Chemical Industry Co., Ltd.) was weighed into a separate vial, and the dodecylphosphonic acid was completely dissolved in 5 mL of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.). The organic solvent used to dissolve the dodecylphosphonic acid is not limited to ethanol, as long as it is compatible with water.

[0086] Five mL of dodecylphosphonic acid dissolved in ethanol was added to a vial containing the MXene particle-containing dispersion, and the mixture was stirred for 24 hours at 800 rpm using a magnetic stirrer at room temperature of 20-25°C to obtain a mixed solution. The mixed solution did not undergo phase separation during or after stirring, indicating that it remained a homogeneous system. The pH of the mixed solution was measured and found to be 6.1. By using the method of this embodiment, the substitution reaction can be carried out in a state where the MXene particles and dodecylphosphonic acid are contained in the same system, which is thought to result in a more efficient substitution reaction and improved ligand coverage of MXene.

[0087] (2) Washing of Ligand-Substituted MXene Particles After stirring, the sample solution was transferred to a 50 mL centrifuge tube and centrifuged at room temperature, 5,000 rpm, and for 5 minutes, after which the supernatant was discarded. Next, 20 mL of ethanol was added to the precipitate to redisperse it. This procedure of adding ethanol to the precipitate, centrifuging, and discarding the supernatant was repeated two more times (a total of three times) to remove unreacted dodecylphosphonic acid and MXene that had not undergone the substitution reaction.

[0088] (3) Preparation of a dispersion containing ligand-substituted MXene particles After discarding the supernatant from the third centrifugation in (2) above, 20 mL of ethanol was added to the precipitate as an organic dispersion medium and dispersed to prepare a dispersion of ligand-substituted MXene particles in the organic dispersion medium. Note that there are no restrictions on the organic dispersion medium used to disperse the ligand-substituted MXene particles, and any organic dispersion medium other than those listed above can be used.

[0089] (4) Evaluation of Ligand Coverage The dispersion containing the ligand-exchanged MXene particles after centrifugation in (2) above was transferred to a 10 mL Petri dish, and the dispersion medium, ethanol, was removed by natural drying to obtain ligand-exchanged MXene particles. As long as the ligand-exchanged MXene particles are obtained, the method is not limited to the above, and the dispersion medium can also be removed by suction filtration or the like.

[0090] The thermal decomposition behavior of the resulting ligand-substituted MXene particles was investigated using a TG-DTA (Bruker: 2000SA) at room temperature to 600°C under N ２The results were obtained under the conditions of a 10°C / min temperature rise rate and a 10°C / min atmosphere. The weight loss results are shown in Figure 2. From Figure 2, weight loss due to the ligand was confirmed around 500°C, and the weight loss rate at 600°C was 19.33%.

[0091] (Calculation of Ligand Substitution Amount) The calculation of the ligand substitution amount will now be described. Because the ligand-substituted MXene particles contain small amounts of water and residual organic dispersion medium (ethanol), weight loss was observed even up to around 100°C. However, since the weight loss up to around 100°C is unrelated to ligand substitution, the absolute value of the weight loss rate at 100°C subtracted from the absolute value of the weight loss rate at 600°C was used as the weight loss rate due to ligand substitution. In this example, the absolute value of the weight loss rate at 600°C (20.43%) minus the absolute value of the weight loss rate at 100°C (1.10%) was used as the weight loss rate due to ligand substitution (also referred to as the "ligand substitution amount"), which was 19.33%.

[0092] (Calculation of Ligand Coverage) Next, the calculation of the ligand coverage will be described. The ligand substitution amount calculated in (Calculation of Ligand Substitution Amount) above is a figure that can only be used when dodecylphosphonic acid is used as the ligand. Assuming that ligands other than dodecylphosphonic acid are also used, the ligand coverage is calculated based on a generalized concept of ligands. In considering the ligand coverage, the following [a] to [c] were first assumed. [a] One ligand is substituted for three Ti—OH groups, and as shown particularly on the left side of the schematic diagram in FIG. 3, the ratio of "(Ti—O) ３ [b] All of the substituents on MXene are Ti-OH, and all of the -OH in all of these Ti-OH are replaced with ligands. [c] In TG-DTA, as shown in Figure 3, only the alkyl chain portion of the ligand is thermally decomposed, resulting in a weight loss.

[0093] The unit cell molecular weights before and after pyrolysis were calculated, and the weight loss rate was roughly estimated to be 33.62% based on the above [a] to [c].

[0094] In fact, the substituents on MXene include not only -OH but also -Cl and -F. Therefore, the proportions of substituents other than -OH were taken into consideration as follows. MXene was analyzed by combustion ion chromatography (IC) to first measure the weight ratios of F and Cl in MXene. These measurements were then used to roughly estimate the proportions of -OH, -F, and -Cl in the substituents on MXene. As a result of this rough calculation, the ratio of MXene's substituents was OH:Cl:F = 65:5:30. The weight loss rate of 33.62%, assuming only -OH as the substituent on MXene, was multiplied by 0.65, the proportion of -OH in the substituents on MXene, to calculate a theoretical weight loss rate of 21.85% due to ligand substitution. This value is based on the assumption that all of the -OH groups in the substituents on MXene are replaced with ligands.

[0095] The ligand coverage was calculated using the weight loss rate (theoretical value) due to ligand substitution calculated as above, from [weight loss rate (measured value) / weight loss rate (theoretical value)] × 100 (%). In this example, the weight loss rate (measured value) due to ligand substitution was 19.33%, and the weight loss rate (theoretical value) due to ligand substitution was 21.85%, and using these values, the ligand coverage was calculated as (19.33% / 21.85%) × 100 = 88.5%.

[0096] (5) Evaluation of Dispersion Stability The dispersion stability was evaluated using the dispersion containing the ligand-substituted MXene particles prepared in (3) above.

[0097] 30 mL of the dispersion containing ligand-substituted MXene particles was added to a 50 mL vial. As shown in Figure 4, an ultraviolet-visible spectrophotometer (Shimadzu Corporation: UV1800) was used to adjust the absorbance at 800 nm, which is characteristic of MXene, to approximately 0.5 (this procedure was performed to roughly equalize the ligand-substituted MXene particle concentration). Hereinafter, the absorbance at 800 nm for the ligand-substituted MXene particles will be referred to as the absorbance value.

[0098] The dispersion was sonicated for 10 minutes to thoroughly disperse the ligand-substituted MXene particles, and then allowed to stand. The supernatant was then removed and its absorbance was measured using a UV-visible spectrophotometer. The supernatant was collected gently to avoid stirring up the precipitate. This procedure of removing the supernatant and measuring its absorbance was repeated at regular intervals to evaluate the sedimentation rate (i.e., dispersion stability) of the ligand-substituted MXene particles over time. The results are shown in Figures 5 and 6. Figure 5 shows the absorbance measured at wavelengths of 200 to 900 nm after standing for 0, 5, 24, and 144 hours. 6 is a graph showing the ratio of absorbance (absorbance to initial absorbance) at a standing time of 5 hours, 24 hours, and 144 hours to the initial absorbance, where the absorbance (initial absorbance) at a wavelength of 800 nm in FIG. 5 is set to 1.0 (also referred to as "absorbance (normalized)") In this example, the relationship between the measured standing time and the ratio of absorbance to initial absorbance (absorbance (normalized)) was determined from the measurement results, or the time at which the ratio of absorbance to initial absorbance reached 0.5, which was determined by directly reading from the graph, was used to evaluate dispersion stability. A longer time indicates better dispersion stability. In Example 1-1, the relationship between the measured standing time and the ratio of absorbance to initial absorbance (absorbance (normalized)) was determined, and the time at which the ratio of absorbance to initial absorbance reached 0.5 was calculated from the relationship, which was 347 hours.

[0099] Example 1-2 Ligand-substituted MXene particles were prepared in the same manner as in Example 1-1 (1), except that the weighed amount of dodecylphosphonic acid was changed from 165.2 mg to 99.1 mg or 132.2 mg.

[0100] (Evaluation of Ligand Coverage) The ligand coverage was evaluated in the same manner as in (4) of Example 1-1. The results are shown in Table 1 together with the results of Example 1-1.

[0101] The results in Table 1 show that there is a correlation between the amount of dodecylphosphonic acid used during synthesis and the ligand coverage rate, and that a smaller amount of dodecylphosphonic acid tends to result in a lower ligand coverage rate.

[0102] (Evaluation of Dispersion Stability) The dispersion stability of the dispersion containing the ligand-substituted MXene particles was evaluated in the same manner as in (5) of Example 1-1. The results are shown in Table 1 together with the results of Example 1-1.

[0103]

[0104] As shown in Table 1, the dispersion stability of the ligand-substituted MXene particle-containing dispersion increased with increasing ligand coverage. Furthermore, it was found that all ligand-substituted MXene particles with a ligand coverage of 37.5% or higher had a dispersion stability of 50 hours or more.

[0105] [Example 1-3] Ligand-substituted MXene particles were prepared in the same manner as in Example 1-1, except that in (3) of Example 1-1, the organic dispersion medium used to prepare the dispersion containing the ligand-substituted MXene particles was changed from ethanol to 2-propanol or 1-hexanol.

[0106] (Evaluation of Ligand Coverage) The ligand coverage was evaluated in the same manner as in (4) of Example 1-1. The results are shown in Table 2 together with the results of Example 1-1.

[0107] (Evaluation of Dispersion Stability) The dispersion stability of the dispersion containing the ligand-substituted MXene particles was evaluated in the same manner as in (5) of Example 1-1. The results are shown in Table 2 together with the results of Example 1-1.

[0108]

[0109] From the results in Table 2, it was confirmed that all of the ligand-substituted MXene particles with a ligand coverage rate of 37.5% or more had dispersion stability of 50 hours or more.

[0110] Comparative Example 1-1 (1) Synthesis of Ligand-Substituted MXene Particles MXene clay was dispersed in pure water to prepare an MXene particle-containing dispersion adjusted to a 1 mg / mL MXene solids concentration. 20 mL of this MXene particle-containing dispersion was prepared and transferred to a 50 mL vial containing a stirrer. Subsequently, 10 μL of hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the MXene particle-containing dispersion to acidify the pH of the MXene particle-containing dispersion from approximately 7 to 2.5. 33.0 mg (0.13 mmol) of dodecylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was weighed into a separate vial, and the dodecylphosphonic acid was completely dissolved in 20 mL of 1-hexanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0111] To a vial containing the MXene particle-containing dispersion, 20 mL of dodecylphosphonic acid dissolved in 1-hexanol was added, and the mixture was stirred for 24 hours at a stirring speed of 1,500 rpm using a magnetic stirrer at room temperature of 20 to 25°C to obtain a mixed solution. Unlike the mixed solution obtained in Example 1-1, this mixed solution separated into two phases: an aqueous phase and a 1-hexanol phase. Furthermore, addition of hydrochloric acid to the MXene particle-containing dispersion caused the MXene to aggregate.

[0112] (2) Washing of Ligand-Substituted MXene Particles After stirring, the 1-hexanol phase in the sample solution was transferred to a 50 mL centrifuge tube and centrifuged at room temperature, 8,000 rpm, and for 8 minutes, after which the supernatant was discarded. Next, 20 mL of ethanol was added to the precipitate to redisperse it. This procedure of adding ethanol to the precipitate, centrifuging, and discarding the supernatant was repeated two more times (a total of three times) to remove unreacted dodecylphosphonic acid.

[0113] (3) Preparation of Ligand-Substituted MXene Particle-Containing Dispersion and (4) Evaluation of Ligand Coverage A ligand-substituted MXene particle-containing dispersion was prepared in the same manner as in Example 1-1 (3), and then the ligand-substituted MXene particles were obtained. The thermal decomposition behavior of the ligand-substituted MXene particles was then confirmed in the same manner as in Example 1-1 (4).

[0114] (Calculation of Ligand Substitution Amount) The calculation of the ligand substitution amount will now be described. Because the ligand-substituted MXene particles contain traces of moisture and residual organic dispersion medium (1-hexanol), weight loss was observed near 100°C and 200°C. However, since the weight loss at these temperatures is unrelated to ligand substitution, the weight loss rate due to ligand substitution was determined by subtracting the absolute value of the weight loss rate at 200°C from the absolute value of the weight loss rate at 600°C. In this example, the weight loss rate due to ligand substitution (amount of ligand substitution) was determined by subtracting the absolute value of the weight loss rate at 200°C (2.62%) from the absolute value of the weight loss rate at 600°C (5.74%), yielding 3.12%. Next, the ligand coverage was calculated in the same manner as in Example 1-1 (4), and was found to be 14.2%. (5) Evaluation of Dispersion Stability The dispersion stability of the ligand-substituted MXene particle-containing dispersion was evaluated in the same manner as in Example 1-1 (5). As a result, the time required for the ratio of absorbance to the initial absorbance to reach 0.5 was 9 hours.

[0115] Comparative Example 1-2 Ligand-substituted MXene particles were prepared in the same manner as in Comparative Example 1-1 (1), except that the weighed amount of dodecylphosphonic acid was changed from 33.0 mg to 99.1 mg, 132.2 mg, or 165.2 mg.

[0116] (Evaluation of Ligand Coverage) The ligand coverage was evaluated in the same manner as in (4) of Example 1-1. The results are shown in Table 3 together with the results of Comparative Example 1-1.

[0117] (Evaluation of Dispersion Stability) The dispersion stability of the dispersion containing the ligand-substituted MXene particles was evaluated in the same manner as in (5) of Example 1-1. The results are shown in Table 3 together with the results of Comparative Example 1-1.

[0118]

[0119] As shown in Table 3, in the comparative method, even when the amount of dodecylphosphonic acid used in the synthesis of ligand-substituted MXene particles was increased from 33.0 mg to 165.2 mg, the ligand coverage was only about 32%, and it was not possible to increase the ligand coverage. Furthermore, it was found that all ligand-substituted MXene particles with a ligand coverage of less than 37.5% had a dispersion stability of less than 50 hours.

[0120] [Comparative Example 1-3] Ligand-substituted MXene particles were prepared in the same manner as in Comparative Example 1-1, except that in (1) of Comparative Example 1-1, the weighed amount of dodecylphosphonic acid was changed to 33.0 mg (0.13 mmol) (same as in Comparative Example 1-1) or 165.2 mg, and in (3) of Comparative Example 1-1, the dispersion medium used to prepare the ligand-substituted MXene particle-containing dispersion was changed to 2-propanol or 1-hexanol instead of ethanol.

[0121] (Evaluation of Ligand Coverage) The thermal decomposition behavior of the ligand-substituted MXene particles was confirmed in the same manner as in Example 1-1 (4). The results are shown in Table 4.

[0122] (Evaluation of Dispersion Stability) The dispersion stability of the dispersion containing the ligand-substituted MXene particles was evaluated in the same manner as in (5) of Example 1-1. The results are shown in Table 4.

[0123]

[0124] Table 4 shows that all of the ligand-substituted MXene particles with a ligand coverage rate of less than 37.5% had a dispersion stability of less than 50 hours.

[0125] Comparing Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3, the production process for ligand-substituted MXene particles did not use hydrochloric acid and was a mixed homogeneous system rather than a two-phase separation system, thereby increasing the frequency of contact between the ligand and MXene, and as a result, the ligand coverage rate on MXene dramatically improved from approximately 14% to approximately 89%.

[0126] Figure 7 shows the relationship between ligand coverage and dispersion stability, based on the results of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3. Figure 7 shows that a dramatic increase in the ligand coverage of MXene from approximately 14% to approximately 89% dramatically improved dispersion stability, from 9 hours to 347 hours. In particular, when the ligand coverage was 37.5% or higher, the dispersion stability was 50 hours or higher, demonstrating high dispersion stability.

[0127] In Example 2, a film was formed using a dispersion of ligand-substituted MXene particles, and the electrical conductivity of the resulting ligand-substituted MXene film was evaluated. Specifically, in Example 2, clay (MXene clay) containing MXene particles (precursor particles) obtained in the preparation of the MXene particles (precursor particles) described above was used, and the following procedures were carried out: (1) synthesis of ligand-substituted MXene particles, (2) washing of the ligand-substituted MXene particles, (3) preparation of a dispersion containing ligand-substituted MXene particles, (4) film formation using the dispersion containing ligand-substituted MXene particles, and (5) evaluation of the electrical conductivity of the ligand-substituted MXene film, as described in detail below.

[0128] (1) Synthesis of Ligand-Substituted MXene Particles MXene clay was dispersed in pure water to prepare an MXene particle-containing dispersion adjusted to a MXene solids concentration of 1 mg / mL. 20 mL of this MXene particle-containing dispersion was prepared and transferred to a 50 mL vial containing a stirrer. 63.4 mg (0.65 mmol) of methylphosphonic acid (Tokyo Chemical Industry Co., Ltd.) was weighed into another vial, and the methylphosphonic acid was completely dissolved in 5 mL of ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.). The organic solvent used to dissolve the methylphosphonic acid is not limited to ethanol, as long as it is compatible with water.

[0129] Five mL of methylphosphonic acid dissolved in ethanol was added to a vial containing the MXene particle-containing dispersion, and the mixture was stirred for 24 hours at a stirring speed of 800 rpm using a magnetic stirrer at room temperature of 20-25°C to obtain a mixed solution. The mixed solution did not undergo phase separation during stirring or when stirring was stopped, indicating that it was a homogeneous system. The pH of the mixed solution was measured and found to be 6.5. By producing MXene using the method of this embodiment, the substitution reaction can be carried out in a state where MXene and methylphosphonic acid are contained in the same system, which is thought to result in a more efficient substitution reaction and improved ligand coverage of MXene.

[0130] (2) Washing of Ligand-Substituted MXene Particles After stirring, the sample solution was transferred to a 50 mL centrifuge tube and centrifuged at room temperature, 5,000 rpm, and for 5 minutes, after which the supernatant was discarded. Next, 20 mL of ethanol was added to the precipitate to redisperse it. This procedure of adding ethanol to the precipitate, centrifuging, and discarding the supernatant was repeated two more times (a total of three times) to remove unreacted methylphosphonic acid.

[0131] (3) Preparation of a dispersion containing ligand-substituted MXene particles After discarding the supernatant from the third centrifugation in (2) above, 20 mL of ethanol was added to the precipitate as an organic dispersion medium and dispersed to prepare a dispersion containing ligand-substituted MXene particles in the organic dispersion medium. Note that there are no restrictions on the organic dispersion medium used to disperse the ligand-substituted MXene particles, and any organic dispersion medium other than those listed above can be used.

[0132] (4) Film Formation Using Ligand-Substituted MXene Particle-Containing Dispersion 80 mL of the ligand-substituted MXene particle-containing dispersion prepared in (3) above was prepared. Using a spray coater (Muramatsu: M1822J), the ligand-substituted MXene particle-containing dispersion was applied to a glass substrate as follows. First, a 3 cm square glass substrate (SCHOTT: Tempax) was cleaned with oxygen plasma for 1 minute and set on the stage of the spray coater. Next, the ligand-substituted MXene particle-containing dispersion was applied to the glass substrate under the following spray coating conditions to form a film. The resulting spray film (ligand-substituted MXene film) was dried in a vacuum dryer at 80°C for 16 hours to obtain a ligand-substituted MXene film. Furthermore, by varying the amount of methylphosphonic acid used in the above "(1) Synthesis of Ligand-Substituted MXene Particles" above, several ligand-substituted MXene films with different ligand coverage rates were obtained, as shown in Table 5 below. The ligand coverage was determined in the same manner as in (4) of Example 1-1. (Spray coating conditions) Syringe flow rate: 5.0 mL / min Atomization pressure: 0.5 MPa Distance between nozzle tip and substrate: 15 cm Sweep speed: 15 cm / s Stage temperature: 25°C

[0133] (5) Evaluation of the Conductivity of Ligand-Substituted MXene Films The conductivity (σ) of the ligand-substituted MXene films prepared in (4) above was calculated according to the following formula (1) using the surface resistance and film thickness measurements of the ligand-substituted MXene films, as described in detail below. The surface resistance of the ligand-substituted MXene films was measured using a Loresta (MCP-T370, manufactured by Nitto Seiko Co., Ltd.), and the film thickness of the ligand-substituted MXene films was measured using a stylus-type surface profiler (Dektak8, manufactured by ULVAC Co., Ltd.). Film thickness was measured at three locations per sample, and the average value was used. The conductivity (σ) of the ligand-substituted MXene films calculated using the following formula (1) is shown in Table 5 below, along with the ligand coverage. Figure 8 is a graph created based on the results of Table 5, showing the relationship between the ligand coverage and the conductivity of the ligand-substituted MXene films. σ=1 / ρ=1 / (Rs·t) (1) In formula (1), σ [S / cm] is the conductivity of the film, ρ [Ω·m] is the resistivity, Rs [Ω / square] is the surface resistance, and t [m] is the film thickness.

[0134]

[0135] All of the samples in Table 5 above have a ligand coverage rate of 37.5% or more, and even exceed 37.5%, so it has been separately confirmed that all of the ligand-substituted MXene particles have dispersion stability of 50 hours or more.

[0136] From Table 5 above, when the ligand coverage was 75.4% or more, the dispersion stability in ethanol was further improved, resulting in improved film quality and a dramatic increase in electrical conductivity. When the ligand coverage was greater than 75.4% and reached 85.3%, the dispersion stability in ethanol was further improved, further improving the film quality of the sprayed film obtained, and the electrical conductivity, which was 0.016 S / cm at a ligand coverage of 51.6%, improved to 95.6 S / cm, approximately 6,000 times higher.

[0137] Ligand-substituted MXene particles were prepared in the same manner as in Comparative Example 1-1, except that 63.4 mg (0.65 mmol) of methylphosphonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of dodecylphosphonic acid in (1) of Comparative Example 1-1. The ligand-substituted MXene particles were then washed, and a dispersion containing the ligand-substituted MXene particles was prepared, in the same manner as in (2) and (3) of Example 2.

[0138] Next, in the same manner as in Example 2(4), a film was formed using the dispersion containing the ligand-substituted MXene particles to obtain a ligand-substituted MXene film.

[0139] The conductivity of the resulting ligand-substituted MXene film was evaluated in the same manner as in Example 2 (5). The ligand coverage was determined in the same manner as in Example 1-1 (4). The results showed that the ligand coverage was 30.5%, the surface resistivity was 3,920,000 Ω / square, and the film thickness was 2.55 μm. The conductivity calculated from these values ​​was 0.0010 S / cm.

[0140] A comparison of Example 2 and Comparative Example 2 reveals that the ligand-substituted MXene film (two-dimensional particle-containing film) according to this embodiment exhibits sufficiently high conductivity. This is thought to be because, while the ligand-substituted MXene particles aggregate in the ligand-substituted MXene particle-containing dispersion in Comparative Example 2, the ligand-substituted MXene particles are well dispersed in the ligand-substituted MXene particle-containing dispersion in Example 2, resulting in improved film quality for the resulting spray film, as described above.

[0141] The two-dimensional particles, two-dimensional particle-containing dispersions, two-dimensional particle-containing composites, and two-dimensional particle-containing films of the present disclosure can be used in any suitable applications, and can be particularly preferably used, for example, as electrodes in electrical devices.

[0142] The disclosure of the present specification may include the following aspects: <1> A two-dimensional particle including one or more layers, wherein the layers are represented by the following formula: M ｍ X ｎ (wherein M is at least one metal of Group 3, 4, 5, 6 or 7, X is a carbon atom, a nitrogen atom or a combination thereof, n is 1 or more and 4 or less, and m is greater than n and 5 or less), and modified or terminated T present on the surface of the layer body, wherein T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and the M atom of the layer body and a heteroatom of a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group have a structure in which the M atom of the layer body is covalently or ionically bonded via an oxygen atom derived from the hydroxyl group of the layer body, and the substitution rate of the hydroxyl groups present on the surface of the layer body with the structure is 37.5% or more. <2> The layer body is Ti ３ C ２The two-dimensional particle according to <1>, wherein the compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is a phosphonic acid having a saturated hydrocarbon group or an unsaturated hydrocarbon group. <3> The two-dimensional particle according to <1> or <2>, wherein the compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is a phosphonic acid having a saturated hydrocarbon group or an unsaturated hydrocarbon group. <4> A two-dimensional particle-containing dispersion comprising the two-dimensional particle according to any one of <1> to <3> and an organic dispersion medium. <5> The two-dimensional particle-containing dispersion according to <4>, wherein the organic dispersion medium is one or more selected from the group consisting of ethanol, 2-propanol, and 1-hexanol. <6> A two-dimensional particle-containing composite comprising the two-dimensional particle-containing dispersion according to <4> or <5> and a polymer material. <7> A two-dimensional particle-containing film comprising the two-dimensional particle according to any one of <1> to <3>, wherein the substitution rate is 75.4% or more. <8> (a) A precursor particle comprising one or more layers, wherein the layer is a compound represented by the following formula: M ｍ X ｎ (wherein M is at least one Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and a modified or terminated T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and includes at least a hydroxyl group) present on the surface of the layer body; (b) preparing an aqueous dispersion containing the precursor particles, and a compound-containing organic solution in which a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is dissolved in an organic solvent compatible with the aqueous dispersion; and (c) mixing and stirring the aqueous dispersion containing the precursor particles and the compound-containing organic solution, to obtain a structure in which M atoms of the layer body and heteroatoms of the heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups of the layer body. <9> The method for producing two-dimensional particles according to <8>, wherein the aqueous dispersion containing the precursor particles has a pH in the range of 6 to 8.

[0143] This application claims priority from Japanese Patent Application No. 2023-131268, which is incorporated herein by reference.

[0144] 1a, 1b Layer body (M ｍ X ｎ layer) 3a, 5a, 3b, 5b Modification or termination T 7a, 7b MXene layer 10a, 10b MXene particle

Claims

1. A two-dimensional particle comprising one or more layers, said layers being represented by the following formula: M ｍ X ｎ (wherein M is at least one type of Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and modified or terminated T present on a surface of the layer body, wherein T is at least one type selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and the M atom of the layer body and a heteroatom of a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group have a structure in which the M atom of the layer body and a heteroatom of the heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via an oxygen atom derived from the hydroxyl group of the layer body, and a substitution rate of 37.5% or more of the hydroxyl groups present on the surface of the layer body with the structure.

2. The layer body is Ti ３ C ２ The two-dimensional particle of claim 1 , 3. The two-dimensional particle according to claim 1 or 2, wherein the compound having a saturated or unsaturated hydrocarbon group is a phosphonic acid having a saturated or unsaturated hydrocarbon group.

4. A two-dimensional particle-containing dispersion liquid comprising the two-dimensional particle according to any one of claims 1 to 3 and an organic dispersion medium.

5. The two-dimensional particle-containing dispersion liquid according to claim 4, wherein the organic dispersion medium is one or more selected from the group consisting of ethanol, 2-propanol, and 1-hexanol.

6. A two-dimensional particle-containing composite comprising the two-dimensional particle-containing dispersion according to claim 4 or 5 and a polymeric material.

7. A two-dimensional particle-containing film comprising the two-dimensional particles according to any one of claims 1 to 3, wherein the substitution rate is 75.4% or more.

8. (a) A precursor particle comprising one or more layers, said layers being represented by the following formula: M ｍ X ｎ (wherein M is at least one type of Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; n is 1 or more and 4 or less; and m is greater than n and 5 or less), and a modification or termination T (T is at least one type selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom and a hydrogen atom, and includes at least a hydroxyl group) present on the surface of the layer body; (b) preparing an aqueous dispersion containing the precursor particles, and a compound-containing organic solution in which a heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group is dissolved in an organic solvent compatible with the aqueous dispersion; and (c) mixing and stirring the aqueous dispersion containing the precursor particles and the compound-containing organic solution, to obtain a structure in which M atoms of the layer body and heteroatoms of the heteroatom-containing compound having a saturated hydrocarbon group or an unsaturated hydrocarbon group are covalently or ionically bonded via oxygen atoms derived from the hydroxyl groups of the layer body. A method for producing two-dimensional particles, comprising:

9. The method for producing two-dimensional particles according to claim 8, wherein the aqueous dispersion containing the precursor particles has a pH in the range of 6 to 8.

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