Two-dimensional particles, conductive film, conductive paste, and method for producing two-dimensional particles

Abstract

The present invention aims to provide two-dimensional particles that can provide a conductive film that can maintain high conductivity even under high humidity conditions, and a method for producing such two-dimensional particles. The two-dimensional particles of the present invention are two-dimensional particles having one or more layers, Contains a metal cation and a chlorine atom, The layer has 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 to 4, m is greater than n and less than or equal to 5) and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, an amino group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, and a hydrogen atom) present on the surface of the layer body, The metal cation comprises at least one cation selected from the group consisting of Na and K, The Li content is less than 0.002 mass %.

Description

[Technical field]

[0001] The present invention relates to a method for producing two-dimensional particles, a conductive film, and a conductive paste two-dimensional particle. [Background technology]

[0002] In recent years, MXene has been attracting attention as a new material with high electrical conductivity. MXene is a type of so-called two-dimensional material, and as described below, it is a layered material having the form of one or more layers. In general, MXene has the form of particles (which may include powders, flakes, nanosheets, etc.) or array structures (films, fibers, coatings, compositions, etc.) of such layered materials.

[0003] Currently, various researches are being conducted on the application of MXene to various electrical devices. For the above applications, it is required to further increase the electrical conductivity of materials containing MXene. As part of the research, a delamination process for MXene obtained as an intercalated multilayer or a single layer exfoliated colloid has been investigated.

[0004] Non-Patent Document 1 shows that the amount of Li between MXene layers can be controlled by adding hydrochloric acid or the like to the suspension obtained by intercalation using Li to adjust the pH to about 2.9.

[0005] Non-Patent Document 2 shows that a delamination treatment of multi-layer MXene was performed by shaking hands with TMAOH (tetramethylammonium hydroxide).

[0006] In addition, Non-Patent Document 3 describes that Li cations exist in the interlayer space of MXene due to the LiCl used in the chemical etching, and that the structure of the powder changes when the Li cations are exchanged with other metal ions. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Hongwu chen et al., "Pristine Titanium Carbide MXene Films with Environmentally Stable Conductivity and Superior Mechanical Strength" Adv. Funct. Mater. 2020, 30, 1906996 [Non-Patent Document 2] Mohamed Alhabeb et al., "Guidelines for Synthesis and Processing of Two-Dimensional Titanium Carbide (Ti3C2Tx MXene)" Chem. Mater. 2017, 29, 7633-7644 [Non-Patent Document 3] Michael Ghidiu et al., "Ion-Exchange and Cation Solvation Reactions in Ti3C2 MXene" Chem. Mater. 2016, 28, 10, 3507-3514 Summary of the Invention [Problem to be solved by the invention]

[0008] In the MXene described in Non-Patent Document 1, Li is not completely removed, and therefore the electrical conductivity decreases under high humidity conditions. In the MXene described in Non-Patent Document 2, TMAOH used in the delamination treatment of the multilayer MXene remains, resulting in low electrical conductivity, which further decreases due to moisture absorption, and therefore the reliability is not fully satisfactory. In addition, in the MXene described in Non-Patent Document 3, although the Li cations are exchanged with other metal ions, the MXene remains as multilayer MXene, resulting in low electrical conductivity, and since it is a multilayer MXene, it is not easy to form a conductive film.

[0009] The present invention aims to provide two-dimensional particles that can provide a conductive film that can maintain high conductivity even under high humidity conditions, and a method for producing such two-dimensional particles. [Means for solving the problem]

[0010] The present invention includes the following inventions. [1] A two-dimensional particle having one or more layers, Contains a metal cation, The layer has 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, m is greater than n and less than or equal to 5) and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, an amino group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, and a hydrogen atom) present on the surface of the layer body, the modified or terminal T comprises a chlorine atom, The metal cation comprises at least one cation selected from the group consisting of Na and K, The Li content is less than 0.002% by mass. [2] The two-dimensional particle according to [1], wherein the content of chlorine atoms, as measured by combustion ion chromatography, is 3 mass% or more in the total of the layer and the metal cations. [3] The two-dimensional particle according to [1] or [2], wherein the total content of Na and K is 0.1% by mass or more and 10% by mass or less. [4] The two-dimensional particle according to any one of [1] to [3], wherein the average value of the major axis of the two-dimensional surface is 1 μm or more and 20 μm or less. [5] The two-dimensional particle according to any one of [1] to [4], which has an average thickness of 1 nm or more and 10 nm or less. [6] A conductive film comprising the two-dimensional particle according to any one of [1] to [5]. [7] The conductive film according to [6], having a conductivity of 2,000 S / cm or more. [8] A conductive paste comprising the two-dimensional particles according to any one of [1] to [5] and a dispersion medium. [9] A conductive composite material comprising the two-dimensional particle according to any one of [1] to [5] and a resin.

[10] An electromagnetic shield comprising the two-dimensional particle according to any one of [1] to [5].

[11] An adsorbent comprising the two-dimensional particle according to any one of [1] to [5].

[12] A bioelectrode comprising the two-dimensional particle according to any one of [1] to [5].

[13] (a) The formula: M m AX 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; A is at least one Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and less than or equal to 5) providing a precursor represented by (b) performing an etching treatment using an etching solution to remove at least a portion of the A atoms from the precursor; (c) performing a water washing treatment, which includes a step of washing the etched product obtained by the above etching treatment with water; (d) performing an intercalation treatment, which includes a step of mixing the water-washed product obtained by the water washing with a metal-containing compound; (e) carrying out a delamination treatment, which includes a step of stirring the intercalation product obtained by the intercalation treatment; (f) The delamination product obtained by the delamination process is washed with water to obtain two-dimensional particles. Including, The concentration of chlorine atoms in the etching solution is 10 mol / L or more, The method for producing two-dimensional particles, wherein the metal-containing compound contains at least one selected from the group consisting of Na and K. Effect of the Invention

[0011] According to the present invention, it is possible to realize two-dimensional particles capable of maintaining high electrical conductivity even under high humidity conditions, and it is also possible to provide a method for producing such two-dimensional particles. [Brief description of the drawings]

[0012] [Figure 1] 1A-1B are schematic cross-sectional views showing MXene particles of layered material in one embodiment of the present invention, where (a) shows a single-layer MXene particle and (b) shows a multi-layer (illustratively two-layer) MXene particle. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing a conductive film in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] (Embodiment 1: Two-dimensional particles) Hereinafter, a two-dimensional particle in one embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0014] The two-dimensional particles in this embodiment are two-dimensional particles of layered material having one or more layers and comprise metal cations.

[0015] The layer has 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, m is greater than n and less than or equal to 5) and a modification or terminal T (T is at least one selected from the group consisting of a hydroxyl group, an amino group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, and a hydrogen atom) present on a surface of the layer body (more specifically, on at least one of the two opposing surfaces of the layer body), wherein the modification or terminal T includes at least a chlorine atom.

[0016] The layered material may be understood as a layered compound, and may be referred to as "M m X n T s ", where s is an arbitrary 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. T may preferably be 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.

[0017] 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, Sc, Y, W, and Mn, more preferably at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn, and even more preferably at least one selected from the group consisting of Ti, V, Cr, and Mo.

[0018] MXene is a compound represented by the above formula: 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, V2 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(1.3 and 0.6) are 1.3(=4 / 3) and 0.6(=2 / 3)). The 3 C 2 ,The 3 N 2 ,The 3 (CN)、Zr 3 C 2 、(Ti,V) 3 C 2 ,(The 2 Nb)C 2 ,(The 2 Ta)C 2 ,(The 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 2V)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,V)C3 , (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.) (Mo,V) 5 C 4

[0019] Typically, in the above formula, M can be titanium or vanadium, and X can be a carbon atom, a nitrogen atom, or both. For example, the MAX phase is 3 AlC 2 and MXene is Ti 3 C 2 T s (In other words, M is Ti, X is C, n is 2, and m is 3).

[0020] In the present invention, MXene may contain a relatively small amount of A atoms derived from the MAX phase of the precursor, for example, 10 mass% or less of the original A atoms. The amount of residual A atoms may be preferably 8 mass% or less, more preferably 6 mass% or less. However, even if the amount of residual A atoms exceeds 10 mass%, there may be cases where there is no problem depending on the application and use conditions of the two-dimensional particles.

[0021] In this specification, the layer may be referred to as an MXene layer, and the two-dimensional particles may be referred to as MXene two-dimensional particles or MXene particles.

[0022] The two-dimensional particle 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 m X n The MXene layer 7a has a layer body 1a and a modification or termination T3a, 5a present on the surface of the layer body 1a (more specifically, on at least one of the two surfaces facing each other in each layer). m X n T s ", where s is an arbitrary number. Note that in FIG. 1(a), the metal cation is not shown.

[0023] The two-dimensional particle of this embodiment may include one or more layers. As a multiple layer MXene particle (multilayer MXene particle), as shown in FIG. 1(b), there may be mentioned, but is not limited to, a two-layer MXene particle 10b. In FIG. 1(b), 1b, 3b, 5b, and 7b are the same as 1a, 3a, 5a, and 7a in FIG. 1(a). The two adjacent MXene layers (e.g., 7a and 7b) of the multilayer MXene particle may not necessarily 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, in which the multilayer MXene particles 10b are individually separated and exist in one layer, and the unseparated multilayer MXene particles 10b remain. Note that metal cations are not shown in FIG. 1(b).

[0024] Although this embodiment is not limited thereto, the thickness of each layer (corresponding to the above-mentioned 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 (which can vary mainly depending on the number of M atomic layers contained in each layer). For each stack of the multilayer MXene particle that can be contained, the interlayer distance (or gap dimension, shown as Δd in FIG. 1(b)) can 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 can be 2 to 20,000.

[0025] In the two-dimensional particle of this embodiment, the multilayer MXene particles that may be included are preferably MXene particles having a small number of layers obtained through a delamination process. The "small number of layers" refers to, for example, a number of stacked MXene layers of 6 or less. The thickness in the stacking direction of the multilayer MXene particles having a small number of layers is preferably 15 nm or less, and more preferably 10 nm or less. Hereinafter, these "multilayer MXene particles having a small number of layers" may be referred to as "few-layered MXene particles". Furthermore, the single-layered MXene particles and the few-layered MXene particles may be collectively referred to as "single-layered / few-layered MXene particles".

[0026] The two-dimensional particles of this embodiment preferably contain single-walled MXene particles and few-walled MXene particles, i.e., single-walled and few-walled MXene particles. In the two-dimensional particles of this embodiment, the proportion of single-walled and few-walled MXene particles having a thickness of 15 nm or less is preferably 90% by volume or more, more preferably 95% by volume or more.

[0027] The metal cation is derived from a metal-containing compound used in the method for producing two-dimensional particles described below, and contains at least one cation selected from the group consisting of Na and K.

[0028] The metal cations preferably do not contain Li cations. The term "metal cations do not contain Li cations" means that the concentration of Li cations is less than 20 mass ppm in the total amount of metal cations when measured, for example, by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0029] The metal cations are typically present on the layer, i.e., they may be in contact with the layer, or may be present on the layer via another element.

[0030] The content of the metal cations in the two-dimensional particles (e.g., the sum of the layer and the metal cations) may be, for example, 20% by weight or less, even 10% by weight or less, in particular 5% by weight or less, in particular 3% by weight or less, and may be, for example, 0.1% by weight or more, even 0.2% by weight or more.

[0031] The content of the metal cations can be measured, for example, by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0032] The two-dimensional particle may also have chlorine atoms other than those present as the modifications or terminal T's.

[0033] The content of chlorine atoms in the total of the layer and the metal cations is 3% by mass or more, preferably 3.3% by mass or more, more preferably 3.5% by mass or more, and preferably 7% by mass or less, more preferably 5% by mass or less, and more preferably 4.5% by mass or less. The content of chlorine atoms in the two-dimensional particles is the content of chlorine atoms contained in the layer and the metal cations, and even when the two-dimensional particles are mixed with other materials, the chlorine atoms contained in components other than the layer and the metal cations are not included in the content.

[0034] The content of chlorine atoms in the two-dimensional particles can be measured by combustion ion chromatography.

[0035] In this specification, when a certain element is referred to as an "atom," 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.

[0036] The two-dimensional particles have a suppressed Li content. When the two-dimensional particles are used, a conductive film capable of maintaining high conductivity can be provided even under high humidity conditions, such as a relative humidity of 99%. The Li content in the two-dimensional particles (e.g., the total of the layer and the metal cations) is less than 0.002% by mass, preferably 0.001% by mass or less, and more preferably 0.0001% by mass or less.

[0037] The Li content can be measured, for example, by inductively coupled plasma atomic emission spectrometry (ICP-AES), etc. The detection limit of Li measured by ICP-AES is 0.0001 mass %.

[0038] The two-dimensional particles of this embodiment do not contain amines. As described in Non-Patent Document 2, when delamination treatment of MXene is performed using TMAOH, a single layer of MXene is obtained, but even after washing, TMAOH remains on the surface of the MXene layer, which causes a decrease in electrical conductivity. TMAOH can be removed at high temperatures of 250°C to 500°C, but at such high temperatures, MXene may be oxidized and decomposed. In contrast, the two-dimensional particles of this embodiment do not use TMAOH for delamination treatment of MXene, and do not contain amines. In this specification, "does not contain amines" means that the amount of triethylamine (m / z = 42, 53, 54) derived from TMAOH is 10 mass ppm or less when measured using a gas chromatography mass spectrometry (GC-MS) device.

[0039] In this specification, a two-dimensional particle refers to a particle having a ratio of (average major axis of the two-dimensional surface of the two-dimensional particle) / (average thickness of the two-dimensional particle) of 1.2 or more, preferably 1.5 or more, and more preferably 2 or more. The average major axis of the two-dimensional surface of the two-dimensional particle and the average thickness of the two-dimensional particle may be determined by the method described below.

[0040] (Average value of the longest axis of the two-dimensional surface of a two-dimensional particle) The two-dimensional particles of this embodiment have an average major axis of the two-dimensional surface of 1 μm or more and 20 μm or less. Hereinafter, the average major axis of the two-dimensional surface may be referred to as the "average flake size."

[0041] The larger the average flake size, the higher the conductivity of the conductive film. The two-dimensional particles of this embodiment have a large average flake size of 1.0 μm or more, so a film formed using these two-dimensional particles, for example a film obtained by stacking these two-dimensional particles, can achieve a conductivity of 2000 S / cm or more. The average value of the major axis of the two-dimensional surface is preferably 1.5 μm or more, more preferably 2.5 μm or more. In Non-Patent Document 3, delamination of MXene is performed by subjecting it to ultrasonic treatment, but since the major axis of most of the MXene is reduced to about several hundred nm by ultrasonic treatment, it is considered that the film formed by the single-layer MXene obtained in Non-Patent Document 3 has low conductivity.

[0042] The average value of the major axis of the two-dimensional surface is 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less, from the viewpoint of dispersibility in the solution.

[0043] The long diameter of the two-dimensional plane refers to the long diameter when each MXene particle is approximated to an ellipse in an electron microscope photograph as shown in the Examples below, and the average long diameter of the two-dimensional plane refers to the number average of the long diameters of 80 particles or more. As the electron microscope, a scanning electron microscope (SEM) or a transmission electron microscope (TEM) can be used.

[0044] The average major axis of the two-dimensional particles of the present embodiment may be measured by dissolving the conductive film containing the two-dimensional particles in a solvent and dispersing the two-dimensional particles in the solvent, or by measuring the average major axis of the conductive film from an SEM image.

[0045] (Average thickness of two-dimensional particles) The average thickness of the two-dimensional particles of this embodiment is preferably 1 nm or more and 10 nm or less. The thickness is preferably 7 nm or less, more preferably 5 nm or less. On the other hand, considering the thickness of a single-layer MXene particle, the lower limit of the thickness of the two-dimensional particles may be 1 nm.

[0046] The average thickness of the two-dimensional particles is determined as a number average dimension (eg, a number average of at least 40 particles) based on atomic force microscope (AFM) or transmission electron microscope (TEM) photographs.

[0047] (Embodiment 2: Method for producing two-dimensional particles) Hereinafter, a method for producing two-dimensional particles in one embodiment of the present invention will be described in detail, but the present invention is not limited to this embodiment.

[0048] The method for producing two-dimensional particles according to the present embodiment includes the steps of: (a) the formula: M m AX 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; A is at least one Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and less than or equal to 5) providing a precursor represented by (b) performing an etching treatment using an etching solution to remove at least a portion of the A atoms from the precursor; (c) performing a water washing treatment, which includes a step of washing the etched product obtained by the above etching treatment with water; (d) performing an intercalation treatment, which includes a step of mixing the water-washed product obtained by the water washing with a metal-containing compound; (e) carrying out a delamination treatment, which includes a step of stirring the intercalation product obtained by the intercalation treatment; (f) The delamination product obtained by the delamination process is washed with water to obtain two-dimensional particles. Including, The concentration of chlorine atoms in the etching solution is 10 mol / L or more, The metal-containing compound contains at least one selected from the group consisting of Na and K.

[0049] Usually, when an intercalation treatment is performed using a metal-containing compound containing a cation of a metal in the third to fifth periods of the periodic table, the hydration enthalpy of these metal cations is lower than that of Li ions, so delamination hardly progresses. However, according to the study by the present inventors, even when a metal compound containing a metal cation other than Li ions is used, water can easily penetrate between layers by setting the concentration of chlorine atoms in the etching solution to 10 mol / L or more, and delamination can progress sufficiently. Although not limited to a specific theory, it is believed that this is because the steric effect of chlorine atoms is fully exerted in the etching solution.

[0050] Each step will be described in detail below.

[0051] ·Process (a) First, a predetermined precursor is prepared. The predetermined precursor that can be used in this embodiment is the MAX phase, which is a precursor of MXene. The following formula: M m AX 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; A is at least one Group 12, 13, 14, 15, or 16 element; n is 1 or more and 4 or less, m is greater than n and less than or equal to 5) It is expressed as:

[0052] The above M, X, n, and m are as described in the first embodiment. A is at least one element of Groups 12, 13, 14, 15, and 16, and is usually an A group element, typically Groups IIIA and IVA, and more specifically may include 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.

[0053] The MAX phase is M m X n (each X may have a crystal lattice in which it is located in the octahedral array of M) between which a layer composed of A atoms is located. 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 (collectively referred to as "M m X n and a layer of A atoms (also referred to as an "A atom layer") arranged as a layer next to the (n+1)th layer of M atoms, but is not limited thereto.

[0054] 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-shaped MAX phase). The sintered body is then pulverized with an end mill to obtain a powdered MAX phase for the next process.

[0055] Particles with similar layered structures can also be used as the MAX phase. Such materials include Zr 2 Al 3 C 4 , Zr 3 Al 3 C 5 , Zr 4 (AlC 2 )3 , Zr 2 Al 4 C 5 , Zr 2 Al 3 C 4 , Zr 3 Al 3 C 5 and Zr 2 Al 3 C 5 Examples include:

[0056] ·Process (b) In step (b), an etching treatment is carried out using an etching solution to remove at least a part of the A atoms from the precursor.

[0057] The etching solution contains chlorine atoms. The concentration of chlorine atoms in the etching solution is 10 mol / L or more, preferably 10.5 mol / L or more, and may be, for example, 20 mol / L or less, further 15 mol / L or less.

[0058] The etching solution preferably contains HCl and may further contain HF. The concentration of HCl in the etching solution is 10 mol / L or more, preferably 10.5 mol / L or more, and may be, for example, 20 mol / L or less, or further 15 mol / L or less. The concentration of HF in the etching solution is preferably 10 mass% or less, more preferably 6 mass% or less, and may be 0 mass% or more, for example, 1 mass% or more, or further 3 mass% or more.

[0059] The etching solution preferably does not contain lithium atoms. Here, the term "does not contain Li atoms" means that the Li concentration in the etching solution is less than 20 ppm by mass when measured by, for example, combustion ion chromatography.

[0060] The etching procedure and other conditions using the above etching solution may be those conventionally used.

[0061] ·Process (c) The etched product obtained by the etching process is washed with water. By washing with water, the acid used in the etching process 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 stirred, centrifuged, etc. may be added. Stirring methods include stirring using a hand shake, an automatic shaker, a shear mixer, a pot mill, etc. The degree of stirring, such as the stirring speed and stirring time, may be adjusted according to the amount and concentration of the acid-treated product to be treated. The washing with water may be performed one or more times. It is preferable to wash with water multiple times. For example, the steps (i) to (iii) of (i) adding water (to the etched product or the remaining precipitate obtained in (iii) below) and stirring, (ii) centrifuging the stirred product, and (iii) discarding the supernatant after centrifugation may be performed two or more times, for example, 15 times or less.

[0062] ·Process (d) An intercalation treatment is carried out, which includes a step of mixing the water-washed product obtained by the water washing with a metal-containing compound containing metal cations, whereby the metal cations are intercalated between the layers.

[0063] The metal cation includes at least one selected from the group consisting of Na cations and K cations.

[0064] Examples of the metal-containing compound containing the metal cation include ionic compounds in which the metal cation is bound to a cation or an anion, such as iodides, phosphates, sulfides including sulfates, nitrates, acetates, and carboxylates of the metal cations.

[0065] The content of the metal-containing compound in the intercalation treatment formulation containing the metal-containing compound is preferably 0.001% by mass or more, 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-containing compound in the intercalation treatment formulation is preferably 10% by mass or less, more preferably 1% by mass or less.

[0066] The intercalation compound preferably does not contain lithium atoms. Here, the "Li atom-free" of the intercalation compound means that the Li concentration in the intercalation compound is less than 20 ppm by mass as measured, for example, by combustion ion chromatography.

[0067] The specific method of the intercalation treatment is not particularly limited, and for example, the water-washed product may be mixed with a metal-containing compound and 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, and the stirring time can be set according to the production scale of the single-walled / few-walled MXene particles, and can be set, for example, between 12 and 24 hours.

[0068] ·Process (e) In step (e), a delamination treatment is performed, which includes a step of stirring the intercalation product obtained by the intercalation treatment. This delamination treatment can divide the MXene particles into a single layer or a few layers.

[0069] The conditions of the delamination treatment are not particularly limited, and the delamination treatment can be carried out by a known method. For example, examples of the stirring method include ultrasonic treatment, hand shaking, and stirring using an automatic shaker. The degree of stirring, such as the stirring speed and stirring time, may be adjusted according to the amount and concentration of the material to be treated. For example, the above-mentioned intercalation slurry is centrifuged to discard the supernatant, and then pure water is added to the remaining precipitate, for example, by stirring using a hand shake or an automatic shaker, to perform layer separation. The removal of the unpeeled material can be performed by centrifuging the slurry, discarding the supernatant, and then washing the remaining precipitate with water. For example, (i) pure water is added to the remaining precipitate after discarding the supernatant, and the precipitate is stirred, (ii) centrifuged, and (iii) the supernatant is collected. The steps (i) to (iii) can be repeated at least once, preferably at least twice, but not more than 10 times, to obtain a supernatant containing single-layered and few-layered MXene particles as the delamination treatment product. Alternatively, this supernatant may be centrifuged, the supernatant after centrifugation may be discarded, and clay containing single-layer and few-layer MXene particles may be obtained as a delamination treatment product.

[0070] In the manufacturing method of this embodiment, ultrasonic treatment for delamination is not necessary. If ultrasonic treatment is not performed, particle destruction is unlikely to occur, and it is easy to obtain single-layered or few-layered MXene particles with a large plane parallel to the particle layer, i.e., a large two-dimensional surface.

[0071] The delamination product obtained by stirring can be used as it is as two-dimensional particles containing single-layer and few-layer MXene particles, and may be washed with water if necessary.

[0072] (Embodiment 3: Conductive film) An example of the application of the two-dimensional particles of this embodiment is a conductive film containing the two-dimensional particles. The conductive film of this embodiment will be described with reference to FIG. 2. FIG. 2 illustrates a conductive film 30 obtained by laminating only two-dimensional particles 10, but the present invention is not limited thereto. The conductive film may contain additives such as a binder that are added during film formation as necessary. The additives are preferably 30% by volume or less, more preferably 10% by volume or less, even more preferably 5% by volume or less, and most preferably 0% by volume, in terms of the proportion of the conductive film (when dried).

[0073] As a method for producing a conductive film without using the binder, etc., the supernatant containing the two-dimensional particles obtained by the delamination is suction filtered, or the two-dimensional particles are mixed with a dispersion medium, and the mixture is sprayed in the form of a slurry of a suitable concentration, and then the dispersion medium is removed by drying or the like, once or multiple times to produce a conductive film. The spraying method may be, for example, an airless spray method or an air spray method, and specifically, a method of spraying using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush can be mentioned. Examples of the dispersion medium that can be contained in the slurry include water; organic media such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethylsulfoxide, ethylene glycol, and acetic acid.

[0074] Examples of the binder include acrylic resin, polyester resin, polyamide resin, polyolefin resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyether resin, and polylactic acid.

[0075] The electrical conductivity of the conductive film is preferably 2,000 S / cm or more, more preferably 5,000 S / m or more, and may be, for example, 100,000 S / cm or less, or even 50,000 S / cm or less.

[0076] The conductivity of the conductive film of this embodiment can be calculated by substituting the thickness of the conductive film and the surface resistivity of the conductive film measured by the four-probe method into the following formula. Conductivity [S / cm] = 1 / (thickness of conductive film [cm] × surface resistivity of conductive film [Ω / □])

[0077] Other applications of the two-dimensional particles of the present embodiment include conductive pastes containing the two-dimensional particles and conductive composite materials containing the two-dimensional particles and resins, which are also suitable for applications requiring high electrical conductivity or no decrease in electrical conductivity even under high humidity conditions.

[0078] Resins that can be contained in the conductive paste and conductive composite material include the same resins that can be contained in the conductive film. Dispersion media that can be contained in the conductive paste include water, and organic media such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethylsulfoxide, ethylene glycol, and acetic acid.

[0079] The conductive film of the present embodiment can be used for any suitable application, such as an electrode or electromagnetic shield (EMI shield) in any suitable electric device, which is required to maintain high electrical conductivity even under high humidity conditions.

[0080] The electrodes are not particularly limited, and may be, for example, capacitor electrodes, battery electrodes, bioelectrodes, sensor electrodes, antenna electrodes, etc. By using the conductive film of the present embodiment, it is possible to obtain a large-capacity capacitor and battery, a low-impedance bioelectrode, and a highly sensitive sensor and antenna even in a smaller volume (volume occupied by the device).

[0081] The capacitor may be an electrochemical capacitor. The electrochemical capacitor is a capacitor that utilizes a capacity generated due to a physicochemical reaction between an electrode (electrode active material) and an ion (electrolyte ion) in an electrolyte, and can be used as a device that stores electric energy (electricity storage device). The battery may be a chemical battery that can be repeatedly charged and discharged. The battery may be, for example, a lithium ion battery, a magnesium ion battery, a lithium sulfur battery, a sodium ion battery, or the like, but is not limited thereto.

[0082] The bioelectrode is an electrode for acquiring a biosignal (biosignal sensing electrode). The bioelectrode may be, for example, an electrode for measuring EEG (electroencephalogram), ECG (electrocardiogram), EMG (electromyogram), or EIT (electrical impedance tomography), but is not limited thereto.

[0083] The sensor electrode is an electrode for detecting a target substance, state, abnormality, etc. The sensor may be, for example, a gas sensor, a biosensor (a chemical sensor that utilizes a molecular recognition mechanism of biological origin), etc., but is not limited to these.

[0084] The antenna electrode is an electrode for emitting electromagnetic waves into space and / or receiving electromagnetic waves in space.

[0085] (Embodiment 4: Adsorbent) The two-dimensional particles of the present embodiment can be used as an adsorbent containing the two-dimensional particles. The two-dimensional particles have a reduced Li content, so they can be used in applications requiring biocompatibility, such as separation membranes in artificial dialysis equipment.

[0086] The adsorbent may be composed of only two-dimensional particles, or may further contain one or more of ceramics, metals, and resin materials, etc., as necessary. By forming a composite material (composite) of the two-dimensional particles of this embodiment and one or more of ceramics, metals, and resins, an adsorbent that stably exhibits adsorption performance, for example, urea adsorption performance, can be realized. The ceramics, metals, and resins can be introduced during the production of the adsorbent.

[0087] Examples of the ceramics include metal oxides such as silica, alumina, zirconia, titania, magnesia, cerium oxide, zinc oxide, barium titanate, hexaferrite, mullite, etc., and non-oxide ceramics such as silicon nitride, titanium nitride, aluminum nitride, silicon carbide, titanium carbide, tungsten carbide, boron carbide, titanium boride, etc. Examples of the metals include iron, titanium, magnesium, aluminum, and alloys based on these.

[0088] Examples of the resin include cellulose resin and synthetic resin. The resin is preferably a resin having hydrophilicity. The hydrophilic resin can be prepared by blending a hydrophobic resin (a resin having no hydrophilicity) with a hydrophilic auxiliary, or by subjecting a hydrophobic polymer to a hydrophilic treatment. The resin (preferably a hydrophilic resin) more preferably includes one or more selected from the group consisting of polysulfone, cellulose acetate, regenerated cellulose, polyethersulfone, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymer, polyacrylamide, polyaniline sulfonic acid, and nylon.

[0089] The hydrophilic resin is preferably, for example, a hydrophilic polymer having a polar group, and the polar group is a group that modifies the layer or forms a hydrogen bond with the terminal T. Examples of the hydrophilic resin include water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymer, polyacrylamide, polyaniline sulfonic acid, and nylon, and water-soluble polyurethane, polyvinyl alcohol, and sodium alginate are more preferable, and water-soluble polyurethane is even more preferable.

[0090] Moreover, the hydrophilic resin is preferably biocompatible. Examples of biocompatible resins include resins for hemodialysis and hemofiltration. Specific examples include polymethyl methacrylate, polyacrylonitrile, cellulose, cellulose acetate, polysulfone, polyvinyl alcohol, and vinyl alcohol copolymers such as copolymers of polyvinyl alcohol and ethylene. Examples of biocompatible resins include preferably polysulfone, polymethyl methacrylate, and cellulose acetate, and more preferably polysulfone and polymethyl methacrylate.

[0091] The content of the above resin in the composite material can be set appropriately depending on the application, and may be, in terms of the ratio to the adsorbent (when dry), more than 0 vol.%, for example 80 vol.% or less, further 50 vol.% or less, particularly 30 vol.% or less, particularly 10 vol.% or less, and even more particularly 5 vol.% or less.

[0092] The method for producing the adsorbent formed from the above composite material is not particularly limited. In one embodiment, a sheet-shaped adsorbent containing a resin can be produced by mixing two-dimensional particles and a resin to form a slurry, applying the slurry to a base material (e.g., a substrate) to form a coating film, and drying and / or curing as necessary.

[0093] The two-dimensional particles may be mixed with the resin as they are, or may be dispersed in a dispersion medium to form a dispersion and then mixed with the resin. The dispersion medium is typically water, and may further contain a relatively small amount of other liquid substances in some cases. The content of the other liquid substances in the dispersion medium may be, for example, 30% by mass or less, or 20% by mass or less.

[0094] The two-dimensional particles and the resin can be mixed using a dispersing device such as a homogenizer, a propeller agitator, a thin film rotary agitator, a planetary mixer, a mechanical shaker, or a vortex mixer.

[0095] Methods for applying the above-mentioned slurry to a substrate include, but are not limited to, spray application methods such as airless spray, air spray, etc., specifically, spray application methods using nozzles such as one-fluid nozzles, two-fluid nozzles, and airbrushes; slit coating using a table coater, comma coater, or bar coater; printing methods such as screen printing and metal mask printing; spin coating; dipping; dropping; brush; roller; roll coater; curtain flow coater; roller curtain coater; die coater; and application methods using electrostatic painting.

[0096] Drying and / or curing may be accomplished, for example, at temperatures up to 400° C. using an atmospheric or vacuum oven.

[0097] The above coating and drying steps may be repeated multiple times as necessary until a sheet (film) of the desired thickness is obtained.

[0098] In another embodiment, an adsorbent comprising a ceramic or metal can be produced by mixing, for example, two-dimensional particles with, for example, particulate ceramic or metal, and heating at a low temperature sufficient to maintain the composition of the two-dimensional particles.

[0099] The shape of the adsorbent is not limited to that of the present embodiment. The shape of the adsorbent may be a sheet-like form such as a film, or may be a shape having a thickness, a rectangular parallelepiped, a sphere, a polygon, or the like.

[0100] (Adsorption sheet) An example of a preferred embodiment of the adsorbent of this embodiment is an adsorbent sheet. The adsorbent sheet may be an adsorbent sheet formed of the adsorbent of this embodiment, i.e., two-dimensional particles, or a composite material containing the adsorbent, or may be an adsorbent sheet formed on the surface of a substrate. The substrate may be formed of one or more of the above-mentioned ceramics, metals, and resin materials. Among them, the substrate is preferably an adsorbent sheet formed of the above-mentioned resin and formed with the adsorbent of this embodiment. The adsorbent may be formed on a part of the surface of the substrate, or may be formed on the entire surface of the substrate. The method of forming the adsorbent on the substrate may be the method described above as the method of applying the slurry to the substrate.

[0101] (Use of adsorbent) The adsorbent of the present embodiment can be used, for example, to adsorb polar organic compounds. Polar organic compounds are a general term for organic compounds having polarity, specifically, organic compounds having a polar group. Examples of polar groups include hydroxyl groups (OH groups), NO 2 group, amino group (NH group, NH 2 These polar groups can form hydrogen bonds with hydrogen atoms contained in water molecules. Among polar organic compounds, the adsorption targets include polar solvents such as alcohols having hydroxyl groups, compounds having amino groups, ammonia, etc., and in particular, compounds having one or more of a hydroxyl group and an amino group, and ammonia.

[0102] Among the compounds having one or more of the above hydroxyl group and amino group, examples of the compound having a hydroxyl group include monohydric alcohols having 1 to 22 carbon atoms; polyhydric phenols; polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin; alkanolamines such as triethanolamine; and sugars such as xylose and glucose. Examples of the compound having an amino group include monoamines such as methylamine and dimethylamine; diamines such as ethylenediamine; polyamines such as diethylenetriamine; aromatic amines such as aniline; amino acids such as valine and leucine, urea, uric acid, uric acid salts, and creatinine. Examples of the compound having a hydroxyl group and an amino group include ethanolamine and diethanolamine.

[0103] The adsorbent of the present embodiment is preferably used for adsorbing uremic toxins including, for example, urea, uric acid, creatinine, etc. The adsorbent of the present embodiment can be optimally used for adsorbing urea in particular.

[0104] The adsorbent of this embodiment can be used for adsorbing and removing waste products such as urea in hemodialysis, hemofiltration, hemodiafiltration, peritoneal dialysis, etc. The adsorbent of this embodiment can also be used in artificial dialysis equipment for performing the above-mentioned hemodialysis, hemofiltration, hemodiafiltration, peritoneal dialysis, etc. The form of the above-mentioned adsorbent is not particularly limited, and can be, for example, a porous type, a hollow fiber type, or a flat membrane laminate type.

[0105] Although the two-dimensional particles according to one embodiment of the present invention have been described above in detail, various modifications are possible. Note that the two-dimensional particles of the present invention may be produced by a method different from the production method in the above-mentioned embodiment, and that the production method of the two-dimensional particles of the present invention is not limited to the one that provides the two-dimensional particles in the above-mentioned embodiment. EXAMPLES

[0106] [Examples 1 to 4, Comparative Example 1] In Examples 1 to 4 and Comparative Example 1, two-dimensional particles were obtained by sequentially carrying out the following steps, which are described in detail below: (1) preparation of a precursor (MAX), (2) etching of the precursor, (3) washing, (4) intercalation of metal cations, (5) delamination, and (6) washing with water.

[0107] (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 mixed powder was sintered at 1350°C for 2 hours in an Ar atmosphere. The sintered body (block) was pulverized with an end mill to a maximum dimension of 40 μm or less. As a result, TiC powder was obtained as a precursor (MAX). 3 AlC 2 particles were obtained.

[0108] (2) Etching of Precursor Ti prepared by the above method 3 AlC 2 Etching was performed using particles (powder) under the following etching conditions. 3 AlC 2 A solid-liquid mixture (slurry) containing solid components derived from the powder was obtained. (Etching conditions) Precursor: Ti 3 AlC 2 (Through a 45μm sieve) For the composition of the etching solution, see Table 1. Precursor input: 3.0g Etching container: 100mL Eyeboy Etching temperature: 35℃ Etching time: 24 hours Stirrer speed: 400 rpm

[0109] (3) Cleaning The above slurry was divided into two and placed in two 50 mL centrifuge tubes, respectively, and centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. 40 mL of pure water was added to each centrifuge tube, and the tubes were centrifuged again at 3500 G for 5 minutes to separate and remove the supernatant. This operation was repeated 11 times. After the final centrifugation, the supernatant was discarded, and Ti 3 C 2 T s - Moisture medium clay was obtained.

[0110] (4) Metal cation intercalation Ti prepared by the above method 3 C 2 T s -The metal-containing compound shown in Table 1 was added to the water medium clay and stirred at 20°C to 25°C for 10 hours to perform intercalation using metal cations as intercalators. The detailed intercalation conditions are as follows: (Intercalation conditions) ·Ti 3 C 2 T s - Moisture medium clay (MXene after washing): 0.75g solids -See Table 1 for metal-containing compounds and amounts added. Intercalation vessel: 100mL Eye Boy ·Temperature: 20℃ or higher and 25℃ or lower (room temperature) Duration: 10 hours Stirrer speed: 800 rpm

[0111] (5) Delamination The slurry obtained by intercalation was placed in a 50 mL centrifuge tube, 20 mL of pure water was added, and the mixture was centrifuged at 3500 G using a centrifuge, after which the supernatant was discarded. Next, 40 mL of pure water was added, and the mixture was stirred with a shaker for 15 minutes, centrifuged at 3500 G, and the supernatant was collected as a liquid containing single-layered MXene particles. This operation was repeated four times to obtain a supernatant containing single-layered MXene particles. Furthermore, this supernatant was centrifuged at 4300 G for 2 hours using a centrifuge, and the supernatant was discarded to obtain two-dimensional particles (single-layered MXene particle clay).

[0112] [Table 1]

[0113] (Conductive film manufacturing method) The clay obtained in Examples 1 to 4 and Comparative Example 1 was subjected to suction filtration. After filtration, the clay was vacuum dried at 80°C for 24 hours to produce a conductive film containing two-dimensional particles. A membrane filter (Merck Ltd., Durapore, pore size 0.45 μm) was used as the filter for suction filtration. The above supernatant contained 0.05 g of two-dimensional particle solids and 40 mL of pure water.

[0114] (Measurement of the density of conductive films) The conductive film was punched out into a disk shape with a diameter of 12 mm using a punch, and the mass was measured using an electronic balance and the thickness was measured using a height gauge. The density of the conductive film was calculated from these measurements. The results are shown in Table 1.

[0115] (Method for measuring the conductivity of conductive films) The electrical conductivity of the conductive film containing the obtained two-dimensional particles was determined. The electrical conductivity was determined by measuring the resistivity (Ω) and thickness (μm) at three points per sample, calculating the electrical conductivity (S / cm) from these measurements, and using the average value of the three electrical conductivity values ​​obtained. To measure the resistivity, a simple low resistivity meter (Loresta AX MCP-T370, manufactured by Mitsubishi Chemical Analytical Co., Ltd.) was used to measure the surface resistance of the conductive film by the four-terminal method. To measure the thickness, a micrometer (MDH-25MB, manufactured by Mitutoyo Co., Ltd.) was used. The volume resistivity was then calculated from the obtained surface resistance and the thickness of the conductive film, and the electrical conductivity was calculated by taking the reciprocal of this value, and the E 0 It was decided.

[0116] (Moisture absorption resistance test) The obtained conductive film was placed in a thermo-hygrostat at a relative humidity of 99% and a temperature of 25°C, and taken out at predetermined intervals to measure the conductivity, which was designated as E. 0 The rate of change in electrical conductivity was calculated by dividing the measured value by the measured value.

[0117] (Measurement of chlorine concentration in two-dimensional particles) The chlorine concentrations in the two-dimensional particles obtained in Examples 1 to 4 and Comparative Example 1 were measured using a combustion ion chromatography device (Dionex ICS-5000) manufactured by Thermo Fisher Scientific.

[0118] (Method of detecting elements on the layer surface) The conductive film containing the obtained 2D particles was measured by X-ray photoelectron spectroscopy (XPS) to detect the organic low molecular weight compounds contained in the 2D particles and the elements on the layer surface. For the XPS measurement, Quantum2000 manufactured by ULVAC-PHI, Inc. was used.

[0119] (Method for detecting metal cations) The obtained 2D particles were dissolved by the alkali fusion method, and the solution was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) to detect the metal cations contained in the 2D particles. For the ICP-AES measurement, an iCAP7400 manufactured by Thermo Fisher Scientific was used.

[0120] (Measurement of the average long diameter of the two-dimensional surface of a two-dimensional particle) A slurry of two-dimensional particles dispersed in water was applied to an alumina porous substrate, which was then dried, and scanning electron microscope (SEM) photographs were taken and measurements were performed. The magnification was set to 2,000 times, and in one or more fields of view (approximately 1 to 3 fields of view) of SEM images with a field size of 45 μm × 45 μm, 80 or more two-dimensional particles (MXene particles) that could be visually confirmed were targeted. The shape of the two-dimensional surface of each two-dimensional particle (MXene particle) (the shape seen from a direction perpendicular to the layer of each two-dimensional particle) was approximated to an elliptical shape, and the long diameter was measured. The average value of the long diameters measured for the two-dimensional particles (MXene particles) targeted was taken as the average value of the long diameters of the two-dimensional surfaces of the two-dimensional particles. The SEM image analysis software "A-zo-kun" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) was used to approximate the elliptical shape. When a porous substrate was used as the substrate, fine black spots in the micrographs may be derived from the substrate. Therefore, before image analysis, the porous parts of the background were erased by image processing as necessary.

[0121] The results of these measurements are shown in Table 2.

[0122] [Table 2]

[0123] As can be seen from the results in Table 2 above, the MXene two-dimensional particles obtained in this embodiment do not contain Li, and even when placed under high humidity conditions for a long period of time, the decrease in conductivity is suppressed. Furthermore, the MXene two-dimensional particles obtained in this embodiment have an average major axis value of 1 μm or more on the two-dimensional surface, and an average thickness value of 10 nm or less. Therefore, the MXene two-dimensional particles obtained in this embodiment can be used to produce a film (conductive film) that can be handled without adding a binder.

[0124] In contrast, in Comparative Example 1, since Li was used as the intercalator, the electrical conductivity was significantly reduced when placed under high humidity conditions. [Industrial Applicability]

[0125] The two-dimensional particles, conductive films and conductive pastes of the present invention may be used in any suitable application, and may be particularly preferably used, for example, as electrodes in electrical devices. [Explanation of symbols]

[0126] 1a, 1b layer body (M m X n layer) 3a, 5a, 3b, 5b Modified or terminal T 7a, 7b MXene layers 10, 10a, 10b MXene particles (particles of layered materials) 30 Conductive Film

Claims

1. A two-dimensional particle having one or more layers, comprising a metal cation, wherein the layer has the following formula: M ｍ X ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is 1 or more and 4 or less, m is greater than n and 5 or less) and includes a layer body represented by the formula and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, an amino group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, and a hydrogen atom) present on the surface of the layer body, wherein the modification or termination T includes a chlorine atom, the metal cation includes at least one cation selected from the group consisting of Na and K, and the two-dimensional particle has a Li content of less than 0.002% by mass.

2. The two-dimensional particle according to Claim 1, wherein the chlorine atom content measured by combustion ion chromatography is 3.6% by mass or more in the total of the layer and the metal cation.

3. The two-dimensional particle according to Claim 1, wherein the total content of Na and K is 0.1% by mass or more and 10% by mass or less.

4. The two-dimensional particle according to Claim 1, wherein the average value of the major axis of the two-dimensional plane is 1 μm or more and 20 μm or less.

5. The two-dimensional particle according to Claim 1, wherein the average thickness is 1 nm or more and 10 nm or less.

6. A conductive film comprising the two-dimensional particle according to any one of Claims 1 to 5.

7. The conductive film according to Claim 6, wherein the conductivity is 2,000 S / cm or more.

8. A conductive paste comprising the two-dimensional particle according to any one of Claims 1 to 5 and a dispersion medium.

9. A conductive composite material comprising the two-dimensional particle according to any one of Claims 1 to 5 and a resin.

10. An electromagnetic shield comprising the two-dimensional particle according to any one of Claims 1 to 5.

11. An adsorbent comprising the two-dimensional particle according to any one of Claims 1 to 5.

12. A bioelectrode comprising the two-dimensional particle according to any one of Claims 1 to 5.

13. (a) The following formula: M ｍ AX ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, and 7, X is a carbon atom, a nitrogen atom, or a combination thereof, A is at least one element of Groups 12, 13, 14, 15, and 16, n is 1 or more and 4 or less, m is greater than n and 5 or less) Preparing a precursor represented by (b) Performing an etching process of removing at least a part of A atoms from the above precursor using an etching solution; (c) Performing a water washing process including a step of water washing the etched product obtained by the above etching process; (d) Performing an intercalation process including a step of mixing the water-washed product obtained by the above water washing with a metal-containing compound; (e) Performing a delamination process including a step of stirring the intercalated product obtained by the above intercalation process; (f) Washing the delaminated product obtained by the delamination process with water to obtain two-dimensional particles including the concentration of chlorine atoms in the above etching solution is 10 mol / L or more, and the above metal-containing compound contains at least one selected from the group consisting of Na and K. A method for producing two-dimensional particles.

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