Photothermal conversion material

Abstract

The purpose of the present disclosure is to provide a photothermal conversion material having good infrared light absorption efficiency. Another purpose of the the present disclosure is to provide a method for producing two-dimensional particles used in such a photothermal conversion material. The present invention is a photothermal conversion material comprising two-dimensional particles having one or more layers, wherein the layers include a layer body represented by the formula (M1, M2)n+1Xn (in the formula, M1 is a group 3, 4, 5, 6, or 7 metal, M2 is a group 3, 4, 5, 6, or 7 metal, X is a carbon atom, a nitrogen atom, or a combination thereof, and n is 1-4) and a modification or a terminal T (T includes a chlorine atom) present on the surface of the layer body, and the photothermal conversion material has a maximum absorption wavelength in the near infrared region.

Description

Photothermal conversion materials

[0001] The present disclosure relates to photothermal conversion materials.

[0002] In recent years, MXene has attracted attention as a novel material with photothermal conversion properties. 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. MXene generally has the form of particles of such layered materials (which may include powders, flakes, nanosheets, etc.).

[0003] Non-Patent Document 1 describes Nb, a type of MXene. ２ Photothermal therapy for cancer using C is described.

[0004] H. Lan et al., “A Two-Dimensional Biodegradable Niobium Carbide (MXene) for Photothermal Tumor Eradication in NIR-I and NIR-II Biowindows”, J. Am. Chem. Soc., 139, 16235-16247 (2017).

[0005] Nb described in Non-Patent Document 1 ２ In the case of C, the infrared light absorption efficiency was not fully satisfactory.

[0006] The present disclosure aims to provide a photothermal conversion material that has good infrared light absorption efficiency, and a method for producing two-dimensional particles used in such a photothermal conversion material.

[0007] The photothermal conversion material of the present disclosure comprises two-dimensional particles having one or more layers, wherein the layers are represented by the following formula: (M １ , M ２ ) ｎ＋１ X ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２is a Group 3, 4, 5, 6 or 7 metal, X is a carbon atom, a nitrogen atom or a combination thereof, and n is 1 or more and 4 or less), and a modification or termination T (T includes a chlorine atom) present on the surface of the layer body, and has a maximum absorption wavelength in the near infrared region.

[0008] The method for producing two-dimensional particles provided in the photothermal conversion material of the present disclosure further comprises: (a) forming a compound represented by the following formula: (M １ , M ２ ) ｎ＋１ AX ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２ (b) obtaining an etched product by removing at least a part of the A atoms from the precursor using an etching solution; and (c) obtaining two-dimensional particles (etched and washed product), wherein the etching solution contains an anion containing a fluorine atom and an anion containing a chlorine atom.

[0009] The present disclosure aims to provide a photothermal conversion material that has good infrared light absorption efficiency, and a method for producing two-dimensional particles used in such a photothermal conversion material.

[0010] 1A and 1B are schematic cross-sectional views of layered MXene particles according to one embodiment of the present disclosure, where (a) shows a single-layer MXene particle and (b) shows a multi-layer (exemplarily two-layer) MXene particle.

[0011] (Embodiment 1: Photothermal Conversion Material) The photothermal conversion material of the present disclosure includes a two-dimensional particle having one or more layers, wherein the layers are represented by the following formula: (M １ , M ２ ) ｎ＋１ X ｎ (In the formula, M １is a metal of Groups 3, 4, 5, 6, or 7; M ２ is a Group 3, 4, 5, 6 or 7 metal, X is a carbon atom, a nitrogen atom or a combination thereof, and n is 1 or more and 4 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) present on the surface of the layer body, and has a maximum absorption wavelength in the near infrared region.

[0012] According to the present disclosure, a photothermal conversion material with good infrared light absorption efficiency can be provided. Although the present disclosure should not be interpreted as being limited to a particular theory, the reason why the photothermal conversion material of the present disclosure can exhibit such effects is thought to be as follows. That is, the two-dimensional particles of the present disclosure have a maximum absorption wavelength in the near-infrared region, and therefore are thought to have good near-infrared light absorption efficiency.

[0013] In the present disclosure, photothermal conversion material refers to a material that can absorb light and generate heat energy.

[0014] In the present disclosure, the near-infrared region refers to a wavelength range of 750 nm or more, and may refer to, for example, a region of 750 nm or more and 2,500 nm or less, particularly a region of 900 nm or more and 1,300 nm or less.

[0015] The two-dimensional particles preferably have a maximum absorption wavelength of 900 nm or more and 1,500 nm or less, and more preferably have a maximum absorption wavelength of 1,000 nm or more and 1,300 nm or less. When the two-dimensional particles have a maximum absorption wavelength in this range, the light absorption efficiency in the near-infrared region can be improved.

[0016] The maximum absorption wavelength can be measured by absorbance spectrum measurement. Specifically, it can be measured using a spectrophotometer in the measurement wavelength range of 200 nm to 1300 nm.

[0017] In the present disclosure, 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 possible oxidation numbers of the element.

[0018] In the present disclosure, the two-dimensional particles may be understood as layered materials or layered compounds, and may be referred to as "(M １ , M ２ ) ｎ＋１ X ｎ T ｓ ", where s is an arbitrary number, and conventionally, x or z may be used instead of s.

[0019] In addition, in this disclosure, 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.

[0020] In the above formula of MXene, M １ is at least one metal of Groups 3, 4, 5, 6, and 7, preferably at least one selected from the group consisting of Nb and Br, and more preferably Nb.

[0021] In addition, in the above formula of MXene, M ２ is at least one metal of Groups 3, 4, 5, 6, and 7, preferably at least one selected from the group consisting of Nb and Br, and more preferably Nb.

[0022] M １ and M ２ may be the same as or different from each other.

[0023] n is 1 or more and 4 or less, and typically, n can be 1, 2, 3, or 4, and is preferably 1, but is not limited thereto.

[0024] The modification or terminal 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.

[0025] MXene is a compound represented by the formula: １ , M ２ ) ｎ＋１ 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 ２N, 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" respectively mean approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3)), Ti ３ C ２ , Ti ３ N ２ , Ti ３ (CN), Zr ３ 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 , (Mo２ 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 、(Mo２ 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.)

[0026] Typically, in the above formula, it is preferred that M is niobium and X is a carbon atom or a nitrogen atom. For example, the MAX phase is Nb ２ AlC, and the layer body is Nb ２ C, and MXene is Nb ２ CT ｓ (in other words, M １ and M ２ is Nb, X is C, and n is 1).

[0027] In the present disclosure, MXene may contain a relatively small amount of A atoms derived from the MAX phase of the precursor, for example, 10% by mass or less of the original A atoms. The amount of residual A atoms may be preferably 8% by mass or less, more preferably 6% by mass or less, of the original A atoms. However, even if the amount of residual A atoms exceeds 10% by mass, this may not be a problem depending on the application and use conditions of the two-dimensional particles.

[0028] The two-dimensional particle is an aggregate including one layer of MXene particles (hereinafter simply referred to as "MXene particles") 10a (single-layer MXene particles) as shown in Fig. 1(a). More specifically, the MXene particles 10a are １ , M ２ ) ｎ＋１ X ｎThe layer body ((M １ , M ２ ) ｎ＋１ X 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). １ , M ２ ) ｎ＋１ X ｎ T ｓ ", where s is an arbitrary number.

[0029] The two-dimensional particles may contain one or more layers. Examples of multi-layered MXene particles (multilayered MXene particles) include, but are not limited to, two-layered 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 multilayered 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-layered MXene particles 10a and the multilayered MXene particles 10b, with some unseparated multilayered MXene particles 10b remaining.

[0030] 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 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 0.8 nm to 1.5 nm. The total number of layers may be 2 to 20,000.

[0031] In one aspect, the two-dimensional particles of this embodiment preferably include multilayer MXene particles obtained through a delamination process, which may contain two-dimensional particles with a small number of layers. The term "small number of layers" refers to, for example, six or fewer MXene layers. Furthermore, the thickness of the multilayer MXene particles 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 "few-layered MXene particles." Furthermore, single-layered MXene particles and few-layered MXene particles may be collectively referred to as "single-layered / few-layered MXene particles."

[0032] The two-dimensional particles of this embodiment preferably contain single-layered MXene particles and few-layered MXene particles, i.e., single-layered and few-layered MXene particles. The two-dimensional particles of this embodiment preferably contain single-layered and few-layered MXene particles with a thickness of 15 nm or less in an amount of 90% by volume or more, more preferably 95% by volume or more.

[0033] In one embodiment, the ratio of (average major axis length of the two-dimensional surfaces of the two-dimensional particles) / (average thickness length of the two-dimensional particles) is 1.2 or more, preferably 1.5 or more, and more preferably 2 or more. The average major axis length of the two-dimensional surfaces of the two-dimensional particles and the average thickness length of the two-dimensional particles may be determined by the method described below.

[0034] (Average value of major axes of two-dimensional surfaces of two-dimensional particles) The two-dimensional particles of this embodiment have an average value of major axes of two-dimensional surfaces of 1 μm or more and 20 μm or less. Hereinafter, the average value of major axes of two-dimensional surfaces may be referred to as the "average flake size."

[0035] The larger the average flake size, the higher the conductivity of the film. The two-dimensional particles of this embodiment have an average flake size of 1.0 μm or more, so films formed using these two-dimensional particles, such as films obtained by laminating these two-dimensional particles, can achieve a conductivity of 2000 S / cm or more. The average long diameter of the two-dimensional surface is preferably 1.5 μm or more, more preferably 2.5 μm or more. When MXene is delaminate-treated by ultrasonic treatment, most of the MXene is reduced in diameter to approximately several hundred nanometers in long diameter, and therefore the film formed from the single-layer MXene delaminated by ultrasonic treatment is thought to have low layer orientation.

[0036] 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 dispersion medium.

[0037] The longest diameter of the two-dimensional plane refers to the longest diameter when each MXene particle is approximated to an ellipse in an electron micrograph, as shown in the Examples below, and the average longest diameter of the two-dimensional plane refers to the number average of the longest diameters of 80 or more particles. As the electron microscope, a scanning electron microscope (SEM) or a transmission electron microscope (TEM) can be used.

[0038] The average major axis of the two-dimensional particles of this embodiment may be measured by dissolving a 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 from an SEM image of the film.

[0039] (Average Thickness of Two-Dimensional Particles) The average thickness of the two-dimensional particles of this embodiment is preferably 1 nm or more and 15 nm or less. The thickness is preferably 10 nm or less, more preferably 7 nm or less, and even more preferably 5 nm or less. On the other hand, considering the thickness of the monolayer MXene particles, the lower limit of the thickness of the two-dimensional particles can be 1 nm.

[0040] The average thickness of the two-dimensional particles is determined as a number-average size (for example, a number-average of at least 40 particles) based on atomic force microscope (AFM) or transmission electron microscope (TEM) photographs.

[0041] (Oxygen Atoms, Fluorine Atoms, and Chlorine Atoms) The two-dimensional particles contain at least oxygen atoms, fluorine atoms, and chlorine atoms. Chlorine atoms have a larger atomic radius than fluorine atoms and oxygen atoms, and it is believed that the inclusion of chlorine atoms in addition to fluorine atoms and oxygen atoms can increase the interlayer distance and shift the maximum absorption wavelength to the longer wavelength side. As a result, the photothermal conversion material of the present disclosure can improve the light absorption efficiency in the near-infrared region.

[0042] The oxygen, fluorine and chlorine atoms may be bonded to and adsorbed on the surface of the layer in the form of ions, and the chlorine atoms may be bonded to hydrogen atoms and exist as hydroxyl groups.

[0043] In the two-dimensional particles, the relative content of chlorine atoms to 1 atomic % of niobium atoms may be preferably 1 atomic % or more and 20 atomic % or less, more preferably 10 atomic % or more and 20 atomic % or less, and even more preferably 16 atomic % or more and 20 atomic % or less. ２ When the relative content of chlorine atoms to niobium atoms in C is within this range, the light absorption efficiency in the near-infrared region can be further increased.

[0044] The content of the fluorine atoms may be preferably 1 atomic % or more and 20 atomic % or less, more preferably 1 atomic % or more and 10 atomic % or less, and even more preferably 1 atomic % or more and 8 atomic % or less, based on 100 atomic % of the total amount of the two-dimensional particles. ２ When the content of fluorine atoms in C is within this range, the light absorption efficiency in the near-infrared region can be further improved.

[0045] The contents of niobium atoms, fluorine atoms, and chlorine atoms can be measured by X-ray photoelectron spectroscopy (XPS).

[0046] (Embodiment 2: Method for Producing Two-Dimensional Particles) Hereinafter, a method for producing two-dimensional particles according to one embodiment of the present disclosure will be described in detail, but the present disclosure is not limited to this embodiment.

[0047] The method for producing two-dimensional particles of this embodiment includes: (a) preparing a predetermined precursor; (b) using an etching solution to remove at least some of the A atoms from the precursor to obtain an etched product; (c) mixing the etched product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched product; (e) washing the intercalation product to obtain a washed product; and (f) mixing the washed product to obtain delaminated two-dimensional particles, where the etching solution contains an anion containing a fluorine atom and an anion containing a chlorine atom. Each step is described in detail below.

[0048] Step (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, and is represented by the following formula: (M １ , M ２ ) ｎ＋１ AX ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２ is a 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; and n is 1 or more and 4 or less.

[0049] The above M １ , M ２ , X and n are as described above.

[0050] A is at least one Group 12, 13, 14, 15, or 16 element, and is usually a Group A element, typically Group IIIA or Group IVA, and more particularly 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.

[0051] The MAX phase is (M １ , M ２ ) ｎ＋１ 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. The MAX phase typically has n+1 layers of M １ and M ２ Between each layer of atoms, there is a layer of X atoms (collectively called "(M １ , M ２ ) ｎ＋１ X ｎ layer), the n+1th M １ and M ２ It has a repeating unit in which a layer of A atoms ("A atomic layer") is arranged as the next layer of atoms, but is not limited to this.

[0052] 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.

[0053] Step (b) In step (b), the precursor (M １ , M ２ ) ｎ＋１ AX ｎ At least a part of the A atoms is removed by etching from the precursor. １ , M ２ ) ｎ＋１ X ｎ A processed product (etched product) is obtained in which at least a part of the layer composed of A atoms is removed while the layer represented by the formula (I) is maintained.

[0054] The etching solution contains an anion containing a fluorine atom and an anion containing a chlorine atom, and may be, for example, a mixture of HF and HCl, a mixture of HF and LiCl, a mixture of HCl and LiF, a mixture of HCl and NaF, a mixture of HCl and KF, a mixture of HF, HCl and LiCl, or a mixture of HF, HCl and LiF, and preferably a mixture of HF, HCl and LiCl. The etching solution may be, for example, an aqueous solution.

[0055] The etching solution contains a metal cation (e.g., Li ＋ By including a metal compound (e.g., LiCl, LiF) containing a metal cation, the precursor from which the A atoms have been removed can be intercalated simultaneously with the etching process, and the etching process and the intercalation process can be carried out simultaneously. This allows at least a portion of the A atoms to be removed from the precursor (MAX), and at the same time, the (M １ , M ２ ) ｎ＋１ X ｎ The layer remains, and adjacent multiple (M １ , M ２ ) ｎ＋１ X ｎ An intercalation product is obtained in which metal cations are intercalated between the layers.

[0056] In the etching solution, the HF concentration may be preferably 1 mol / L or more and 22 mol / L or less, more preferably 2 mol / L or more and 20 mol / L or less, and even more preferably 3 mol / L or more and 6 mol / L or less. When the HF concentration is in this range, the etching efficiency of A atoms can be improved.

[0057] In the etching solution, the concentration of HCl in 100% by mass of the total amount of the etching solution may be preferably 2 mol / L to 12 mol / L, more preferably 4 mol / L to 11 mol / L, and even more preferably 9 mol / L to 11 mol / L. When the concentration of HCl is within this range, chlorine atoms are easily introduced into the two-dimensional particles, making it easier to obtain two-dimensional particles with good light absorption efficiency in the near-infrared region.

[0058] In the etching solution, the LiCl concentration may be preferably 1% by mass or more and 10% by mass or less, more preferably 2% by mass or more and 7% by mass or less, and even more preferably 3% by mass or more and 5% by mass or less, based on 100% by mass of the total amount of the etching solution. When the LiCl concentration is in this range, the etching efficiency of A atoms can be improved.

[0059] The etching solution may further contain an acid such as HBr, HI, sulfuric acid, phosphoric acid, or nitric acid.

[0060] As the etching procedure and other conditions using the above etching solution, conditions conventionally used can be adopted.

[0061] After the etching treatment and before the step (c), the etched product may be washed to obtain an etching-washed product. By washing, the acid used in the etching treatment and the like can be sufficiently removed.

[0062] The cleaning can be performed using a cleaning solution, typically by mixing the etched material with the cleaning solution. Such a cleaning solution typically contains water, preferably pure water. Alternatively, a small amount of hydrochloric acid or the like may be further contained in addition to pure water. The amount of cleaning solution to be mixed with the etched material and the method for mixing the etched material with the cleaning solution are not particularly limited. For example, such a mixing method may involve coexisting the etched material with the cleaning solution and then stirring, centrifuging, or the like. Examples of the stirring method 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 etched material to be treated. Washing with the above cleaning solution may be performed one or more times, and it is preferable to perform washing with the cleaning solution multiple times. Specifically, for example, washing with the washing solution may be carried out by sequentially carrying out the following steps: step (i) adding the washing solution (to the treated product or the remaining precipitate obtained in (iii) below) and stirring; step (ii) centrifuging the stirred product; and step (iii) discarding the supernatant after centrifugation. Steps (i) to (iii) may be repeated two or more times, for example, 15 or less times.

[0063] Step (c) In step (c), an intercalation treatment is performed using a metal compound containing a metal cation to intercalate the etched product with the metal cation, thereby obtaining an intercalation-treated product. As a result, the metal cation is intercalated into two adjacent M ｍ X ｎ An intercalated product is obtained in which the intercalation is carried out between the layers. Such an intercalation process may be carried out in a dispersion medium.

[0064] The metal cations may be the same as the metal cations contained in the two-dimensional particles.

[0065] Examples of the metal compound include ionic compounds in which the metal cation and anion are bonded. Examples include sulfide salts including iodides, phosphates, and sulfates of the metal cations, nitrates, acetates, and carboxylates. The metal cation is preferably an alkali metal ion or an alkaline earth metal cation, and more preferably a lithium ion. The metal compound is preferably a metal compound containing an alkali metal ion or an alkaline earth metal ion, more preferably a metal compound containing lithium ion, and even more preferably an ionic compound of lithium ion, and particularly preferably one or more of iodides, phosphates, and sulfides of lithium ion. If lithium ion is used as the metal ion, it is thought that water hydrated with lithium ion has the most negative dielectric constant, making it easier to form a monolayer.

[0066] The specific method for the intercalation treatment is not particularly limited, and for example, the etched and washed product may be mixed with a metal compound and stirred or allowed 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 single-layer / few-layer MXene particles, and can be set, for example, between 12 and 24 hours.

[0067] The intercalation treatment may be carried out in the presence of a dispersion medium, such as water, or an organic medium such as N-methylpyrrolidone, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, dimethyl sulfoxide, ethylene glycol, or acetic acid.

[0068] The order of mixing the dispersion medium, the etched product, and the metal compound is not particularly limited, but in one embodiment, the dispersion medium and the etched product may be mixed together, and then the metal compound may be mixed in. Typically, the etching liquid after the etching treatment may be used as the dispersion medium.

[0069] Step (d): In step (d), the intercalation-treated product is stirred to perform a delamination process for delaminating the intercalation-treated product, thereby obtaining a delamination-treated product. By this stirring, shear stress is applied to the intercalation-treated product, and two adjacent M ｍ X ｎ At least a portion of the space between the layers can be peeled off, and the MXene particles can be divided into a single layer or a few layers.

[0070] The conditions for the delamination treatment are not particularly limited and can be performed by known methods. For example, one method of applying shear stress to the intercalation-treated product is to disperse the intercalation-treated product in a dispersion medium and stir the mixture. Examples of stirring methods include stirring using a mechanical shaker, vortex mixer, homogenizer, ultrasonic treatment, hand shake, automatic shaker, etc. The degree of stirring, such as stirring speed and stirring time, can be adjusted depending on the amount and concentration of the product to be treated. For example, the above-mentioned intercalation-treated slurry can be centrifuged and the supernatant discarded, followed by adding pure water to the remaining precipitate and stirring using, for example, a hand shake or automatic shaker to perform layer separation (delamination). Removal of unexfoliated material can be achieved by centrifuging, discarding the supernatant, and then washing the remaining precipitate with water. For example, (i) pure water can be added to the remaining precipitate after discarding the supernatant, followed by stirring, (ii) centrifuging, and (iii) recovering the supernatant. 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-layer and few-layer MXene particles as a delamination-treated product. Alternatively, the supernatant can be centrifuged and discarded to obtain a clay containing single-layer and few-layer MXene particles as a delamination-treated product.

[0071] Step (e): In step (e), the intercalation-treated product is washed to obtain a washed product. This makes it easy to remove metal compounds and the like used in the intercalation treatment. When the delamination treatment is performed, the following intercalation-treated product can be read as the delamination-treated product.

[0072] In one embodiment, the cleaning can be performed using a cleaning solution, typically by mixing the delamination-treated product with the cleaning solution. In another embodiment, the cleaning can be performed by acid-treating the delamination-treated product and then mixing the acid-treated product with the cleaning solution. The acid used in the acid treatment can be inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid, hydroiodic acid, hydrobromic acid, or hydrofluoric acid; or organic acids such as acetic acid, citric acid, oxalic acid, benzoic acid, or sorbic acid. The acid concentration in the acid solution can be adjusted appropriately depending on the delamination-treated product. The cleaning with the cleaning solution can be performed sequentially by: step (i) adding the cleaning solution to the treated product or the remaining precipitate obtained in (iii) below and stirring; step (ii) centrifuging the stirred product; and step (iii) discarding the supernatant after centrifugation. Steps (i) to (iii) can be repeated two or more times, for example, up to 15 times. The stirring can be carried out using a handshake, an automatic shaker, a shear mixer, a pot mill, or the like. The acid treatment may be carried out one or more times, and if necessary, the operation of mixing with a fresh acid solution (an acid solution not used in the acid treatment) and stirring may be carried out two or more times, for example, up to 10 times. The washing liquid can be the same as the washing liquid in step (c). For example, water may be used as the washing liquid, and pure water is preferred. The mixing can be carried out by the same method as the mixing method in step (c), for example, by stirring, centrifugation, or the like. Stirring methods include stirring methods using a handshake, an automatic shaker, a shear mixer, a pot mill, or the like.

[0073] Step (f): In step (f), the washed product is mixed, whereby the layer is peeled off and delaminate can be achieved.

[0074] The method for mixing the washed product is not particularly limited and can be performed by a known method. For example, a method of stirring and dispersing the washed product can be used. Stirring methods include stirring using a mechanical shaker, vortex mixer, homogenizer, ultrasonic treatment, hand shake, automatic shaker, etc. The degree of stirring, such as stirring speed and stirring time, can be adjusted depending on the amount and concentration of the product to be treated. In one embodiment, the content of the washed product in a mixture containing the washed product can be, for example, 0.5% by mass or more and 10% by mass or less, or even 1% by mass or more and 5% by mass or less.

[0075] When the washed product is mixed, a dispersion medium may be present. A specific example of the dispersion medium is water.

[0076] Although the two-dimensional particles provided in the photothermal conversion material in one embodiment of the present disclosure have been described in detail above, various modifications are possible. Note that the two-dimensional particles in the photothermal conversion material of the present disclosure may be manufactured by a method different from the manufacturing method in the above-mentioned embodiment, and that the manufacturing method of the two-dimensional particles of the present disclosure is not limited to only those that provide the two-dimensional particles in the above-mentioned embodiment.

[0077] (Photothermal conversion material) The photothermal conversion material of the present disclosure includes the two-dimensional particles. The two-dimensional particles of the present disclosure have good light absorption efficiency in the near-infrared region and can be preferably used as a photothermal conversion material.

[0078] The photothermal conversion material can be used, for example, in photothermal therapy, which is one of the cancer treatment methods. Cancer cells are more susceptible to heat than normal cells, and heating them to an appropriate temperature is expected to have the effect of killing only cancer cells while preserving normal cells. In photothermal therapy, the photothermal conversion material is typically accumulated in cancer tissue through the bloodstream, and it is thought that cancer cells can be killed by irradiating the accumulated area with infrared light.

[0079] In the above photothermal conversion material, the content of two-dimensional particles may be preferably 50% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less, based on 100% by mass of the total amount of the photothermal conversion material.

[0080] The photothermal conversion material may contain, in addition to the two-dimensional particles, other materials such as acrylic resin, polyester resin, polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyether resin, polylactic acid, and polyvinyl alcohol, as well as other additives.

[0081] The photothermal conversion material can be mixed with an aqueous medium to form a slurry, and the slurry can be injected into a blood vessel to accumulate in cancer tissue. Therefore, a composition containing the photothermal conversion material and water is also within the scope of the present disclosure. In the composition, the content of the photothermal conversion material can be preferably 1% by mass or more and 90% by mass or less, more preferably 1% by mass or more and 10% by mass or less, based on a total amount (100% by mass) of the composition.

[0082] The two-dimensional particles of the present disclosure have good light absorption efficiency in the near-infrared region and can be preferably used as a photothermal conversion material (particularly a photothermal conversion material used in photothermal therapy for cancer).

[0083] The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited thereto.

[0084] Example 1 In Example 1, two-dimensional particles were produced by sequentially carrying out (1) preparation of a precursor (MAX), (2) etching of the precursor, and (3) cleaning, as detailed below.

[0085] (1) Preparation of Precursor (MAX) Nb powder, Al powder, and C 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 sintered at 1550°C for 2 hours in an Ar atmosphere. The resulting sintered body (block-shaped MAX) was then pulverized with an end mill to a maximum dimension of 40 μm or less. This resulted in the preparation of Nb as a precursor (powder-shaped MAX). ２ AlC particles were obtained.

[0086] (2) Etching of precursor Nb prepared by the above method ２ Etching was performed using AlC particles (powder) under the following etching conditions to remove Nb ２ A solid-liquid mixture (slurry) containing solid components derived from the AlC powder was obtained. (Etching conditions) Precursor: Nb ２ AlC (passed through a 45 μm sieve) Etching solution composition: 49% HF 36 mL + 36% HCl 24 mL Metal salt: LiCl 3 g Precursor input amount: 3.0 g Reaction vessel: 100 mL Eye Boy Etching temperature: 35° C. Etching time: 48 hours Stirrer rotation speed: 400 rpm

[0087] (3) Washing The above slurry was divided into two parts and placed in two 50 mL centrifuge tubes, respectively. After centrifugation at 3500 G for 5 minutes using a centrifuge, the supernatant was discarded. 35 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 Nb ２ CT ｓ - Water medium clay was obtained.

[0088] Examples 2 to 6 Nb was etched in the same manner as in Example 1, except that the composition of the etching solution was changed to the ratio (by mass) of HF and HCl shown in Table 1. ２ CT ｓ - Water medium clay was obtained.

[0089]

[0090] [Comparative Example 1] After preparing a precursor (MAX) in the same manner as in Example 1, the following step (2) was carried out, and cleaning was carried out in the same manner as in Example 1 to obtain Nb ２ C particles were prepared.

[0091] (1) Preparation of precursor (MAX): Same as in Example 1 (2) Etching of precursor The Nb prepared in the above step (1) was ２ Etching was performed using AlC particles (powder) under the following etching conditions to remove Nb ２ A solid-liquid mixture (slurry) containing solid components derived from the AlC powder was obtained. (Etching conditions) Precursor: Ti ３ AlC ２ (Passed through a 45 μm mesh sieve) Etching solution composition: 49% HF 20 mL Precursor input amount: 3.0 g Reaction vessel: 100 mL Eye Boy Etching temperature: 50° C. Etching time: 48 hours Stirrer rotation speed: 400 rpm (3) Cleaning: Same as in Example

[0092] (Method for detecting elements on the layer surface) The obtained conductive film containing two-dimensional particles was measured by X-ray photoelectron spectroscopy (XPS) to detect niobium atoms and chlorine atoms contained in the two-dimensional particles. For the XPS measurement, a Quantum 2000 manufactured by ULVAC-PHI, Inc. was used. The relative content of chlorine atoms to 1 atomic % of niobium atoms (shown as "Cl / Nb" in Table 2) was calculated by dividing the content (atomic %) of detected chlorine atoms by the content (atomic %) of detected niobium atoms.

[0093] (Method of preparing a measurement sample) First, the solid concentration of the monolayered clay after immersion in water was measured. ２ CT ｓ Approximately 0.5 g of clay (monolayer clay) and 10 mL of water were weighed and shaken by hand to prepare a dispersion for film formation. The dispersion for film formation was suction filtered, and ethanol was added dropwise from above, followed by air drying to obtain a free-standing film. ２ CT ｓ The solid content concentration was calculated from the difference in weight between the water medium clay (monolayered clay) and the free-standing film.

[0094] Next, Nb２ CT ｓ - Water medium clay (single-layered clay) was weighed into a glass container, and pure water was added thereto to adjust the dispersion concentration to 20 μm / mL, thereby obtaining a dispersion for measurement.

[0095] (Absorbance spectrum measurement) The absorbance spectrum including the obtained two-dimensional particles was measured using a spectrophotometer (UV-vis / NIR). For the absorbance spectrum measurement, a Hitachi High-Tech Science U-4100 was used. The measurement conditions were: measurement wavelength range 300 nm to 1300 nm, blank pure water, and a cell made of quartz glass.

[0096]

[0097] In the two-dimensional particles obtained in Examples 1 to 6, Nb ２ AlC is etched with HF and HCl, and the surface groups are composed of Cl in addition to O, OH, and F. Therefore, the maximum absorption wavelength is in the near-infrared region (λ = 750 to 1200 nm). Therefore, such two-dimensional particles can be said to be an advantageous material for cancer photothermal therapy using near-infrared light.

[0098] On the other hand, Comparative Example 1 contains Nb ２ In this example, AlC was etched using only HF, and the surface groups did not contain Cl. As a result, the maximum absorption wavelength was in the visible light region, and it is believed that the light absorption efficiency in the near-infrared region was insufficient.

[0099] The present disclosure includes the following aspects. <1> A photothermal conversion material comprising two-dimensional particles having one or more layers, wherein the layers are represented by the following formula: (M １ , M ２ ) ｎ＋１ X ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２is a Group 3, 4, 5, 6 or 7 metal, X is a carbon atom, a nitrogen atom or a combination thereof, and n is 1 or more and 4 or less), and a modification or terminal T (T includes a chlorine atom) present on the surface of the layer body, and the photothermal conversion material has a maximum absorption wavelength in the near-infrared region. <2> The photothermal conversion material according to <1>, which includes at least an oxygen atom, a fluorine atom and a chlorine atom. <3> M １ is Nb, and M ２ is Nb, X is C, and n is 1. <4> The photothermal conversion material according to any one of <1> to <3>, in which the relative content of chlorine atoms to 1 atomic % of niobium atoms is 11 atomic % or more and 20 atomic % or less. <5> A composition comprising the photothermal conversion material according to any one of <1> to <4> and water. <6> (a) A compound represented by the following formula: (M １ , M ２ ) ｎ＋１ AX ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２ (b) using an etching solution to remove at least some of the A atoms from the precursor, thereby obtaining an etched product; (c) mixing the etched product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched product; (e) washing the intercalation product to obtain a washed product; and (f) mixing the washed products to obtain delaminated two-dimensional particles, wherein the etching solution contains an anion containing a fluorine atom and an anion containing a chlorine atom.

[0100] The two-dimensional particles of the present disclosure have good light absorption efficiency in the near-infrared region and can be preferably used as a photothermal conversion material (particularly a photothermal conversion material used in photothermal therapy for cancer).

[0101] 1a, 1b Layer body (M ｍ X ｎ Layer) 3a, 5a, 3b, 5b Modified or terminated T 7a, 7b MXene layer 10, 10a, 10b MXene particle (2D particle of layered material)

Claims

1. A photothermal conversion material comprising two-dimensional particles having one or more layers, wherein the layers are represented by the following formula: (M １ , M ２ ) ｎ＋１ X ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２ is a Group 3, 4, 5, 6 or 7 metal; X is a carbon atom, a nitrogen atom or a combination thereof; and n is 1 or more and 4 or less), and modified or terminated T (T includes a chlorine atom) present on the surface of the layer body, and the photothermal conversion material has a maximum absorption wavelength in the near-infrared region.

2. The photothermal conversion material according to claim 1, which contains at least oxygen atoms, fluorine atoms, and chlorine atoms.

3. M １ is Nb, and M ２ The photothermal conversion material of claim 1 , wherein is Nb, X is C, and n is 1.

4. The photothermal conversion material according to claim 1, wherein the relative content of chlorine atoms to 1 atomic % of niobium atoms is 11 atomic % or more and 20 atomic % or less.

5. A composition comprising the photothermal conversion material according to any one of claims 1 to 4 and water.

6. (a) a compound of the formula: (M １ , M ２ ) ｎ＋１ AX ｎ (In the formula, M １ is a metal of Groups 3, 4, 5, 6, or 7; M ２ (b) using an etching solution to remove at least some of the A atoms from the precursor, thereby obtaining an etched product; (c) mixing the etched product with a metal compound containing a metal cation to obtain an intercalation product in which the metal cation is intercalated into the etched product; (e) washing the intercalation product to obtain a washed product; and (f) mixing the washed products to obtain delaminated two-dimensional particles, wherein the etching solution contains an anion containing a fluorine atom and an anion containing a chlorine atom.

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