Nanosheet, method for producing nanosheet, and integrated body

Abstract

A nanosheet according to one embodiment of the present disclosure comprises an amorphous inorganic oxide having an organic functional group covalently bonded to the surface thereof.

Description

Nanosheets, methods for manufacturing nanosheets, and aggregates

[0001] This disclosure relates to nanosheets, methods for producing nanosheets, and aggregates using nanosheets.

[0002] For example, Patent Document 1 discloses a synthesis technique for amorphous silica nanosheets, which involves producing layered amorphous silica by mixing an alkoxysilane and a nonionic surfactant in an acidic solvent, and then peeling nanosheets from this layered amorphous silica.

[0003] Japanese Patent Publication No. 2023-026142

[0004] Incidentally, there is a need for the development of a highly productive method for manufacturing nanosheets.

[0005] It is desirable to provide nanosheets with excellent productivity, a method for manufacturing nanosheets, and aggregates.

[0006] A nanosheet according to one embodiment of this disclosure is made of an amorphous inorganic oxide on which organic functional groups are covalently bonded to its surface.

[0007] A method for producing nanosheets according to one embodiment of the present disclosure involves preparing a mixture containing water, a metal alkoxide, an acid catalyst, a cationic surfactant, an organic additive, and an aprotic solvent or a protic polar solvent, removing the aprotic solvent or protic polar solvent from the mixture to obtain a layered structure, and then decomposing the layered structure by surface modification.

[0008] An aggregate according to one embodiment of this disclosure contains the nanosheet described above.

[0009] In a nanosheet according to one embodiment of the present disclosure, a method for producing a nanosheet according to one embodiment of the present disclosure, and an aggregate according to one embodiment of the present disclosure, organic functional groups are covalently bonded to the surface of an amorphous inorganic oxide, thereby enabling redispersion in a solvent after solidification.

[0010] Figure 1 is a schematic perspective view of a nanosheet according to one embodiment of the present disclosure. Figure 2 is a flowchart showing the manufacturing process of the nanosheet shown in Figure 1. Figure 3A is a schematic diagram illustrating the manufacturing process of the nanosheet shown in Figure 1. Figure 3B is a schematic diagram showing the process following Figure 3A. Figure 3C is a schematic diagram showing the process following Figure 3B. Figure 4 is a schematic cross-sectional diagram illustrating the structure of a typical nanosheet. Figure 5 is a schematic cross-sectional diagram illustrating the structure of the nanosheet shown in Figure 1. Figure 6 is a scanning electron microscope image of the nanosheet obtained in Experimental Example 1. Figure 7 is a scanning electron microscope image of the nanosheet obtained in Experimental Example 3.

[0011] The embodiments of this technology will be described in detail below with reference to the drawings. The following description is one specific example of the disclosure, and the disclosure is not limited to the following embodiments. Furthermore, the disclosure is not limited to the arrangement, dimensions, and dimensional ratios of each component shown in each figure. The order of description is as follows: 1. Embodiment (Example of a nanosheet made of amorphous inorganic oxide with organic functional groups covalently bonded to its surface) 2. Examples 3. Examples of nanosheet use

[0012] <1. Embodiments> [Nanosheet Structure] Figure 1 schematically shows an example of the structure of a nanostructure (nanosheet 1) according to one embodiment of the present disclosure.

[0013] Nanosheets are two-dimensional nanoscale materials with a molecular-level thickness (approximately 1 nm) and a size (micron level) that is several hundred times larger in the lateral direction. Nanosheets are made of inorganic oxides consisting of a combination of one or more metal atoms, where the metal atoms (M) form a three-dimensional covalent network with oxygen atoms (O) via M-O-M bonds. A common inorganic oxide that constitutes nanosheets is silicon oxide (silica) based on silicon (Si) atoms. Nanosheets are suitably used in reinforced plastics, anti-reflective coatings, thermal insulation materials, semiconductor materials, additives, and catalysts, for example.

[0014] The nanosheet 1 includes, for example, an amorphous silica layer 11 in which amorphous silicon oxide extends in a two-dimensional direction, and an organosilane compound 12 covalently bonded to hydroxyl groups (-OH) that are abundant on the surface of the amorphous silica layer 11.

[0015] Here, the amorphous silica layer 11 corresponds to a specific example of an "amorphous inorganic oxide" as one embodiment of the present disclosure. The organosilane compound 12 corresponds to a specific example of an "organic functional group" as one embodiment of the present disclosure.

[0016] The amorphous silica layer 11 is made of silicon oxide consisting of silicon (Si) atoms or a single Si atom or a combination of Si atoms and other atoms, and the Si atoms form a three-dimensional covalent network with O atoms via Si-O-Si bonds.

[0017] The amorphous silica layer 11 has multiple hydroxyl groups (-OH) on its surface, and some or all of these hydroxyl groups form covalent bonds with the organosilane compound 12. In other words, the surface of the amorphous silica layer 11 is modified by multiple organosilane compounds 12.

[0018] The amorphous silica layer 11 consists of, for example, a single layer of silicon oxide having an amorphous structure, and has a thickness of, for example, 10 nm or less. The amorphous silica layer 11 is, for example, 0.5 μm ２ Having an area of ​​the above, preferably 1 μm ２ It has the above area.

[0019] As described above, the organic silane compound 12 modifies the surface of the amorphous silica layer 11 by covalently bonding with hydroxyl groups that are abundant on the surface of the amorphous silica layer 11. As will be described in detail later, the nanosheet 1 can be redispersed in the solvent after solidification because the surface of the amorphous silica layer 11 is modified by multiple organic silane compounds 12.

[0020] Examples of the organosilane compound 12 include organosilane compounds having a reactive functional group represented by the following general formula (1) or general formula (2).

[0021] (Formula 1) R １ Ｙ Si(OR ２ ) ４－Ｙ ... (1) (Formula 2) R １ Ｙ SiCl ４－Ｙ ... (2) (R １ is any one of a hydrogen atom, a vinyl group, an acryloxy group, a methacryloxy group, an aminopropyl group, a glycidoxypropyl group, and a mercaptopropyl group. R ２ is any one of a methyl group, an ethyl group, a propyl group, and an isopropyl group. Y is an integer of 3 or less.)

[0022] As the organic silane compound 12, an organic silane compound having no reactive functional group represented by the following general formula (3) or general formula (4) can be mentioned.

[0023] (Formula 3) R ３ Ｚ Si(OR ４ ) ４－Ｚ ... (3) (Formula 4) R ３ Ｚ SiCl ４－Ｚ ... (4) (R ３ is any one of a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, a dodecyl group, a hexadecyl group, a vinyl group, and a phenyl group. R ４ is any one of a methyl group, an ethyl group, a propyl group, and an isopropyl group. Z is an integer of 3 or less.)

[0024] The thickness (t) of the nanosheet 1 is, for example, 10 nm or less, preferably 1 nm or more and 5 nm or less. The area of the nanosheet 1 corresponds to the area of the amorphous silica layer 11. That is, the nanosheet 1 has an area of, for example, 0.5 μm ２ or more, preferably 1 μm ２ or more.

[0025] [Method for Producing Nanosheet] FIG. 2 shows the flow of the manufacturing process of the nanosheet 1.

[0026] First, water (e.g., pure water or deionized water), metal alkoxide, catalyst, cationic surfactant, organic additive, and an aprotic or protic polar solvent capable of completely dissolving these are added to a beaker, and this mixture is stirred at room temperature to sufficiently hydrolyze the metal alkoxide (step S101). Thereby, a hydrophilic inorganic oxide precursor is formed.

[0027] Even a molecule in which some alkoxy groups of the metal alkoxide are substituted with non-hydrolyzable functional groups does not hinder the formation of the metal oxide skeleton. As the metal alkoxide, a compound represented by the following general formula (5) can be used. (Chemical formula 5) R ５ Ｘ M(OR ６ ) ４－Ｘ ...(5) (R ５ is any one of a methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, dodecyl group, hexadecyl group, vinyl group, and phenyl group. R ６ is any one of a methyl group, ethyl group, propyl group, and isopropyl group. M is any one of silicon (Si), aluminum (Al), titanium (Ti), tin (Sn), and zinc (Zn). X is an integer of 0 or 2 or less.)

[0028] As the catalyst, for example, acid catalysts such as acetic acid, hydrochloric acid, nitric acid, and sulfuric acid can be used.

[0029] The cationic surfactant is an amphiphilic compound and has a hydrophilic group 131 and a hydrophobic group 132 in the molecule (surfactant molecule 13). As the cationic surfactant, those containing 1 to 3 alkyl chains can be used. Specifically, for example, quaternary ammonium salts, alkyl polyethers, and alkyl sulfates can be mentioned. The length of the hydrophobic group 132 preferably has a length that exhibits sufficient electrostatic interaction to cause self-organization. Specific examples of the hydrophobic group 132 include, for example, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, and their derivatives.

[0030] The organic additive can be an alcohol having 6 to 20 carbon atoms, an alkane having 6 to 20 carbon atoms (C ｎ H ２ｎ＋２ ; n = 6 to 20), 1,3,5 - trimethylbenzene, 1,3,5 - triethylbenzene or 1,3,5 - tripropylbenzene.

[0031] Examples of the protic polar solvent include methanol, ethanol, isopropanol, butanol, acetic acid, formic acid and the like. Examples of the aprotic polar solvent include N - methylpyrrolidone, dichloromethane, tetrahydrofuran, ethyl acetate, acetone, dimethylformamide (DMF), acetonitrile and dimethyl sulfoxide (DMSO) and the like.

[0032] In step S101, water, metal alkoxide, catalyst, cationic surfactant and aprotic or protic polar solvent may be mixed, and after hydrolyzing the metal alkoxide, an organic additive may be added. Alternatively, in step S101, water, metal alkoxide and catalyst may be reacted in advance, and then a cationic surfactant, an organic additive and an aprotic or protic polar solvent may be added.

[0033] Next, the mixed solution is spread on a substrate such as a glass substrate or a silicon substrate, or a container such as a stainless - steel vat or a petri dish to remove the polar solvent. By removing (volatilizing) this polar solvent, the formation and self - organization of the metal oxide (amorphous silica layer 11) are simultaneously induced, and the layered structure 10 shown in FIG. 3A is formed (step S102).

[0034] Specifically, when the inorganic oxide precursor polymerizes, a plurality of amorphous silica layers 11 are formed. At the same time, the hydrophilic group 131 of the surfactant molecule 13 is adsorbed on the surface of each of the plurality of amorphous silica layers 11 by electrostatic interaction. Further, the hydrophobic groups 132 of the plurality of surfactant molecules 13 adsorbed on each of the plurality of nanosheets aggregate by electrostatic interaction. Thereby, a layered structure 10 in which a plurality of amorphous silica layers 11 are laminated with surfactant molecules 13 in between is obtained.

[0035] Polar solvents can be evaporated, for example, by air drying. Alternatively, polar solvents can be evaporated by transferring the mixture to a sealed container and reducing the pressure using a vacuum pump or the like.

[0036] Next, the nanosheet 1 is isolated from the layered structure 10 (step S103). The nanosheet 1 can be isolated as follows.

[0037] In the layered structure 10, multiple amorphous silica layers 11 are coated with multiple surfactant molecules 13, and the layered structure 10 is held together by the interaction of these surfactant molecules 13. When the organic silane compound 12 is covalently bonded to the surface of the amorphous silica layers 11, the surfactant molecules 13 are detached and the layered structure 10 is decomposed.

[0038] Specifically, first, the layered structure 10 obtained in step S102 is dispersed in an organic solvent of any choice, as shown in Figure 3B. Next, the above-mentioned organic silane compound is added to the organic solvent and heated as necessary. As a result, the hydroxyl groups (-OH) abundant on the surface of the amorphous silica layer 11 react with the organic silane compound 12 to form covalent bonds, and the surfactant molecules 13 are detached from the surface of the amorphous silica layer 11, causing the layered structure 10 to decompose, as shown in Figure 3C. Note that the presence or absence of reactive functional groups in the organic silane compound 12 is not a necessary condition, and it is selected from the above-mentioned organic silane compounds depending on the application of the nanosheet 1.

[0039] Subsequently, the nanosheet 1 can be isolated by removing the excess organic silane compound 12 and the detached surfactant molecules 13 by distillation or two-component separation. The surface of the obtained nanosheet 1 is modified with the organic silane compound 12.

[0040] [Effects and Effects] In this embodiment, the nanosheet 1 and its manufacturing method involve preparing a mixture containing water, a metal alkoxide, an acid catalyst, a cationic surfactant, an organic additive, and an aprotic solvent or a protic polar solvent. The aprotic solvent or protic polar solvent is then removed from the mixture to obtain a layered structure 10, which is then decomposed by surface modification. This results in a nanosheet 1 made of an amorphous inorganic oxide with organic functional groups (organosilane compounds 12) covalently bonded to its surface, and allows for redispersion in a suitable solvent even after the solvent used for dispersion has evaporated and the nanosheet has solidified. This will be explained below.

[0041] Nanosheets can be used in a variety of fields, including reinforced plastics, anti-reflective coatings, thermal insulation materials, semiconductor materials, additives, and catalysts. In particular, nanosheets made of inorganic oxides have excellent weather resistance, stability, and high mechanical strength.

[0042] Nanosheets made of inorganic oxides are generally manufactured using the following two methods:

[0043] The first method is called molecular template method. Molecular template method involves creating nanosheets using two-dimensional organic molecules such as graphene oxide as a template. However, molecular template method has a problem in that when the template is removed by firing or other means, the nanosheets bond together and cannot be isolated.

[0044] The second method is called the layered compound method. The layered compound method involves exfoliating layered inorganic oxide compounds to produce nanosheets. However, the nanosheets obtained using the layered compound method are crystalline inorganic oxide nanosheets, and amorphous inorganic oxide nanosheets useful for the various applications mentioned above have not yet been obtained.

[0045] As a method for manufacturing nanosheets that solves the above problems, the aforementioned amorphous silica nanosheet synthesis technology has been reported. This amorphous silica nanosheet synthesis technology involves producing layered amorphous silica by mixing alkoxysilane and a nonionic surfactant in an acidic solvent, and then peeling nanosheets from this layered amorphous silica.

[0046] However, in the above synthesis technique, as shown in Figure 4(A), for example, the hydrophilic group 10131 portion of the nonionic surfactant 1013, which has hydrophilic groups 10131 and hydrophobic groups 10132, penetrates into the layer of amorphous silica nanosheet 1011. The portion in which the hydrophilic group 10131 of the nonionic surfactant 1013 has penetrated into the layer remains as pores H when the nonionic surfactant 1013 is detached, as shown in Figure 4(B), for example, and is easily torn, which is disadvantageous in terms of gas barrier properties and material strength. Furthermore, since the amorphous silica nanosheet 1011 obtained by the above synthesis technique has a surface coated with polymerizable hydroxyl groups, once the solvent used for dispersion is evaporated and it is solidified, the layer surfaces of the amorphous silica nanosheets 1011 bond to each other, making redispersion impossible.

[0047] In contrast, in this embodiment, as described above, a mixture containing water, a metal alkoxide, an acid catalyst, a cationic surfactant, an organic additive, and an aprotic solvent or a protic polar solvent is prepared, and the aprotic solvent or protic polar solvent is removed from the mixture to obtain a layered structure 10. After that, the layered structure 10 is decomposed by surface modification.

[0048] The hydrophilic group 131 portion of a cationic surfactant (for example, a quaternary ammonium salt) consists of one nitrogen atom. Therefore, the depth to which the hydrophilic group 131 penetrates the amorphous silica layer 11 is approximately one nitrogen atom. In other words, the pore H after the surfactant molecule 13 is removed is shallower compared to the case where a nonionic surfactant 1013 is used, as shown in Figure 5(B), for example, which is advantageous in terms of gas barrier properties and material strength.

[0049] Furthermore, in this embodiment, after obtaining the layered structure 10, the amorphous silica layer 11 is surface-modified by reacting hydroxyl groups (-OH) that are abundant on the surface with organic functional groups (for example, organosilane compound 12), so that it can be redispersed in a suitable organic solvent.

[0050] Furthermore, in this embodiment, for example, an alcohol having 6 to 20 carbon atoms is used as an organic additive, so that a layered structure 10 of multiple amorphous silica layers 11 thicker than the amorphous silica nanosheet 1011 is formed. As a result, the amorphous silica layers 11 become less likely to tear, and nanosheets 1 larger than the amorphous silica nanosheet 1011 can be obtained.

[0051] As described above, by using the nanosheet manufacturing method of this embodiment, it is possible to obtain a nanosheet 1 with excellent productivity.

[0052] <2. Examples> Next, examples of the present disclosure will be described.

[0053] (Experimental Example 1) First, water, tetraethoxysilane as a metal alkoxide, hydrochloric acid as a catalyst, deoctadecyldimethylammonium chloride as a surfactant, 1-decanol as an organic additive, and ethanol (a polar solvent) as a solvent were added to a beaker and stirred at room temperature to hydrolyze the metal alkoxide. Next, the mixture was spread in a container to remove the polar solvent and obtain a layered structure. The mixing ratio (molar ratio) of the above materials was water:metal alkoxide:catalyst, surfactant:organic additive:solvent = 3.2:1.0:0.0058:0.2:0.3:10. Subsequently, the layered structure was dispersed in tetrahydrofuran (THF) (solvent), and then surface modification was performed by reacting it with chlorotrimethylsilane as an organosilane compound. After that, excess organosilane compound and detached surfactant molecules were removed by two-liquid layer separation to obtain a nanosheet surface modified with the organosilane compound.

[0054] (Experimental Example 2) Nanosheets were fabricated using the same method as in Experimental Example 1, except that no surface modification was performed.

[0055] (Experimental Example 3) Nanosheets were prepared using the same method as in Experimental Example 1, except that no organic additives were used.

[0056] (Evaluation of Nanosheets) The nanosheets obtained in Experimental Examples 1 and 3 were dissolved in chloroform, dropped onto a silicon (Si) substrate, and spin-coated to prepare samples. The prepared samples were observed using a scanning electron microscope (HITACHI S-5500 microscope) under conditions of 1 kVm and 9.8 mA, and the area of ​​nanosheets contained in the samples was measured.

[0057] Figure 6 shows a scanning electron microscope image of the nanosheet obtained in Experimental Example 1. Figure 7 shows a scanning electron microscope image of the nanosheet obtained in Experimental Example 3. Table 1 summarizes the various materials used in Experimental Examples 1 to 3, the presence or absence of surface modification, and the evaluation results of the obtained nanosheets. The evaluation criterion is the area of ​​the obtained nanosheet (1 μm²). ２ Case A is the above case, and the area of ​​the obtained nanosheet is 1 μm ２ Cases where the result was less than B were designated as B, and cases where the nanosheet was not obtained (did not decompose) were designated as C.

[0058] (Method for measuring the area of ​​nanosheets) First, the obtained nanosheets are dissolved in chloroform, dropped onto a Si substrate, and spin-coated to prepare a sample, which is then observed with a scanning electron microscope. Microscope images are obtained in which all nanosheets present in a 64 × 48 μm field of view of the scanning electron microscope are appropriately magnified and contained in one field of view. The acquired microscope images are binarized using the image analysis software ImageJ (available from the National Institutes of Health, USA). The area of ​​the nanosheet portion is measured from this binarized image. If the total number of nanosheets present in the 64 × 48 μm field of view is 50 or less, the same measurement is performed in another 64 × 48 μm field of view, and this is repeated until the total number of nanosheets is 50 or more. The average value (arithmetic mean) of the areas of all obtained nanosheets is taken as the area of ​​nanosheet 1 of this disclosure.

[0059]

[0060] From the results of Experimental Examples 1 to 3 described above, it was confirmed that nanosheets can be isolated by using the nanosheet manufacturing method of this embodiment. Furthermore, it was confirmed that larger nanosheets can be obtained by using organic additives. The nanosheet obtained in Experimental Example 1 had a thickness of 1.8 nm, and the nanosheet obtained in Experimental Example 3 had a thickness of 1.5 nm.

[0061] <3. Examples of Nanosheet Use> The nanosheet 1 made of amorphous inorganic oxide according to the above embodiment and the aggregate formed using it have weather resistance that prevents degradation even when exposed to ultraviolet light and oxygen for a long time. Furthermore, the nanosheet 1 made of amorphous inorganic oxide according to the above embodiment and the aggregate formed using it have stability in which the dimensional and physical properties change little with respect to temperature and humidity. Moreover, the nanosheet 1 made of amorphous inorganic oxide according to the above embodiment and the aggregate formed using it have strong mechanical strength against external stresses such as tension and bending. Furthermore, the aggregate formed using the nanosheet 1 made of amorphous inorganic oxide according to the above embodiment becomes a porous body having a porous structure due to the gaps that form between the nanosheets.

[0062] Furthermore, since the surface of the nanosheet 1 is coated with an organic silane compound 12, multiple nanosheets 1 cannot form covalent bonds with each other. This prevents aggregation of multiple nanosheets 1. Alternatively, multiple nanosheets 1 may be connected via crosslinking portions made of organic or inorganic materials containing silyl groups, for example. This creates voids between the connected nanosheets 1, making it possible to construct a thermal insulation material with high light transmittance.

[0063] Furthermore, the nanosheets 1 may be connected to each other via crosslinking portions made of inorganic oxides. This makes it possible to construct an insulating material that has high stability against ultraviolet light.

[0064] In other words, nanosheet 1 can be used, for example, as an anti-reflective coating applied to televisions, lenses, and windows, as well as as a heat insulating material used in building materials, electrical appliances, and bathtubs. In addition, nanosheet 1 can be used as a semiconductor material. Furthermore, nanosheet 1 can be used as an additive with moisture-absorbing and deodorizing functions in clothing, electrical appliances, and filters, or as a catalyst in chemical products and filters.

[0065] Specifically, if nanosheet 1 has a light transmittance of, for example, 70% or more, it can be used in car windows and the like. If nanosheet 1 has a light transmittance of, for example, 90% or more, it can be used as a substitute material for building windows, glass substrates, and plastics.

[0066] Furthermore, nanosheet 1 can utilize a silica source derived from rocks as a raw material. In other words, this technology makes it possible to provide a plastic substitute material that primarily uses inorganic oxides derived from rocks as raw materials. Compared to conventional nanocomposite materials and plastic materials, such plastic substitute materials have a lower plastic content, and because the main raw materials are biocompatible and hydrolyzable, the risk of them becoming harmful floating waste even if released into the ocean is reduced. In addition, since the main component generated during incineration is water vapor, greenhouse gas emissions can be reduced.

[0067] Furthermore, the nanosheet 1 and the aggregates formed using it can be used as insulation for glass windows, placed between double-glazed windows, used as insulation for refrigerators and bathtubs, and as transparent plates for solar heat collectors. For example, by applying the nanosheet 1 and the aggregates formed using it to glass windows, a higher insulation effect can be expected than that of windows made of general glass materials, and this insulation effect can reduce the energy consumption of heating and cooling equipment. For example, by applying the nanosheet 1 and the aggregates formed using it to the transparent plate of a solar heat collector, the heat collection efficiency of the solar heat collector can be improved due to its insulation effect.

[0068] In addition, nanosheet 1 and aggregates containing nanosheet 1 have applications similar to general porous materials, such as adsorbents for odor components, bacteria, and viruses, moisture absorbers that maintain a constant humidity level in the air, and sound absorbers that obstruct the propagation of sound waves. Furthermore, because they can be used in applications requiring transparency, they can be applied to structural materials and low-dielectric films in electronic devices such as photocatalysts, artificial photosynthesis devices, solar cells, and semiconductors.

[0069] Furthermore, by mixing the nanosheet 1 with a resin, for example, it can be used as a nanocomposite material with excellent weather resistance, stability, and mechanical strength, such as reinforced plastics, gas barrier coatings, anti-reflective coatings applied to televisions, lenses, and windows, tires, aircraft, and paints.

[0070] Although the present disclosure has been described above with reference to embodiments, examples, and usage examples, the present disclosure is not limited to the above embodiments, and can be modified in various ways.

[0071] For example, in the above embodiment, an amorphous silica layer 11 in which amorphous silicon oxide extends in a two-dimensional direction was shown as an example of an amorphous inorganic oxide as one specific example of an amorphous inorganic oxide as one embodiment of the present disclosure, but the present invention is not limited thereto. Examples of amorphous inorganic oxides constituting the nanosheet of the present disclosure include aluminum oxide, titanium oxide, tin oxide, and zinc oxide.

[0072] Furthermore, the effects described herein are merely illustrative and not limited to those described herein, and other effects may also occur.

[0073] Furthermore, this technology can also be configured as follows. According to this technology with the following configuration, it is possible to provide nanosheets, a method for manufacturing nanosheets, and assemblies with excellent productivity. (1) Nanosheets made of amorphous inorganic oxide with organic functional groups covalently bonded to the surface. (2) Thickness of 10 nm or less and 0.5 μm ２(1) A nanosheet having a sheet shape with the above area. (3) A nanosheet having a thickness of 1 nm to 5 nm as described in (1) or (2). (4) The amorphous inorganic oxide is 1 μm ２(1) The nanosheet according to any one of (1) to (3) above, having the above area. (5) The nanosheet according to any one of (1) to (4) above, wherein the amorphous inorganic oxide is amorphous silicon oxide. (6) The nanosheet according to any one of (1) to (5) above, wherein the organic functional group is an organosilane compound. (7) A method for producing a nanosheet, comprising preparing a mixture containing water, a metal alkoxide, an acid catalyst, a cationic surfactant, an organic additive, and an aprotic solvent or a protic polar solvent, removing the aprotic solvent or the protic polar solvent from the mixture to obtain a layered structure, and then decomposing the layered structure by surface modification. (8) The method for producing a nanosheet according to (7), wherein silicon alkoxide is used as the metal alkoxide. (9) The method for producing a nanosheet according to (7) or (8), wherein acetic acid, hydrochloric acid, nitric acid, or sulfuric acid is used as the acid catalyst. (10) A method for producing a nanosheet according to any one of (7) to (9), wherein a quaternary ammonium salt is used as the cationic surfactant. (11) A method for producing a nanosheet according to any one of (7) to (10), wherein at least one of an alcohol having 6 to 20 carbon atoms, an alkane having 6 to 20 carbon atoms, 1,3,5-trimethylbenzene, 1,3,5-triethylbenzene, and 1,3,5-tripropylbenzene is used as the organic additive. (12) A method for producing a nanosheet according to any one of (7) to (11), wherein the aprotic solvent or the protic polar solvent is removed by air-drying the mixture. (13) A method for producing a nanosheet according to any one of (7) to (11), wherein the aprotic solvent or the protic polar solvent is removed by reducing the pressure of the mixture in a sealed container. (14) A method for producing a nanosheet according to any one of (7) to (13), wherein the layered structure is dispersed in an organic solvent and then an organosilane compound is added to obtain a nanosheet surface-modified with the organosilane compound. (15) An aggregate containing a nanosheet made of an amorphous inorganic oxide on which organic functional groups are covalently bonded to the surface.(16) The aggregate according to (15) having a porous structure.

[0074] This application claims priority based on Japanese Patent Application No. 2024-205371, filed with the Japan Patent Office on 26 November 2024, and all contents of that application are incorporated herein by reference.

[0075] Those skilled in the art will understand that various modifications, combinations, subcombinations, and changes can be conceived depending on design requirements and other factors, and that these fall within the scope of the attached claims and their equivalents.

Claims

1. Nanosheets made of amorphous inorganic oxides with organic functional groups covalently bonded to their surface.

2. Thickness of 10 nm or less and 0.5 μm ２ The nanosheet according to claim 1, having a sheet shape with the above area.

3. The nanosheet according to claim 1, having a thickness of 1 nm or more and 5 nm or less.

4. The amorphous inorganic oxide is 1 μm ２ A nanosheet according to claim 1, having the above area.

5. The nanosheet according to claim 1, wherein the amorphous inorganic oxide is amorphous silicon oxide.

6. The nanosheet according to claim 1, wherein the organic functional group is an organosilane compound.

7. A method for producing nanosheets, comprising: preparing a mixture containing water, a metal alkoxide, an acid catalyst, a cationic surfactant, an organic additive, and an aprotic solvent or a protic polar solvent; removing the aprotic solvent or the protic polar solvent from the mixture to obtain a layered structure; and then decomposing the layered structure by surface modification.

8. The method for producing a nanosheet according to claim 7, wherein silicon alkoxide is used as the metal alkoxide.

9. The method for producing nanosheets according to claim 7, wherein acetic acid, hydrochloric acid, nitric acid, or sulfuric acid is used as the acid catalyst.

10. The method for producing nanosheets according to claim 7, wherein a quaternary ammonium salt is used as the cationic surfactant.

11. The method for producing nanosheets according to claim 7, wherein at least one of the following is used as the organic additive: an alcohol having 6 to 20 carbon atoms, an alkane having 6 to 20 carbon atoms, 1,3,5-trimethylbenzene, 1,3,5-triethylbenzene, and 1,3,5-tripropylbenzene.

12. The method for producing nanosheets according to claim 7, wherein the aprotic solvent or the protic polar solvent is removed by air-drying the mixed solution.

13. The method for producing nanosheets according to claim 7, wherein the aprotic solvent or the protic polar solvent is removed by reducing the pressure of the mixture in a sealed container.

14. A method for producing a nanosheet according to claim 7, wherein the layered structure is dispersed in an organic solvent, and then an organosilane compound is added to obtain a nanosheet surface-modified with the organosilane compound.

15. An aggregate containing nanosheets made of amorphous inorganic oxides with organic functional groups covalently bonded to their surface.

16. The aggregate according to claim 15, having a porous structure.

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