Structure and method for manufacturing the structure

Abstract

A structure according to one embodiment of the present disclosure is formed by accumulating structural units in which a plurality of nanoparticles are connected like a string of beads, wherein a solution in which the structure is dissolved using tetrahydrofuran as a solvent, when centrifuged for 10 minutes under conditions in which the minimum rotation radius is 8.5 cm, the maximum rotation radius is 23.2 cm, and the angular velocity is 10,000 rpm, generates not more than 1.0 wt% of a sedimentation component.

Description

[Technical Field]

[0001] This disclosure relates, for example, to a structure using nanoparticles and a method for manufacturing the structure. [Background technology]

[0002] For example, Patent Document 1 discloses a method for producing a mesoporous silica porous film with improved handling, leveling, and uniform film formation during film formation. Specifically, a sol of mesoporous silica nanoparticles coated with a nonionic surfactant and containing a cationic surfactant within its pores is prepared, and the nonionic surfactant encapsulating the mesoporous silica nanoparticles in the sol, or the cationic surfactant encapsulated within the pores of both the nonionic surfactant and the mesoporous silica nanoparticles, is removed. Subsequently, the mesoporous silica nanoparticles are separated, and a dispersion solution is prepared by dispersing the mesoporous silica particles in an organic solvent using ultrasonic dispersion. This solution is then applied to a substrate and dried to obtain a mesoporous silica porous film. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-118345 [Overview of the Initiative]

[0004] By the way, in porous structures, there is a desire to improve production yield.

[0005] It is desirable to provide a structure and a method for manufacturing the structure that can improve production yield.

[0006] The structure according to an embodiment of the present disclosure is a structure formed by integrating structural units in which a plurality of nanoparticles are connected in a string-like manner. When a solution in which the structure is dissolved using tetrahydrofuran as a solvent is centrifuged for 10 minutes under the conditions of a minimum rotation radius of 8.5 cm, a maximum rotation radius of 23.2 cm, and an angular velocity of 10,000 rpm, the sedimentation component is 1.0 wt% or less.

[0007] A method for manufacturing a structure according to an embodiment of the present disclosure includes adding an amphiphilic molecule or an organosilane molecule to a dispersion in which a plurality of nanoparticles are dispersed to coat the surfaces of the plurality of nanoparticles, and further adding a crosslinking agent to connect the plurality of nanoparticles to each other via a crosslinked portion composed of the crosslinking agent to synthesize a nanoparticle conjugate, and applying the dispersion in which the nanoparticle conjugate is dispersed onto a substrate.

[0008] The heat insulating material according to an embodiment of the present disclosure includes the structure according to an embodiment of the present disclosure.

[0009] In the structure according to an embodiment of the present disclosure and the method for manufacturing the structure according to an embodiment of the present disclosure, when a solution in which the structure is dissolved using tetrahydrofuran as a solvent is centrifuged for 10 minutes under the conditions of a minimum rotation radius of 8.5 cm, a maximum rotation radius of 23.2 cm, and an angular velocity of 10,000 rpm, a structure is formed in which sedimentation components are 1.0 wt% or less and structural units in which a plurality of nanoparticles are connected in a string-like manner are integrated. As a result, the redissolution of the structure after manufacturing becomes possible.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram showing a schematic configuration of a structure according to an embodiment of the present disclosure. [Figure 2] It is an enlarged schematic diagram of a part of the structure shown in FIG. 1. [Figure 3] It is a diagram for explaining the aspect of the structure shown in FIG. 1. [Figure 4A] It is a schematic diagram showing an example of the structure of the nanoparticles shown in FIG. 1. [Figure 4B] It is a schematic diagram showing another example of the structure of the nanoparticles shown in FIG. 1. [Figure 5A] This diagram illustrates the spatial arrangement of multiple nanoparticles within a structure. [Figure 5B] This diagram illustrates the spatial arrangement of multiple nanoparticles within a structure. [Figure 5C] This diagram illustrates the spatial arrangement of multiple nanoparticles within a structure. [Figure 5D] This diagram illustrates the spatial arrangement of multiple nanoparticles within a structure. [Figure 6] This is a characteristic diagram showing the spatial arrangement of multiple nanoparticles within a structure and the relationship between particle size and transmittance. [Figure 7] This is an image of the structure of this embodiment as captured using a transmission electron microscope. [Figure 8A] This is a schematic diagram illustrating an example of how nanoparticles are linked together when using the nanoparticles shown in Figure 4A. [Figure 8B] This is a schematic diagram illustrating another example of the linkage between nanoparticles when using the nanoparticles shown in Figure 4B. [Figure 9] This is a characteristic diagram showing the relationship between particle size and the ratio of settled material. [Figure 10] Figure 1 is a flowchart illustrating an example of the manufacturing process for the structure shown. [Figure 11] This flowchart illustrates another example of the manufacturing process for the structure shown in Figure 1. [Modes for carrying out the invention]

[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 this disclosure, and this disclosure is not limited to the following embodiments. Furthermore, this 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 structure formed by the accumulation of structural units in which multiple nanoparticles are linked together in a bead-like manner) 1-1. Structure 1-2. Method for manufacturing structures 1-3. Action and Effects 2. Examples of using structures

[0012] <1. Embodiment> (1-1. Structure of the Structure) Figure 1 schematically shows an example of the general configuration of a structure (structure 1) according to one embodiment of the present disclosure. Figure 2 is an enlarged view of a part of structure 1 shown in Figure 1. Figure 3 illustrates the configuration of structure 1 shown in Figure 1. Structure 1 is used, for example, as an anti-reflective film, a heat insulating material, a semiconductor material, an additive, or a catalyst. Structure 1 of this embodiment, as shown in Figure 3, is a porous body formed by the accumulation of structural units (connected bodies 10) in which a plurality of nanoparticles 11 are linked together in a bead-like manner, and which are soluble in a predetermined organic solvent. Specifically, structure 1 is dissolved in tetrahydrofuran (THF) as a solvent, and when the solution is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, the settling component is 1.0 wt% or less.

[0013] The multiple nanoparticles 11 are composite oxides of metal atoms. Specifically, they are oxides of light-transmitting zirconium (Zr), titanium (Ti), tin (Sn), silicon (Si), aluminum (Al), or zinc (Zn). Oxides of tungsten (W) or yttrium (Y), which are colored but light-transmitting, can also be used. Among the above metal oxides, it is preferable to use Si oxide or Al oxide, which have a low refractive index and are particularly light-transmitting, as the multiple nanoparticles 11.

[0014] Multiple nanoparticles 11 are coated on the surface with an amphiphilic molecule 12, for example, as shown in Figure 4A. Alternatively, the nanoparticles 11 are inactivated on the surface by reacting with an organosilane molecule 13, for example, as shown in Figure 4B. As a result, the multiple nanoparticles 11 cannot form covalent bonds with each other.

[0015] Figures 5A to 5D illustrate the possible spatial arrangements of multiple nanoparticles 11 within structure 1. In structure 1, each of the multiple nanoparticles 11 is covalently bonded to 1 to 3 other nanoparticles 11, for example, via a crosslinking portion 21, which will be described later.

[0016] For example, in a cubic close-packed structure as shown in Figure 5A, one nanoparticle 11 has 12 bonding points with other nanoparticles 11, and its packing density is 74 volume%. In a simple cubic structure as shown in Figure 5B, one nanoparticle 11 has 6 bonding points with other nanoparticles 11, and its packing density is 52 volume%. In a diamond structure as shown in Figure 5C, one nanoparticle 11 has 4 bonding points with other nanoparticles 11, and its packing density is 34 volume%. In a chain-like or network-like structure as shown in Figure 5D, one nanoparticle 11 has 1 to 3 bonding points with other nanoparticles 11, and its packing density is between 1 volume% and 74 volume%. Of these, the multiple nanoparticles 11 constituting structure 1 are fixed by having 4 or more bonding points with each other and become insoluble in a given solvent. Therefore, considering the resolubility of structure 1 in a solvent, the packing density of the multiple nanoparticles 11 is preferably 74 volume% or less, and more preferably less than 34 volume%.

[0017] The packing density can be measured using the following method.

[0018] First, the structure 1 to be measured is processed and thinned using methods such as Focused Ion Beam (FIB). When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the transmission electron microscope (TEM) image of the cross-section described later. The carbon film is formed on the surface of structure 1 by vapor deposition. The tungsten film is formed on the surface of structure 1 by vapor deposition or sputtering. As a result, a cross-section of structure 1 is formed by thinning.

[0019] The cross-section of the obtained thin section sample is observed using a transmission electron microscope (FEI Tecnai G2) with an acceleration voltage of 200kV and a field of view of 50nm × 50nm, allowing for the observation of multiple nanoparticles 11, and a TEM image is taken. The imaging position is randomly selected from the thin section sample, and for example, five fields of view are observed. Next, using TEM image analysis software, for example, the total area (number of pixels) occupied by the cross-section of the nanoparticles in one field of view is calculated, and the ratio of the total area (number of pixels) of the entire field of view (nanoparticle area ratio) is calculated. Subsequently, the above nanoparticle area ratio is calculated for each of the five fields of view, and then the arithmetic mean of these ratios is calculated and taken as the packing density.

[0020] It is preferable that the structure 1 has a predetermined light transmittance. For example, if the structure 1 has a transmittance of 70% or more, it can be used as an anti-reflective coating for automobile windows, etc. Alternatively, if the structure 1 has a transmittance of 90% or more, it can be used as a substitute material for, for example, building windows, glass substrates, or plastics.

[0021] Figure 6 shows the transmittance at a wavelength of 550 nm when a structure 1 with a thickness of 1 mm is formed. For example, when the multiple nanoparticles 11 constituting structure 1 take the lowest density structure, such as a chain structure or a network structure, the multiple nanoparticles 11 may all exist in a state of primary particle size, or, as shown in Figure 5B, for example, secondary particles formed by the aggregation of multiple nanoparticles 11 may be included. In a low-density structure 1, the effect of light scattering by secondary particles cannot be ignored. Therefore, when the multiple nanoparticles 11 take the chain structure or a network structure, a transmittance of 70% can be obtained if the primary particle size is 21 nm or less. Furthermore, when the multiple nanoparticles 11 constituting structure 1 take the closest packed structure, a transmittance of 70% can be obtained if the primary particle size is 11 nm or less. Moreover, a transmittance of 90% can be obtained if the primary particle size is 7 nm or less.

[0022] The primary particle size of the nanoparticle 11 can be determined as follows.

[0023] First, the structure 1 to be measured is processed and thinned using methods such as FIB. When using the FIB method, a carbon film and a tungsten film are formed as protective films as a pretreatment before observing the TEM image of the cross-section described later. The carbon film is formed on the surface of structure 1 by vapor deposition. The tungsten film is formed on the surface of structure 1 by vapor deposition or sputtering. As a result, a cross-section of structure 1 is formed by thinning.

[0024] The cross-section of the obtained thin section sample will be observed using a transmission electron microscope (FEI Tecnai G2) with an acceleration voltage of 200kV and a field of view of 50nm × 50nm, allowing for the observation of multiple nanoparticles 11. A TEM image will then be taken. The imaging position will be randomly selected from the thin section sample.

[0025] Next, 50 nanoparticles 11 whose diameter is clearly identifiable in the direction of the observation plane are selected from the captured TEM images. If there are fewer than 50 nanoparticles 11 with clearly identifiable diameters within one captured field of view, 50 nanoparticles 11 with clearly identifiable diameters in the direction of the observation plane are selected from multiple fields of view. Figure 7 is an illustrative image of a TEM image taken of structure 1 using a transmission electron microscope. For example, in Figure 7, nanoparticles a and b, whose diameters are clearly identifiable, are selected. On the other hand, nanoparticles c and d, for example, are not suitable for measurement because their shapes cannot be confirmed due to overlapping nanoparticles 11 in the depth direction of observation. The maximum diameter of each of the 50 selected nanoparticles 11 is measured.

[0026] Here, the maximum diameter is defined as the maximum distance between two parallel lines drawn from any angle so as to be tangent to the contour of the nanoparticle 11 (the so-called maximum Ferret diameter). When measuring the maximum diameter (maximum Ferret diameter), the diameter of the particle portion excluding the alkoxy groups and reactive functional groups modified on the surface of the nanoparticle 11 is measured. By calculating the median of the 50 maximum diameters (maximum Ferret diameters) obtained in this way, the primary particle diameter (average particle diameter) of the nanoparticle 11 is obtained.

[0027] In the structure 1, as described above, a plurality of nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 or organosilane molecules 13 form a connected body 10 that is connected to each other via a crosslinking portion 21.

[0028] The amphiphilic molecule 12 is for coating the surface of the nanoparticle 11 to prevent the bonding of the plurality of nanoparticles 11 to each other. Specific examples of the amphiphilic molecule 12 include surfactants, amino acid molecules, and polymers such as phospholipids and block copolymers of polyalkylene glycols.

[0029] The organosilane molecule 13 is, like the amphiphilic molecule 12, for inactivating the surface of the nanoparticle 11 to prevent the bonding of the plurality of nanoparticles 11 to each other. The organosilane molecule 13 preferably has a reactive functional group that forms a covalent bond with the nanoparticle 11 and also forms a covalent bond with the crosslinking portion 21. Examples of the reactive functional group include vinyl group, methacryl group, acryl group, glycidyl group, mercapto group, amino group, hydrosilyl group, hydroxyl group, carboxyl group, cyano group, amino group, cyano group, etc. Examples of the organosilane compound having the above reactive functional group include those represented by the following general formula (1) or general formula (2). [Chemical formula 1] R 1 X Si(OR 2 ) 4-X ···(1) R 1 X SiCl 4-X ···(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. X is an integer of 3 or less.)

[0030] The presence or absence of amphiphilic molecules 12 and organosilane molecules 13 coating the surface of the nanoparticles 11, and the manner of bonding between the nanoparticles 11 and the amphiphilic molecules 12 or organosilane molecules 13, can be confirmed, for example, by component analysis or compositional analysis. Examples of component analysis and compositional analysis include Fourier transform infrared spectroscopy (FT-IR), gas chromatography (GC), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR), and energy-dispersive X-ray spectroscopy (EDX). The presence or absence of amphiphilic molecules 12 and organosilane molecules 13 coating the surface of the nanoparticles 11, and the manner of bonding between the nanoparticles 11 and the amphiphilic molecules 12 or organosilane molecules 13, can be analyzed using one or more of the above analytical methods.

[0031] As described above, the crosslinking portion 21 connects multiple nanoparticles 11 to each other. Specifically, the crosslinking portion 21 is an organic or inorganic substance that directly covalently bonds with the nanoparticles 11, for example, as shown in Figure 8A. Alternatively, the crosslinking portion 21 is an organic or inorganic substance that indirectly covalently bonds with the nanoparticles 11 via an organic silyl group (organosilane molecule 13), for example, as shown in Figure 8B. The crosslinking portion 21 forms a covalent bond with one or two nanoparticles 11.

[0032] Examples of such crosslinked portions 21 include crosslinking agents having two or more reaction sites. Among these, examples of crosslinking agents that directly form covalent bonds with nanoparticles 11 include silane compounds represented by the following general formulas (3), (4), (5), or (6). [Case 2] R 3 Y Si(OR 4 ) 4-Y ...(3) R 3 Y SiCl 4-Y ...(4) (R 4 O) 3-Y R 3 Y Si-R 5 -SiR 3Y (OR 4 ) 3-Y ...(5) Cl 3-Y R 3 Y Si-R 5 -SiR 3 Y Cl 3-Y ...(6) (R 3 R is one of the following: a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a phenyl group. 4 R is one of the following: a methyl group, an ethyl group, a propyl group, or an isopropyl group. 5 (Y is one of the following groups: methylene, ethylene, propylene, butylene, pentylene, hexylene, or phenylene. Y is 0 or an integer less than or equal to 2.)

[0033] Crosslinking agents that indirectly covalently bond to nanoparticles 11 via organosilyl groups (organosilane molecules 13) include those having two or more reactive functional groups that react with the functional groups of organosilane molecules 13. Examples of such crosslinking agents include polyfunctional allyl (vinyl), polyfunctional thiol, polyfunctional (meth)acrylate, and polyfunctional glycidyl.

[0034] Specific examples of polyfunctional allyl (vinyl) include diallyl ether, diallyl sulfide, diallylamine, diallyl adipate, diallyldimethylsilane, diallyl isophthalate, diallylurea, dimethyldivinylsilane, divinyltetramethyldisiloxane, hexadiene, tetraallyloxyethane, triallyl cyanurate, and triallylamine.

[0035] Specific examples of polyfunctional thiols include ethanedithiol, propanedithiol, hexanedithiol, pentaerythritol tetrakis(mercaptoacetate), pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris(2-(3-sulfanylbutanoyloxy)ethyl)-1,3,5-triazinan-2,4,6-trione, and trimethylolpropane tris(3-mercaptobutyrate).

[0036] Specific examples of polyfunctional (meth)acrylates include diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, tetraethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

[0037] Specific examples of polyfunctional glycidyls include glycidyl ether type epoxy resins such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and resorcinol diglycidyl ether, as well as diglycidyl phthalate esters and diglycidyl dimer esters, triglycidyl ether triphenylmethane, tetraglycidyl ether tetraphenylethane, bisphenol S diglycidyl ether, cresol novolac glycidyl ether, triglycidyl isocyanurate, and tetrabrom bisphenol A diglycidyl ether.

[0038] In the structure 1 of this embodiment, one nanoparticle 11 is covalently bonded to one to three other nanoparticles via a cross-linking portion 21, and the structure is a porous body formed by the accumulation of structural units (connecting bodies 10) in which multiple nanoparticles 11 are linked together in a bead-like manner.

[0039] As shown in Figure 3, structure 1 exists, for example, in a membrane, with bead-like interconnects 10 intertwined with each other, and has numerous voids inside due to steric hindrance. The bead-like interconnects 10 are held together only by weak van der Waals forces and can be dissolved with a suitable solvent.

[0040] Here, "dissolved" refers to a state in which the bead-like interconnected elements 10 mix with other liquids to form a homogeneous phase solution, without precipitation or phase separation. The bead-like interconnected elements 10 remain in the same chemical state in the solution, with each individual bead-like interconnected element 10 dispersed in the solvent.

[0041] Specifically, in this embodiment, when a solution of structure 1 dissolved in tetrahydrofuran (THF) is centrifuged for 10 minutes under the following conditions: a set temperature of 25°C, a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, the precipitated component is 1.0 wt% or less.

[0042] The weight of the precipitated components is measured using the following method. First, 1000 ml of the THF solution in which structure 1 is dissolved is centrifuged for 10 minutes under the above conditions using a high-capacity refrigerated centrifuge (Model 8730: Kubota Shoji Co., Ltd.) swing rotor RS-4000, and the supernatant is separated to remove the precipitate. Next, the precipitate is heated at 50°C for 1 hour to dry thoroughly. After that, the weight of the precipitate is measured.

[0043] Figure 9 shows the relationship between particle size and the ratio of settled material, calculated using Stokes' formula based on the measurement conditions described below. [Measurement conditions] Equipment: High-capacity refrigerated centrifuge (Model 8730: Kubota Shoji Co., Ltd.) Inglot RS-4000 Conditions: Sample volume 1000 ml, THF solvent, minimum turning radius 8.5 cm, maximum turning radius 23.2 cm Centrifugal separation at an angular velocity of 10,000 rpm for 10 minutes. Assumed sample: Nanostructure ≤ 11 nm :Foreign matter from several μm to several tens of μm : Insoluble components ≥ 100 μm

[0044] Under the above measurement conditions, if the particle size of the multiple nanoparticles 11 constituting structure 1 is 11 nm or less, then structure 1 is uniformly dispersed in the solvent, and it can be assumed that its sedimentation velocity is substantially the same as that of nanoparticles. The foreign matter is assumed to be manufacturing foreign matter consisting of the same components as the multiple nanoparticles 11 constituting structure 1. The insoluble component is assumed to be a component that does not dissolve in the THF solvent.

[0045] As shown in Figure 9, when particles smaller than 11 nm are dissolved, the proportion of precipitated components under these conditions is less than 1%. If the nanostructures are insoluble in YHF solvent, they will all precipitate under these conditions, thus failing to meet the above proportion. Furthermore, this centrifugation operation can remove foreign matter ranging from a few micrometers to tens of micrometers that is generated during manufacturing.

[0046] (1-2. Method of manufacturing the structure) Figure 10 shows an example of the manufacturing process for structure 1. Below, we will first describe a method for manufacturing structure 1, in which multiple nanoparticles 11, each coated with an amphiphilic molecule 12, are linked together by a crosslinking portion 21.

[0047] (Method for manufacturing a structure using multiple nanoparticles whose surfaces are coated with amphiphilic molecules) First, multiple nanoparticles 11 are synthesized using a liquid-phase method (step S101). Generally, methods for producing nanoparticles are broadly classified into two types: gas-phase and liquid-phase. However, minute nanoparticles 11 with a diameter of 10 nm or less can be isolated without aggregation by using the liquid-phase method. As a precursor for the liquid-phase method, a metal alkoxide molecule represented by the following general formula (7), which can form a three-dimensional metal oxide skeleton (MOM) through hydrolysis and condensation polymerization reactions, can be selected. The metal alkoxide molecule may be a molecule in which some alkoxy groups are replaced with non-hydrolyzable functional groups, and this does not hinder the formation of the metal oxide skeleton. After dissolving the above precursor in water or an organic solvent, the pH of the solution is adjusted to be acidic or basic. This initiates the polymerization reaction, and metal oxide nanoparticles (nanoparticles 11) are formed. [C3] R 6 Z M(OR 7 ) 4-Z ...(7) (R 6 R is one of the following groups: 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, phenyl group, acryloxy group, methacryloxy group, aminopropyl group, glycidoxypropyl group, and mercaptopropyl group. 7 (where M is one of the following: a hydrogen atom, a methyl group, an ethyl group, a propyl group, or an isopropyl group. M is one of the following: Si, Al, Ti, Sn, or Zn. Z is 0 or an integer less than or equal to 2.)

[0048] Furthermore, the manufacturing method is not limited to the above, as long as the diameter of the final nanoparticles 11 is 11 nm or less. Examples of references are given below. For example, Reference 1 (T. Yokoi et al. Chem. Mater. 2009, 21, 3719-3729) reports the formation of 8 nm diameter silica nanoparticles in an aqueous solution in the presence of amino acids, and the nanoparticles can be isolated without aggregation by coating the surface with amino acid molecules. Reference 2 (S. Sakamoto et al. Langmuir 2018, 34, 1711-1717) reports the formation of 3 nm diameter silica nanoparticles and titanium oxide nanoparticles using an inverse micelle-type liquid crystal phase as a template, and the nanoparticles can be isolated without aggregation by coating the surface with surfactant molecules.

[0049] Next, multiple nanoparticles 11 are dispersed in a solvent for surface modification (step S102). To the dispersion of multiple nanoparticles 11, an amphiphilic molecule 12, such as a surfactant molecule, an amino acid molecule, or a polymer, is added. The added surfactant molecule, amino acid molecule, or polymer adsorbs onto the surface of the nanoparticles 11 and prevents aggregation of the nanoparticles. Depending on the manufacturing method described in references 1 and 2 above, nanoparticles 11 whose surfaces are coated with surfactant molecules, amino acid molecules, or polymers can be obtained. In that case, the addition of amphiphilic molecules 12 can be omitted. Furthermore, if necessary, the surface of multiple nanoparticles 11 may be further modified with an organosilane compound.

[0050] Next, nanoparticle links are synthesized by crosslinking the nanoparticles 11 with a crosslinking agent (silane compound) (step S103). A silane compound having two or more reaction sites is added as a crosslinking agent to a dispersion containing nanoparticles 11 whose surfaces are coated with amphiphilic molecules 12 such as surfactant molecules, amino acid molecules, or polymers. The amount of silane compound added is such that 1 to 3 nanoparticles 11 are bound to one nanoparticle 11. After adding the silane compound, the dispersion is heated as needed. As a result, the crosslinking reaction of the nanoparticles 11 proceeds in the dispersion, and bead-like nanoparticle links are formed. The dispersion maintains its solution state without losing fluidity.

[0051] Subsequently, the dispersion is applied to the substrate (step S104), and then dried to obtain structure 1 (step S105). Methods for removing the solvent and drying include, for example, drying at atmospheric pressure and increased temperature. If there is concern about the collapse of structure 1 due to interfacial tension during drying, it is preferable to use supercritical drying or freeze-drying. In this embodiment, the surfaces of multiple nanoparticles 11, which cause high interfacial tension, are inactivated by being coated with amphiphilic molecules 12. Therefore, compared to the case where the surface is not coated, structure 1 is less likely to collapse during drying. As a result, for example, a porous film-like structure 1 can be obtained.

[0052] Figure 11 shows a flowchart illustrating another example of the manufacturing process for structure 1. Below, we will describe a method for manufacturing structure 1, in which multiple nanoparticles 11, each coated with an organic silane molecule 13, are linked together by a cross-linking portion 21.

[0053] (Method for manufacturing a structure using multiple nanoparticles whose surfaces are coated with organosilane molecules) First, multiple nanoparticles 11 are synthesized using a liquid-phase method in the same manner as the nanoparticles 11 whose surface is coated with amphiphilic molecules 12 as described above (step S201). Next, the multiple nanoparticles 11 are dispersed in a solvent for surface modification (step S202). Here, instead of amphiphilic molecules 12, an organic silane compound (silane coupling agent) represented by the above general formula (1) or general formula (2) is added to the dispersion. After adding the silane coupling agent, heating is performed as needed to cause the nanoparticles 11 and the organic silane molecules 13 to react and form covalent bonds, thereby inactivating the surface of the nanoparticles 11 and preventing aggregation of the nanoparticles 11.

[0054] In the crosslinking reaction in the next step S203, not all of the reactive functional groups modified on the surface of the multiple nanoparticles 11 are used for crosslinking. Therefore, instead of using the organosilane compound represented by general formula (1) or general formula (2), organometallic compounds without reactive functional groups represented by general formula (8) or general formula (9) below may be used in part. [C4] R 8 X M(OR 9 ) 4-X ...(8) R 8 X MCr 4-X ...(9) (R 8 R is one of the following groups: 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. 9 (This group is one of the following: methyl, ethyl, propyl, or isopropyl. M is one of the following: Si, Al, Ti, Sn, or Zn. X is an integer less than or equal to 3.)

[0055] Next, nanoparticle links are synthesized by crosslinking the nanoparticles 11 with a crosslinking agent having two or more reactive functional groups (step S203). A silane compound such as the polyfunctional allyl (vinyl), polyfunctional thiol, polyfunctional (meth)acrylate, and polyfunctional glycidyl mentioned above is added as a crosslinking agent to a dispersion containing nanoparticles 11 whose surfaces are coated with organic silane molecules 13. After adding the silane compound, heating or light irradiation is performed as necessary. As a result, a crosslinking reaction proceeds in the dispersion via the crosslinking agent between the functional groups of the organic silane molecules 13 surface-modified on each of the multiple nanoparticles 11, forming a chain of nanoparticle links. The dispersion maintains its solution state without losing fluidity. If the crosslinking reaction is an organic reaction such as a radical reaction, cationic polymerization, or anionic polymerization, an appropriate reaction initiator may be added.

[0056] Subsequently, the dispersion is applied to the substrate (step S204) in the same manner as the nanoparticles 11 whose surface is coated with amphiphilic molecules 12 as described above, and then dried to obtain structure 1 (step S205). Through this process, for example, a porous membrane-like structure 1 is obtained.

[0057] Furthermore, whether the multiple nanoparticles 11 constituting structure 1 each possess 1 to 3 bonding points with other nanoparticles 11, and whether their packing density is 74 volume% or less, more preferably less than 34 volume%, can be determined by imaging using a transmission electron microscope (see, for example, Figure 7). When imaged with a transmission electron microscope, additive components made of organic materials such as resin are not visible, so it can be determined that adjacent particles are cross-linked.

[0058] (1-3. Action and Effects) In the structure 1 of this embodiment, structure 1 is dissolved in THF as a solvent, and when the solution is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, a porous body is formed in which multiple nanoparticles 11 are linked together in a bead-like manner, resulting in a sedimentary component of 1.0 wt% or less. This will be described below.

[0059] Porous materials can be used in a variety of applications due to their properties such as low refractive index, low dielectric constant, high thermal insulation, high specific surface area, and moisture absorption and deodorization. Common examples of porous materials include activated carbon made from carbon and silica gel made from silica, but they can also be synthesized from other metal oxides and have structures such as sparse structures formed by the linkage of fine particles, structures with tunnel-like through-pores formed in the bulk, and structures consisting of a three-dimensional network of regularly arranged molecular skeletons. Porous materials are classified into three types according to their pore size, for example, micropores (~2nm), mesopores (2nm~50nm), and macropores (50nm~).

[0060] Generally, porous materials are synthesized in solution using a batch method, and the resulting porous materials are in bulk or powder form. However, porous materials obtained in this way have limited applications because they are difficult to form films on objects and are opaque.

[0061] In response to this, as mentioned above, methods for manufacturing mesoporous silica porous films have been developed that improve handling, leveling, and uniform film formation during film formation by applying a dispersion of mesoporous silica nanoparticles. However, porous films formed using the above method solidify immediately upon formation and cannot be redissolved. Therefore, a decrease in production yield due to equipment malfunctions during manufacturing and contamination with foreign matter remains a challenge.

[0062] In the structure 1 of this embodiment, for example, one nanoparticle 11 is covalently bonded to one to three nanoparticles via a cross-linking portion 21, and a porous body is formed by the accumulation of linked bodies 10 in which multiple nanoparticles 11 are linked together in a bead-like manner. When a solution of structure 1 dissolved in THF as a solvent is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, the amount of settled components is 1.0 wt% or less. This makes it possible to redissolve structure 1 after manufacturing.

[0063] Therefore, even if foreign matter is mixed in due to equipment malfunction or the like during manufacturing, the structure 1 of this embodiment can improve production yield by undergoing a predetermined removal process after redissolution.

[0064] Furthermore, in this embodiment, the structure 1 uses multiple nanoparticles 11 made of light-transmitting oxide metal oxides such as zirconium (Zr), titanium (Ti), tin (Sn), silicon (Si), aluminum (Al), or zinc (Zn). This makes it possible to use it in a wide range of fields, such as optical components like anti-reflective coatings and lenses.

[0065] <2. Examples of using structures> The structure 1 according to the above embodiment can be used in various cases, such as the following:

[0066] Structure 1 can be used, for example, as an anti-reflective coating for televisions, lenses, windows, etc. Structure 1 can be used, for example, as an insulating material for building materials, electrical appliances, bathtubs, etc. Structure 1 can be used, for example, as a semiconductor material. Structure 1 can be used, for example, as an additive for clothing, wallpaper, filters, etc. Structure 1 can be used, for example, as a catalyst for chemical products, filters, etc.

[0067] Although the present disclosure has been described above with reference to embodiments and examples of use, the present disclosure is not limited to the above embodiments and can be modified in various ways.

[0068] Furthermore, the effects described herein are merely illustrative and not limited to those described herein, and other effects may also occur.

[0069] Furthermore, this technology can also be configured as follows. According to this configuration, when a solution in which the structure is dissolved in tetrahydrofuran as a solvent is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, a structure is formed in which multiple nanoparticles linked together in a bead-like manner accumulate, with a sedimentary component of 1.0 wt% or less. This makes it possible to redissolve the structure after manufacturing. Therefore, it is possible to improve the production yield. (1) A structure formed by the accumulation of structural units in which multiple nanoparticles are linked together in a bead-like manner, When a solution of the structure dissolved in tetrahydrofuran as a solvent is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, the precipitated component is 1.0 wt% or less. structure. (2) The structure according to (1), wherein the plurality of nanoparticles have a plurality of crosslinking portions on their surface, and the plurality of nanoparticles are connected to each other via the crosslinking portions. (3) The structure according to (1) or (2), wherein each of the plurality of nanoparticles is linked to one or more and three or fewer of the aforementioned nanoparticles. (4) The structure according to any one of (1) to (3), wherein the plurality of nanoparticles have a plurality of crosslinking portions on their surface, and the plurality of nanoparticles are covalently bonded to each other via the crosslinking portions. (5) The structure according to any one of (1) to (4) above, wherein the packing density of the plurality of nanoparticles is 74 volume% or less. (6) The structure according to any one of (1) to (4) above, wherein the packing density of the plurality of nanoparticles is less than 34 volume%. (7) The structure according to any one of (1) to (6) above, wherein the primary particle size of the plurality of nanoparticles is 11 nm or less. (8) The structure according to any one of (1) to (6) above, wherein the primary particle size of the plurality of nanoparticles is 7 nm or less. (9) The structure according to any one of (1) to () above, wherein the crosslinked portion is an organic or inorganic substance that is directly covalently bonded to each of the plurality of nanoparticles. (10) The structure according to any one of (2) to (9), wherein the crosslinked portion is an organic or inorganic substance that is covalently bonded to each of the plurality of nanoparticles via a silyl group. (11) The structure according to any one of (2) to (10), wherein the surfaces of the plurality of nanoparticles whose crosslinked portions are not bonded are coated with amphiphilic molecules. (12) The structure according to (11), wherein the amphiphilic molecule is a surfactant molecule, an amino acid molecule, or a polymer. (13) The structure according to (12), wherein the polymer is a block copolymer of a phospholipid or a polyalkylene glycol. (14) The structure according to any one of (2) to (13), wherein the surfaces of the plurality of nanoparticles whose crosslinked portions are not bonded are inactivated by an organosilane compound. (15) The structure according to any one of (1) to (14) above, wherein each of the plurality of nanoparticles is a metal oxide. (16) The structure according to any one of (1) to (15), wherein each of the plurality of nanoparticles is an oxide of zirconium, titanium, tin, silicon, aluminum, or zinc. (17) The structure according to any one of (1) to (16), wherein each of the plurality of nanoparticles is an oxide of silicon or aluminum. (18) By adding amphiphilic molecules or organosilane molecules to a dispersion containing multiple nanoparticles, the surfaces of the multiple nanoparticles are coated. Furthermore, a crosslinking agent is added to link the plurality of nanoparticles together via the crosslinking portion made of the crosslinking agent, thereby synthesizing a nanoparticle conjugate. The dispersion containing the nanoparticle aggregates is applied onto a substrate. A method for manufacturing a structure.

Claims

1. A structure formed by the accumulation of structural units in which multiple nanoparticles are linked together in a bead-like manner, When a solution of the structure dissolved in tetrahydrofuran as a solvent is centrifuged for 10 minutes under conditions of a minimum turning radius of 8.5 cm, a maximum turning radius of 23.2 cm, and an angular velocity of 10,000 rpm, the precipitated component is 1.0 wt% or less. structure.

2. The structure according to claim 1, wherein the plurality of nanoparticles have a plurality of crosslinking portions on their surface, and the plurality of nanoparticles are connected to each other via the crosslinking portions.

3. The structure according to claim 1, wherein each of the plurality of nanoparticles is linked to one to three of the aforementioned nanoparticles.

4. The structure according to claim 1, wherein the plurality of nanoparticles have a plurality of crosslinking portions on their surface, and the plurality of nanoparticles are covalently bonded to each other via the crosslinking portions.

5. The structure according to claim 1, wherein the packing density of the plurality of nanoparticles is 74 volume% or less.

6. The structure according to claim 1, wherein the packing density of the plurality of nanoparticles is less than 34 volume%.

7. The structure according to claim 1, wherein the primary particle diameter of the plurality of nanoparticles is 11 nm or less.

8. The structure according to claim 1, wherein the primary particle diameter of the plurality of nanoparticles is 7 nm or less.

9. The structure according to claim 2, wherein the crosslinked portion is an organic or inorganic substance that is directly covalently bonded to each of the plurality of nanoparticles.

10. The structure according to claim 2, wherein the crosslinked portion is an organic or inorganic substance that is covalently bonded to each of the plurality of nanoparticles via a silyl group.

11. The structure according to claim 2, wherein the surfaces of the plurality of nanoparticles whose crosslinked portions are not bonded are coated with amphiphilic molecules.

12. The structure according to claim 11, wherein the amphiphilic molecule is a surfactant molecule, an amino acid molecule, or a polymer.

13. The structure according to claim 12, wherein the polymer is a block copolymer of a phospholipid or a polyalkylene glycol.

14. The structure according to claim 2, wherein the surfaces of the plurality of nanoparticles whose cross-linked portions are not bonded are inactivated by an organosilane compound.

15. The structure according to claim 1, wherein each of the plurality of nanoparticles is a metal oxide.

16. The structure according to claim 1, wherein each of the plurality of nanoparticles is an oxide of zirconium, titanium, tin, silicon, aluminum, or zinc.

17. The structure according to claim 1, wherein each of the plurality of nanoparticles is an oxide of silicon or aluminum.

18. By adding amphiphilic molecules or organosilane molecules to a dispersion containing multiple nanoparticles, the surfaces of the multiple nanoparticles are coated. Furthermore, a crosslinking agent is added to link the plurality of nanoparticles together via the crosslinking portion made of the crosslinking agent, thereby synthesizing a nanoparticle conjugate. The dispersion containing the nanoparticle aggregates is applied onto a substrate. A method for manufacturing a structure.

Images