Keithium compound coated metal microparticles

Abstract

To provide a silicon compound coated-metal fine particle having controlled properties.SOLUTION: The present invention provides a silicon compound coated-metal fine particle in which the surface of a metal fine particle composed of at least one metal element or metalloid element is at least partially coated with a silicon compound. A percentage of Si-OH bonds included in the silicon compound coated-metal fine particle is controlled in a range of 0.1% or more and 70% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to silicon compound-coated metal nanoparticles. [Background technology]

[0002] Metal nanoparticles are materials used in a wide range of applications, including magnetic materials, conductive materials, colorants, and catalysts. In particular, their properties are improved when the particles are 1 μm or smaller, making them suitable for compositions such as dispersions. However, in all applications, while the properties that arise or improve as metal nanoparticles are miniaturized, they also become more susceptible to explosive reactions due to rapid oxidation in the atmosphere, and the expected properties of the metal nanoparticles are easily lost due to oxidation or hydroxylation upon contact with moisture. As a result, it has been difficult to maximize the properties of metal nanoparticles.

[0003] In solving these problems, coating the surface of metal nanoparticles with silicon compounds such as silica is effective, as described in Patent Documents 1 and 2. However, in these conventional techniques, controlling the coating state itself was difficult, so coating with silicon compounds impaired the effects originally expected of metal nanoparticles, and silicon compound-coated metal nanoparticles with strictly controlled properties could not be obtained, and the factors influencing the properties of metal nanoparticles coated with silicon compounds were not clearly understood.

[0004] Patent Document 3 describes a method for manufacturing coated particles in which the coating rate of particles is controlled by the amount of silica coating on the surface of the metal particles for the purpose of controlling conductivity. However, in order to improve insulation, it is naturally necessary to increase the coating rate, and silicon compound coated metal nanoparticles that have undergone such treatment to increase the coating rate have problems such as significantly reduced dispersibility in various dispersion media or failure to produce the expected effect. Therefore, there has been a demand from the industry for silicon compound coated metal nanoparticles in which the amount of silica coating on the metal nanoparticles is reduced as much as possible.

[0005] Regarding silica coating, Patent Document 4 describes silica-coated metal oxide particles that have been further surface-treated with a hydrophobic agent such as dimethylethoxysilane. However, it does not disclose any silica-coated metal fine particles, and merely describes treating silica-coated metal oxide particles with a hydrophobic agent to improve their dispersibility in oily dispersion media such as polyglyceryl triisostearate, silicone oil, and squalane for cosmetic purposes. Furthermore, Patent Document 4 also describes the infrared absorption spectrum at 1150-1250 cm⁻¹. -1 The peak observed is described as the absorption of bending vibrations of Si-OH, but it should normally be attributed to Si-O bonds, and the description of Si-OH is a clear error. Furthermore, the ratio of two different peaks in the infrared absorption spectrum described in Patent Document 4 is clearly unrelated to the properties of silica-coated metal nanoparticles. Therefore, in Patent Document 4, the influence of the ratio of Si-OH bonds in the silica-coated metal oxide or the ratio of Si-OH bonds to the ratio of Si-O bonds on the properties of the nanoparticles has not been found, and silicon compound-coated metal nanoparticles with strictly controlled properties have not been obtained.

[0006] Patent Document 5 by the present applicant describes a method for producing uniform metal nanoparticles by depositing various nanoparticles, such as metal nanoparticles and magnetic nanoparticles, between relatively rotating processing surfaces that can approach and separate from each other. However, while Patent Document 5 describes the production of uniform metal nanoparticles, it does not describe silicon compound-coated metal nanoparticles, and naturally, it does not describe the control of the properties of such silicon compound-coated metal nanoparticles, particularly the dispersibility of silicon compound-coated metal nanoparticles by controlling the Si-O bonds or Si-OH bonds contained in the silicon compound. In other words, it does not show how to control the properties exhibited by silicon compound-coated metal nanoparticles, and there was a need for silicon compound-coated metal nanoparticles with strictly controlled properties. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-264611 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-088156 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-219869 [Patent Document 4] International Publication No. WO 2000 / 042112 Pamphlet [Patent Document 5] International Publication No. WO 2009 / 008393 Pamphlet [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] In view of such circumstances, an object of the present invention is to provide silicon compound-coated metal fine particles with controlled properties. That is, an object is to coat metal fine particles with a silicon compound and control the properties in order to maximize the properties expected of the metal fine particles or to supplement such properties. The present invention utilizes the fact that the Si-OH bond or the ratio of the Si-OH bond / Si-O bond in the coated silicon compound changes in the method for producing the silicon compound-coated metal fine particles and in environmental changes after production. The inventor of the present application has found that the ratio of the Si-OH bond or the ratio of the Si-OH bond / Si-O bond contained in the silicon compound-coated metal fine particles can be controlled within a specific range, and by controlling the ratio of the Si-OH bond or the ratio of the Si-OH bond / Si-O bond within that specific range, properties such as the dispersibility of the silicon compound-coated metal fine particles can be precisely controlled, and thus the present invention has been completed. In view of the above circumstances, another object of the present invention is to provide various compositions using silicon compound-coated metal fine particles with precisely controlled properties. [Means for Solving the Problems]

[0009] That is, the present invention is a silicon compound-coated metal fine particle in which at least a part of the surface of metal fine particles composed of at least one metal element or metalloid element is coated with a silicon compound, and the ratio of Si-OH bonds contained in the silicon compound-coated metal fine particles is controlled to be 0.1% or more and 70% or less.

[0010] The present invention is also a silicon compound-coated metal fine particle in which at least a part of the surface of metal fine particles composed of at least one metal element or metalloid element is coated with a silicon compound, and the ratio of Si-OH bonds to the ratio of Si-O bonds contained in the silicon compound-coated metal fine particles, that is, the Si-OH bond / Si-O bond ratio, is controlled to be 0.001 or more and 700 or less.

[0011] The present invention also preferably has the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated metal fine particles controlled by modification treatment of functional groups.

[0012] The present invention also preferably has the modification treatment of the functional groups being at least one selected from substitution reaction, addition reaction, elimination reaction, dehydration reaction, condensation reaction, reduction reaction, and oxidation reaction.

[0013] The present invention also preferably has the silicon compound-coated metal fine particles being those in which at least a part of the surface of one metal fine particle is coated with a silicon compound, the primary particle diameter of the metal fine particles being 1 μm or less, and the primary particle diameter of the silicon compound-coated metal fine particles being 100.5% or more and 190% or less of the primary particle diameter of the metal fine particles.

[0014] The present invention also preferably has the silicon compound-coated metal fine particles being core-shell type silicon compound-coated metal fine particles in which the entire surface of one metal fine particle serving as a core is coated with a silicon compound serving as a shell.

[0015] Further, in the present invention, the silicon compound-coated metal fine particles are obtained by coating at least a part of the surface of an aggregate in which a plurality of metal fine particles are aggregated with a silicon compound, the diameter of the aggregate is 1 μm or less, and the particle diameter of the silicon compound-coated metal fine particles is preferably 100.5% or more and 190% or less of the diameter of the aggregate.

[0016] Further, in the present invention, it is preferable that the metal element or metalloid element contains at least one selected from the group consisting of silver, copper, and nickel.

[0017] Further, in the present invention, the ratio of the Si-OH bond or the ratio of the Si-OH bond / Si-O bond is obtained by waveform separation of peaks in the infrared absorption spectrum of the silicon compound-coated metal fine particles measured using the total reflection method (ATR method) in the wavenumber range from 750 cm -1 to 1300 cm -1 and is preferably obtained by waveform separation of peaks in the infrared absorption spectrum of the silicon compound-coated metal fine particles measured using the total reflection method (ATR method) in the wavenumber range from 750 cm

[0018] Further, in the present invention, the Si-OH bond is attributed to the peak having the largest area ratio among the peaks separated by waveform separation of peaks in the infrared absorption spectrum of the silicon compound-coated metal fine particles measured using the total reflection method (ATR method) in the wavenumber range from 750 cm -1 to 1300 cm -1 and is in the wavenumber range from 850 cm -1 to 980 cm -1 separated by waveform separation. The ratio of the Si-OH bond is preferably the ratio of the area of the peak attributed to the Si-OH bond to the total area of the peaks obtained by waveform separation of peaks in the wavenumber range from 750 cm -1 to 1300 cm -1 in the infrared absorption spectrum of the silicon compound-coated metal fine particles measured using the total reflection method (ATR method).

[0019] Further, in the present invention, the Si-O bond is obtained by waveform separation of peaks in the infrared absorption spectrum of the silicon compound-coated metal fine particles measured using the total reflection method (ATR method) in the wavenumber range from 750 cm -1 to 1300 cm -1The peak in the region was obtained by waveform separation, at a wavenumber of 1000 cm². -1 More than 1300cm -1 Among the peaks originating from Si-O bonds that were waveform-separated in the following region, the peak with the largest area ratio was attributed to the Si-OH bond, and the Si-OH bond was found at wavenumber 750 cm⁻¹ in the infrared absorption spectrum of the silicon compound-coated metal nanoparticles measured using the total internal reflection (ATR) method. -1 From 1300cm -1 The peak in the region was obtained by waveform separation, at wavenumber 850 cm⁻¹. -1 From 980cm -1 Among the peaks originating from Si-OH bonds that were waveform-separated in the region, the peak with the largest area ratio is assigned to it, and it is preferable that the Si-OH bond / Si-O bond ratio is the ratio of the area of ​​the peaks assigned to Si-OH bonds to the area of ​​the peaks assigned to Si-O bonds.

[0020] Furthermore, it is preferable that the silicon compound-coated metal nanoparticles are obtained by depositing metal nanoparticles between relatively rotating processing surfaces that can approach and separate from each other, and then continuously coating the surface of the metal nanoparticles with a silicon compound following the deposition.

[0021] Furthermore, in the present invention, it is preferable that the silicon compound coated metal nanoparticles contain silicon inside the metal nanoparticles at least before heat treatment, and that, after heat treatment, the silicon has migrated from the inside of the metal nanoparticles toward the outer periphery compared to before heat treatment.

[0022] Furthermore, it is preferable that the dispersibility of the silicon compound-coated metal nanoparticles in the solvent is controlled by controlling the ratio of Si-OH bonds to 0.1% or more and 70% or less, or the ratio of Si-OH bonds to Si-O bonds to 0.001 or more and 700 or less.

[0023] The present invention can also be implemented as a coating composition, a transparent material composition, a magnetic material composition, a conductive composition, a coloring composition, a reaction composition, or a catalyst composition containing silicon compound-coated metal fine particles. [Effects of the Invention]

[0024] According to the present invention, silicon compound-coated metal nanoparticles with controlled properties such as dispersibility can be provided by controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles. By controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio, compositions that are more accurately suited to the diverse applications and desired properties of silicon compound-coated metal nanoparticles can be easily designed compared to conventional methods. [Brief explanation of the drawing]

[0025] [Figure 1] This shows the STEM mapping results of the silicon compound-coated silver nanoparticles obtained in Example 1-1. [Figure 2] This shows the line analysis results of the silicon compound-coated silver nanoparticles obtained in Example 1-1. [Figure 3] This shows the waveform separation results for the region between wavenumbers 750 cm⁻¹ and 1300 cm⁻¹ in the FT-IR measurement results of silicon compound-coated silver nanoparticles obtained in Examples 1-7. [Figure 4] This shows the XRD measurement results of the silicon compound-coated silver nanoparticles obtained in Example 1-1. [Figure 5] This is a TEM image observed using a collodion membrane prepared from an aqueous dispersion of silicon compound-coated silver nanoparticles obtained in Example 1-1. [Figure 6] This shows the STEM mapping results of silicon compound-coated silicon-aluminum doped iron nanoparticles obtained in Example 5-5. [Figure 7] This shows the XRD measurement results of silicon compound-coated silicon-aluminum doped iron nanoparticles obtained in Example 5-5. [Figure 8]This figure shows an enlarged view of the region where peaks were observed in the XRD measurement results of silicon compound-coated silicon aluminum-doped iron nanoparticles obtained in Example 5-5, and compares the peak list with the Fe(Metal) peak in the database. [Modes for carrying out the invention]

[0026] Hereinafter, an example of an embodiment of the present invention will be described based on the drawings. However, the embodiments of the present invention are not limited to those described below.

[0027] (Silicon compound coated metal fine particle composition-1) The silicon compound coated metal nanoparticles according to the present invention are silicon compound coated metal nanoparticles whose properties, such as dispersibility, are controlled by controlling the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound metal nanoparticles. The silicon compound coated metal nanoparticles according to the present invention are particularly suitable for coating compositions used for applying to coating films and painted bodies, transparent material compositions used for kneading into or coating transparent agents such as glass, films, and transparent resins, magnetic material compositions used for adding to magnetic fluids and magnetic materials, conductive compositions used for adding to electronic materials and semiconductor materials, coloring compositions used for coloring coating films, painted bodies, or transparent agents, reaction compositions used as materials for various chemical reactions, or catalyst compositions.

[0028] (Silicon compound coated metal fine particle composition-2) The silicon compound coated metal nanoparticles according to the present invention are silicon compound coated metal nanoparticles in which the ratio of Si-OH bonds contained in the silicon compound coated metal nanoparticles is controlled to be in the range of 0.1% to 70%, or in particular, the ratio of Si-OH bonds / Si-O bonds is controlled to be in the range of 0.001 to 700. This makes it possible to strictly control the dispersibility with respect to hydrophilic or lipophilic dispersion media when used in the above-mentioned various compositions. For example, by using silicon compound coated metal nanoparticles in which the ratio of Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds contained in the silicon compound coated metal nanoparticles is controlled for different octanol / water partition coefficients of dispersion media, the dispersibility with respect to the dispersion media is strictly controlled, so that when used in the target composition, the silicon compound metal nanoparticles can fully exhibit the properties required. The inventors of the present invention have found that while it is difficult to control the ratio of Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds contained in the silicon compound coated metal nanoparticles when they are outside the above range, it is extremely easy to control when they are within the above range. Normally coated silicon compounds are treated with various functional groups depending on the dispersion medium used to obtain a good dispersion state, and the functional groups are selected depending on whether an aqueous or non-aqueous dispersion medium is used. For example, silicon compounds to which various functional groups such as phenolic hydroxyl groups, carboxyl groups, carbonyl groups, amino groups, nitro groups, sulfo groups, alkyl groups, etc. are attached are used, but as the particle size decreases, the dispersion state deteriorates due to aggregation, and it was difficult to achieve the desired result by selecting functional groups alone. Under these circumstances, we discovered that the desired dispersion state can be obtained by controlling the Si-OH bond / Si-O bond ratio even when various functional groups are selected, and thus completed the present invention. That is, information on various bonds can be obtained from the FT-IR spectrum, and in particular, the wavenumber 750 cm⁻¹ -1 From 1300cm -1By controlling the ratio of peak areas attributed to Si-OH bonds and Si-O bonds obtained by waveform separation of peaks in the region, the desired dispersion state can be achieved. We have found that silicon compound coated metal nanoparticles with precisely controlled dispersibility in various solvents can be produced, and that the stability of the silicon compound coated metal nanoparticles themselves and their storage stability in powder form can be controlled, making them suitable for use in the various compositions mentioned above.

[0029] (Silicon compound coated metal fine particle composition-3) In the silicon compound-coated metal nanoparticles according to the present invention, the ratio of Si-OH bonds contained in the silicon compound-coated metal nanoparticles is controlled to a range of 0.1% to 70%, or the ratio of Si-OH bonds / Si-O bonds is controlled to a range of 0.001 to 700%. As a result, in addition to the above-mentioned dispersibility and stability, absorption characteristics, transmission characteristics, or reflection characteristics to electromagnetic waves such as ultraviolet light, visible light, or near-infrared light, as well as plasmon characteristics, are controlled, making them suitable for use in transparent agent compositions for glass, films, transparent resins, etc., and coating compositions such as coating films and painted bodies. Furthermore, when silicon compound-coated metal nanoparticles, in which the surface of metal nanoparticles consisting of at least one metal element or metalloid element is coated with a silicon compound, are used as a magnetic material composition, they are formed in nano-sized magnetic domains insulated by the silicon compound, allowing for isolated control of magnetic anisotropy and consequently control of coercivity. In other words, they are more suitable than any conventional magnetic material composition. They are also suitable as internal electrodes for electronic components. For example, when used as an internal electrode in a multilayer ceramic capacitor, the dispersion is processed into a multilayer coating and then fired in a reducing atmosphere. During firing, the silicon compound migrates to the surface of the electrode and forms a thin insulating film at the boundary between the electrode layer and the dielectric layer, greatly improving the performance of the multilayer ceramic capacitor. Furthermore, whether silicon compound-coated metal nanoparticles are used as the magnetic material composition or as an internal electrode material, slurry formation is a crucial factor. It is essential to form a slurry in which the silicon compound is dispersed without aggregation in an appropriate dispersion medium. The Si-OH bond / Si-O bond ratio affects the coating formation state and the state after firing depending on the firing conditions. Si-O bonds tend to be water-repellent or lipophilic, while Si-OH bonds tend to be hydrophilic, and their ratio is a dominant factor in dispersion. The firing temperature and atmosphere are also important factors in controlling moisture evaporation, the progress of reduction, and insulation.

[0030] Furthermore, in the case of silicon compound-coated metal nanoparticles with semiconductor properties, the semiconductor properties such as conductivity, insulation, and their temperature dependence are controlled, making them suitable for use in semiconductor compositions. Although the factors that enable this control are not clear, the inventors believe that each of the Si-OH bonds or Si-O bonds contained on the surface of the particles has the property of absorbing waves of different energies by vibrating, and that by controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles, the types of different energies absorbed by each of the Si-OH bonds or Si-O bonds can be controlled. In addition, at the end sites of bonds where free electrons can move freely between atoms, such as Si-Si bonds between metalloid silicon elements or Si-M bonds between silicon (Si) and other metal elements or metalloid elements like M, i.e., at the surface of the particles, the free electrons are in an activated state because they have nowhere to go, and can therefore be said to be in a state where new bonds can always be created. The inventors believe that metal elements containing activated electrons, or metalloid elements such as silicon, form bonds with surrounding oxygen, for example. The resulting silicon-oxygen bonds (Si-O bonds) or metal-oxygen bonds (MO bonds) then react with other elements or functional groups to transform into the most stable bonds under the environment in which the particles are placed, such as silicon-oxygen bonds (Si-OH bonds) or metal-hydroxyl group bonds (M-OH bonds). In other words, since the Si-O bonds or MO bonds and Si-OH bonds or M-OH bonds on the surface of these particles are in equilibrium, the ratio of Si-OH bonds / Si-O bonds or M-OH bonds / MO bonds can be controlled by treating the particles under specific environmental conditions. The influence of these ratios on the properties of the particles increases as the particle size decreases. Therefore, the inventors have found that the properties of silicon compound-coated metal nanoparticles can be precisely controlled by strictly controlling the Si-OH bond / Si-O bond ratio.

[0031] When using silicon compound-coated metal nanoparticles according to the present invention as a catalyst, in addition to controlling the dispersibility described above, it is also possible to control the catalytic activity by controlling the coating state of the silicon compound-coated metal nanoparticles. For example, when used in a liquid, the coating rate is controlled by dissolving at least a portion of the silicon compound coating the surface during use. As the surface active sites of the coated metal nanoparticles are exposed due to the dissolution of the silicon compound coating, the catalytic activity of the metal nanoparticles is exhibited or improved. In this case, to control the catalytic activity, the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles can be controlled to control the solubility or dissolution rate in the liquid of the silicon compound coating at least a portion of the surface of the metal nanoparticles. This allows for the control and improvement of the catalyst's properties, making it suitable for use in catalyst compositions. Similarly, when the silicon compound-coated metal nanoparticles of the present invention are used as reaction materials such as oxidizing agents or reducing agents, it is possible to control the desired reaction between the metal nanoparticles contained in the silicon compound-coated metal nanoparticles and the reactants by controlling the solubility or dissolution rate of the silicon compound coating at least a portion of the surface of the metal nanoparticles in the liquid, thereby improving the yield and selectivity of the reaction product. Therefore, they can also be suitably used in reaction compositions.

[0032] (Morphology of silicon compound-coated metal nanoparticles - 1) The silicon compound-coated metal nanoparticles according to the present invention are silicon compound-coated metal nanoparticles in which at least a portion of the surface of the metal nanoparticles is coated with a silicon compound, and the metal is a metal nanoparticle containing one or more different elements of metal elements or metalloid elements on the chemical periodic table. The metal elements in the present invention are not particularly limited, but preferably include metal elements such as Ag, Cu, Fe, and Al. The metalloid elements in the present invention are not particularly limited, but preferably include metalloid elements such as Si, Ge, As, Sb, Te, and Se. These metals and metalloids may be metal nanoparticles consisting of a single metal element, alloy nanoparticles consisting of multiple metal elements, or alloy nanoparticles containing metal elements and metalloid elements.

[0033] (Morphology of silicon compound-coated metal nanoparticles - 2) The silicon compound-coated metal nanoparticles according to the present invention are not limited to those composed solely of metal. They can also be made to contain compounds other than metal to an extent that does not affect the present invention. For example, silicon compound-coated metal nanoparticles can be made in which at least a portion of the surface of metal nanoparticles or alloy nanoparticles containing compounds other than metal is coated with a silicon compound. Examples of the compounds other than metal include oxides or hydroxides, nitrides, carbides, various salts such as nitrates, sulfates, or carbonates, and hydrates or organic solvent hydrates.

[0034] (Morphology of silicon compound-coated metal nanoparticles - 3) The silicon compound coated metal nanoparticles of the present invention are silicon compound coated metal nanoparticles in which the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio, which is the ratio of Si-OH bonds to Si-O bonds, is controlled. Therefore, the silicon compound coated metal nanoparticles of the present invention contain at least silicon (Si) and oxygen (O). As a method for evaluating the presence of silicon (Si) and oxygen (O), it is preferable to observe multiple particles using a transmission electron microscope (TEM) or scanning electron microscope (STEM) and confirm the abundance ratio and location of silicon relative to elements other than silicon in each particle using an energy-dispersive X-ray analyzer (EDS). As an example, one method is to identify the abundance ratio (molar ratio) of elements other than silicon and silicon contained in one silicon compound coated metal nanoparticle and calculate the average value and coefficient of variation of the molar ratio in multiple silicon compound coated metal nanoparticles to evaluate uniformity, or to identify the location of silicon contained in the silicon compound coated metal nanoparticles by mapping. In the present invention, it is preferable that the silicon compound-coated metal nanoparticles are such that silicon and oxygen can be detected near the surface layer of the silicon compound-coated metal nanoparticles in STEM mapping or line analysis. Coating the surface of the metal nanoparticles with a silicon compound has the advantage of imparting chemical stability such as water resistance and acid / alkali resistance to the metal nanoparticles.

[0035] (Explanation of Si-OH and Si-O bonds - 1) In the present invention, various properties such as the dispersibility of silicon compound-coated metal nanoparticles are controlled by controlling the ratio of Si-OH bonds contained in silicon compound-coated metal nanoparticles, or the Si-OH bond / Si-O bond ratio, which is the ratio of Si-OH bonds to Si-O bonds. The Si-OH bond ratio or the Si-OH bond / Si-O bond ratio can be determined, for example, from the results of FT-IR measurement. Here, IR is an abbreviation for infrared absorption spectroscopy. (Hereinafter simply referred to as IR measurement.) In addition, the Si-OH bond ratio or the Si-OH bond / Si-O bond ratio may be measured by methods other than IR measurement, such as X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (solid-state NMR), and electron energy loss spectroscopy (EELS).

[0036] (Explanation of Si-OH and Si-O bonds - Part 2) In the present invention, the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in silicon compound coated metal nanoparticles is determined by the infrared absorption spectrum measurement of silicon compound coated metal nanoparticles at wavenumber 750 cm⁻¹. -1 From 1300cm -1 It is preferable to obtain the peak in the region by waveform separation, at wavenumber 850 cm⁻¹. -1 From 980cm -1 It is preferable to assign the peak with the largest area ratio to the peak derived from the Si-OH bond among the peaks derived from the Si-OH bond that are waveform-separated in the region, at a wavenumber of 1000 cm⁻¹. -1 More than 1300cm -1 It is preferable to assign the peak with the largest area ratio to the peak derived from the Si-O bond among the peaks derived from the Si-O bond that have been waveform-separated in the following region. Typically, the above wavenumber is 750 cm⁻¹. -1 From 1300cm -1 Preferably, the ratio of the area of ​​the peaks attributed to the Si-OH bond to the total area of ​​the peaks obtained by waveform separation of the peaks in the region is defined as the Si-OH bond ratio, and the ratio of the area of ​​the peaks attributed to the Si-O bond to the total area of ​​the peaks is defined as the Si-O bond ratio, and the above wavenumber is 750 cm⁻¹.-1 From 1300cm -1 It is preferable to calculate the Si-OH bond / Si-O bond ratio from the ratio of Si-OH bonds to the Si-O bond ratio obtained by waveform separation of the peaks in the region. That is, the ratio is controlled for functional group bonds that are different from the types of bonds described in at least Patent Document 4.

[0037] (Explanation of amorphous silicon compounds) In the present invention, the silicon compound coating at least a portion of the surface of the metal nanoparticles preferably contains amorphous silicon oxide in order to easily control the ratio of Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds. There are no particular limitations on the method for evaluating whether the silicon compound contains amorphous silicon oxide, but examples include a method that combines confirmation of the presence of Si and O by STEM mapping and confirmation of the presence of silicon oxide by infrared absorption spectroscopy with the absence of peaks originating from crystalline silica (SiO2) in XRD measurements, or a method that confirms that no crystal lattice is observed in the areas where Si and O are detected in TEM observation or STEM observation.

[0038] (Method for controlling Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds - 1) In the present invention, there are no particular limitations on the method for controlling the Si-OH bond or Si-OH bond / Si-O bond ratio, but it is preferable to control the Si-OH bond or Si-OH bond / Si-O bond ratio by modifying the functional groups contained in the silicon compound coated metal nanoparticles. The modification of the functional groups can be performed by conventionally known methods such as substitution reactions, addition reactions, elimination reactions, dehydration reactions, condensation reactions, reduction reactions, or oxidation reactions on the functional groups contained in the silicon compound coated metal nanoparticles, thereby controlling the Si-OH bond or Si-OH bond / Si-O bond ratio. The modification of the functional groups can be used to control the Si-OH bond or Si-OH bond / Si-O bond ratio to be high or low. As an example, a method can be used to control the ratio of Si-OH bonds or Si-OH / Si-O bonds by esterification achieved through a dehydration-condensation reaction in which a carboxylic acid such as acetic anhydride is reacted with the Si-OH bonds contained in silicon compound-coated metal nanoparticles, resulting in the removal of OH from the carboxyl group (-COOH) and H from the hydroxyl group (-OH) in the Si-OH group. In esterification, in addition to methods using acid anhydrides, methods using mixed acid anhydrides, acid halides, or dehydrating agents such as carbodiimide can also be used. In addition to the above esterification, it is also possible to control the ratio of Si-OH bonds or Si-OH / Si-O bonds by methods such as reacting alkyl halides, aryl halides, or heteroaryl halides with the Si-OH groups, preferably in the presence of an acid catalyst, to create ether bonds between the alkyl halides and Si by dehydration, or by reacting isocyanates or thioisocyanates with the Si-OH to create (thio)urethane bonds.

[0039] Regarding the substance that acts on the Si-OH bond, the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio in silicon compound coated metal nanoparticles may be controlled by using a substance containing a fluorine-containing functional group or a hydrophilic or lipophilic functional group. In the present invention, it is not limited to directly acting other substances or functional groups on the Si-OH bond or Si-O bond to create new bonds. For example, the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio can be controlled by acting a carbodiimide on a carboxylic acid contained in the particles, or by acting an ethylene oxide on the Si-OH bond to create a bond such as Si-O-(CH2)2-OH, or by acting an epihalohydrin. In addition, the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio can also be controlled by acting hydrogen peroxide or ozone on the silicon compound coated metal nanoparticles. Furthermore, when precipitating silicon compound-coated metal nanoparticles in a liquid, it is possible to control the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio by methods such as controlling the formulation of the metal raw material solution and metal precipitation solvent used for precipitating the silicon compound-coated metal nanoparticles, or by controlling the pH. Also, as an example of a dehydration reaction, the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio can be controlled by heat treatment of the silicon compound-coated metal particles. When controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio by heat treatment of silicon compound-coated metal nanoparticles, this can be done by dry heat treatment or by heat treatment in the state of a dispersion in which the silicon compound-coated metal nanoparticles are dispersed in a dispersion medium.

[0040] (Method for controlling Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds - 2) In addition to reactions such as dehydration, the functional group modification treatment of silicon compound-coated metal nanoparticles according to the present invention can be performed by reducing or oxidizing reactions, such as treating the silicon compound-coated metal nanoparticles in a reducing or oxidizing atmosphere, to control the ratio of Si-OH bonds or Si-OH / Si-O bonds. For example, by treating the powder of silicon compound-coated metal nanoparticles in a furnace with a reducing gas such as hydrogen, ammonia, hydrogen sulfide, sulfur dioxide, or nitric oxide, or an oxidizing gas such as oxygen, ozone, or nitrogen dioxide, the oxidation number of Si and M contained in the silicon compound-coated metal nanoparticles, which are coated with a silicon compound on at least a portion of the surface of the metal nanoparticles, can be changed to control the ratio of Si-OH bonds or Si-OH / Si-O bonds. These functional group modification treatments, including the above-mentioned oxidation or reduction treatments, may be performed in combination, such as by performing heat treatment and reduction treatment simultaneously.

[0041] (Method for controlling Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds - 3) Furthermore, as described later, silicon compound-coated metal nanoparticles may be dispersed in a target solvent, and a substance containing functional groups may be added to the dispersion and subjected to stirring or other treatments to control the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio. Alternatively, the metal raw material solution, metal deposition solvent, and silicon compound raw material solution may be mixed to precipitate the silicon compound-coated metal nanoparticles, and the dispersion solution containing these nanoparticles may be subjected to stirring or other treatments to control the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio. In addition, this can also be achieved by constructing a device that connects a dispersion device and a filtration membrane, and removing impurities from a slurry containing silicon compound-coated metal nanoparticles by dispersion treatment of particles and cross-flow membrane filtration, etc., by changing the slurry temperature or the temperature of the washing solution used in the cross-flow. In this case, since a uniform modification treatment can be applied to the primary particles of the silicon compound-coated metal nanoparticles, particularly the surface of each primary particle, there is an advantage in that the control of the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles in the present invention, as well as the control of properties such as dispersibility, can be performed more precisely and uniformly.

[0042] The pH adjustment when precipitating the silicon compound-coated metal nanoparticles may be adjusted by including a pH adjusting agent such as an acidic or basic substance in at least one of the various solutions and solvents in the present invention, or by changing the flow rate when mixing the fluid containing the metal raw material solution and the fluid containing the metal deposition solvent.

[0043] The method for changing the functional groups contained in the silicon compound coated metal nanoparticles according to the present invention is not particularly limited. It may be carried out by dispersing the silicon compound coated metal nanoparticles in a target solvent, adding a substance containing functional groups to the dispersion and subjecting it to treatment such as stirring, or by mixing a fluid containing silicon compound coated metal nanoparticles and a fluid containing a substance containing functional groups using a microreactor described in Patent Document 5.

[0044] Substances containing functional groups are not particularly limited, but include substances containing functional groups that can substitute for hydroxyl groups contained in silicon compound-coated metal nanoparticles, such as acylation agents like acetic anhydride and propionic anhydride; methylation agents like dimethyl sulfate and dimethyl carbonate; and silane coupling agents like chlorotrimethylsilane and methyltrimethoxysilane. Other examples include substances containing hydrophobic CF bonds, such as fluorine-containing compounds like trifluoroacetic acid and trifluoromethanesulfonic acid or their anhydrides; fluorine-containing silane coupling agents like triethoxy-1H,1H,2H,2H-heptadecafluorodecylsilane and trimethoxy(3,3,3-trifluoropropyl)silane; and fluorine compounds such as trifluoromethane and trifluoroethane. Furthermore, it is also possible to control the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated oxide particles by reacting them with gases such as trifluoromethane or trifluoroethane. Specifically, when using materials containing functional groups that can be substituted for these hydroxyl groups, it is possible to control the ratio of Si-OH bonds.

[0045] As described above, the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio can also be controlled by reacting the oxide particles with hydrogen peroxide or ozone. The method for reacting the silicon compound coated metal nanoparticles with hydrogen peroxide or ozone is not particularly limited. The silicon compound coated metal nanoparticles may be dispersed in a solvent of choice, and the dispersion may be treated by adding a solution such as hydrogen peroxide or ozone or an aqueous solution containing them and stirring, or by mixing a fluid containing silicon compound coated metal nanoparticles with a fluid containing hydrogen peroxide or ozone using a microreactor as described in Patent Document 5.

[0046] The above-mentioned dispersion can be a liquid dispersion in which silicon compound-coated metal nanoparticles are dispersed in a liquid dispersion medium such as water, an organic solvent, or a resin, or it can be a dispersion in the form of a coating film prepared using a dispersion containing silicon compound-coated metal nanoparticles. When heat treatment is performed on the dispersion containing silicon compound-coated metal nanoparticles, particle aggregation can be suppressed compared to dry heat treatment. Furthermore, for example, when the silicon compound-coated metal nanoparticles of the present invention are used in a coating film, the properties of the silicon compound-coated metal nanoparticles can be controlled by controlling the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles by heat treatment or other methods after the silicon compound-coated metal nanoparticles have formed a coating film. This is suitable for reducing the number of steps and for precise control of properties.

[0047] In addition to the above-mentioned coating applications, silicon compound-coated metal nanoparticles can also be suitably used in transparent material compositions for use in glass, films, and transparent resins of buildings, for example. By dispersing silicon compound-coated metal nanoparticles in glass or resin, they can be suitably used for shielding against electromagnetic waves such as ultraviolet and near-infrared rays. Therefore, they can also be suitably used as silicon compound-coated metal microcompositions for ultraviolet or near-infrared protection. Furthermore, similar to the above-mentioned coating applications, after dispersing silicon compound-coated metal nanoparticles in glass or transparent resin to form a film, it is possible to control the properties of the silicon compound-coated metal nanoparticles by controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles through functional group modification treatment such as heat treatment. This is suitable for reducing the number of processes and for precise control of properties, similar to the above-mentioned coating applications.

[0048] In the present invention, the primary particle size of the metal nanoparticles in silicon compound coated metal nanoparticles is preferably 1 μm or less, and more preferably 1 nm or more and 1 μm or less. Furthermore, the primary particle size of the coated silicon compound coated metal nanoparticles is also preferably 1 μm or less, and more preferably 1 nm or more and 0.5 μm or less. Since the Si-OH bonds or Si-O bonds contained in the silicon compound coated metal nanoparticles are mainly located on the surface of the particles, it is assumed that the properties of the silicon compound coated metal nanoparticles can be precisely controlled. Therefore, silicon compound coated metal nanoparticles with a primary particle size of 1 μm or less have a larger surface area compared to silicon compound coated metal nanoparticles with a primary particle size of more than 1 μm, and it is thought that controlling the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio of the silicon compound coated metal nanoparticles has a greater influence on the properties of the silicon compound coated metal nanoparticles, such as their dispersibility. Therefore, in the case of silicon compound coated metal nanoparticles with a primary particle size of 1 μm or less, there is an advantage in that by controlling the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound coated metal nanoparticles, predetermined properties (in particular, properties suitable for use in coating compositions intended for use in coating films and coated bodies, transparent material compositions intended for use in coated bodies, glass, transparent resins and films where transparency is required, magnetic material compositions intended for use in magnetic materials such as magnetic fluids, semiconductor compositions intended for use in semiconductors, conductive compositions intended for use as conductive materials, reaction compositions intended for use as reaction materials, or catalytic compositions intended for use as catalytic materials) can be suitably exhibited.

[0049] In the silicon compound-coated metal nanoparticles according to the present invention, it is preferable that the ratio of the average primary particle diameter of the silicon compound-coated metal nanoparticles to the average primary particle diameter of the metal nanoparticles before coating with the silicon compound is 100.5% or more and 190% or less. If the coating of the silicon compound on the metal nanoparticles is too thin, the effects related to the properties of the silicon compound-coated metal nanoparticles may not be exhibited. Therefore, it is preferable that the average primary particle diameter of the silicon compound-coated metal nanoparticles is 100.5% or more of the average primary particle diameter of the metal nanoparticles. If the coating is too thick or if coarse aggregates are coated, it becomes difficult to control the properties. Furthermore, if the thickness of the coating exceeds 1 μm, there is a possibility that the peaks originating from the Si-OH bond and the peaks originating from the Si-O bond in the IR measurement results will overlap. Therefore, it is preferable that the average primary particle diameter of the silicon compound-coated metal nanoparticles is 190% or less of the average primary particle diameter of the metal nanoparticles. Various compositions according to the present invention include metal nanoparticles in which at least a part of the surface is coated with a silicon compound, i.e., silicon compound-coated metal nanoparticles themselves. The silicon compound-coated metal nanoparticles according to the present invention may be core-shell type silicon compound-coated metal nanoparticles in which the entire surface of a core metal nanoparticle is uniformly coated with a silicon compound. Furthermore, while it is preferable that the silicon compound-coated metal nanoparticles are silicon compound-coated metal nanoparticles in which at least a portion of the surface of a single metal nanoparticle is coated with a silicon compound, rather than multiple metal nanoparticles being aggregated, it is also acceptable for silicon compound-coated metal nanoparticles to be silicon compound-coated metal nanoparticles in which at least a portion of the surface of an aggregate formed by the aggregation of multiple metal nanoparticles is coated with a silicon compound. However, in that case, silicon compound-coated metal nanoparticles in which aggregates exceeding a certain size are coated with a silicon compound are undesirable because it is more difficult to obtain the above-mentioned properties such as dispersibility compared to silicon compound-coated metal nanoparticles in which at least a portion of the surface of a single metal nanoparticle is coated with a silicon compound. Here, the aggregates exceeding a certain size refer, for example, to aggregates whose size exceeds 1 μm. Furthermore, it is preferable that the particle size of the silicon compound-coated metal nanoparticles, in which at least a portion of the surface of an aggregate formed by the aggregation of multiple metal nanoparticles is coated with a silicon compound, is 100.5% or more and 190% or less of the diameter of the aggregate.The diameter of the aggregate mentioned above is defined as the distance between the maximum outer circumferences of the aggregates.

[0050] (Method for producing silicon compound-coated metal nanoparticles: preferred method) As an example of a method for producing silicon compound-coated metal nanoparticles according to the present invention, it is preferable to use a method in which a metal raw material solution containing at least raw materials for metal nanoparticles to be coated with a silicon compound and a metal deposition solvent containing at least a metal deposition substance for precipitating the metal nanoparticles are prepared, metal nanoparticles are precipitated in a mixed fluid obtained by mixing the metal raw material solution and the metal deposition solvent by methods such as reaction, crystallization, precipitation, and coprecipitation, and the mixed fluid containing the precipitated metal nanoparticles is mixed with a silicon compound raw material solution containing at least raw materials for the silicon compound to be coated, thereby coating at least a portion of the surface of the metal nanoparticles with the silicon compound. Furthermore, if the metal nanoparticles are alloy nanoparticles and the purpose is to produce silicon compound-coated alloy nanoparticles, the different metal elements or metalloid elements contained in the metal nanoparticles may be contained together in the metal raw material solution, or they may be contained in the metal raw material solution and the metal deposition solvent respectively, or they may be contained in both the metal raw material solution and the metal deposition solvent or in the silicon compound raw material solution.

[0051] The raw materials for the silicon compound-coated metal nanoparticles in this invention are not particularly limited. Any material that can be transformed into silicon compound-coated metal nanoparticles by methods such as reaction, crystallization, precipitation, and coprecipitation can be used. In this invention, compounds of metal elements or metalloid elements are collectively referred to as compounds. While the compounds are not particularly limited, examples include salts, oxides, hydroxides, hydroxide oxides, nitrides, carbides, complexes, organic salts, organic complexes, organic compounds, or their hydrates, organic solvent dihydrates, etc., of metals or metalloid elements. It is also possible to use elemental metals or metalloids. Salts of metals or metalloids are not particularly limited, but examples include nitrates, nitrites, sulfates, sulfites, carbonates, formates, acetates, phosphates, phosphites, hypophosphites, chlorides, oxysalts, acetylacetonates, or their hydrates, organic solvent dihydrates, etc., of metals or metalloids. Examples of organic compounds include alkoxides of metals or metalloids. These metal or metalloid compounds may be used individually or as a mixture of several or more. In the present invention, when the metals constituting the silicon compound-coated metal nanoparticles are multiple different metal elements or metalloid elements, if the main metal element is M1 and the secondary metal element or metalloid element is M2, it is preferable that the molar ratio of M2 to M1 (M2 / M1) is 0.01 or more and 1.00 or less.

[0052] Furthermore, examples of raw materials for silicon compounds according to the present invention include silicon oxides and hydroxides, other silicon salts and alkoxides, and hydrates thereof. While not particularly limited, examples of raw materials for silicon compounds include silicates such as sodium silicate, phenyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-trifluoropropyl-trimethoxysilane, methacryloxypropyltriethoxysilane, tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and oligomer condensates of TEOS, such as ethyl silicate 40, tetraisopropylsilane, tetrapropoxysilane, tetraisobutoxysilane, tetrabutoxysilane, and similar substances. Additionally, other siloxane compounds, bis(triethoxysilyl)methane, 1,9-bis(triethoxysilyl)nonane, diethoxydichlorosilane, triethoxychlorosilane, etc., may also be used as raw materials for silicon compounds.

[0053] Furthermore, if the raw materials for the metal nanoparticles or silicon compounds used for coating are solids, it is preferable to use them in a molten state or in a state where they are mixed or dissolved in a solvent described later (including in a molecularly dispersed state). Even if the raw materials are liquids or gases, it is preferable to use them in a state where they are mixed or dissolved in a solvent described later (including in a molecularly dispersed state).

[0054] The metal precipitate material is not particularly limited as long as it is a material that can precipitate the raw materials for silicon compound-coated metal nanoparticles contained in the metal raw material solution as silicon compound-coated metal nanoparticles. For example, it is preferable to use a reducing agent that can reduce metal or metalloid ions contained in the metal raw material solution. The reducing agent is not particularly limited, but all reducing agents that can reduce the metal elements or metalloid elements constituting the silicon compound-coated metal nanoparticles can be used. For example, hydride reducing agents such as sodium borohydride and lithium borohydride, aldehydes such as formalin and aldehydes, sulfites, carboxylic acids or lactones such as formic acid, oxalic acid, succinic acid, ascorbic acid, and citric acid, monoalcohols such as methanol, ethanol, butanol, isopropyl alcohol, and octanol, alicyclic monoalcohols such as terpineol, aliphatic diols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, and tetraethylene glycol, polyhydric alcohols such as glycerin and trimethylolpropane, polyethylene glycol Examples include polyethers such as polypropylene glycol, alkanolamines such as diethanolamine and monoethanolamine, phenols such as hydroquinone, resorcinol, and aminophenol, sugars such as glucose and fructose, or sodium citrate, hypochlorous acid or its salts, transition metal ions (such as titanium and iron ions), hydrazines, amines such as triethylamine, triethanolamine, dimethylaminoethanol, octylamine, and dimethylaminoborane, and pyrrolidones (polyvinylpyrrolidone, 1-vinyl-2-pyrrolidone, methylpyrrolidone). Reducing gases such as hydrogen gas and ammonia gas can also be used.

[0055] Furthermore, the above-mentioned metal raw material solution and metal deposition solvent may contain acidic or basic substances. Examples of basic substances include metal hydroxides such as sodium hydroxide and potassium hydroxide, metal alkoxides such as sodium methoxide and sodium isopropoxide, amine compounds such as triethylamine, diethylaminoethanol and diethylamine, and ammonia.

[0056] Examples of acidic substances include inorganic acids such as aqua regia, hydrochloric acid, nitric acid, fuming nitric acid, sulfuric acid, and fuming sulfuric acid, as well as organic acids such as formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid, trifluoroacetic acid, trichloroacetic acid, and citric acid. The above basic and acidic substances can also be used to precipitate silicon compound-coated metal nanoparticles or compounds for coating.

[0057] (solvent) Examples of solvents used in metal raw material solutions, metal deposition solvents, or silicon compound raw material solutions include water, organic solvents, or mixed solvents consisting of a combination thereof. Examples of water include tap water, deionized water, pure water, ultrapure water, RO water (reverse osmosis water), etc. Examples of organic solvents include alcohol compound solvents, amide compound solvents, ketone compound solvents, ether compound solvents, aromatic compound solvents, carbon disulfide, aliphatic compound solvents, nitrile compound solvents, sulfoxide compound solvents, halogen compound solvents, ester compound solvents, ionic liquids, carboxylic acid compounds, sulfonic acid compounds, etc. Each of the above solvents may be used individually or in combination. Examples of alcohol compound solvents include monohydric alcohols such as methanol and ethanol, and polyols such as ethylene glycol and propylene glycol.

[0058] (Dispersants, etc.) Various dispersants and surfactants may be used as needed and for the purpose, as long as they do not adversely affect the production of silicon compound-coated metal nanoparticles according to the present invention. While not particularly limited, various commercially available products, products, or newly synthesized dispersants can be used. Examples include anionic surfactants, cationic surfactants, nonionic surfactants, and dispersants such as various polymers. These may be used individually or in combination of two or more. The above-mentioned surfactants and dispersants may be contained in at least one of the metal raw material solution and metal deposition solvent fluids. Furthermore, the above-mentioned surfactants and dispersants may be contained in a fluid different from both the metal raw material solution and the metal deposition solvent.

[0059] (Method for producing silicon compound-coated metal nanoparticles: Method overview) In the step of coating at least a portion of the surface of the metal nanoparticles with a silicon compound, it is preferable to coat the metal nanoparticles with the silicon compound before they aggregate. When mixing the silicon compound raw material solution with the fluid containing the metal nanoparticles, it is important to add the silicon compound raw material solution at a rate faster than the metal nanoparticles precipitate and then aggregate, so that the silicon compound precipitates on the surface of the metal nanoparticles. Furthermore, by adding the silicon compound raw material solution to the fluid containing the metal nanoparticles, the pH of the fluid containing the metal nanoparticles and the concentration of the silicon compound raw material gradually change. If the silicon compound for coating the surface of the particles precipitates after the conditions have changed from conditions where particles are easily dispersed to conditions where they are easily aggregated, it may become difficult to coat the particles before they aggregate to such an extent that the properties of the present invention cannot be exhibited. It is preferable to apply the silicon compound raw material contained in the silicon compound raw material solution immediately after the metal nanoparticles have precipitated. It is preferable to obtain silicon compound-coated metal nanoparticles by depositing metal nanoparticles between relatively rotating processing surfaces that can approach and separate, as described in Patent Document 5, and then continuously coating the surface of the metal nanoparticles with a silicon compound following the deposition of the metal nanoparticles. By changing the temperature, pH, and formulation conditions when obtaining the silicon compound-coated metal nanoparticles, it is possible to precisely control the production of the silicon compound-coated metal nanoparticles of the present invention, the ratio of Si-OH bonds or Si-OH bond / Si-O bond ratio, and the properties of the silicon compound-coated metal nanoparticles as a result. By setting the temperature above a certain level when obtaining the silicon compound-coated metal nanoparticles, it is possible to produce silicon compound-coated metal nanoparticles that have a hollow layer between the metal nanoparticles and the layer of silicon compound coating. This method utilizes the fact that the shrinkage rate of the silicon compound is smaller than that of the metal nanoparticles in silicon compound-coated metal nanoparticles, by coating the surface of metal nanoparticles deposited in an environment above a certain temperature with a silicon compound at a similar temperature, and then cooling it to a low temperature such as room temperature. In the present invention, the temperature for obtaining silicon compound-coated metal nanoparticles having the above-mentioned hollow layer is preferably 150°C or higher, and more preferably 200°C or higher.

[0060] (Method for producing silicon compound-coated metal nanoparticles: apparatus) One example of a method for producing silicon compound-coated metal nanoparticles according to the present invention is to produce silicon compound-coated metal nanoparticles by using a microreactor or by carrying out a dilute reaction in a batch container. Alternatively, an apparatus and method as described in Japanese Patent Application Publication No. 2009-112892, proposed by the present applicant, may be used to produce silicon compound-coated metal nanoparticles. The apparatus described in Japanese Patent Publication No. 2009-112892 comprises a stirring tank having an inner surface with a circular cross-sectional shape, and a stirring tool attached to the inner surface of the stirring tank with a small gap between them. The stirring tank is equipped with at least two fluid inlets and at least one fluid outlet. From one of the fluid inlets, a first fluid to be treated containing one of the reactants is introduced into the stirring tank, and from the other fluid inlet, a second fluid to be treated containing one reactant different from the first fluid to be treated is introduced into the stirring tank from a different flow path than the first fluid to be treated. At least one of the stirring tank and the stirring tool rotates at high speed relative to the other, causing the fluid to be treated to become a thin film, and reactants contained in at least the first and second fluids to be treated react with each other in this thin film. It is stated that three or more introduction pipes may be provided to introduce three or more fluids to be treated into the stirring tank, as shown in Figures 4 and 5 of the same publication. An example of the above microreactor is an apparatus based on the same principle as the fluid processing apparatus described in Patent Document 5.

[0061] A method for producing silicon compound-coated metal nanoparticles according to the present invention, different from the above method, is a method of treating nanoparticles of a substance that can serve as a precursor to the metal contained in the metal nanoparticles in a reducing atmosphere. Specifically, this method involves preparing silicon compound-coated precursor nanoparticles in which at least a portion of the surface of nanoparticles containing the precursor is coated with a silicon compound, or silicon-doped precursor nanoparticles in which nanoparticles containing the precursor are doped with silicon, and then treating the silicon compound-coated precursor nanoparticles or silicon-doped precursor nanoparticles in a reducing atmosphere. Examples of the precursor include oxides or hydroxides, nitrides, carbides, nitrates, sulfates, carbonates, and various salts, as well as hydrates and organic solvent dihydrates, that contain the metal element or metalloid element constituting the metal nanoparticles. For example, silicon compound-coated precursor nanoparticles, such as silicon compound-coated iron oxide particles, can be reduced to silicon compound-coated iron particles by heat treatment in a reducing atmosphere such as a hydrogen atmosphere. Furthermore, even if the silicon compound-coated precursor fine particles are reduced to silicon by treatment in a reducing atmosphere, they can be converted to silicon compounds such as silicon oxides by treatment in an atmospheric environment such as air, thus enabling the production of silicon compound-coated metal fine particles in the same manner as described above. Thus, by treating silicon compound-coated precursor fine particles containing the precursor of the metal fine particles in a reducing atmosphere, it is possible to substantially simultaneously produce silicon compound-coated metal fine particles and control the ratio of Si-OH bonds or Si-OH bonds / Si-O bonds, and it is also possible to more precisely control the ratio of Si-OH bonds or Si-OH bonds / Si-O bonds.

[0062] Furthermore, silicon compound-coated metal nanoparticles according to the present invention can also be obtained by treating silicon-doped precursor nanoparticles, which contain silicon as a precursor, in a reducing atmosphere. For example, first, silicon-doped iron oxide particles, which are silicon-doped precursor particles, can be heat-treated in a reducing atmosphere to reduce both silicon and iron, thereby obtaining silicon-iron alloy particles. Next, by treating the obtained silicon-iron alloy particles in an oxidizing atmosphere such as air, the silicon contained in the surface of the silicon-iron alloy particles is oxidized to form silicon compounds such as silicon oxides, making it possible to produce silicon compound-coated metal nanoparticles such as silicon compound-coated iron particles or silicon compound-coated silicon-iron alloy particles.

[0063] Furthermore, the inventors have found that silicon contained in metal particles or precursor particles such as oxides undergoes a change in which it moves from the inside to the outside of the particles due to heat treatment. Even when particles fuse together, the inventors have found that the amount of silicon and silicon compounds can be reduced to a state where they do not contain silicon or silicon compounds in the fused areas between particles, and that the surface of particles whose particle size has increased due to fusion compared to before treatment can be coated with a silicon compound. Silicon compound-coated metal nanoparticles produced by these methods, which contain silicon inside the metal nanoparticles at least before heat treatment, and in which the silicon has migrated from the inside to the outer circumference of the metal nanoparticles after heat treatment compared to before heat treatment, have the advantage of being able to simultaneously reduce the precursor particles or control the particle size, and control the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio. However, the present invention is not limited to simultaneously performing the above reduction and the control of the Si-OH bond ratio or the Si-OH bond / Si-O bond ratio. Furthermore, for example, when the silicon compound coated metal nanoparticles according to the present invention are used as a conductive material such as wiring material, the metal elements contained in the silicon compound coated metal nanoparticles can be used to form conductive wiring, and at the same time, the outer periphery of the wiring can be coated with the silicon compound. This has the advantage of protecting the metal forming the wiring from moisture and preventing oxidation by the silicon compound on the outer periphery of the wiring. In this invention, the reduction treatment of the silicon compound coated precursor nanoparticles or silicon-doped precursor nanoparticles may be carried out by a dry method or a wet method.

[0064] When obtaining silicon compound-coated metal nanoparticles by reduction of the silicon compound-coated precursor nanoparticles or silicon-doped precursor nanoparticles described above, it is preferable that the particle size of the silicon compound-coated precursor nanoparticles is 100 nm or less. Having a particle size of 100 nm or less allows for uniform reduction treatment of the silicon compound-coated metal nanoparticles, and has the advantage of simultaneously controlling the ratio of Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds. Furthermore, it has the advantage that even base metals, which were previously difficult to reduce except by methods such as electroreduction using large amounts of energy such as electricity, can be reduced to metal nanoparticles. The method for producing the silicon compound precursor nanoparticles described above is not particularly limited, but similar to the silicon compound-coated metal nanoparticles described above, precursor nanoparticles may be produced using the apparatus described in Patent Document 5, or by using a grinding method such as a bead mill, and after production, the silicon compound may be coated onto the precursor particles using a reaction vessel or the above-mentioned microreactor.

[0065] (Correspondence with priority claim applications) The inventors of the present invention have discovered that the properties of silicon compound-coated metal nanoparticles, such as their dispersibility, can be controlled by controlling the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles, thereby completing the present invention. The coating of the surface of various nanoparticles with a silicon compound, and the acquisition of silicon compound-coated metal oxide nanoparticles in which the silicon compound is a silicon oxide, which can serve as a precursor to silicon compound-coated metal nanoparticles, are disclosed in the basic application of this application, Japanese Patent Application No. 2016-111346, and it has been found that these can be reduced to metal in a reducing atmosphere. The inventors of the present invention have further discovered, as disclosed in another basic application of this application, PCT / JP2016 / 83001, that the properties of silicon compound-coated metal nanoparticles, such as their dispersibility, can be controlled by controlling the Si-OH bonds contained in these silicon compound-coated metal nanoparticles in a specific atmosphere. [Examples]

[0066] The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, pure water with an electrical conductivity of 0.84 μS / cm (measurement temperature: 25°C) was used as the pure water.

[0067] (Preparation of samples for TEM observation and preparation of samples for STEM observation) The silicon compound-coated metal nanoparticles obtained in the examples were dispersed in a dispersion medium, and the resulting dispersion was dropped onto a collodion membrane and dried to obtain a sample for TEM observation or STEM observation.

[0068] (Transmission electron microscope and energy-dispersive X-ray spectrometer: TEM-EDS analysis) For observation and quantitative analysis of silicon compound-coated metal nanoparticles by TEM-EDS analysis, a transmission electron microscope, JEM-2100 (manufactured by JEOL Ltd.), equipped with an energy-dispersive X-ray analyzer, JED-2300 (manufactured by JEOL Ltd.), was used. Observation conditions included an acceleration voltage of 80 kV and an observation magnification of 25,000x or higher. Particle diameter was calculated from the distance between the maximum outer circumferences of the silicon compound-coated metal nanoparticles observed by TEM, and the average value (average primary particle diameter) was calculated from the results of measuring the particle diameter of 100 particles. The molar ratio of the elemental components constituting the silicon compound-coated metal nanoparticles was calculated by TEM-EDS, and the average value was calculated from the results of calculating the molar ratio for 10 or more particles.

[0069] (Scanning transmission electron microscope and energy-dispersive X-ray spectrometer: STEM-EDS analysis) For the mapping and quantification of elements contained in silicon compound-coated metal nanoparticles using STEM-EDS analysis, an atomic-resolution analytical electron microscope, JEM-ARM200F (manufactured by JEOL Ltd.), equipped with an energy-dispersive X-ray analyzer, Centurio (manufactured by JEOL Ltd.), was used. The observation conditions were an acceleration voltage of 80 kV, an observation magnification of 50,000x or more, and an analysis was performed using a beam diameter of 0.2 nm.

[0070] (X-ray diffraction measurement) For X-ray diffraction (XRD) measurements, a powder X-ray diffraction analyzer EMPYREAN (manufactured by PANalytical Division, Spectris Corporation) was used. The measurement conditions were: measurement range: 10 to 100 [°2θ] Cu versus cathode, tube voltage 45kV, tube current 40mA, and scanning speed 0.3° / min. XRD measurements were performed using the dried powder of silicon compound-coated metal nanoparticles obtained in each example.

[0071] (FT-IR measurement) For FT-IR measurements, a Fourier transform infrared spectrophotometer, FT / IR-6600 (manufactured by JASCO Corporation), was used. The measurement conditions were the ATR method under a nitrogen atmosphere, with a resolution of 4.0 cm. -1 The cumulative number of cycles is 1024. The wavenumber in the IR spectrum is 750 cm⁻¹. -1 From 1300cm -1 The waveform separation of the peaks was performed by curve fitting using the spectral analysis program included with the control software for the FT / IR-6600, so that the sum of squared residuals was 0.01 or less. The measurements were taken using the dried powder of silicon compound-coated metal fine particles obtained in the examples.

[0072] (Particle size distribution measurement) For particle size distribution measurement, a particle size analyzer, UPA-UT151 (manufactured by Nikkiso Co., Ltd.), was used. The measurement conditions were as follows: the dispersion medium containing the silicon compound coated metal obtained in the examples was used as the measurement solvent, and the particle refractive index and density were taken from the values ​​of the main metal element or metalloid element constituting the metal nanoparticles in the silicon compound coated metal nanoparticles obtained in the examples.

[0073] (Example 1) Example 1 shows an example in which silicon compound coated metal nanoparticles were produced using an apparatus based on the principle described in Patent Document 5, and the dispersibility in various dispersion media was controlled by controlling the ratio of Si-OH bonds or the Si-OH bond / Si-O bond ratio contained in the silicon compound coated metal nanoparticles. Using a high-speed rotary dispersion emulsifier called Creamix (product name: CLM-2.2S, manufactured by M-Technique Co., Ltd.), a metal raw material solution (solution A), a metal deposition solvent (solution B), and a silicon compound raw material solution (solution C) were prepared. Specifically, based on the formulation of the metal raw material solution shown in Example 1 in Table 1, each component of the metal raw material solution was homogeneously mixed using Creamix by stirring at a preparation temperature of 50°C and a rotor rotation speed of 20,000 rpm for 30 minutes to prepare the metal raw material solution. Furthermore, based on the formulation of the metal deposition solvent shown in Example 1 of Table 2, each component of the metal deposition solvent was homogeneously mixed using a Creamix at a preparation temperature of 25°C and a rotor speed of 8000 rpm for 30 minutes to prepare the metal deposition solvent. In addition, based on the formulation of the silicon compound raw material solution shown in Example 1 of Table 3, each component of the silicon compound raw material solution was homogeneously mixed using a Creamix at a preparation temperature of 20°C and a rotor speed of 6000 rpm for 10 minutes to prepare the silicon compound raw material solution. For the substances indicated by the chemical formulas or abbreviations listed in Tables 1 to 3, the following were used: MeOH = methanol (manufactured by Mitsubishi Chemical Corporation), EG = ethylene glycol (manufactured by Kishida Chemical Co., Ltd.), KOH = potassium hydroxide (manufactured by Nippon Soda Co., Ltd.), NaOH = sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.), TEOS = tetraethyl orthosilicate (manufactured by Wako Pure Chemical Industries, Ltd.), AgNO3 = silver nitrate (manufactured by Kanto Chemical Co., Ltd.), NaBH4 = sodium tetrahydroborate (manufactured by Wako Pure Chemical Industries, Ltd.), HMH = hydrazine monohydrate (manufactured by Kanto Chemical Co., Ltd.), PVP = polyvinylpyrrolidone K = 30 (manufactured by Kanto Chemical Co., Ltd.), DMAE = 2-dimethylaminoethanol (manufactured by Kanto Chemical Co., Ltd.), and H2SO4 = concentrated sulfuric acid (manufactured by Kishida Chemical Co., Ltd.).

[0074] Next, the prepared metal raw material solution, metal deposition solvent, and silicon compound raw material solution were mixed using the fluid processing apparatus described in Patent Document 5 by the applicant. Here, the fluid processing apparatus described in Patent Document 5 is the apparatus shown in Figure 1(B) of the said publication, in which the openings d20 and d30 of the second and third inlet sections are formed in a ring shape, and the openings in the central part of the processing surface 2 are concentric rings surrounding the central opening. Specifically, the metal raw material solution or metal deposition solvent was introduced as solution A from the first inlet section d1 between the processing surfaces 1 and 2, and while the processing section 10 was operated at a rotation speed of 1130 rpm, the other liquid from the metal raw material solution or metal deposition solvent, different from the liquid introduced as solution A, was introduced as solution B from the second inlet section d2 between the processing surfaces 1 and 2, and the metal raw material solution and metal deposition solvent were mixed in a thin film fluid, and core silver nanoparticles were deposited between the processing surfaces 1 and 2. Next, the silicon compound raw material solution was introduced as solution C from the third introduction section d3 between the processing surfaces 1 and 2, and mixed with a mixed fluid containing core silver nanoparticles in a thin film fluid. The silicon compound precipitated on the surface of the core silver nanoparticles, and the discharge liquid containing the silicon compound coated silver nanoparticles (hereinafter referred to as the silicon compound coated silver nanoparticle dispersion) was discharged from between the processing surfaces 1 and 2 of the fluid apparatus. The discharged silicon compound coated silver nanoparticle dispersion was collected in beaker b via vessel v.

[0075] Table 4 shows the operating conditions of the fluid processing apparatus, as well as the Si / M molar ratio (Si / Ag in Example 1) calculated from TEM-EDS analysis based on TEM observation results of the obtained silicon compound-coated silver nanoparticles, along with the calculated values ​​from the formulations and introduction flow rates of solutions A, B, and C. The introduction temperature (supply temperature) and introduction pressure (supply pressure) of solutions A, B, and C shown in Table 4 were measured using thermometers and pressure gauges installed in the sealed introduction passages (first introduction section d1, second introduction section d2, and third introduction section d3) leading between processing surfaces 1 and 2. The introduction temperature of solution A shown in Table 2 is the actual temperature of solution A under the introduction pressure in the first introduction section d1, the introduction temperature of solution B is the actual temperature of solution B under the introduction pressure in the second introduction section d2, and the introduction temperature of solution C is the actual temperature of solution C under the introduction pressure in the third introduction section d3.

[0076] A pH meter, model D-51, manufactured by Horiba, Ltd., was used for pH measurement. The pH of solutions A, B, and C was measured at room temperature before introducing them into the fluid processing device. Furthermore, since it is difficult to measure the pH of the mixed fluid immediately after mixing the metal raw material solution and the metal deposition solvent, and the pH of the fluid containing the core silver nanoparticles immediately after mixing the silicon compound raw material solution, the pH of the silicon compound-coated silver nanoparticle dispersion, which was discharged from the device and collected in beaker b, was measured at room temperature.

[0077] Dry powder and wet cake samples were prepared from a dispersion of silicon compound-coated silver microparticles discharged from a fluid processing device and collected in beaker b. The preparation method followed the standard procedure for this type of processing: the discharged dispersion of silicon compound-coated silver microparticles was collected, the silicon compound-coated silver microparticles were allowed to settle, and the supernatant was removed. Then, washing and settling were repeatedly performed with 100 parts by mass of pure water until the conductivity of the washing solution containing the silicon compound-coated silver microparticles was 10 μS / cm or less. Finally, a portion of the resulting wet cake of silicon compound-coated silver microparticles was dried at -0.10 MPaG at 25°C for 20 hours to obtain dry powder. The remainder was used as the wet cake sample.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] Examples 1-1 to 1-3 aimed to change the ratio of Si-OH bonds or the Si-OH / Si-O bond ratio by precipitating metal nanoparticles and changing the processing temperature when the silicon compound-containing fluid (silicon compound raw material solution) was reacted with the metal nanoparticles. Examples 1-4 to 1-6 changed the concentration of sulfuric acid in the silicon compound-containing fluid compared to Example 1-1, thereby precipitating metal nanoparticles and changing the pH when the silicon compound-containing fluid was reacted with the metal nanoparticles. Examples 1-7 to 1-9 changed the formulations of the metal raw material solution, metal precipitation solvent, and silicon compound raw material solution, and changed the processing temperature.

[0083] As a further example of modifying the functional groups contained in silicon compound-coated silver nanoparticles, hydrogen peroxide was applied to the silicon compound-coated silver nanoparticles obtained in Example 1-1. Specifically, the silicon compound-coated silver nanoparticles obtained in Example 1-1 were added to propylene glycol to a concentration of 0.1% by mass as silicon compound-coated silver nanoparticles, and homogeneously mixed and dispersed using a high-speed rotary dispersion emulsifier, Creamix (product name: CLM-2.2S, manufactured by M-Technique Co., Ltd.), by stirring at a preparation temperature of 30°C and a rotor speed of 20,000 rpm for 30 minutes to prepare a dispersion of silicon compound-coated silver nanoparticles. While stirring the above dispersion at 20,000 rpm using Creamix, 35% by mass hydrogen peroxide solution (manufactured by Kanto Chemical Co., Ltd.) was added, and the process was continued for 30 minutes while maintaining the rotation speed of Creamix at 20,000 rpm and the processing temperature between 30°C and 35°C. After processing, dried powder and wet cake samples of silicon compound-coated silver nanoparticles were prepared using the same method as in Examples 1-1 to 1-9. The amount of hydrogen peroxide added was such that in Example 1-10, the hydrogen peroxide was 0.005 mol relative to the silver contained in the silicon compound-coated silver nanoparticles; in Example 1-11, it was 0.01 mol; and in Example 1-12, it was 0.1 mol.

[0084] The silicon compound-coated silver nanoparticles of Example 1-1 were heat-treated using an electric furnace as a treatment to modify the functional groups contained in the silicon compound of the silicon compound-coated silver nanoparticles. The heat treatment conditions were as follows: Example 1-1: untreated, Example 1-13: 100°C for 30 minutes, Example 1-14: 200°C for 30 minutes, Example 1-15: 300°C for 30 minutes.

[0085] The silicon compound-coated silver nanoparticles of Example 1-1 were treated in a desiccator under a fuming sulfuric acid atmosphere to introduce sulfo groups by reacting sulfonic acid with the Si-OH groups contained in the silicon compound-coated silver nanoparticles, as a treatment to modify the functional groups contained in the silicon compound. The heat treatment conditions were as follows: Example 1-1: untreated, Example 1-16: 120 minutes at room temperature (25°C), Example 1-17: 480 minutes at warm temperature (25°C).

[0086] Figure 1 shows the STEM mapping results of the silicon compound-coated silver nanoparticles obtained in Example 1-1, and Figure 2 shows the line analysis results at the dashed lines in the HAADF image of Figure 1. In Figure 1, (a) is the dark-field image (HAADF image), (b) is the mapping result for oxygen (O), (c) is for silicon (Si), and (d) is for silver (Ag). Figure 2 shows the line analysis results at the dashed lines in the HAADF image of Figure 1, indicating the atomic % (mol %) of the elements detected in the line portion from one end of the particle to the other. As can be seen in Figure 2, oxygen and silicon were detected at both ends of the analysis range in the line analysis, but silver was not detected up to a few nanometers inside from the end of the particle, indicating that the surface of the silver nanoparticles is coated with a silicon compound containing silicon oxide. As can be seen in Figures 1 and 2, the silicon compound-coated silver nanoparticles obtained in Example 1-1 were observed as silver nanoparticles in which the entire particle was covered with a silicon compound. The silicon compound-coated oxide particles obtained in Examples 1-2 to 1-17 also yielded the same STEM mapping and line analysis results as in Example 1-1. However, in Example 1-6, silicon compound-coated silver nanoparticles were observed in which not the entire silver nanoparticle was covered with the silicon compound, but rather only a portion of the surface of the silver nanoparticle was coated with a silicon compound containing silicon oxide. In the present invention, silicon compound-coated metal nanoparticles can be implemented in which at least a portion of the surface of the metal nanoparticle is coated with the silicon compound. Furthermore, in Examples 1-9, 1-14, and 1-15, a hollow layer was observed between the silver nanoparticle and the silicon compound coating its surface.

[0087] Figure 3 shows the FT-IR measurement results for the silicon compound-coated silver nanoparticles obtained in Examples 1 and 7, at a wavenumber of 750 cm². -1 From 1300cm -1 The results of waveform separation for the region are shown. As can be seen in Figure 3, in this embodiment, wavenumber 750 cm⁻¹ -1 From 1300cm -1 Waveform separation of the peak in the region revealed that the wavenumber is 850 cm. -1 From 950cm -1Among the peaks originating from Si-OH bonds that were waveform-separated in the region, the peak with the largest area ratio was assigned as the peak originating from Si-OH bonds, and the wavenumber was 1000 cm. -1 More than 1300cm -1 Among the peaks originating from Si-O bonds that were waveform-separated in the following region, the peak with the largest area ratio was assigned as the peak originating from Si-O bonds, at a wavenumber of 750 cm⁻¹. -1 From 1300cm -1 The ratio of the area of ​​peaks attributed to the Si-OH bond to the total area of ​​peaks obtained by waveform separation in the region was defined as the Si-OH bond ratio, and the ratio of the area of ​​peaks attributed to the Si-O bond was defined as the Si-O bond ratio, thereby calculating the Si-OH bond ratio and the Si-OH bond / Si-O bond ratio.

[0088] Figure 4 shows the XRD measurement results of the silicon compound-coated silver nanoparticles obtained in Example 1-1. As can be seen in Figure 4, only peaks originating from Ag were detected in the XRD measurement. That is, it was confirmed that the silicon compound containing silicon oxide, which was confirmed in the above STEM and IR measurements, is an amorphous silicon compound. Similar XRD measurement results were obtained for Examples 1-2 to 1-15.

[0089] Table 5 shows the average primary particle diameter, Si-OH bond ratio (Si-OH bond ratio), Si-O bond ratio (Si-O bond ratio), and Si-OH bond / Si-O bond ratio (Si-OH bond / Si-O bond ratio) of silicon compound coated silver nanoparticles obtained in Examples 1-1 to 1-15, as well as the dispersed particle diameter of the dispersion liquid obtained by dispersing the silicon compound coated silver nanoparticles obtained in each example in pure water or toluene (manufactured by Kanto Chemical Co., Ltd.) as a dispersion medium, using the volume-average particle diameter obtained from particle size distribution measurements. In these examples, dispersibility was evaluated as one of the properties of silicon compound coated metal nanoparticles, and dispersibility was evaluated by the dispersed particle diameter and the ratio of the dispersed particle diameter to the average primary particle diameter (dispersed particle diameter / average primary particle diameter). The dispersion was prepared by adding silicon compound-coated silver nanoparticles to each dispersion medium in an amount of 0.1% by mass, and then homogeneously mixing and dispersing them using a Creamix at a preparation temperature of 30°C and a rotor speed of 20,000 rpm for 30 minutes.

[0090] [Table 5]

[0091] As shown in Table 5, increasing the Si-OH bond ratio and the Si-OH bond / Si-O bond ratio tended to reduce the dispersed particle size and the dispersed particle size / average primary particle size when using pure water and ethanol as the dispersion medium. Conversely, decreasing the Si-OH bond / Si-O bond ratio tended to reduce the dispersed particle size and the dispersed particle size / average primary particle size when using toluene as the dispersion medium. Furthermore, in Examples 1-16 and 1-17, hydrophilic sulfo groups were confirmed in the IR measurement results. However, decreasing the Si-OH bond ratio or the Si-OH bond / Si-O bond ratio reduced dispersibility in pure water and improved dispersibility in toluene. Figure 5 shows a TEM image observed using a collodion membrane prepared from an aqueous dispersion of silicon compound-coated silver fine particles obtained in Example 1-1.

[0092] In Examples 2 to 4 below, silicon compound-coated metal nanoparticles were produced by changing the metal element in the silicon compound-coated metal nanoparticles (Examples 2 and 3) or changing the processing apparatus (Example 4). Although the different metal elements or processing apparatuses were under different conditions, the conditions with the same branch number in each example indicate that the objective for producing silicon compound-coated metal nanoparticles was the same and that the silicon compound-coated metal nanoparticles were produced or processed under similar conditions. The same applies to the list of analysis and evaluation results for each example (Example 2: [Table 10], Example 3: [Table 15], Example 4: [Table 16]).

[0093] (Example 2) In Example 2, we describe silicon compound-coated copper nanoparticles, in which at least a portion of the surface of copper nanoparticles is coated with a silicon compound. The nanoparticles were prepared under the same conditions as in Example 1, except for the preparation conditions shown in Tables 6 to 9. The analysis and evaluation results of the obtained silicon compound-coated copper nanoparticles are shown in Table 10. Regarding the substances indicated by chemical formulas and abbreviations in Tables 6 to 8, as a different substance from the substances shown in Tables 1 to 3, Cu(NO3)2·3H2O was replaced with copper nitrate trihydrate (manufactured by Wako Pure Chemical Industries, Ltd.), while the other substances were the same as in Example 1.

[0094] (Example 3) In Example 3, we describe silicon compound-coated nickel nanoparticles, in which at least a portion of the surface of nickel nanoparticles is coated with a silicon compound. The nanoparticles were prepared under the same conditions as in Example 1, except that the preparation conditions were shown in Tables 11 to 14. The analysis and evaluation results of the obtained silicon compound-coated nickel nanoparticles are shown in Table 15. Regarding the substances indicated by chemical formulas and abbreviations in Tables 11 to 13, Ni(NO3)2·6H2O was replaced with nickel nitrate hexahydrate (manufactured by Kanto Chemical Co., Ltd.) as a different substance from the substances shown in Tables 1 to 3 or Tables 6 to 8, while the other substances were the same as those used in Example 1 or Example 2.

[0095] In Examples 2 and 3, the results of STEM mapping, line analysis, and XRD measurements were similar to those in Example 1. In Example 2, only peaks originating from Cu were detected in the XRD measurement results, and in Example 3, only peaks originating from Ni were detected in the XRD measurement results.

[0096] As shown in Tables 10 and 15, the same results as in Example 1 were obtained for silicon compound-coated copper nanoparticles and silicon compound-coated nickel nanoparticles. It was found that the dispersibility of silicon compound-coated metal nanoparticles can be controlled within the range of 0.1% to 70% for the Si-OH bond ratio and 0.001 to 700 for the Si-OH bond / Si-O bond ratio, even if the metal nanoparticles are of different types of metal.

[0097] [Table 6]

[0098] [Table 7]

[0099] [Table 8]

[0100] [Table 9]

[0101] [Table 10]

[0102] [Table 11]

[0103] [Table 12]

[0104] [Table 13]

[0105] [Table 14]

[0106] [Table 15]

[0107] (Example 4) As Example 4, silicon compound-coated silver nanoparticles were produced under the same conditions as in Example 1, except that the apparatus and the mixing and reaction method of liquids A, B, and C described in Japanese Patent Publication No. 2009-112892 were used. Here, the apparatus described in Japanese Patent Publication No. 2009-112892 is the apparatus shown in Figure 1 of the same publication, with an inner diameter of 80 mm, a gap of 0.5 mm between the outer end of the stirring tool and the inner circumferential surface of the stirring tank, and a rotation speed of 7200 rpm for the stirring blades. Liquid A was introduced into the stirring tank, and liquid B was added to a thin film made of liquid A that was pressed against the inner circumferential surface of the stirring tank and mixed and reacted.

[0108] The results of STEM mapping, line analysis, and XRD measurements were the same as those obtained in Example 1.

[0109] Table 16 shows the analysis and evaluation results for the silicon compound-coated silver nanoparticles obtained in Example 4. As can be seen in Table 16, in Example 4, which was conducted using an apparatus different from the one described in Patent Document 5, it was found that the dispersibility could be controlled by controlling the Si-OH bond ratio or the Si-OH bond / Si-O bond ratio contained in the silicon compound-coated metal nanoparticles, similar to Examples 1 to 3.

[0110] [Table 16]

[0111] (Example 5) Example 5 presents an example of producing silicon compound-coated metal nanoparticles using silicon compound-coated precursor particles and controlling the ratio of Si-OH bonds or Si-OH bonds / Si-O bonds. Silicon compound-coated silicon aluminum-doped iron oxide nanoparticles were prepared as silicon compound-coated precursor nanoparticles. The preparation conditions were based on the formulation conditions shown in Tables 17 to 19, and the processing conditions were as shown in Table 20, except that the silicon compound-coated silicon aluminum-doped iron oxide nanoparticles were prepared in the same manner as in Example 1. Note that in the initial stage of Example 5, in order to produce oxide particles, the metal raw material solution is described as the oxide raw material solution and the metal deposition solvent as the oxide deposition solvent. Furthermore, for the substances indicated by the chemical formulas or abbreviations listed in Tables 17 to 19, the following substances were used that differed from those shown in Tables 1 to 1, Tables 6 to 8, or Tables 11 to 13: Fe(NO3)3·9H2O was replaced with iron nitrate nonahydrate (manufactured by Kanto Chemical Co., Ltd.), and Al(NO3)3·9H2O was replaced with aluminum nitrate nonahydrate (manufactured by Kanto Chemical Co., Ltd.). For all other substances, the same substances as in Examples 1 to 4 were used.

[0112] [Table 17]

[0113] [Table 18]

[0114] [Table 19]

[0115] [Table 20]

[0116] In Example 5, silicon compound-coated silicon-aluminum doped iron oxide fine particles were subjected to heat treatment in a reduction furnace using a reducing atmosphere by flowing hydrogen-containing argon gas through the furnace. Table 21 shows the hydrogen concentration in the gas flowing through the reduction furnace, the treatment temperature, the treatment time, and the average primary particle size, Si-OH bond ratio, Si-O bond ratio, and Si-OH / Si-O bond ratio of the obtained silicon compound-coated metal fine particles. The dispersed particle size of the dispersion liquid obtained by dispersing the silicon compound-coated metal fine particles in each example in pure water and toluene (manufactured by Kanto Chemical Co., Ltd.) as dispersion media is also shown, using the volume-average particle size obtained from particle size distribution measurements. (Note that the results for silicon compound-coated metal fine particles are for Examples 5-1 to 5-10.)

[0117] [Table 21]

[0118] Figure 6 shows the STEM mapping results of silicon compound-coated silicon-aluminum doped iron nanoparticles obtained in Example 5-5. As seen in Figure 5, it can be seen that the surface of the silicon-aluminum doped iron nanoparticles is coated with a silicon compound containing silicon oxide. Similar STEM mapping results were obtained for Examples 5-1 to 5-4 and Examples 5-6 to 5-8. Furthermore, it was confirmed that the silicon contained in the silicon-aluminum doped iron nanoparticles migrated toward the vicinity of the particle surface as the processing temperature increased or the processing time was extended.

[0119] XRD measurement results showed that silicon compound-coated silicon-aluminum doped iron nanoparticles obtained under the conditions of Examples 5-1 to 5-3 also showed peaks of oxides such as magnetite. However, silicon-aluminum doped iron nanoparticles obtained under Examples 5-4 to 5-8 did not show oxide peaks, but rather peaks close to those of iron alone. As a representative example, the measurement results for Example 5-5 are shown in Figure 7. Figure 8 shows the peak positions of iron (Fe: Metal) in the database relative to the peak list of measurement results shown in Figure 7, with magnified views of the area around each peak. As can be seen in Figure 8, the XRD measurement results for the silicon-aluminum doped iron nanoparticles obtained in Example 5-5 show peaks close to those of iron, but the peak positions are shifted relative to iron itself. It is thought that the above XRD measurement results were obtained because the silicon-aluminum doped iron nanoparticles are composed of a solid solution of iron, silicon, and aluminum.

[0120] As shown in Table 21, silicon compound coated metal nanoparticles can be obtained by treating silicon compound coated precursor nanoparticles in a reducing atmosphere, and it was also found that the dispersibility of silicon compound coated metal nanoparticles can be controlled by controlling the Si-OH bond / Si-O bond ratio contained in the silicon compound coated metal nanoparticles.

Claims

1. A conductive composition comprising silicon compound-coated metal nanoparticles in which a portion of the surface of metal nanoparticles made of at least one metal element or metalloid element is coated with a silicon compound, The ratio of Si-OH bonds contained in the above silicon compound-coated metal nanoparticles is controlled to be between 0.1% and 70%. The above Si-OH bond is attributed to the peak with the largest area ratio among the peaks derived from Si-OH bonds that were waveform-separated in the wavenumber region of 850 cm⁻¹ to 980 cm⁻¹, obtained by waveform separation of the peaks in the wavenumber region of 750 cm⁻¹ to 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method). The ratio of the above Si-OH bond is the ratio of the area of ​​the peak attributed to the above Si-OH bond to the total area of ​​the peaks obtained by waveform separation of the peaks in the wavenumber region of 750 cm⁻¹ to 1300 cm⁻¹. The above silicon compound coated metal nanoparticles are characterized in that a portion of the surface of a single metal nanoparticle is coated with a silicon compound, the primary particle diameter of the metal nanoparticle is 1 μm or less, and the primary particle diameter of the silicon compound coated metal nanoparticle is 100.5% or more and 190% or less of the primary particle diameter of the metal nanoparticle.

2. A conductive composition comprising silicon compound-coated metal nanoparticles in which a portion of the surface of metal nanoparticles made of at least one metal element or metalloid element is coated with a silicon compound, The ratio of Si-OH bonds contained in the above silicon compound-coated metal nanoparticles is controlled to be between 0.1% and 70%. The above Si-OH bond is attributed to the peak with the largest area ratio among the peaks derived from Si-OH bonds that were waveform-separated in the wavenumber region of 850 cm⁻¹ to 980 cm⁻¹, obtained by waveform separation of the peaks in the wavenumber region of 750 cm⁻¹ to 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method). The ratio of the above Si-OH bond is the ratio of the area of ​​the peak attributed to the above Si-OH bond to the total area of ​​the peaks obtained by waveform separation of the peaks in the wavenumber region of 750 cm⁻¹ to 1300 cm⁻¹. The above-mentioned silicon compound-coated metal nanoparticles are characterized in that a portion of the surface of an aggregate formed by the aggregation of multiple metal nanoparticles is coated with a silicon compound, the diameter of the aggregate is 1 μm or less, and the particle size of the silicon compound-coated metal nanoparticles is 100.5% or more and 190% or less of the diameter of the aggregate.

3. A conductive composition comprising silicon compound-coated metal nanoparticles in which a portion of the surface of metal nanoparticles made of at least one metal element or metalloid element is coated with a silicon compound, The Si-OH bond / Si-O bond ratio, which is the ratio of Si-OH bonds to Si-O bonds in the silicon compound-coated metal nanoparticles mentioned above, is controlled to be between 0.001 and 700. The above Si-O bond is attributed to the peak with the largest area ratio among the peaks derived from Si-O bonds that were waveform-separated in the wavenumber region between 1000 cm⁻¹ and 1300 cm⁻¹, obtained by waveform-separating the peaks in the wavenumber region between 750 cm⁻¹ and 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method), and the above Si-OH bond is attributed to the peak with the largest area ratio among the peaks derived from Si-OH bonds that were waveform-separated in the wavenumber region between 850 cm⁻¹ and 980 cm⁻¹, obtained by waveform-separating the peaks in the wavenumber region between 750 cm⁻¹ and 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method), and the above Si-OH bond / Si-O bond ratio is the ratio of the area of ​​the peak attributed to the Si-OH bond to the area of ​​the peak attributed to the Si-O bond. The above silicon compound coated metal nanoparticles are characterized in that a portion of the surface of a single metal nanoparticle is coated with a silicon compound, the primary particle diameter of the metal nanoparticle is 1 μm or less, and the primary particle diameter of the silicon compound coated metal nanoparticle is 100.5% or more and 190% or less of the primary particle diameter of the metal nanoparticle.

4. A conductive composition comprising silicon compound-coated metal nanoparticles in which a portion of the surface of metal nanoparticles made of at least one metal element or metalloid element is coated with a silicon compound, The Si-OH bond / Si-O bond ratio, which is the ratio of Si-OH bonds to Si-O bonds in the silicon compound-coated metal nanoparticles mentioned above, is controlled to be between 0.001 and 700. The above Si-O bond is attributed to the peak with the largest area ratio among the peaks derived from Si-O bonds that were waveform-separated in the wavenumber region between 1000 cm⁻¹ and 1300 cm⁻¹, obtained by waveform-separating the peaks in the wavenumber region between 750 cm⁻¹ and 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method), and the above Si-OH bond is attributed to the peak with the largest area ratio among the peaks derived from Si-OH bonds that were waveform-separated in the wavenumber region between 850 cm⁻¹ and 980 cm⁻¹, obtained by waveform-separating the peaks in the wavenumber region between 750 cm⁻¹ and 1300 cm⁻¹ in the infrared absorption spectrum of the silicon compound coated metal nanoparticles measured using the total internal reflection method (ATR method), and the above Si-OH bond / Si-O bond ratio is the ratio of the area of ​​the peak attributed to the Si-OH bond to the area of ​​the peak attributed to the Si-O bond. The above-mentioned silicon compound-coated metal nanoparticles are characterized in that a portion of the surface of an aggregate formed by the aggregation of multiple metal nanoparticles is coated with a silicon compound, the diameter of the aggregate is 1 μm or less, and the particle size of the silicon compound-coated metal nanoparticles is 100.5% or more and 190% or less of the diameter of the aggregate.

5. The ratio of Si-OH bonds or the ratio of Si-OH bonds / Si-O bonds is measured at wavenumber 750 cm in the infrared absorption spectrum of the silicon compound-coated metal nanoparticles using total internal reflection (ATR) method. -1 From 1300cm -1 The conductive composition according to any one of claims 1 to 4, characterized in that it is obtained by waveform separation of peaks in the region.

6. The ratio of the above Si-OH bonds is controlled to be between 0.1% and 70%, or the ratio of the above Si-OH bonds to Si-O bonds is controlled to be between 0.001 and 700. The conductive composition according to any one of claims 1 to 5, characterized in that the dispersibility of the silicon compound-coated metal fine particles in the solvent is controlled.

7. An electronic material or semiconductor material comprising the conductive composition according to any one of claims 1 to 6.

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