Cerium oxide nanoparticles, dispersions containing cerium oxide nanoparticles, oxidizing agents, antiviral agents and antibacterial agents

Abstract

The present invention addresses the problem of providing: nanoparticles of cerium oxide having high oxidizing performance, antiviral performance, and antibacterial performance; and a dispersion including nanoparticles of cerium oxide. The present invention is nanoparticles of cerium oxide produced by adding an oxidizing agent to a solution that contains a boron compound represented by general formula (I) and cerium(III) ions.　Formula (I): BRn(OR')3-n In formula (I), n is an integer of 0-2, R represents either a C1-4 alkyl group, a phenyl group, or a tolyl group, and R' represents either a C1-4 alkyl group, a phenyl group, or a tolyl group. When multiple R or R' are present, each may be the same or different.

Description

[Technical Field]

[0001] The present invention relates to cerium oxide nanoparticles, a dispersion containing the nanoparticles, an oxidizing agent containing the nanoparticles or the dispersion, and an antiviral agent. and antibacterial Agent Regarding. [Background technology]

[0002] In recent years, with increasing awareness of safety and hygiene management, antibacterial technology that decomposes harmful substances and microorganisms has attracted attention. For example, titanium dioxide has the ability to oxidize and decompose organic substances through its photocatalytic properties, and its performance has been evaluated in the decomposition reaction of organic dyes. In addition to being used as an antibacterial agent, such oxidative decomposition properties are expected to be used in applications such as decomposing various harmful substances, including low-molecular-weight substances such as acetaldehyde and ammonia, allergens, and viruses. On the other hand, cerium oxide nanoparticles (nanoceria) have catalytic activity similar to that of oxidizing enzymes such as oxidase and peroxidase, and are expected to be used as oxidizing agents. Because this catalytic activity does not require a special light source such as ultraviolet light, it is expected that nanoceria will be used to decompose harmful substances even in situations where titanium oxide is difficult to use, such as indoors or in dark places.

[0003] When metal nanoparticles that tend to aggregate are used as oxidizing agents, a stabilizer compound is used during synthesis to stably disperse the resulting nanoparticles. For example, in the case of cerium oxide nanoparticles, a particle dispersion is obtained by oxidizing cerium (III) ions with hydrogen peroxide using polyacrylic acid as a stabilizer, or by neutralizing cerium (III) ions with an alkali in ammonia water using dextran as a stabilizer.

[0004] Here, Non-Patent Document 1 describes a method for synthesizing cerium oxide nanoparticles whose surfaces are coated with polyacrylic acid or dextran. Non-Patent Document 1 discloses that, in particular, when polyacrylic acid is used as a stabilizer, oxidase activity, which is a value indicating oxidizing performance, increases.

[0005] Furthermore, Patent Document 1 discloses a polishing composition containing colloidal ceria whose surface has been modified with boric acid, and describes that the particles are negatively charged and thus stably dispersed over a wide pH range.

[0006] Furthermore, Patent Document 2 discloses a reverse micelle composition in which nanoceria and boric acid stabilized with organic carboxylic acids such as ethylenediaminetetraacetic acid (EDTA) and lactic acid are dispersed in hydrocarbon liquid or diesel fuel, and describes that adding this composition to fuel improves the efficiency of diesel engines. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] A. Asati,Angew. Chem. Int. Ed. 2009, 48, 2308-2312. [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-183631 [Patent Document 2] Special Publication No. 2010-502821 Summary of the Invention [Problem to be solved by the invention]

[0009] The present inventors have investigated applications that utilize the oxidizing properties of cerium oxide nanoparticles. However, when oxidatively decomposing organic dyes using cerium oxide nanoparticles whose surfaces are coated with polyacrylic acid as described in Non-Patent Document 1 or commercially available cerium oxide nanoparticles, the decomposition rate was low. Furthermore, a production method based on Patent Document 1 in which boric acid is added to cerium oxide nanoparticles to modify their surfaces also resulted in a low decomposition rate. Furthermore, a dispersion based on Patent Document 2 in which boric acid is added to cerium oxide nanoparticles stabilized with EDTA / lactic acid also resulted in a low decomposition rate. Based on these results, further investigations were conducted with the goal of finding cerium oxide nanoparticles with high oxidizing properties. [Means for solving the problem]

[0010] In order to solve the above problems, the present inventors have focused on a method for producing cerium oxide nanoparticles, and have studied stabilizers in particular. As a result, they have found that the stabilizers of the general formula BR n (OR') 3-n We have found that a dispersion containing cerium oxide nanoparticles, produced by adding an oxidizing agent to a solution containing a boron compound represented by the formula (I) and cerium (III) ions, exhibits a high oxidative decomposition rate of organic dyes. We have also found that the dispersion produced in this manner also has high antiviral performance, leading to the completion of the present invention.

[0011] The present invention is as follows. (1) Cerium oxide nanoparticles produced by adding an oxidizing agent to a solution containing a boron compound represented by the following general formula (I) and cerium (III) ions: BR n (OR') 3-n (I) In formula (I), n is an integer of 0 to 2, R is any one of an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group, and R' is any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group. When there are multiple R or R', they may be the same or different. (2) The cerium oxide nanoparticles according to (1), wherein the pH of the solution when the oxidizing agent is added is 5 or higher. (3) Cerium oxide nanoparticles according to (1) or (2), wherein the boron compound represented by the general formula (I) is boric acid, a borate ester, a boronic acid, a boronate ester, borinic acid, a borinic acid ester, or a borate salt. (4) Cerium oxide nanoparticles according to any one of (1) to (3), containing 0.001 moles or more of boron per mole of elemental cerium. (5) Cerium oxide nanoparticles containing a boron compound represented by the general formula (I), the cerium oxide nanoparticles according to any one of (1) to (4), having absorption maxima between 5726 and 5729 eV and between 5735 and 5739 eV in an XANES spectrum. (6) Cerium oxide nanoparticles according to any one of (1) to (5), containing 0.0001 moles or more of a transition metal per mole of elemental cerium.

[0012] (7) Cerium oxide nanoparticles containing a boron compound represented by the following general formula (I), which have absorption maxima between 5726 and 5729 eV and between 5735 and 5739 eV in an XANES spectrum. BR n (OR') 3-n (I) In formula (I), n is an integer of 0 to 2, R is any one of an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group, and R' is any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group. When there are multiple R or R', they may be the same or different. (8) The cerium oxide nanoparticles according to (7), wherein the boron compound represented by the general formula (I) is boric acid, a borate ester, a boronic acid, a boronic acid ester, borinic acid, a borinic acid ester, or a borate. (9) A dispersion containing cerium oxide nanoparticles according to any one of (1) to (8). (10) An oxidizing agent comprising the cerium oxide nanoparticles according to any one of (1) to (8) or the dispersion according to (9). (11) An antiviral agent comprising the cerium oxide nanoparticles according to any one of (1) to (8) or the dispersion according to (9). (12) An antibacterial agent comprising the cerium oxide nanoparticles according to any one of (1) to (8) or the dispersion according to (9). [Effects of the Invention]

[0013] The cerium oxide nanoparticles of the present invention or a dispersion containing the nanoparticles can be used to oxidatively decompose organic matter and various hazardous substances at a higher yield than conventional cerium oxide nanoparticles. Furthermore, the cerium oxide nanoparticles of the present invention or a dispersion containing the nanoparticles can be used as a high-performance antiviral and antibacterial agent that inactivates various viruses. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows the Ce L3 edge XANES spectra of the cerium oxide nanoparticles prepared in Example 1 and Comparative Example 2, measured in Example 18. [Figure 2] FIG. 2 shows the Ce L3 edge XANES spectra of the cerium oxide nanoparticles prepared in Example 2 and Comparative Example 5, measured in Example 18. [Figure 3] FIG. 3 shows the Ce L3 edge XANES spectra of the cerium oxide nanoparticles prepared in Example 12 and Comparative Example 2, measured in Example 18. [Figure 4] FIG. 4 shows the Ce L3 edge XANES spectra of cerium oxide crystals, cerium carbonate (III), cerium nitrate (III), and ammonium cerium nitrate (IV), measured in Reference Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] The cerium oxide nanoparticles of the present invention may be referred to herein simply as the nanoparticles of the present invention, and the dispersion containing the cerium oxide nanoparticles of the present invention may be referred to herein simply as the dispersion of the present invention.

[0016] The cerium oxide nanoparticles of the present invention are produced by adding an oxidizing agent to a solution containing a boron compound represented by the following general formula (I) and cerium (III) ions. The synthesis of the cerium oxide nanoparticles of the present invention uses a water-soluble cerium salt as one of the raw materials, and the synthesis is carried out in water or a solvent compatible with water. In one embodiment, a boron compound having the structure represented by general formula (I) is used as a stabilizer, from the viewpoint of having appropriate hydrophilicity and possessing the property of stably dispersing nanoparticles by forming a complex with the hydroxyl groups of metal oxides. BR n (OR') 3-n (I) In formula (I), n is an integer of 0 to 2, R is any one of an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group, and R' is any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group. Multiple R or R' may be the same or different.

[0017] More preferred embodiments of the boron compound used in the present invention include boric acid (in the general formula (I), n=0, R=H, R'=H), boric acid ester (in the general formula (I), n=0, R=H, R'=alkyl, etc.), boronic acid (in the general formula (I), n=1, R=alkyl, etc., R'=H), boric acid ester (in the general formula (I), n=1, R=alkyl, etc., R'=alkyl, etc.), borinic acid (in the general formula (I), n=2, R=alkyl, etc., R'=H), boric acid ester (in the general formula (I), n=2, R=alkyl, etc., R'=alkyl, etc.), and boric acid salts. In the present invention, boric acid salts are a general term that includes salts of boric acid and salts of metaboric acid, polyboric acid, etc., which are formed by dehydration condensation of boric acid. These borates are in an equilibrium state between boric acid and tetrahydroxyboric acid in aqueous solution, and therefore take the boric acid structure shown in general formula (I) in solution. The counter ion of boric acid in the borate salt can be any ion, such as lithium ion, sodium ion, potassium ion, or ammonium ion.

[0018] Examples of such boron compounds include boric acid, boric acid esters such as trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, and triisobutyl borate, and boronic acids such as methylboronic acid, ethylboronic acid, propylboronic acid, isopropylboronic acid, butylboronic acid, isobutylboronic acid, and phenylboronic acid. Examples of boric acid salts include lithium salts, sodium salts, potassium salts, and ammonium salts of boric acid, metaboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, hexaboric acid, and octaboric acid.

[0019] The cerium oxide nanoparticles according to the present invention preferably contain 0.001 to 10 moles of boron per mole of elemental cerium, more preferably 0.001 to 1 mole.

[0020] In the present invention, cerium oxide nanoparticles are composed of a mixture of Ce2O3 and CeO2. In addition to the oxide form, cerium oxide may also be in the form of a hydroxide or oxyhydroxide. The ratio of Ce2O3 to CeO2 can be calculated as the ratio of cerium (III) to cerium (IV) using X-ray photoelectron spectroscopy (XPS) or other methods.

[0021] The cerium oxide nanoparticles of the present invention can further contain transition metals from groups 3 to 12 of the periodic table. These metals take on a valence of 2+ to 3+, which can be expected to improve performance by creating lattice defects when doped into cerium oxide nanoparticles, or by causing a valence change of cerium oxide, such as between O and 1+, between 1+ and 2+, or between 2+ and 3+, depending on the redox potential, thereby improving performance. These transition metals are preferably transition metals of periods 4 to 6, and more preferably Ti, Mn, Fe, Co, Ni, Cu, Zn, Zr, and Ag, because they are easily doped into cerium oxide nanoparticles and further improve the antibacterial and antiviral effects. These transition metals can be added during synthesis in the form of salts such as organic acid salts (e.g., carboxylates, sulfonates), phosphorus oxo acid salts (e.g., phosphates, phosphonates), inorganic acid salts (e.g., nitrates, sulfates, carbonates), halides, hydroxides, etc. These salts may be dissolved in the synthesis solvent.

[0022] The dispersion containing cerium oxide nanoparticles of the present invention is produced by a production method in which an oxidizing agent is added to a solution containing a boron compound and cerium (III) ions. The production method for the dispersion of cerium oxide nanoparticles of the present invention is described below.

[0023] The first step is to obtain a solution containing a boron compound and cerium (III) ions. The boron compound solution used in this step can be prepared by dissolving the boron compound in any solvent. The solvent is preferably water or a water-compatible solvent. Specific examples of water-compatible solvents include methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, tetrahydrofuran, acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, and oligoethylene glycol. When the boron compound contains a substituent with three or fewer carbon atoms, the boron compound is preferably dissolved in water. When the boron compound contains a substituent with four or more carbon atoms, the boron compound is preferably dissolved in a 50% aqueous ethylene glycol solution. When the boron compound is poorly soluble in the solvent, it may be dissolved by heating or ultrasonic treatment.

[0024] The amount of the boron compound may be in the range of 0.1 to 1000 molar equivalents relative to the cerium (III) ion, preferably 1 to 200 molar equivalents, more preferably 5 to 200 molar equivalents, and most preferably 10 to 100 molar equivalents.

[0025] To obtain a solution containing a boron compound and cerium (III) ions, a solution of the boron compound and a solution containing cerium (III) ions may be prepared separately and then mixed together, or, if the solvent for the solution of the boron compound is water or a solvent compatible with water, a cerium (III) salt may be added to the solution of the boron compound and then mixed together. A solution containing cerium(III) ions can be prepared by dissolving a cerium(III) salt, such as cerium(III) nitrate hexahydrate, in a suitable solvent.

[0026] The amount of cerium (III) salt to be mixed with the boron compound solution is such that the final concentration in the reaction solution is in the range of 0.01% by mass to 10% by mass. The mixed solution is preferably mixed for 5 minutes or more until the solution becomes homogeneous.

[0027] In the first step, the solution containing the boron compound and cerium (III) ions preferably does not contain a trivalent or higher carboxylic acid, such as the compounds shown below. Even if it is contained, the amount thereof is preferably 0.1 equivalents or less, more preferably 0.01 equivalents or less, relative to the cerium (III) ions. Specific examples of trivalent or higher carboxylic acids include nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), glycoletherdiaminetetraacetic acid (EGTA), diethylenetriaminopentaacetic acid (DTPA), citric acid, hydroxyethylethylenediaminetetraacetic acid (HEDTA), polyacrylic acid, and / or salts thereof.

[0028] When doping the cerium oxide nanoparticles of the present invention with a metal, a transition metal may be further added in the first step. The transition metal may be added directly as a solid metal salt to a solution containing a boron compound and cerium(III) ions or a cerium(III) salt, or a solution prepared by dissolving the metal salt in any solvent may be added to a solution containing a boron compound and cerium(III) ions or a cerium(III) salt. The amount of the transition metal is preferably in the range of 0.0001 mol to 0.3 mol per mol of cerium (III) ions, and more preferably in the range of 0.001 mol to 0.2 mol. Note that the amount of the transition metal does not include the amount of elements other than the transition metal contained in the transition metal salt.

[0029] The second step is a step of adding an oxidizing agent to the mixed solution obtained in the first step. Examples of oxidizing agents used in the second step include nitric acid, potassium nitrate, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, halogens, hydrogen halides, permanganates, chromic acid, dichromate, oxalic acid, hydrogen sulfide, sulfur dioxide, sodium thiosulfate, sulfuric acid, and hydrogen peroxide. Among these, hydrogen peroxide is particularly preferred. The amount of oxidizing agent added is 0.1 to 10 molar equivalents relative to cerium(III) ions, preferably 0.5 to 2 molar equivalents.

[0030] When an oxidizing agent is added to a solution containing a boron compound and cerium(III) ions, the cerium(III) ions are oxidized to cerium(IV), initiating a reaction to form cerium oxide particles composed of a mixture of Ce2O3 and CeO2. During this reaction, the solution turns yellow, orange, red, brown, or other colors. This coloration occurs as the cerium(III) ions are converted to cerium(IV), and the degree of coloration is determined by the ratio of cerium(III) to cerium(IV) present on the surface of the cerium oxide nanoparticles. The end of the reaction can be determined when the color change ceases.

[0031] The cerium oxide nanoparticle formation reaction can be carried out at any pH. However, because the reaction proceeds more easily in a weakly acidic to basic environment, the pH of the solution when the oxidizing agent is added is preferably adjusted to 5 or higher, more preferably 6 or higher, and even more preferably 7 or higher. To adjust the pH, aqueous sodium hydroxide or aqueous ammonia can be used. Furthermore, since the pH of the solution becomes more acidic as the reaction proceeds, the pH of the reaction solution may be maintained at 5 or higher from the time of adding the oxidizing agent until the end of the reaction. The reaction typically completes within 5 minutes to 1 hour, yielding a dispersion containing the cerium oxide nanoparticles of the present invention. For example, adding 1 ml of a 10% by weight aqueous solution of cerium(III) nitrate hexahydrate to a 284 mg / 50 ml aqueous solution of boric acid adjusted to pH 8, followed by the addition of 1 ml of a 1.2% by weight aqueous solution of hydrogen peroxide, and stirring at room temperature, causes the solution to turn orange, and the particle formation reaction is completed within approximately 10 minutes, yielding the dispersion of the present invention.

[0032] The reaction for forming cerium oxide nanoparticles can be carried out at any temperature between 4°C and 230°C. Heating to temperatures above 100°C can be carried out by hydrothermal treatment, using a cooling bath, such as Yamato Scientific Co., Ltd.'s BBL101. Heating can be carried out using a hot bath, such as Tokyo Rikakiki Co., Ltd.'s OHB-1100S. For heating below 100°C, the reaction solution can be placed in a glass container and heated. For hydrothermal treatment above 100°C, the reaction solution can be placed in a pressure-resistant container consisting of a PTFE inner cylinder and a pressure-resistant stainless steel outer cylinder. Hydrothermal treatment can also be carried out by placing the reaction solution in a medium bottle and using a sterilizer, such as Tommy Kogyo Co., Ltd.'s LSX-500.

[0033] The pH of the dispersion of the present invention may be adjusted after the reaction is completed. The pH of the dispersion of the present invention may be in the range of pH 1 to 10, and preferably pH 2 to 8. The pH may be adjusted by adding a buffer solution, or an acid such as nitric acid, sulfuric acid, or hydrochloric acid, or a base such as sodium hydroxide or potassium hydroxide. The pH of the dispersion may also be adjusted after purification of the dispersion, such as filtration with an ultrafiltration membrane or dialysis with a semipermeable membrane, as described below.

[0034] After the reaction is complete, the dispersion of the present invention can be filtered using an ultrafiltration membrane or dialyzed using a semipermeable membrane to remove unreacted oxidizing agent, cerium (III) ions, and excess boron compounds remaining in the dispersion after the reaction is complete. Cerium oxide nanoparticles can then be isolated from the dispersion of the present invention using the method described below.

[0035] After the purification, the dispersion of the present invention may be subjected to a heat treatment at any temperature between 30°C and 230°C. Heating at 100°C or higher can be performed by hydrothermal treatment at 100°C to 230°C. For heating, a hot bath such as the OHB-1100S manufactured by Tokyo Rikakiki Co., Ltd. can be used. For heating at 100°C or lower, the purified dispersion may be placed in a glass container and heated. For hydrothermal treatment at 100°C or higher, the purified dispersion may be placed in a pressure-resistant container consisting of a PTFE inner cylindrical container and a pressure-resistant stainless steel outer cylindrical container and heated. The hydrothermal treatment can also be performed by placing the purified dispersion in a medium bottle and using a sterilization device such as the LSX-500 manufactured by Tomy Kogyo Co., Ltd.

[0036] The cerium oxide nanoparticles of the present invention can be isolated by drying the dispersion of the present invention using an evaporator, freeze dryer, or the like. Alternatively, the cerium oxide nanoparticles can be isolated by dropping the dispersion of the present invention onto a substrate such as glass, plastic, or ceramic and air-drying, drying in a desiccator, or drying with a dryer or drier. Alternatively, the dispersion of the present invention can be dropped onto a heat block and heated to volatilize the solvent. Alternatively, the dispersion of the present invention can be dried using a spray dryer or the like to volatilize the solvent. Alternatively, the cerium oxide nanoparticles can be isolated by centrifuging the dispersion of the present invention to precipitate the cerium oxide nanoparticles and removing the supernatant. Alternatively, the dispersion of the present invention can be filtered by ultrafiltration or suction filtration to completely remove water, thereby isolating the cerium oxide nanoparticles on a filtration membrane. To improve the efficiency of the drying process in the above procedure, an azeotropic solvent may be added to the dispersion of the present invention, or the solvent in the dispersion may be replaced with a solvent with a lower boiling point. In order to improve the efficiency of the centrifugation operation, a coprecipitant may be added to the dispersion of the present invention, or a solvent that increases the ionic strength or decreases the dispersibility of the nanoparticles may be added. Prior to the above operation, the dispersion of the present invention may be fractionated by size based on the nanoparticles using an ultrafiltration membrane or centrifugation.

[0037] The dispersion of the present invention may contain an ionic component, such as a component that provides buffering properties, such as acetic acid, phthalic acid, succinic acid, carbonic acid, Tris(hydroxymethyl)aminomethane (Tris), 2-Morpholinoethanesulfonic acid monohydrate (MES), Bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane (Bis-Tris), N-(2-Acetamido)iminodiacetic acid (ADA), Piperazine-1,4-bis(2-ethanesulfonic acid) (PIPES), N-(2-Acetamido)-2-aminoethanesulfonic acid (ACES), 2-Hydroxy-3-morpholinopropanesulfonic acid (MOPSO), N,N-Bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), 3-Morpholinopropanesulfonic acid (MOPS), N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (ADA), or N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (ADA). acid(TES), 2-[4-(2-Hydroxyethyl)-1-piperazinyl]ethanesulfonic acid(HEPES), 2-Hydroxy-N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic(TAPSO), Piperazine-1,4-bis(2-hydroxy-3-propanesulfonic acid)(POPSO), 2-Hydroxy-3-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid(HEPSO), 3-[4-(2-Hydroxyethyl)-1-piperazinyl]propanesulfonic acid(HEPPS), (Tricine), N,Examples of ionic components include N-Bis(2-hydroxyethyl)glycine (Bicine) and N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS), and components that do not impart buffering properties include sodium chloride and potassium chloride. These ionic components can be added so that the final concentration is in the range of 0.1 mM to 1 M. These ionic components may be added to the dispersion after the reaction is completed, or after filtration through an ultrafiltration membrane, or may be used as a dialysis solution, or may be added to the dispersion after dialysis. They may also be added to dried cerium oxide nanoparticles to form a dispersion.

[0038] The dispersion of the present invention may be stored as a dispersion after completion of the reaction, or may be stored as a purified product obtained by filtering the dispersion after completion of the reaction using an ultrafiltration membrane or by dialyzing it using a semipermeable membrane, or may be stored as isolated cerium oxide nanoparticles after drying using an evaporator or freeze dryer. Furthermore, the dispersion may be stored as a dispersion containing an added solvent component such as the above-mentioned azeotropic solvent or an ionic component, or as a dispersant with an adjusted pH. When storing, refrigeration is preferred.

[0039] The hydrodynamic diameter of the cerium oxide nanoparticles of the present invention is determined by measuring dynamic light scattering to derive an autocorrelation function, analyzing it using the Marquadt method, and calculating the average particle diameter from a number-transformed histogram. Dynamic light scattering measurements are performed using an ELS-Z manufactured by Otsuka Electronics Co., Ltd. The hydrodynamic diameter of the cerium oxide nanoparticles may be 1 nm or more and 1000 nm or less, and preferably 1 nm or more and 200 nm or less.

[0040] The hydrodynamic diameter of the cerium oxide nanoparticles of the present invention can be controlled by the reaction temperature, which can be set at any temperature between about 4 and 90°C. A lower reaction temperature will yield particles with a smaller diameter, while a higher reaction temperature will yield particles with a larger diameter.

[0041] The cerium oxide nanoparticles or dispersions thereof of the present invention may be sterilized before use by passing them through a sterilizing filter, by autoclaving (e.g., at 120°C for 20 minutes), or by irradiating them with 254 nm ultraviolet light.

[0042] In the cerium oxide nanoparticles of the present invention, the energy states of cerium(III) and cerium(IV) in CeO and CeO can be observed by X-ray absorption fine structure (XAFS) spectroscopy. In the XAFS spectrum, the structure approximately 20 eV from the absorption edge is called XANES (X-ray absorption near edge structure), and the extended X-ray absorption fine structure that appears approximately 100 eV or more higher from the absorption edge is called EXAFS (Extended X-ray Absorption Fine Structure). Information about the valence and structure of the target atom can be obtained from XANES. EXAFS analysis, using Fourier transform (equivalent to FT-EXAFS / radial distribution function) of the real spectrum, provides information about the sample's local structure, atomic species, valence, and distance around the target atom. The energy states of cerium(III) and cerium(IV) in the redox reaction of cerium oxide are reflected in the peak position and peak intensity ratio of the maximum absorption peak in the XANES spectrum. The cerium oxide nanoparticles of the present invention have absorption maxima between 5726 and 5729 eV and 5735 and 5739 eV in the Ce L3-edge XANES spectrum obtained by X-ray absorption fine structure spectroscopy. That is, the cerium oxide nanoparticles of the present invention contain a boron compound represented by the general formula (I) and have absorption maxima between 5726 and 5729 eV and 5735 and 5739 eV in the XANES spectrum. In another embodiment, the cerium oxide nanoparticles of the present invention are produced by adding an oxidizing agent to a solution containing the boron compound represented by the general formula (I) and cerium(III) ions, and have absorption maxima between 5726 and 5729 eV and 5735 and 5739 eV in the XANES spectrum.

[0043] The cerium oxide nanoparticles or dispersions of the present invention can be used as oxidizing agents. For example, by utilizing their oxidizing properties, they can be used as homogeneous catalysts in organic synthesis reactions and polymer polymerization, or as wet etching solutions for semiconductors. Furthermore, by utilizing their oxidizing properties, they can be used as a solution to replace oxidizing enzyme solutions. Specifically, they can be used in detection reactions using antibody-antigen reactions and nucleic acid hybridization, or in tissue staining, as a replacement for oxidase or peroxidase solutions. They can also be used in electrochemical detection reactions by coating electrodes with cerium oxide nanoparticles to immobilize them. Furthermore, they can be used as bleaches and disinfectants by utilizing their oxidizing properties to decompose and remove dirt, odors, allergens, bacteria, fungi, and mold. Specifically, they can be used as bleaches to clean clothing, tableware, kitchens, toilets, washrooms, bathrooms, medical equipment, and other surfaces. Cleaning methods include soaking, spraying, and spraying using a humidifier or nebulizer. They can also be added to swimming pools, bathtubs, and hot springs as disinfectants, or used in body soap, hand washing detergent, disinfectant, gargle, mouthwash, hand gel, disinfectant spray, germicidal spray, deodorizing spray, wet tissue, and disinfectant sheets. Furthermore, the cerium oxide nanoparticles of the present invention may be left on an object after the cleaning or disinfection process, so that their deodorizing, antiviral, antibacterial, and antifungal effects can be sustained. Their performance as an oxidizing agent can be evaluated by the fading reaction of organic dyes, which will be described later.

[0044] When used as an oxidizing agent, the cerium oxide nanoparticles or dispersions thereof of the present invention can be used in combination with alcohols, surfactants, disinfectants, and natural organic substances. Examples of alcohols include ethanol and isopropyl alcohol. Examples of surfactants include benzalkonium chloride, benzethonium chloride, and alkylpolyaminoethylglycine. Examples of disinfectants include chlorhexidine, acrinol, merbromin, and crystal violet. Examples of natural organic substances include polyphenols, catechin, tannic acid, chitin, chitosan, isothiocyanates, hinokitiol, limonene, polylysine, terpenoids, saponins, flavonoids, and carotenes. When used, these may be combined in combination.

[0045] When the cerium oxide nanoparticles or dispersion thereof of the present invention are used as an oxidizing agent, they can be used in combination with other known oxidizing agents, such as hypochlorous acid, sodium hypochlorite, povidone-iodine, hydrogen peroxide, ozone water, and peracetic acid, or a combination of two or more of these.

[0046] The discoloration reaction of organic dyes is also used to evaluate the photocatalytic performance of titanium oxide, and the decomposition rate of the resulting dye is used as an indicator of the oxidative decomposition properties of organic matter. Because harmful substances such as low-molecular-weight compounds like acetaldehyde and ammonia, and allergens, are organic substances, these properties make titanium oxide promising for use as an antibacterial agent and for decomposing various harmful substances. Similarly, if the cerium oxide nanoparticles or dispersions thereof of the present invention have a high dye decomposition rate, they are likely to be used as antibacterial agents and for decomposing various harmful substances.

[0047] Specifically, the decomposition rate of the dye is calculated as follows. First, the dispersion of the present invention is mixed with an organic dye such as Acid Red 94 (AR94) and left to stand for a predetermined time. As a control, the same treatment is carried out on a solution of AR94 that does not contain cerium oxide nanoparticles. After the reaction, the absorption spectra of all the solutions are measured. For analysis, the absorbance at 552 nm, which is the maximum absorption wavelength of AR94, is used. The absorbance of the control (I c The difference between the absorbance (I) of the solution containing the cerium oxide nanoparticles of the present invention and the absorbance (I) of the solution containing the cerium oxide nanoparticles of the present invention (I c -I) and calculate the ratio of the absorbance to the control [((I c -I) / I c ) × 100] is calculated as the decomposition rate.

[0048] Furthermore, one preferred embodiment of the dispersion of the present invention is a dispersion containing a boron compound and cerium oxide nanoparticles, the dispersion containing cerium oxide nanoparticles having a decomposition rate of 25% or more in a decomposition reaction of Acid Red 94 at 40°C for 1 hour. Since the decomposition rate of Acid Red 94 is 25% or more in a decomposition reaction of Acid Red 94 at 40°C for 1 hour, the dispersion can be used as an oxidizing agent. The decomposition rate of Acid Red 94 in a decomposition reaction of Acid Red 94 at 40°C for 1 hour is preferably 50% or more, and particularly preferably 70% or more.

[0049] The cerium oxide nanoparticles or dispersions of the present invention can be used as an additive for imparting oxidation performance when they are added to fibers, tubes, beads, rubber, films, plastics, etc. during molding, or by coating the surfaces of these, for processing to provide deodorizing, antiallergic, antibacterial, antifungal, etc. Products processed with the cerium oxide nanoparticles or dispersions of the present invention include, for example, kitchen sink drain cover covers, drain stoppers, window glass fixing gaskets, mirror fixing gaskets, waterproof gaskets for bathrooms, washbasins, and kitchens, refrigerator door lining gaskets, bath mats, non-slip rubber for washbasins and chairs, hoses, shower heads, gaskets used in water purifiers, plastic products for water purifiers, gaskets used in washing machines, plastic products for washing machines, masks, medical caps, medical shoe covers, air conditioner filters, air purifier filters, vacuum cleaners, etc. Examples of suitable applications include car filters, ventilation fan filters, vehicle filters, air conditioning filters, air conditioner fins, air conditioner outlet louvers, and other plastic parts and blower fans, car air conditioner fins, car air conditioner outlet louvers, and other plastic parts and blower fans, clothing, bedding, netting for screen doors, chicken coop netting, mosquito netting, and other netting, wallpaper, windows, blinds, interior materials for buildings such as hospitals, interior materials for trains and automobiles, vehicle seats, blinds, chairs, sofas, virus-handling equipment, and building materials such as doors, ceiling panels, floor panels, and windows. Thus, products processed with the cerium oxide nanoparticles of the present invention or a dispersion thereof can be used as sanitary materials in a variety of fields.

[0050] The cerium oxide nanoparticles or dispersion thereof of the present invention can be used as an antiviral agent. To evaluate their performance as an antiviral agent, the cerium oxide nanoparticles or dispersion thereof of the present invention are brought into contact with or mixed with a virus, and then the amount of virus is quantified. Methods for quantifying the virus include measuring the amount of virus antigens by ELISA, quantifying viral nucleic acids by PCR, measuring the infectivity titer by the plaque method, and measuring the infectivity titer by the 50% infectivity dose assay. In the present invention, the antiviral performance is preferably measured by measuring the infectivity titer by the plaque method or the 50% infectivity dose assay. The unit of the virus infectivity titer is TCID when tested on cultured cells in the 50% infectivity dose assay. 50 (Tissue culture infectious dose 50), EID 50 (Egg infectious dose 50), LD in animals 50 The infectivity titer is expressed as Lethal dose 50 (Lethal dose 50). Methods for calculating the infectivity titer from the data obtained in the 50% infectivity dose measurement method include the Reed-Muench method, the Behrens-Kaeber method, and the Spearman-Karber method, but in the present invention, it is preferable to use the Reed-Muench method. The standard for judging antiviral activity is generally that the antiviral activity is judged to be effective if the logarithmic reduction in infectivity titer is 2.0 or more compared to the infectivity titer before the application of the cerium oxide nanoparticles of the present invention or a control not containing the nanoparticles of the present invention.

[0051] Furthermore, a preferred embodiment of the dispersion containing cerium oxide nanoparticles of the present invention comprises a boron compound and cerium oxide nanoparticles, and has a viral infectivity titer (TCID) of 50% in a virus inactivation test using a cell culture as determined by a 50% infectious dose measurement method. 50 The logarithmic reduction in the viral infectivity titer (TCID) in a virus inactivation test is 2.0 or more compared to the infectivity titer before the application of the cerium oxide nanoparticles of the present invention or a control not containing the nanoparticles of the present invention. 50When the logarithmic reduction in virus infectivity is 2.0 or more, the compound can be used as an antiviral agent. The logarithmic reduction in virus infectivity is preferably 2.5 or more, and particularly preferably 3.0 or more.

[0052] Examples of viruses that can be inactivated by the cerium oxide nanoparticles or dispersions thereof of the present invention include rhinovirus, poliovirus, foot-and-mouth disease virus, rotavirus, norovirus, enterovirus, hepatovirus, astrovirus, sapovirus, hepatitis E virus, influenza A, B, and C viruses, parainfluenza virus, mumps virus, measles virus, human metapneumovirus, respiratory syncytial virus, Nipah virus, Hendra virus, yellow fever virus, dengue virus, Japanese encephalitis virus, West Nile virus, hepatitis B and C viruses, eastern and western equine encephalitis virus, Onyong-nyong virus, rubella virus, and Lassa virus. , Junin virus, Machupo virus, Guanarito virus, Sabia virus, Crimean-Congo hemorrhagic fever virus, sandfly fever, hantavirus, Sin Nombre virus, rabies virus, Ebola virus, Marburg virus, bat lyssavirus, human T-cell leukemia virus, human immunodeficiency virus, human coronavirus, SARS-CoV, SARS-CoV 2, human porvovirus, polyomavirus, human papillomavirus, adenovirus, herpesvirus, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, smallpox virus, monkeypox virus, cowpox virus, molluscipox virus, and parapox virus.

[0053] When used as an antiviral agent, the cerium oxide nanoparticles of the present invention or a dispersion thereof can be kneaded as an additive into materials such as fibers, tubes, beads, rubber, films, and plastics, or coated on the surface of these materials. For example, they can be used in a variety of fields, including masks, medical caps, medical shoe covers, air conditioner filters, air purifier filters, vacuum cleaner filters, ventilation fan filters, vehicle filters, air conditioning filters, plastic parts and blower fans such as air conditioner fins and air conditioner outlet louvers, car air conditioner fins and car air conditioner outlet louvers, plastic parts and blower fans, clothing, bedding, nets for screen doors, chicken coop nets, and mosquito nets, wallpaper, windows, blinds, interior materials for buildings such as hospitals, interior materials for trains and automobiles, vehicle seats, blinds, chairs, sofas, virus-handling equipment, and building materials such as doors, ceiling panels, floor panels, and windows.

[0054] The cerium oxide nanoparticles or dispersions thereof of the present invention can be used as antibacterial agents. An example of a method for evaluating antibacterial performance is EN1040:2005, the European Norm (EN) standard test method. In this test method, a bacterial solution is added to a test solution containing the active ingredient of the antibacterial agent, and the number of bacterial cells is measured after a certain period of time. The bacterial solution contains 0.85% NaCl and 0.1% tryptone as medium components and is mixed so that the volume ratio of test solution to bacterial solution is 9:1. Antibacterial activity is generally determined to be present if the logarithmic reduction in bacterial cell count is 2.0 or greater compared to the number of bacterial cells before application of the cerium oxide nanoparticles of the present invention or a control without the nanoparticles of the present invention. Methods for quantifying bacterial cell count include measuring bacterial cell mass by turbidity (OD600), measuring bacterial cell mass by colony formation assay, and quantifying nucleic acid in bacterial cells by PCR. In the present invention, antibacterial performance is preferably measured by measuring the infectivity titer by turbidity measurement or colony formation assay.

[0055] Furthermore, one preferred embodiment of the dispersion containing the cerium oxide nanoparticles of the present invention contains a boron compound and cerium oxide nanoparticles, and the logarithmic reduction in bacterial cell count is 2.0 or more relative to the infectivity titer before the cerium oxide nanoparticles of the present invention are applied or to a control not containing the nanoparticles of the present invention. Since the logarithmic reduction in bacterial cell count in an antibacterial test is 2.0 or more, the dispersion can be used as an antibacterial agent. The logarithmic reduction in bacterial cell count is preferably 2.5 or more, and particularly preferably 3.0 or more.

[0056] Examples of microorganisms against which the cerium oxide nanoparticles or dispersions of the present invention exhibit antibacterial activity include the following: Bacteria include Gram-positive and Gram-negative bacteria. Gram-negative bacteria include, for example, Escherichia bacteria such as Escherichia coli, Salmonella bacteria such as Salmonella, Pseudomonas bacteria such as Pseudomonas aeruginosa, Shigella bacteria such as Shigella, Klebsiella bacteria such as Klebsiella pneumoniae, and Legionella bacteria such as Legionella pneumophila. Gram-positive bacteria include, for example, Staphylococcus bacteria such as Staphylococcus, Bacillus bacteria such as Bacillus subtilis, and Mycobacterium bacteria such as Mycobacterium tuberculosis. Fungi include fungi and yeast. Examples of fungi include filamentous fungi of the genus Aspergillus such as Aspergillus niger, filamentous fungi of the genus Penicillium such as Penicillium niger, filamentous fungi of the genus Cladosporium such as Aspergillus niger, filamentous fungi of the genus Alternaria such as Sooty mold, filamentous fungi of the genus Trichoderma such as Aspergillus oryzae, and filamentous fungi of the genus Chaetomium such as Chaetomium niger. Examples of yeasts include yeasts of the genus Saccharomyces such as baker's yeast and brewer's yeast, and yeasts of the genus Candida such as Candida albicans.

[0057] The cerium oxide nanoparticles or dispersions thereof of the present invention can be added to disinfectants to impart antiviral or antibacterial effects to the disinfectants. The disinfectants may contain disinfecting components such as chlorine-based, iodine-based, peroxide-based, aldehyde-based, phenol-based, biguanide-based, mercury-based, alcohol-based, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and naturally occurring substances as active ingredients.

[0058] In the case of a liquid disinfectant, the concentration of the cerium oxide nanoparticles of the present invention can be set arbitrarily between 0.0001% by mass and 10% by mass.

[0059] Examples of chlorine-based disinfecting components include sodium hypochlorite, chlorine, and chlorinated isocyanuric acid.

[0060] Examples of iodine-based disinfectants include iodine, povidone iodine, nonoxynol iodine, and phenoxy iodine.

[0061] Examples of peroxide-based disinfectants include hydrogen peroxide, potassium permanganate, peracetic acid, organic peracids, sodium percarbonate, sodium perborate, and ozone.

[0062] Examples of aldehyde disinfectants include glutaraldehyde, phthalal, and formaldehyde.

[0063] Examples of phenolic disinfectant components include isopropylmethylphenol, thymol, eugenol, triclosan, cresol, phenol, chlorocresol, parachlorometacresol, parachlorometaxylenol, orthophenylphenol, alkyl parahydroxybenzoate, resorcinol, hexachlorophene, salicylic acid or its salts, etc.

[0064] Examples of biguanide disinfectants include chlorhexidine, chlorhexidine gluconate, and chlorhexidine hydrochloride.

[0065] Examples of mercury-based disinfectants include mercurochrome, mercuric chloride, and thimerosal.

[0066] Examples of alcohol-based disinfectant components include ethanol, isopropanol, etc. In this case, the concentration of the alcohol-based disinfectant component may be 30 to 80% by mass.

[0067] Examples of anionic surfactant disinfectant components include alkylbenzene sulfonates, fatty acid salts, higher alcohol sulfates, polyoxyethylene alkyl ether sulfates, α-sulfofatty acid esters, α-olefin sulfonates, monoalkyl phosphate esters, and alkanesulfonates.

[0068] Examples of cationic surfactant disinfecting components include alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, polyhexamethylene biguanide, and benzethonium chloride.

[0069] Examples of amphoteric surfactant disinfecting components include alkylamino fatty acid salts, alkylbetaines, and alkylamine oxides.

[0070] Examples of disinfectant ingredients in nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene-polyoxypropylene alkyl ethers, polyoxyethylene-polyoxybutylene alkyl ethers, alkylamine ethoxylates, alkylamine alkoxylates, polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene-polyoxypropylene block copolymers (reverse type), ethylene oxide-propylene oxide adducts of polyhydric alcohols, alkyl glucosides, and fatty acid alkanolamides.

[0071] Examples of naturally derived disinfectant ingredients include plant-based agents such as hinokitiol, anethole, anise oil, borneol, camphor, carvone, cassia oil, chenopodium oil, cineole, citral, citronellal, eugenol, pinene, geraniol, lemon oil, liolol, menthol, orange oil, safrole, thymol, and polyphenols (flavanols, gallotannins, ellagitannins, and phlorotannins); animal-based agents such as chitin and chitosan made from crustacean shells, and baked shell powder obtained by baking scallop or oyster shells; microbial agents such as polylysine; and enzyme-based agents such as lysozyme. Antibacterial peptides that are produced by living organisms to defend themselves against external microorganisms can also be used, such as histatin, defensin, lactoferrin, lactoferrcin (a breakdown product of lactoferrin), magainin, cecropin, and melititin.

[0072] Plant extracts can also be used as naturally occurring disinfecting ingredients. Specific examples include grapefruit seed extract, celandine (Chenopodiaceae), etc., Iridaceae, etc., St. John's wort (Hyperiaceae), etc., Burseraceae, Gilead balsam (Gilead balsam), etc., Campanulaceae, etc., Asteraceae, echinacea, chamomile, burdock, goldenrod, narrow-leaved holly (Asteraceae), Coptis japonica (Ranunculaceae), etc., Caprifoliaceae, honeysuckle (Honeysuckle), Lauraceae, etc., Moraceae, etc., Lamiaceae, Scutellaria, oregano, Japanese holly, sage, thyme, mountain mint, Japanese perilla, lavender, rosemary, etc., Zingiberaceae, ginger, etc., Caprifoliaceae, Sambucus nigra, etc., Pinaceae, etc.,, Apiaceae, umbellata, bonsai, etc. Examples of plant extracts include those from plants such as: Polygonaceae (willow), Polygonaceae (willow), Ericaceae (cornus), Houttuynia cordata, Tribulus terrestris, Vitaceae (cayenne), Allspice, tea tree, eucalyptus, clove, etc., Leguminosae (sophora), Sophora japonica, Rosewood, and Purple jasmine, etc., Hamamelidaceae (watermelon), etc., Rutaceae (Phenocarpus amurense, Citrus unshiu, etc.), Boraginaceae (comfrey), etc., Berberidaceae (barberry), Nandina, etc.,, Magnoliaceae (magnoliaceae), Burntwood and rose, etc.,, Mistletoe, etc.,, Liliaceae (anemone), Balsam, and Glycyrrhiza, etc.,, Gentianaceae (jasmine), etc., Moso bamboo, etc.,, and Fucophyllum nodosum, etc.,,

[0073] Ultrafine bubbles include those with a particle diameter of 500 nm or less that contain one or more gases selected from air, oxygen, hydrogen, nitrogen, carbon dioxide, argon, neon, xenon, fluorinated gases, ozone, and inert gases. Ultrafine bubbles are also called nanobubbles. The concentration should be 100,000 bubbles / ml or more.

[0074] In addition to the disinfectant components described above, the disinfectant containing the cerium oxide nanoparticles or a dispersion thereof of the present invention can contain other optional components depending on the formulation, such as solvents, wetting agents, thickeners, antioxidants, pH adjusters, amino acids, preservatives, sweeteners, flavorings, surfactants, colorants, auxiliaries for enhancing the bactericidal effect, chelating agents, UV absorbers, antifoaming agents, enzymes, and formulation stabilizers.

[0075] The disinfectant containing the cerium oxide nanoparticles or a dispersion thereof of the present invention can be provided in various forms, such as liquid, gel, or powder. The liquid disinfectant can be provided as a lotion, spray, or the like, and can be filled into a bottle with a measuring cap, a trigger-type spray container, a squeeze-type or dispenser-type pump spray container, or the like, and used by spraying or atomizing. The liquid disinfectant can be impregnated into sheet-shaped paper or cloth, filled into a container such as a bottle or bucket, and provided as a wet wipe.

[0076] The cerium oxide nanoparticles of the present invention can be used for antibacterial treatment by adding them to fibers, tubes, beads, rubber, films, plastics, etc. during molding, or by applying them as a dispersion to the surface of these. Examples of items that can be antibacterial treated with the cerium oxide nanoparticles or dispersion of the present invention include kitchen sink drain cover chrysanthemum-shaped drain stoppers, window glass fixing gaskets, mirror fixing gaskets, waterproof gaskets for bathrooms, washstands, and kitchens, refrigerator door lining gaskets, bath mats, non-slip rubber for washbasins and chairs, hoses, shower heads, gaskets used in water purifiers, plastic products for water purifiers, gaskets used in washing machines, plastic products for washing machines, masks, medical caps, medical shoe covers, air conditioner filters, air purifier filters, cleaning products, etc. Examples of suitable applications include machine filters, ventilation fan filters, vehicle filters, air conditioning filters, plastic parts such as air conditioner fins and air conditioner outlet louvers, as well as blower fans, car air conditioner fins and car air conditioner outlet louvers, clothing, bedding, nets such as screen door nets, chicken coop nets and mosquito nets, wallpaper, windows, blinds, interior materials for buildings such as hospitals, interior materials for trains and automobiles, vehicle seats, blinds, chairs, sofas, virus-handling equipment, and building materials such as doors, ceiling panels, floor panels and windows. Thus, products processed with the cerium oxide nanoparticle dispersion of the present invention can be used in a variety of fields as sanitary materials.

[0077] The cerium oxide nanoparticles of the present invention or a dispersion thereof can be added to a paint to impart an antiviral effect to the paint. In this case, the paint may contain a resin emulsion composition for the purpose of immobilizing the cerium oxide nanoparticles of the present invention in the paint film.

[0078] Examples of resin emulsion compositions include synthetic resin emulsions composed of resin components such as vinyl acetate resin emulsions, vinyl chloride resin emulsions, epoxy resin emulsions, acrylic resin emulsions, urethane resin emulsions, acrylic silicone resin emulsions, fluororesin emulsions, and composites of these. The mass ratio of the cerium oxide nanoparticles of the present invention to be added to the paint to the solid content in the resin emulsion can be set at any value between 0.01:99.99 and 99.99:0.01.

[0079] The ethylene-vinyl acetate copolymer resin emulsion is a copolymer of ethylene and vinyl acetate monomer, and may further comprise a vinyl monomer having a functional group such as an amino group, a secondary amino group, a tertiary amino group, a quaternary amino group, a carboxyl group, an epoxy group, a sulfonic acid group, a hydroxyl group, a methylol group, or an alkoxy acid group.

[0080] Vinyl chloride copolymer resin emulsions are obtained by polymerizing vinyl chloride, and may be further copolymerized with a vinyl monomer having a functional group such as an amino group, a secondary amino group, a tertiary amino group, a quaternary amino group, a carboxyl group, an epoxy group, a sulfonic acid group, a hydroxyl group, a methylol group, or an alkoxy acid group.

[0081] Monomers that can be used to prepare the acrylic resin emulsion include (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, octadecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate; acrylic acid, methacrylic acid, β-carboxyethyl (meth)acrylate, 2-(meth)acryloylpropionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid, unsaturated bond-containing monomers having a carboxyl group such as phosphate half ester, maleic acid half ester, maleic anhydride, and itaconic anhydride; glycidyl group-containing polymerizable monomers such as glycidyl (meth)acrylate and allyl glycidyl ether; hydroxyl group-containing polymerizable monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, and glycerol mono(meth)acrylate; ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diallyl phthalate, divinylbenzene, and allyl (meth)acrylate.

[0082] Monomers that can be used to prepare the urethane resin emulsion include, as polyisocyanate components, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and dodecamethylene diisocyanate. Examples of the diisocyanate include diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate. Examples of the diol component include polyester polyol, polyether polyol, polycarbonate polyol, polyacetal polyol, polyacrylate polyol, polyesteramide polyol, polythioether polyol, and polyolefin polyol such as polybutadiene-based polyol.

[0083] Examples of silicon-containing acrylic monomers that can be used to prepare the acrylic silicone resin emulsion include γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, and γ-(meth)acryloxypropylmethyldiethoxysilane.

[0084] Examples of monomers that can be used to prepare the fluororesin emulsion include fluoroolefins (vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, pentafluoroethylene, hexafluoropropylene, etc.), and fluorine-containing (meth)acrylates (trifluoroethyl (meth)acrylate, pentafluoropropyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate, etc.).

[0085] The coating material containing the cerium oxide nanoparticles or a dispersion thereof of the present invention may optionally contain pigments, matting agents, aggregates, fibers, crosslinking agents, plasticizers, preservatives, antifungal agents, antibacterial agents, antifoaming agents, viscosity modifiers, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, UV absorbers, light stabilizers, antioxidants, adsorbents, etc. These components can be blended into the coating composition either alone or in combination.

[0086] The paint containing the cerium oxide nanoparticles or a dispersion thereof of the present invention can be used, for example, to paint the interior surfaces of buildings. Examples of interior surfaces include substrates such as mortar, concrete, gypsum board, siding board, extruded board, slate board, asbestos cement board, fiber-mixed cement board, calcium silicate board, ALC board, metal, wood, glass, rubber, ceramics, fired tile, porcelain tile, plastic, and synthetic resin, as well as wallpaper, and coating films formed on these substrates. The paint can also be applied to the exterior surfaces of buildings and structures other than buildings. [Example]

[0087] The present invention will be further illustrated by the following examples. Materials and Methods Cerium (III) nitrate hexahydrate, boric acid, sodium tetraborate decahydrate (borax), ethylene glycol, and 30% by mass hydrogen peroxide were obtained from Fujifilm Wako Pure Chemical Industries, Ltd. Acid Red 94, trimethyl borate, triethyl borate, isopropyl borate, methylboronic acid, ethylboronic acid, phenylboronic acid, EDTA·2Na, and DL-lactic acid were obtained from Tokyo Chemical Industry Co., Ltd. The commercially available cerium oxide dispersion (Product No. 796077) used in the comparative examples was obtained from Merck. Amicon Ultra 15 (30 kDa) used for purification was purchased from Merck Millipore. Other reagents were purchased from Fujifilm Wako Pure Chemical Industries, Ltd., Tokyo Chemical Industry Co., Ltd., and Sigma-Aldrich Japan LLC, and were used as is without further purification. The hydrodynamic diameter of the cerium oxide nanoparticles was measured using the Zeta Potential and Particle Measurement System ELS-Z manufactured by Otsuka Electronics Co., Ltd., and the plate reader for absorbance measurement was the SpectraMax iD3 manufactured by Molecular Devices.

[0088] Example 1: Preparation of a dispersion of cerium oxide nanoparticles stabilized with boric acid 50 ml of water was added to a recovery flask, 284 mg of boric acid was dissolved in it, and the pH was adjusted to 8.0 with sodium hydroxide. 1 ml of a 10% by mass aqueous solution of cerium (III) nitrate hexahydrate was added and stirred at room temperature for 10 minutes. 1 ml of a 1.2% by mass aqueous solution of hydrogen peroxide was then added dropwise and reacted at room temperature for 1 hour. After the reaction, nitric acid was added and the mixture was stirred at room temperature for 2 hours. The reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 10 kD, yielding an orange dispersion containing cerium oxide nanoparticles.

[0089] Example 2: Preparation of a dispersion of cerium oxide nanoparticles stabilized with trimethyl borate A reaction was carried out under the same conditions as in Example 1, except that 388 mg of trimethyl borate was used instead of 284 mg of boric acid, to obtain an orange dispersion liquid containing cerium oxide nanoparticles.

[0090] Example 3: Preparation of a dispersion of cerium oxide nanoparticles stabilized with triethyl borate A reaction was carried out under the same conditions as in Example 1, except that 545 mg of triethyl borate was used instead of 284 mg of boric acid, to obtain an orange dispersion liquid containing cerium oxide nanoparticles.

[0091] Example 4: Preparation of a dispersion of cerium oxide nanoparticles stabilized with triisopropyl borate A reaction was carried out under the same conditions as in Example 1, except that 702 mg of triisopropyl borate was used instead of 284 mg of boric acid, and 50 ml of 50% by volume ethylene glycol water was used instead of 50 ml of water, to obtain an orange dispersion containing cerium oxide nanoparticles.

[0092] Example 5: Preparation of a dispersion of cerium oxide nanoparticles stabilized with sodium tetraborate A reaction was carried out under the same conditions as in Example 1, except that 1.42 g of sodium tetraborate decahydrate (borax) was used instead of 284 mg of boric acid, to obtain an orange dispersion containing cerium oxide nanoparticles.

[0093] Example 6: Preparation of a dispersion of cerium oxide nanoparticles stabilized with methylboronic acid A reaction was carried out under the same conditions as in Example 1, except that 223 mg of methylboronic acid was used instead of 284 mg of boric acid, to obtain a light brown dispersion containing cerium oxide nanoparticles.

[0094] Example 7: Preparation of a dispersion of cerium oxide nanoparticles stabilized with ethylboronic acid A reaction was carried out under the same conditions as in Example 1, except that 276 mg of ethylboronic acid was used instead of 284 mg of boric acid, to obtain a light brown dispersion containing cerium oxide nanoparticles.

[0095] Example 8: Preparation of a dispersion of cerium oxide nanoparticles stabilized with phenylboronic acid A reaction was carried out under the same conditions as in Example 1, except that 455 mg of phenylboronic acid was used instead of 284 mg of boric acid, and 50 ml of 50% by volume ethylene glycol water was used instead of 50 ml of water, to obtain a brown dispersion containing cerium oxide nanoparticles.

[0096] (Example 9) Preparation of a dispersion of cerium oxide nanoparticles using boric acid as a stabilizer (pH of boric acid solution: 4.0) The reaction was carried out under the same conditions as in Example 1, except that the pH of the boric acid solution was set to 4.0, to obtain a yellow dispersion containing cerium oxide nanoparticles.

[0097] (Example 10) Preparation of a dispersion of cerium oxide nanoparticles using boric acid as a stabilizer (pH of boric acid solution: 5.0) The reaction was carried out under the same conditions as in Example 1, except that the pH of the boric acid solution was adjusted to 5.0, to obtain an orange dispersion liquid containing cerium oxide nanoparticles.

[0098] Example 11: Preparation of a dispersion of cerium oxide nanoparticles using boric acid as a stabilizer (boric acid solution heated to 70°C) The reaction was carried out under the same conditions as in Example 1, except that the stirring after the addition of nitric acid was carried out at 70° C., to obtain an orange dispersion liquid containing cerium oxide nanoparticles.

[0099] Example 12: Preparation of a dispersion of cerium oxide nanoparticles using boric acid as a stabilizer (boric acid solution heated to 90°C) The reaction was carried out under the same conditions as in Example 1, except that the stirring after the addition of nitric acid was carried out at 90° C., to obtain an orange dispersion liquid containing cerium oxide nanoparticles.

[0100] Comparative Example 1: Preparation of a dispersion of cerium oxide nanoparticles using polyacrylic acid as a stabilizer For comparison of oxidation activity, cerium oxide nanoparticles stabilized with polyacrylic acid were prepared with reference to Non-Patent Document 1. 1 ml of a 10% by mass aqueous solution of cerium (III) nitrate hexahydrate was added to 50 ml of a 1% by mass aqueous solution of sodium polyacrylate, and the mixture was stirred at room temperature for 5 minutes. 1 ml of a 1.2% by mass aqueous solution of hydrogen peroxide was then added, and the mixture was heated to 40°C and reacted for 1 hour. The reaction solution was purified using an ultrafiltration membrane with a molecular weight cutoff of 30 kD, yielding a yellow dispersion containing cerium oxide nanoparticles.

[0101] Comparative Example 2: Preparation of a dispersion of cerium oxide nanoparticles with post-addition of boric acid To compare the oxidation performance with that of Example 1, a dispersion was prepared using a manufacturing method in which boric acid was added to and adsorbed onto a dispersion of cerium oxide nanoparticles, based on Patent Document 1 (JP 2003-183631 A). A commercially available dispersion of cerium oxide nanoparticles (IV) (Merck, 796077) was diluted to 0.2 mg / ml, and 284 mg of boric acid was added to 50 ml of the diluted solution, followed by stirring at 60°C for 2 hours. The reaction solution was then purified using an ultrafiltration membrane with a molecular weight cutoff of 10 kD, yielding a brown dispersion containing cerium oxide nanoparticles.

[0102] (Comparative Example 3) Preparation of a dispersion of cerium oxide nanoparticles using EDTA / lactic acid as a stabilizer With reference to Patent Document 2 (JP-A No. 2010-502821), a dispersion of cerium oxide nanoparticles stabilized with EDTA / lactic acid was prepared in order to compare the oxidation performance with that of Example 1. 0.8g of cerium(III) nitrate hexahydrate, 0.25g of EDTA·2Na, and 0.25g of DL-lactic acid were dissolved in 50ml of water and adjusted to pH 9.5 with 30% aqueous ammonia. 640μl of 30% hydrogen peroxide was added dropwise and stirred for 1 hour to obtain a brown aqueous solution. The reaction solution was then purified using an ultrafiltration membrane with a molecular weight cutoff of 3kD, yielding a brown dispersion containing cerium oxide nanoparticles stabilized with EDTA / lactic acid.

[0103] Comparative Example 4: Preparation of a dispersion of cerium oxide nanoparticles stabilized with EDTA / lactic acid and post-added boric acid The dispersion containing cerium oxide nanoparticles stabilized with EDTA / lactic acid obtained in Comparative Example 3 was diluted to 0.2 mg / ml, and 284 mg of boric acid was added to 50 ml of the diluted solution. The reaction solution was then purified using an ultrafiltration membrane with a molecular weight cutoff of 3 kD to obtain a brown aqueous solution containing cerium oxide nanoparticles.

[0104] Comparative Example 5: Preparation of a dispersion of cerium oxide nanoparticles with post-addition of triethyl borate A reaction was carried out under the same conditions as in Comparative Example 2, except that 545 mg of triethyl borate was used instead of 284 mg of boric acid, to obtain a brown dispersion containing cerium oxide nanoparticles.

[0105] Example 13: Measurement of the hydrodynamic diameter of cerium oxide nanoparticles The hydrodynamic diameters of the cerium oxide nanoparticles prepared in Examples 1 to 12 were measured by dynamic light scattering (DLS). Water was used as the solvent during the measurement, and the average particle size of the hydrodynamic diameter was obtained by number conversion. The obtained values ​​are shown in Table 1. The average particle diameter was 3.4 to 71.0 nm, and all were confirmed to be nanoparticles.

[0106] [Table 1]

[0107] (Example 14) Measurement of oxidation performance by dye decomposition test To 60 μl of the dispersion of cerium oxide nanoparticles from Examples 1 to 12, prepared to a concentration of 2 mg / ml, 60 μl of 0.5 mg / ml Acid Red 94 (AR94) as a sample containing organic matter and 1.38 ml of distilled water were added, and the mixture was left to stand at 40°C for 1 hour using a heat block to allow the dye to decompose. As a control, a solution of AR94 not containing cerium oxide nanoparticles was also subjected to the same treatment. After the reaction, 100 μl of each solution was diluted with 1.9 ml of distilled water, and the absorption spectrum was measured. No change in the absorption spectrum of the control sample was observed before and after heating. The absorbance at 552 nm, the maximum absorption wavelength of AR94, was used for the analysis. The absorbance of each dispersion (I) and the absorbance of the control (I c ) and calculate the absorbance of the control (I c The decomposition rate was calculated as the ratio of the total amount of chloroform to the total amount of chloroform. The results are shown in Table 2. From these results, it was confirmed that the dispersions containing cerium oxide nanoparticles of Examples 1 to 12 have oxidation performance capable of decomposing dyes at a high decomposition rate. On the other hand, the oxidation performance was measured in the same manner for the dispersions of commercially available cerium oxide nanoparticles and the dispersions of cerium oxide nanoparticles prepared in Comparative Examples 1 to 5, but decomposition of the dye was hardly observed.

[0108] [Table 2]

[0109] (Example 15) Virus inactivation test This test was carried out at the Kitasato Research Center for Environmental Sciences. 0.9 ml of the dispersion of cerium oxide nanoparticles prepared in Examples 1, 11, and 12, adjusted to 5 mg / ml, was mixed with 0.1 ml of a virus solution (feline calicivirus, F-9, ATCC, VR-782, norovirus surrogate) and allowed to react for 1 hour. PBS was then added as a stop solution to stop the action against the virus. This solution was used as a stock solution for the sample for virus titer measurement, and TCID 50 The infectivity titer was measured by the method. The log reduction in infectivity titer relative to the infectivity titer before the application of cerium oxide nanoparticles is shown in Table 3. From these results, since the log reduction values ​​of the cerium oxide nanoparticles of Examples 1, 11, and 12 were 3.7 to 4.7, it was confirmed that the cerium oxide nanoparticles of the present invention have a virus inactivation rate of 99.9% or more and have very high antiviral activity. Furthermore, the dispersion of cerium oxide nanoparticles obtained in Example 1 was sterilized by passing it through a 0.2 μm sterilization filter, by autoclave (hydrothermal treatment at 120°C for 20 minutes), and by irradiating it with 254 nm ultraviolet light. These were then evaluated in the same manner. As a result, it was confirmed that the virus inactivation rate was the same regardless of the sterilization treatment used, and that the dispersion had extremely high antiviral activity. On the other hand, the dispersion of cerium oxide nanoparticles prepared in Comparative Example 1 had a logarithmic reduction value of -0.5, and no virus inactivation performance was confirmed.

[0110] [Table 3]

[0111] (Example 16) Virus inactivation test against novel coronavirus This test was carried out at the Japan Textile Products Quality Technology Center, a general incorporated foundation. 0.9 ml of the dispersion of cerium oxide nanoparticles prepared in Example 12 at 5 mg / ml was mixed with 0.1 ml of a virus solution (severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), NIID isolate; JPN / TY / WK-521 (distributed by the National Institute of Infectious Diseases)) and allowed to react for 1 hour. PBS was then added as a stop solution to stop the action against the virus. This solution was used as a stock solution for the sample for virus titer measurement, and the infectivity titer was measured by plaque assay. The logarithmic reduction in the infectivity titer relative to the infectivity titer before the application of cerium oxide nanoparticles is shown in Table 4. From these results, it was confirmed that the logarithmic reduction value of the cerium oxide nanoparticles of Example 12 was 3.03 or more, and that the virus inactivation rate of the cerium oxide nanoparticles of the present invention against the novel coronavirus was 99.9% or more.

[0112] [Table 4]

[0113] (Example 17) Quantitative determination of Ce and B using ICP atomic emission spectrometry and ICP-MS The dispersions of cerium oxide nanoparticles from Examples 1, 2, and 12 were weighed into Teflon (registered trademark) containers and thermally decomposed with sulfuric acid, nitric acid, and hydrochloric acid. The solution was then concentrated until white sulfuric acid smoke was released, and the solution was dissolved in dilute aqua regia to a constant volume. Ce in the resulting constant-volume solution was quantified by ICP atomic emission spectrometry, and B by ICP mass spectrometry. The ICP atomic emission spectrometer used was a PS3520VDDII (manufactured by Hitachi High-Tech Science), and the ICP mass spectrometer was an Agilent 8800 (manufactured by Agilent Technologies). The obtained values ​​are shown in Table 5. The amount of boric acid was confirmed to be 0.016 to 0.0541 mol per 1 mol of Ce.

[0114] [Table 5]

[0115] (Example 18) XAFS analysis of cerium oxide nanoceria The dispersion of cerium oxide nanoparticles of the present invention, prepared in Example 1 to a concentration of 10 mg / ml, was irradiated with X-rays, and the amount of X-ray absorption was measured to determine the X-ray absorption fine structure spectrum. The measurement conditions were as follows: experimental facility: High Energy Accelerator Research Organization Photon Factory BL12C; spectrometer: Si(111)2 crystal spectrometer; absorption edge: Ce L3 absorption edge; detection method: transmission; and detector: ion chamber. The Ce L3 edge XANES spectrum is shown in Figure 1. The vertical axis was set by taking the absorption edge (E0) at 5724.4 eV in the spectrum, and calculating the ratio between the average absorption value in the range of -150 to -30 eV from E0 as 0 and the average absorption value in the range of +150 to +400 eV from E0 as 1. Furthermore, the dispersion of cerium oxide nanoparticles prepared in Comparative Example 2 was also subjected to XAFS observation under the same procedures and conditions, and the obtained Ce L3 edge XANES spectrum is shown in FIG.

[0116] XAFS observation was also carried out on the dispersions of cerium oxide nanoparticles prepared in Example 2 and Comparative Example 5 under the same procedures and conditions, and the obtained Ce L3 edge XANES spectra are shown in FIG.

[0117] XAFS observation was also carried out on the dispersions of cerium oxide nanoparticles prepared in Example 12 and Comparative Example 2 under the same procedures and conditions, and the obtained Ce L3 edge XANES spectra are shown in FIG.

[0118] These results revealed that the nanoparticles of Example 1 have absorption maxima at 5727.974 eV and 5736.694 eV, the nanoparticles of Example 2 have absorption maxima at 5727.705 eV and 5736.964 eV, and the nanoparticles of Example 12 have absorption maxima at 5728.078 eV and 5736.568 eV, and have absorption maxima at 5726-5729 eV and 5735-5739 eV. On the other hand, the cerium oxide nanoparticles of Comparative Example 2 had absorption maxima at 5729.732 eV and 5736.694 eV, and the cerium oxide nanoparticles of Comparative Example 5 had absorption maxima at 5729.810 eV and 5736.568 eV. It was found that although they had absorption maxima between 5735 and 5739 eV, they did not have absorption maxima between 5726 and 5729 eV.

[0119] (Reference Example 1) XAFS observation XAFS observations were performed using the same procedures and conditions as in Examples 1, 2, and 12 and Comparative Examples 2 and 5, except that non-nanoparticle cerium oxide crystals and the cerium salts cerium(III) carbonate, cerium(III) nitrate, and ammonium cerium(IV) nitrate were used. The resulting Ce L3 edge XANES spectra are shown in Figure 4. It was found that cerium oxide crystals had absorption maxima at 5729.810 eV and 5736.568 eV, cerium(III) carbonate had an absorption maxima at 5725.161 eV, cerium(III) nitrate had an absorption maxima at 5725.316 eV, and ammonium cerium(IV) nitrate had absorption maxima at 5725.796 eV and 5736.105 eV, whereas none of the known cerium salts or cerium compounds had absorption maxima between 5726 and 5729 eV or between 5735 and 5739 eV.

[0120] Example 19: Dispersion containing cerium oxide nanoparticles doped with 0.1 mole of Cu(II) compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 1, except that after the addition of cerium nitrate, 23 μL of a 1 M aqueous solution of copper (II) sulfate pentahydrate (0.1 mol per 1 mol of cerium nitrate hexahydrate) was then added, to obtain a yellowish-white dispersion containing cerium oxide nanoparticles.

[0121] Example 20: Dispersion containing cerium oxide nanoparticles doped with 0.05 moles of Cu(II) compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 19, except that the amount of 1 M copper (II) sulfate pentahydrate aqueous solution added was 11.5 μL (0.05 mol per 1 mol of cerium nitrate hexahydrate), and a yellowish-white dispersion containing cerium oxide nanoparticles was obtained.

[0122] Example 21: Dispersion containing cerium oxide nanoparticles doped with 0.01 mole of Cu(II) compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 19, except that the amount of 1 M copper (II) sulfate pentahydrate aqueous solution added was 2.3 μL (0.01 mol per 1 mol of cerium nitrate hexahydrate), to obtain an orange dispersion containing cerium oxide nanoparticles.

[0123] Example 22: Dispersion containing cerium oxide nanoparticles doped with 0.1 mole of Fe(II) compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 1, except that after the addition of cerium nitrate, 23 μL of a 1 M aqueous solution of iron (II) sulfate heptahydrate (0.1 mol per 1 mol of cerium nitrate hexahydrate) was then added, to obtain a yellowish-white dispersion containing cerium oxide nanoparticles.

[0124] Example 23: Dispersion containing cerium oxide nanoparticles doped with 0.05 moles of Fe(II) compound, stabilized with boric acid In Example 22, the reaction was carried out under the same conditions as in Example 22, except that the amount of 1 M aqueous solution of iron (II) sulfate heptahydrate added was 11.5 μL (0.05 mol per 1 mol of cerium nitrate hexahydrate), and a yellowish-white dispersion containing cerium oxide nanoparticles was obtained.

[0125] Example 24: Dispersion containing cerium oxide nanoparticles doped with 0.01 mole of Fe(II) compound, stabilized with boric acid In Example 22, the reaction was carried out under the same conditions as in Example 22, except that 2.3 μL (0.01 mol per 1 mol of cerium nitrate hexahydrate) of 1 M aqueous solution of iron (II) sulfate heptahydrate was added, to obtain an orange dispersion containing cerium oxide nanoparticles.

[0126] Example 25: Dispersion containing cerium oxide nanoparticles doped with 0.05 moles of Fe(III) compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 20, except that the 1 M aqueous solution of copper (II) sulfate pentahydrate added was replaced with a 1 M aqueous solution of iron (III) chloride, to obtain an orange dispersion containing cerium oxide nanoparticles.

[0127] Example 26: Dispersion containing cerium oxide nanoparticles doped with 0.05 mol of Co compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 20, except that the 1 M aqueous solution of copper (II) sulfate pentahydrate added was replaced with a 1 M aqueous solution of cobalt (II) chloride, to obtain an orange dispersion containing cerium oxide nanoparticles.

[0128] Example 27: Dispersion containing cerium oxide nanoparticles doped with 0.05 moles of Zn compound, stabilized with boric acid The reaction was carried out under the same conditions as in Example 20, except that the 1 M aqueous solution of copper (II) sulfate pentahydrate added was replaced with a 1 M aqueous solution of zinc (II) nitrate, and an orange dispersion containing cerium oxide nanoparticles was obtained.

[0129] Example 28: Measurement of the hydrodynamic diameter of metal-doped cerium oxide nanoparticles The hydrodynamic diameters of the cerium oxide nanoparticles prepared in Examples 19 to 27 were measured by dynamic light scattering (DLS). Water was used as the solvent during the measurements, and the average particle size of the hydrodynamic diameter was calculated by number conversion. The obtained values ​​are shown in Table 6. The average particle diameter was 3.1 to 45.2 nm, and all were confirmed to be nanoparticles.

[0130] [Table 6]

[0131] (Example 29) Quantitative determination of Ce, Cu, Fe, Co, and Zn using ICP atomic emission spectrometry and ICP-MS The samples of Examples 19 to 27 were weighed into Teflon (registered trademark) containers and thermally decomposed with sulfuric acid, nitric acid, and hydrochloric acid. The solution was concentrated until white sulfuric acid smoke was generated, and then dissolved in dilute aqua regia to a constant volume. Ce in the resulting constant-volume solution was quantified by ICP atomic emission spectrometry, and Cu, Fe, Co, and Zn were quantified by ICP mass spectrometry. The ICP atomic emission spectrometer used was a PS3520VDDII (manufactured by Hitachi High-Tech Science), and the ICP mass spectrometer used was an Agilent 8800 (manufactured by Agilent Technologies). The obtained values ​​are shown in Table 6. The actual amount of transition metal added was 0.00027 to 0.036 per mole of Ce, and it was confirmed that all of them were nanoparticles.

[0132] (Example 30) Antibacterial test against Escherichia coli E. coli pre-cultured in LB medium was suspended in a bacterial suspension preparation solution (0.1% tryptone, 0.85% NaCl) and incubated for 10 8 A bacterial solution containing 100 CFU / ml of cerium oxide nanoparticles was prepared. 0.1 ml of this bacterial solution was mixed with 0.9 ml of the 1 mg / ml dispersion of cerium oxide nanoparticles prepared in Examples 1, 12, 20, 23, and 25 to 27, and the mixture was allowed to stand at room temperature for one hour. A dilution series was then prepared using this mixture as the stock solution, and plated on LB agar medium to measure the number of colonies. The logarithmic reduction in the number of colonies relative to the number of colonies before the application of cerium oxide nanoparticles is shown in Table 7 as the antibacterial activity value. These results confirmed that the antibacterial activity values ​​of the cerium oxide nanoparticles of Examples 1 and 12 were 2.2 to 2.3, confirming their antibacterial performance. Furthermore, the antibacterial activity values ​​of the cerium oxide nanoparticles of Examples 20, 23, and 25 to 27 were 3.0 to 5.6, indicating that doping with metal species improved their antibacterial performance. On the other hand, the cerium oxide nanoparticles prepared in Comparative Example 1 had a logarithmic reduction value of 0.64, resulting in low antibacterial activity.

[0133] [Table 7]

Claims

1. The cerium oxide nanoparticles contain a boron compound represented by the following general formula (I), and have absorption maxima between 5726 and 5729 eV and between 5735 and 5739 eV in the XANES spectrum: BR n (OR’) 3-n (I) (In general formula (I), n is an integer of 0 to 2, R is any one of an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group, and R' is any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, and a tolyl group. When there are multiple R or R', they may be the same or different.)

2. 2. The cerium oxide nanoparticles according to claim 1, wherein the boron compound represented by the general formula (I) is boric acid, a borate ester, a boronic acid, a boronic acid ester, borinic acid, a borinic acid ester, or a borate salt.

3. A dispersion containing the cerium oxide nanoparticles according to claim 1 or 2.

4. An oxidizing agent comprising the cerium oxide nanoparticles according to claim 1 or 2 or the dispersion according to claim 3.

5. An antiviral agent comprising the cerium oxide nanoparticles according to claim 1 or 2 or the dispersion according to claim 3.

6. An antibacterial agent comprising the cerium oxide nanoparticles according to claim 1 or 2 or the dispersion according to claim 3.

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