Nanoparticles of cerium oxide, dispersions, oxidizing agents, antioxidants, and methods for producing nanoparticles of cerium oxide, methods for producing dispersions, methods for producing oxidizing agents, and methods for producing antioxidants

Abstract

The present invention addresses the problem of finding: cerium oxide nanoparticles having high oxidation performance and anti-oxidation performance; and a dispersion which contains the cerium oxide nanoparticles. The present invention provides: cerium oxide nanoparticles which are produced by mixing a solution of an alicyclic amine represented by formula (I) with a solution containing cerium (III) ions or a cerium (III) salt, and adding an oxidant to the mixture; and a dispersion which contains the cerium oxide nanoparticles.

Description

Technical Field

[0001] The present invention relates to cerium oxide nanoparticles, a dispersion containing the nanoparticles, a method for producing the cerium oxide nanoparticles, The method for producing the dispersion, and an oxidizing agent and an antioxidant containing the cerium oxide nanoparticles or the dispersion. , the method for producing the oxidizing agent and the method for producing the antioxidant It relates thereto.

Background Art

[0002] In recent years, with the increasing awareness of safety and hygiene management, antibacterial technologies for decomposing harmful substances and microorganisms have attracted attention. For example, titanium oxide has the property of oxidatively decomposing organic substances due to its photocatalytic properties and is evaluated in decomposition reactions of organic dyes and the like. Such oxidative decomposition properties are expected to be used not only as an antibacterial agent but also in applications for decomposing various harmful substances such as low-molecular-weight substances such as acetaldehyde and ammonia, allergens, and viruses.

[0003] On the other hand, cerium oxide nanoparticles (nanoceria) have catalytic activities similar to those of redox enzymes such as catalase, oxidase, peroxidase, and superoxide dismutase, and are expected to be applied as oxidizing agents and antioxidants. Since these catalytic activities do not require a special light source such as ultraviolet light, it is expected to be used in applications different from those of titanium oxide.

[0004] However, generally, nanoparticles tend to aggregate. Therefore, a method is used in which a compound serving as a stabilizer coexists during synthesis and the obtained nanoparticles are stably dispersed. In the case of cerium oxide nanoparticles, for example, polyacrylic acid is used as a stabilizer to oxidize cerium(III) ions with hydrogen peroxide to obtain a particle dispersion, or dextran is used as a stabilizer to perform alkali neutralization of cerium(III) ions in ammonia water to obtain a particle dispersion.

[0005] Here, Non-Patent Document 1 describes a method for synthesizing cerium oxide nanoparticles whose surfaces are coated with polyacrylic acid or dextran. In Non-Patent Document 1, it is disclosed that, particularly when polyacrylic acid is used as a stabilizer, the oxidase activity, which is a value indicating oxidation performance, increases.

[0006] In addition, Patent Document 1 describes a method for synthesizing cerium oxide nanoparticles whose surfaces are coated with chelating agents such as citric acid or ethylenediaminedisuccinic acid (EDDS). In particular, it is disclosed that when citric acid / EDDS is used as a stabilizer, the catalase activity, which is a value indicating antioxidant performance, increases.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The inventors of the present invention examined the use of cerium oxide nanoparticles. However, as a result of the dye decomposition test described later, when attempting the oxidative decomposition of an organic dye using cerium oxide nanoparticles whose surfaces are coated with polyacrylic acid (Comparative Example 1) prepared by the production method described in Non-Patent Document 1 or a commercially available solution of cerium oxide nanoparticles, it was found that the decomposition rate was very low. Based on these results, further investigations were carried out with the objective of obtaining cerium oxide nanoparticles having high oxidation performance.

Means for Solving the Problems

[0010] In order to solve the above problems, the present inventors focused on and studied a method for producing cerium oxide nanoparticles. As a result, it was found that a dispersion containing cerium oxide nanoparticles can be obtained by mixing a solution of an alicyclic amine represented by the general formula (I) as a stabilizer with a solution containing cerium(III) ions or a cerium(III) salt and adding an oxidizing agent. On the other hand, when piperidine, which has a structure different from that of the general formula (I), was used as a stabilizer, a dispersion containing cerium oxide nanoparticles could not be obtained, and it was found that the structure of the stabilizer is important for obtaining a dispersion containing cerium oxide nanoparticles. Then, when an attempt was made to oxidatively decompose an organic dye using the dispersion thus produced, it was found that the decomposition rate increased. Further, it was also found that this oxidation performance was not confirmed simply by adding the alicyclic amine represented by the general formula (I) to the dispersion of cerium oxide nanoparticles, and it is a property dependent on the production method. Furthermore, it was found that the dispersion of cerium oxide nanoparticles thus produced has high antioxidant activity even when compared with the solution of cerium oxide nanoparticles described in Patent Document 1, and the present invention was completed.

[0011] Through the above studies, the present inventors completed the present invention. The present invention is as follows. (1) Cerium oxide nanoparticles produced by mixing a solution of an alicyclic amine represented by the following general formula (I) with a solution containing cerium(III) ions or a cerium(III) salt and adding an oxidizing agent. [Chemical formula] In formula (I), X represents NR 2 , O, S, and R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an aminoalkyl group having 1 to 4 carbon atoms, or a sulfonic acid alkyl group having 1 to 4 carbon atoms. R 1 and R 2 may be the same or different.

[0012] The cerium oxide nanoparticles according to (1), wherein when adding an oxidizing agent, the pH is adjusted to 5 or higher. (3) Among the general formula (I), X is NR 2 , O, R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 2 to 3 carbon atoms, an aminoalkyl group having 2 to 3 carbon atoms, or a sulfonic acid alkyl group having 2 to 3 carbon atoms. The cerium oxide nanoparticles according to (1) or (2). (4) The alicyclic amine represented by the general formula (I) is piperazine, 1-methylpiperazine, N,N'-dimethylpiperazine, 1-ethylpiperazine, N,N'-diethylpiperazine, 1-(2-hydroxyethyl)piperazine, 1,4-bis(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, piperazine-1,4-bis(2-ethanesulfonic acid), morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4-(2-aminoethyl)morpholine, 4-(2-hydroxyethyl)morpholine, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid. The cerium oxide nanoparticles according to any one of (1) to (3). (5) The cerium oxide nanoparticles containing the alicyclic amine represented by the general formula (I), which have maximum absorption at 5726.0 to 5729.0 eV and 5735.0 to 5739.0 eV in the Ce L3-edge XANES spectrum obtained by X-ray absorption fine structure spectrum measurement. (6) A dispersion containing the cerium oxide nanoparticles according to any one of (1) to (5). (7) An oxidizing agent containing the cerium oxide nanoparticles according to any one of (1) to (5) or the dispersion according to (6). (8) An antioxidant containing the cerium oxide nanoparticles according to any one of (1) to (5) or the dispersion according to (6). (9) A method for producing cerium oxide nanoparticles, which comprises mixing a solution of an alicyclic amine represented by the general formula (I) with a solution containing cerium(III) ions or a cerium(III) salt, and adding an oxidizing agent.

Advantages of the Invention

[0013] When a dispersion containing the cerium oxide nanoparticles of the present invention is used, harmful substances can be oxidized and decomposed at a higher yield than conventional cerium oxide nanoparticles, and active species can be eliminated at a higher yield than conventional cerium oxide nanoparticles.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] The dispersion containing the cerium oxide nanoparticles of the present invention may be described herein as the dispersion of the present invention or the dispersion liquid of the present invention. In the synthesis of cerium oxide nanoparticles, one of the raw materials is a water-soluble cerium salt, and the synthesis is carried out in water or a solvent compatible with water. From the viewpoint of having appropriate hydrophilicity and being compatible with the property of forming an amine complex with metal ions, a preferred embodiment of the alicyclic amine used in the present invention is the alicyclic amine represented by the chemical formula (I).

Chemical Formula

[0016] In a more preferred embodiment of the alicyclic amine used in the present invention, in the above chemical formula (I), X is NR 2 , O, and R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 2 to 3 carbon atoms, an aminoalkyl group having 2 to 3 carbon atoms, or a sulfonic acid alkyl group having 2 to 3 carbon atoms. R 1 and R 2 may be the same or different.

[0017] In one embodiment, examples of such alicyclic amines include piperazine, 1-methylpiperazine, N,N'-dimethylpiperazine, 1-ethylpiperazine, N,N'-diethylpiperazine, 1-(2-hydroxyethyl)piperazine, 1,4-bis(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, piperazine-1,4-bis(2-ethanesulfonic acid), morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4-(2-aminoethyl)morpholine, 4-(2-hydroxyethyl)morpholine, 2-morpholinoethanesulfonic acid, and 3-morpholinopropanesulfonic acid.

[0018] In the present invention, the cerium oxide nanoparticles are composed of a mixture of Ce2O3 and CeO2. It is known that cerium oxide can actually include forms such as hydroxides and oxyhydroxides in addition to the above oxide forms. The ratio of Ce2O3 to CeO2 can be calculated by X-ray photoelectron spectroscopy (XPS) or the like as the ratio of cerium(III) to cerium(IV).

[0019] The cerium oxide nanoparticles of the present invention or a dispersion containing the same are produced by a production method in which a solution of an alicyclic amine represented by the following general formula (I) is mixed with a solution containing cerium(III) ions or a cerium(III) salt, and an oxidizing agent is added. Hereinafter, the production method of the cerium oxide nanoparticles of the present invention or a dispersion containing the same will be described.

Chemical formula

[0020] The first step is a step of mixing a solution of an alicyclic amine represented by the general formula (I) with a solution containing cerium(III) ions or a cerium(III) salt to obtain a mixed solution. The solution of the alicyclic amine used in this step can be prepared by dissolving the alicyclic amine in an arbitrary solvent. The solvent is preferably water or a solvent compatible with water. Specific examples of the solvent compatible with water include methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, tetrahydrofuran, acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, oligoethylene glycol, and the like. When the alicyclic amine is difficult to dissolve, it may be dissolved by heating or ultrasonic treatment.

[0021] The amount of the alicyclic amine may be in the range of 0.1 to 100 molar equivalents relative to the cerium(III) ions.

[0022] The method for mixing the solution of the alicyclic amine and the solution containing cerium(III) ions or the cerium(III) salt may be to prepare and mix the solution of the alicyclic amine and the solution containing cerium(III) ions respectively. When the solvent of the solution of the alicyclic amine is water or a solvent compatible with water, the cerium(III) salt may be added to the solution of the alicyclic amine and mixed. The solution containing cerium(III) ions may be prepared by dissolving the cerium(III) salt in an arbitrary solvent. For the cerium(III) salt, for example, cerium(III) nitrate hexahydrate may be used.

[0023] The amount of the cerium(III) salt can be mixed with the solution of the alicyclic amine so that the final concentration of 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 uniform.

[0024] In the first step, it is preferable that the solution containing the alicyclic amine and the cerium(III) ions does not contain a carboxylic acid having three or more valences, for example, the compounds shown below. Even if it is contained, the amount is preferably 0.1 equivalent or less, more preferably 0.01 equivalent or less, relative to the cerium(III) ions. Specifically, the carboxylic acid having three or more valences includes nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), ethylenediaminedisuccinic acid (EDDS), glycol ether diamine tetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), citric acid, hydroxyethylethylenediaminetetraacetic acid (HEDTA), polyacrylic acid and / or their salts.

[0025] The second step is a step of adding an oxidizing agent to the mixed solution obtained in the first step. Examples of the oxidizing agent used in the second step include nitric acid, potassium nitrate, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, halogen, hydrogen halide, permanganate, chromic acid, dichromic acid, oxalic acid, hydrogen sulfide, sulfur dioxide, sodium thiosulfate, sulfuric acid, hydrogen peroxide, etc. Among these, hydrogen peroxide is particularly preferable. The addition amount may be 0.1 equivalent or more and 10 equivalents or less, preferably 0.5 equivalent or more and 2 equivalents or less, as a molar equivalent to cerium(III) ions.

[0026] When an oxidizing agent is added to a mixed solution of an alicyclic amine and cerium(III) ions, the cerium(III) ions are oxidized to cerium(IV), and the formation reaction of cerium oxide particles composed of a mixture of Ce2O3 and CeO2 is initiated. Also, during the reaction, the solution is colored yellow, orange, red, brown, etc. This is the coloration due to the change of cerium(III) ions to cerium(IV), and the degree of coloration is determined by the ratio of cerium(III) and cerium(IV) present on the surface of the cerium oxide nanoparticles. The end of the reaction can be judged by the disappearance of the color change. At this time, the particle formation reaction depends on pH, and the reaction proceeds in a weakly acidic to basic range. Since the pH tends to be acidic as the reaction proceeds, it is preferable to adjust the reaction solution to pH 5 or higher, more preferably pH 6 or higher, and even more preferably pH 7 or higher from the time of adding the oxidizing agent until the end of the reaction. When adjusting the pH, an aqueous sodium hydroxide solution, an aqueous ammonia solution, etc. can be used. Usually, the reaction ends in about 5 minutes to 1 hour, and a dispersion containing the cerium oxide nanoparticles of the present invention is obtained. For example, when 200 μl of a 10 mass% aqueous solution of cerium(III) nitrate hexahydrate is added to a 24.6 mg / 10 ml solution of piperazine dihydrochloride monohydrate, and then 200 μl of a 1.2 mass% aqueous hydrogen peroxide solution is added and stirred at room temperature, the solution changes to orange and the reaction ends in about 10 minutes.

[0027] The dispersion of the present invention may use the dispersion liquid after the reaction as it is, but it can also be filtered through an ultrafiltration membrane or dialyzed with a semipermeable membrane to remove unreacted oxidizing agent, cerium (III) ions, and excess alicyclic amine remaining in the dispersion liquid after the reaction. Thereafter, the dispersion of the present invention can be dried using an evaporator, a freeze dryer, etc., to take out the nanoparticles of cerium oxide.

[0028] In addition to the nanoparticles of cerium oxide and water as the solvent, the dispersion of the present invention may contain other solvent components compatible with water. Examples of other solvent components include methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, tetrahydrofuran, acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), glycerol, ethylene glycol, oligoethylene glycol, etc. These solvent components can be contained so as to be 90% by volume or less. These solvent components may be added to the dispersion liquid after the reaction, may be added after filtration through an ultrafiltration membrane, may be used as a dialysis solution, or may be added to the dispersion liquid after dialysis. They may also be added to the dried nanoparticles of cerium oxide to form a dispersion liquid.

[0029] The dispersion of the present invention may contain ionic components. As the ionic components, as components imparting buffering performance, 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 (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 these include N-Bis(2-hydroxyethyl)glycine (Bicine) and N-Tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid (TAPS), and examples of components that do not impart buffering performance include sodium chloride and potassium chloride. These ionic components can be added so that their final concentrations are in the range of 0.1 mM to 1 M. These ionic components may be added to the dispersion after the reaction is completed, may be added after filtration through an ultrafiltration membrane, may be used as a dialysis solution, or may be added to the dispersion after dialysis. They may also be added to the dried cerium oxide nanoparticles to form a dispersion.,

[0030] The dispersion of the present invention may have its pH adjusted after purification. The pH of the dispersion of the present invention may be in the range of pH 2 to 12, preferably pH 4 to 10, and more preferably pH 5 to 8. The pH may be adjusted by adding a buffer solution, or may be adjusted by adding an acid such as nitric acid, sulfuric acid, or hydrochloric acid, or a base such as sodium hydroxide or potassium hydroxide.

[0031] The dispersion of the present invention may be stored as the reaction solution after the above reaction is completed as it is, or may be stored as a purified product obtained by filtering the dispersion after the reaction is completed through an ultrafiltration membrane or a purified product obtained by dialysis through a semipermeable membrane. It may also be stored as a dispersion containing the above solvent components and ionic components, or may be stored after adjusting the pH. When stored as a dispersion, refrigerated storage is preferred.

[0032] The cerium oxide nanoparticles of the present invention can be obtained as a dried product by taking them out from the dispersion produced as described above and drying them. For example, after filtering the solution after the reaction through an ultrafiltration membrane or dialyzing it through a semipermeable membrane to remove unreacted oxidizing agent, cerium(III) ions, and excess alicyclic amine remaining in the solution after the reaction, the cerium oxide nanoparticles can be obtained by drying using an evaporator, a freeze dryer, or the like. Specifically, ultrafiltration membranes such as Amicon Ultra of Merck & Co., Inc. and Vivaspin of GE Healthcare, or semipermeable membranes such as Spectra / Por of Spectrum Laboratories, Inc. can be used. As the drying conditions for the taken-out dispersion, the temperature and pressure conditions in the state diagram where the solvent becomes a gas may be used. For example, when the nanoparticles are in aqueous dispersion, the evaporator may be set to 40 °C and 50 hPa or less to remove water. As the evaporator, for example, N-1200A of Tokyo Rikakikai Co., Ltd. can be used. Also, the freeze dryer may be set to -40 °C and 20 Pa to remove water. As the freeze dryer, for example, FDU-1200 of Tokyo Rikakikai Co., Ltd. can be used. Further, drying can also be carried out by heating with an oil bath to 100 °C or higher or heating with a constant temperature dryer to 80 °C or higher.

[0033] The hydrodynamic diameter exhibited by the cerium oxide nanoparticles in the dispersion of the present invention is measured by dynamic light scattering to derive an autocorrelation function, analyzed by the Marquadt method, and calculated as the average particle diameter from the number-converted histogram. For the measurement of dynamic light scattering, ELS-Z of Otsuka Electronics Co., Ltd. is used. The hydrodynamic diameter exhibited by the cerium oxide nanoparticles in the dispersion may be 1 or more and 1000 nm or less, preferably 1 or more and 200 nm or less.

[0034] The hydrodynamic diameter exhibited by the cerium oxide nanoparticles in the dispersion of the present invention can be adjusted by the molar equivalent of the alicyclic amine to cerium(III) ions. If the molar equivalent is low, particles with a large particle size are obtained, and if the molar equivalent is high, particles with a small particle size are obtained.

[0035] The energy states of cerium(III) and cerium(IV) in Ce2O3 and CeO2 can be observed by X-ray Absorption Fine Structure (XAFS) measurements. In the XAFS spectrum, the structure approximately 20 eV from the absorption edge is called X-ray Absorption Near Edge Structure (XANES), and the extended X-ray absorption fine structure that appears on the higher energy side more than approximately 100 eV from the absorption edge is called Extended X-ray Absorption Fine Structure (EXAFS). Information regarding the valence and structure of the target atom can be obtained from XANES, and in EXAFS analysis, information regarding the local structure of the sample, the atomic species, valence, and distance around the target atom can be obtained by Fourier transformation of the actual spectrum (corresponding to the radial distribution function of FT-EXAFS). The energy states of cerium(III) and cerium(IV) regarding the redox reaction of cerium oxide are reflected in the peak position and peak intensity ratio of the maximum absorption in the XANES spectrum. The cerium oxide nanoparticles of the present invention have maximum absorption between 5726.0 eV and 5729.0 eV and between 5735.0 eV and 5739.0 eV in the Ce L3-edge XANES spectrum obtained by X-ray absorption fine structure spectrum measurement.

[0036] The dispersion of the present invention may be sterilized before use. Examples of the sterilization method include passing through a sterilizing filter.

[0037] The cerium oxide nanoparticles of the present invention or a dispersion containing the nanoparticles can be used as an oxidizing agent. For example, by utilizing the oxidizing action, it can be used in homogeneous catalysts in organic synthesis reactions and polymerizations, or as a wet etching solution for semiconductors. Further, by utilizing the oxidizing action, it can be used as a solution to replace the oxidase solution. Specifically, instead of oxidase or peroxidase solutions, it can be used in detection reactions using antibody-antigen reactions or nucleic acid hybridization, or in tissue staining, or can be used in electrochemical detection reactions by coating electrodes to immobilize the cerium oxide nanoparticles. Additionally, by utilizing the oxidizing action, it can be used as a bleaching agent or disinfectant for decomposing and removing stains, odors, allergens, viruses, bacteria, fungi, and molds. Specifically, it can be used for cleaning clothes, tableware, kitchens, toilets, washrooms, bathrooms, medical instruments, etc. as a bleaching agent. Also, it can be added to pools, bathtubs, hot springs as a disinfectant, or can be used as body soap, hand wash detergent, disinfectant, gargle, mouthwash, etc. Such performance as an oxidizing agent can be evaluated by the discoloration reaction of organic dyes described later.

[0038] In addition, the cerium oxide nanoparticles of the present invention or the dispersion containing the nanoparticles can be added during the molding of fibers, tubes, beads, rubbers, films, plastics, etc. as additives for imparting oxidation performance, or applied to the surfaces of these to be used for anti-odor, anti-allergy, anti-virus, antibacterial, and anti-mold treatments. Examples of the products processed with the nanoparticles or the dispersion of the present invention include, for example, a drainage port chrysanthemum crack cover for a kitchen sink, a drainage port stopper, a packing for fixing a window glass, a packing for fixing a mirror, a waterproof packing for a bathroom, a washbasin, and a kitchen, a packing for lining the inside of a refrigerator door, a bath mat, an anti-slip rubber for a washbasin and a chair, a hose, a shower head, a packing used for a water purifier, a plastic product of a water purifier, a packing used for a washing machine, a plastic product of a washing machine, a mask, a medical cap, a medical shoe cover, a filter for an air conditioner, a filter for an air cleaner, a filter for a vacuum cleaner, a filter for a ventilation fan, a filter for a vehicle, a filter for air conditioning, a fin of an air conditioner, a louver of an air conditioner outlet, etc., plastic parts such as a blower fan, a fin of a car air conditioner, a louver of a car air conditioner outlet, etc., plastic parts such as a blower fan, clothing, bedding, a net for a screen door, a net for a chicken coop, nets such as a mosquito net, wallpaper, windows, blinds, interior materials for buildings such as in a hospital, interior materials for trains and automobiles, vehicle seats, blinds, chairs, sofas, facilities for handling viruses, doors, ceiling boards, floor boards, windows, etc., building materials, etc. Thus, the products processed with the nanoparticles or the dispersion of the present invention can be used in various fields as sanitary materials.

[0039] The fading reaction of the organic dye is also used to evaluate the photocatalytic performance of titanium oxide, and the decomposition rate of the obtained dye is used as an index of the property of oxidatively decomposing organic substances. 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 Orange 7 (AO7) and allowed to stand for a predetermined time. As a control, the same treatment is also performed on a solution of AO7 that does not contain cerium oxide nanoparticles. After the reaction, the absorption spectra of all the solutions are measured. For the analysis, the absorbance at 485 nm, which is the maximum absorption wavelength of AO7, is used. The difference between the absorbance of the control and the absorbance of the solution containing the dispersion of the present invention is taken, and the ratio to the absorbance of the control is calculated as the decomposition rate.

[0040] Moreover, a preferred embodiment of the oxidizing agent of the present invention contains a solution of an alicyclic amine represented by the following general formula (I) and cerium oxide nanoparticles, and has a decomposition rate of 30% or more in the decomposition reaction of Acid Orange at 40°C for 1 hour, and is a dispersion containing cerium oxide nanoparticles.

Chemical formula

[0041] The cerium oxide nanoparticles of the present invention or a dispersion containing the nanoparticles can be used as an antioxidant. In the present invention, the antioxidant refers to a substance having reducibility and suppressing lipid peroxidation or reacting with reactive oxygen species (superoxide ion, hydroxyl radical, hydrogen peroxide, etc.) to suppress their actions (Standard Chemical Terminology Dictionary, 2nd Edition, Maruzen Publishing). For example, by utilizing such antioxidant action, it can be used as a reducing agent in organic chemical reactions or a radical terminator in polymer polymerization. Also, by utilizing the antioxidant action, it can be added to a cell culture medium or applied to a culture vessel such as a petri dish to protect cells from oxidative stress. Furthermore, by applying it to the skin as a cosmetic, it can be used to protect the skin from lipid peroxides and reactive oxygen species. Additionally, by utilizing the antioxidant action, it can be used as a substance to replace an antioxidant enzyme solution. Specifically, as a substitute for a catalase solution, by coating an electrode to immobilize cerium oxide nanoparticles, it can be used in a detection reaction of hydrogen peroxide or an electrochemical detection reaction. Also, it can be used as a neutralizing solution for hydrogen peroxide industrially used in food, semiconductor, fiber, pulp and paper manufacturing, disinfection of public baths, and slime removal in pipes. Such performance can be evaluated by catalase activity and the like described later. Additionally, the dispersion of the present invention can be added as an antioxidant during the molding of rubber and plastic, or added to fuel, detergent, food, and animal feed. Such performance as an antioxidant can be evaluated by a scavenging reaction of active species and the like described later.

[0042] Furthermore, the cerium oxide nanoparticles of the present invention or a dispersion containing the nanoparticles can be used as a pharmaceutical for humans or animals related to oxidative stress and inflammation as an antioxidant. Specifically, by administering the dispersion of the present invention to a subject by a local, enteral or parenteral method such as injection, drip or transplantation, it can be used for the prevention and treatment of oxidative stress-related diseases such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, and ischemia-reperfusion injury. In addition, by coating the dispersion of the present invention as an antioxidant on the surface of medical devices such as cannulas, catheters or stents and artificial organs represented by dialysis membranes, inflammation can be reduced locally or systemically.

[0043] The catalase activity can be determined according to the protocol using AmplexRed Catalase Assay Kit (A22180) of Thermo Fisher Scientific as shown in Japanese Patent Application Laid-Open No. 2018-508568. The Reaction Buffer contained in the kit, the dispersion of the present invention, and an aqueous hydrogen peroxide solution are mixed and allowed to stand for 30 minutes to carry out the decomposition reaction of hydrogen peroxide. The reaction solution is passed through a 30 kD ultrafiltration membrane, and the flow-through solution is mixed with the Working Solution contained in the kit and reacted at 37°C for 30 minutes. Resorufin generated by the reaction is excited at 544 nm, and the fluorescence intensity at 590 nm is measured. The catalase activity of the dispersion of the present invention is calculated by comparing it with a calibration curve prepared with a catalase standard of known activity value contained in the kit. For the measurement of catalase activity, EnzyChrom Catalase Assay Kit of BioAssay System or the like can also be used.

[0044] A preferred embodiment of the dispersant of the present invention contains a solution of an alicyclic amine represented by the following general formula (I) and cerium oxide nanoparticles, and uses the AmplexRed Catalase Assay Kit (A22180) of Thermo Fisher Scientific at a concentration of 4 μg / ml of the cerium oxide nanoparticles. It is a dispersion containing cerium oxide nanoparticles having a catalase activity of 0.5 U / ml or more in the decomposition reaction of hydrogen peroxide solution. [Chemical formula] In formula (I), X represents NR 2 , O, S, and R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an aminoalkyl group having 1 to 4 carbon atoms, or a sulfonic acid alkyl group having 1 to 4 carbon atoms. R 1 and R 2 may be the same or different. By having a catalase activity of 0.5 U / ml or more in the decomposition reaction of hydrogen peroxide solution using the AmplexRed Catalase Assay Kit (A22180), it can be used as an antioxidant. The catalase activity is preferably 0.7 U / ml or more, and particularly preferably 0.8 U / ml or more.

[0045] The scavenging reaction of active species can be measured as the dye retention rate by the method as shown in Y. Xue, J. Phys. Chem. C 2011, 115, 4433 - 4438. Specifically, an aqueous solution of iron(II) chloride and an aqueous solution of hydrogen peroxide are mixed to generate hydroxyl radicals by the Fenton reaction. Then, the dispersion of the present invention is added thereto to perform a radical scavenging reaction. This mixed solution is mixed with an organic dye such as methylene blue and allowed to stand for a predetermined time. As a control, the same treatment is also performed on a solution not containing the dispersion of the present invention. Further, a methylene blue solution having the same concentration as the reaction solution is prepared as a reference solution, and the absorption spectrum of the above solution is measured. For the analysis, the absorbance at 664 nm, which is the maximum absorption wavelength of methylene blue, is used. The absorbance (I0) of the reference solution and the absorbance (I c) The difference (ΔI0), the absorbance (I) of the solution containing the dispersion of the present invention, and the absorbance (I c ) of the control are calculated. The ratio of the latter (ΔI) to the former (ΔI0) is calculated as the decomposition rate and taken as the dye retention rate. This value is an indicator of the radical scavenging performance. The dye retention rate can also be determined using methyl violet instead of methylene blue.

Example

[0046] The present invention will be further specifically described by the following examples. <Materials and Methods> Piperazine dihydrochloride monohydrate, 1-(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, morpholine, 2-morpholinoethanesulfonic acid, Acid Orange 7 were obtained from Tokyo Chemical Industry Co., Ltd., and cerium(III) nitrate hexahydrate and 30% by mass hydrogen peroxide solution were obtained from FUJIFILM Wako Pure Chemical Corporation. The commercially available cerium oxide dispersion (796077) used in the comparative example was obtained from Merck. AmplexRed Catalase Assay Kit (A22180) was obtained from Thermo Fisher Scientific. For other reagents, they were purchased from FUJIFILM Wako Pure Chemical Corporation, Tokyo Chemical Industry Co., Ltd., and Sigma-Aldrich Japan K.K. and used as they were without any special purification. For the measurement of the hydrodynamic diameter of the dispersion containing the nanoparticles of cerium oxide of the present invention, the zeta potential / particle measurement system ELS-Z of Otsuka Electronics Co., Ltd. was used. The thermoblock used was ND-SO1 of Nisshin Rika.

[0047] (Comparative Example 1) Dispersion containing nanoparticles of cerium oxide with polyacrylic acid as a stabilizer Referring to Non-Patent Document 1, for the comparison of oxidation activities, a dispersion containing nanoparticles of cerium oxide prepared using a stabilizer different from the present invention was prepared. To 10 ml of a 1 mass% aqueous solution of sodium polyacrylate, 200 μl of a 10 mass% aqueous solution of cerium(III) nitrate hexahydrate was added, and the mixture was stirred at room temperature for 5 minutes. Then, 200 μl of a 1.2 mass% aqueous hydrogen peroxide solution was added, and the mixture was heated to 40 °C and reacted for 1 hour. The reaction solution was purified with a 30 kD ultrafiltration membrane to obtain a yellow dispersion containing cerium oxide nanoparticles.

[0048] (Comparative Example 2) Preparation of a dispersion of cerium oxide nanoparticles using piperidine as a stabilizer Piperidine was used as an alicyclic amine not corresponding to the general formula (I). To 10 ml of a 6.6 mg / 10 ml aqueous piperidine solution, 200 μl of a 10 mass% aqueous solution of cerium(III) nitrate hexahydrate was added, the pH was adjusted to 7, and the mixture was stirred at room temperature for 5 minutes. Then, 200 μl of a 1.2 mass% aqueous hydrogen peroxide solution was added, and the mixture was reacted at room temperature for 1 hour. No coloration of the reaction solution was confirmed, and a particle dispersion could not be obtained.

[0049] (Comparative Example 3) Preparation of a dispersion of cerium oxide nanoparticles with piperazine added later To compare the oxidation performance due to the difference between the dispersion containing cerium oxide nanoparticles of Example 1 prepared by adding an oxidizing agent in the coexistence of piperazine as a stabilizer and a cerium(III) salt, and its production method, a dispersion was prepared by a production method in which piperazine was added later to cerium oxide nanoparticles (IV) and adsorbed. A commercially available dispersion of cerium oxide nanoparticles (Merck, 796077) was diluted to 0.2 mg / ml, 24.6 mg of piperazine was added to 10 ml of the diluted solution, and the mixture was stirred at room temperature for 1 hour. Then, the solution was purified with a 30 kD ultrafiltration membrane to obtain a brown aqueous solution containing cerium oxide nanoparticles.

[0050] (Comparative Example 4) Preparation of a dispersion containing cerium oxide nanoparticles using citric acid and ethylenediaminedisuccinic acid (EDDS) as stabilizers For the purpose of comparing the dispersion containing cerium oxide nanoparticles prepared using a stabilizer different from the present invention with the antioxidant performance, referring to Patent Document 1 (Japanese Patent Publication No. 2018-508568), a dispersion containing cerium oxide nanoparticles was prepared using citric acid / EDDS as a stabilizer. 0.8 g of cerium nitrate, 0.24 g of citric acid monohydrate, and 0.41 g of EDDS were dissolved in water and adjusted to pH 9.5 with 30% aqueous ammonia. Then, 640 μl of 30% hydrogen peroxide was added dropwise while stirring, and the mixture was stirred for 1 hour to obtain a brown aqueous solution. Thereafter, the solution was purified with a 3 kD ultrafiltration membrane to obtain a brown dispersion containing cerium oxide nanoparticles.

[0051] (Comparative Example 5) Preparation of a dispersion of cerium oxide nanoparticles with post-added 1-(2-hydroxyethyl)piperazine To compare the dispersion containing the cerium oxide nanoparticles of Example 2 with the oxidation performance due to the difference in the production method, a dispersion of nanoparticles was prepared by a production method in which 1-(2-hydroxyethyl)piperazine was post-added to and adsorbed on cerium oxide nanoparticles (IV). A brown aqueous solution containing cerium oxide nanoparticles was obtained under the same operations and conditions as in Comparative Example 3, except that 20.0 mg of 1-(2-hydroxyethyl)piperazine was used instead of piperazine.

[0052] (Example 1) Preparation of a dispersion of cerium oxide nanoparticles using piperazine as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2, except that the stabilizer was an aqueous solution of piperazine dihydrochloride monohydrate at 24.6 mg / 10 ml, to obtain an orange aqueous solution containing cerium oxide nanoparticles.

[0053] (Example 2) Preparation of a dispersion of cerium oxide nanoparticles using 1-(2-hydroxyethyl)piperazine as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2, except that the stabilizer was an aqueous solution of 1-(2-hydroxyethyl)piperazine at 20 mg / 10 ml, to obtain an orange aqueous solution containing cerium oxide nanoparticles.

[0054] (Example 3) Dispersion of cerium oxide nanoparticles with N-(2-aminoethyl)piperazine as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2 except that the stabilizer was an aqueous solution of N-(2-aminoethyl)piperazine at 20 mg / 10 ml, and a yellow aqueous solution containing cerium oxide nanoparticles was obtained.

[0055] (Example 4) Dispersion of cerium oxide nanoparticles with 1,4-bis(2-aminoethyl)piperazine as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2 except that the stabilizer was an aqueous solution of 1,4-bis(2-aminoethyl)piperazine at 31 mg / 10 ml, and an orange aqueous solution containing cerium oxide nanoparticles was obtained.

[0056] (Example 5) Dispersion of cerium oxide nanoparticles with 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2 except that the stabilizer was an aqueous solution of 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid at 36.8 mg / 10 ml, and an orange aqueous solution containing cerium oxide nanoparticles was obtained.

[0057] (Example 6) Dispersion of cerium oxide nanoparticles with morpholine as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2 except that the stabilizer was an aqueous solution of morpholine at 13.5 mg / 10 ml, and a yellow aqueous solution containing cerium oxide nanoparticles was obtained.

[0058] (Example 7) Dispersion of cerium oxide nanoparticles with 2-morpholinoethanesulfonic acid as a stabilizer In Comparative Example 2, the reaction was carried out under the same conditions as in Comparative Example 2 except that the stabilizer was an aqueous solution of 2-morpholinoethanesulfonic acid at 33 mg / 10 ml, and an orange aqueous solution containing cerium oxide nanoparticles was obtained.

[0059] (Example 8) Measurement of the hydrodynamic diameter of the dispersion containing cerium oxide nanoparticles The hydrodynamic diameter of the nanoparticles in the dispersion containing the cerium oxide nanoparticles prepared in Examples 1 to 7 was measured by dynamic light scattering (DLS). The solvent during the measurement was water, and the average particle diameter of the hydrodynamic diameter was obtained by number conversion. The obtained values are shown in Table 1.

Table 1

[0060] (Example 9) Measurement of oxidation performance by dye decomposition test To 30 μl of each of the dispersions of the present invention prepared in Examples 1 to 7 prepared to be 2 mg / ml, 60 μl of 0.5 mg / ml acid orange 7 (AO7) as a sample containing an organic substance and 1.41 ml of distilled water were added respectively, and they were allowed to stand at 40 °C for 1 hour using a heat block to carry out the decomposition reaction of the dye. As a control, the same treatment was also carried out on a solution of AO7 containing no cerium oxide nanoparticles. After the reaction, 100 μl of each solution was taken and diluted with 1.9 ml of distilled water, and the absorption spectrum was measured. No change in the absorption spectrum was observed for the control sample before and after heating. For the analysis, the absorbance at 485 nm, which is the maximum absorption wavelength of AO7, was used. The difference in absorbance between the absorbance of each dispersion and the absorbance of the control was taken, and the ratio of each absorbance difference to the absorbance of the control was calculated as the decomposition rate (%). The results are shown in Table 2. From these results, it was confirmed that the dispersion containing the cerium oxide nanoparticles of the present invention has an oxidation performance capable of decomposing the dye at a high decomposition rate. On the other hand, for the dispersions prepared using stabilizers different from the present invention in Comparative Example 1, the dispersion prepared by post-adding piperazine in Comparative Example 3, and the dispersion prepared by post-adding 1-(2-hydroxyethyl)piperazine in Comparative Example 5, the oxidation performance was measured in the same manner, but almost no decomposition of the dye was confirmed.

[0061]

Table 2

[0062] (Example 10) Measurement of antioxidant performance by measuring catalase activity Catalase activity was measured using AmplexRed Catalase Assay Kit (A22180) from Thermo Fisher Scientific according to the protocol. Briefly, 50 μl of Reaction Buffer, 25 μl of the dispersion of the present invention prepared in Examples 1 to 7 at 16 μg / ml, and 25 μl of 40 μM hydrogen peroxide aqueous solution were mixed and allowed to stand for 30 minutes to carry out the decomposition reaction of hydrogen peroxide. The reaction solution was passed through a 30 kD ultrafiltration membrane, 100 μl of the flow-through solution was mixed with 50 μl of the Working Solution, and reacted at 37 °C for 30 minutes. Resorufin produced by the reaction was excited at 544 nm, and the fluorescence intensity at 590 nm was measured. The catalase activity of the dispersion of the present invention was calculated from the calibration curve prepared with a standard sample of catalase with a known activity value. The results are shown in Table 3. From these results, it was confirmed that the dispersion containing the cerium oxide nanoparticles of the present invention has high catalase activity. On the other hand, for the nanoparticle dispersion prepared in Comparative Example 4, the antioxidant performance was measured in the same manner, but the catalase activity was lower compared to the dispersion of the present invention.

[0063]

Table 3

[0064] (Example 11) Measurement of antioxidant performance by radical scavenging test using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) 100 μl of 0.3 mM DPPH ethanol solution and 100 μl of the dispersion prepared in Examples 1 and 2 adjusted to 0.5 mg / ml were mixed and allowed to stand at room temperature for 30 minutes. As a control, the same treatment was also performed on a solution containing no cerium oxide nanoparticles. In addition, a reference solution was prepared by mixing 100 μl of 0.3 mM DPPH ethanol solution and 100 μl of distilled water. The absorption spectra of the above solutions were measured. For the analysis, the absorbance at 517 nm, which is the maximum absorption wavelength of DPPH, was used. The difference between the absorbance of the reference solution and the absorbance of the control, and the difference between the absorbance of each dispersion and the absorbance of the control were calculated. The ratio of the latter absorbance difference to the former absorbance difference was calculated as the DPPH retention rate (%), and the value obtained by subtracting the DPPH retention rate from 100 was defined as the DPPH elimination rate (%). The results are shown in Table 4. From these results, it was confirmed that the dispersion containing the nanoparticles of cerium oxide of the present invention has high radical scavenging performance. On the other hand, for the dispersion of the nanoparticles prepared in Comparative Example 4, the radical scavenging performance was measured in the same manner, but the DPPH elimination rate was lower than that of the dispersants of Examples 1 and 2.

[0065]

Table 4

[0066] (Example 12) XAFS Observation X-ray absorption fine structure spectra were measured by irradiating X-rays to the dispersions (8 mg / ml) of the nanoparticles of cerium oxide of the present invention prepared in Examples 1 and 2, respectively, and measuring the absorption amount. The measurement conditions were as follows: the experimental facility was the Photon Factory BL12C of the High Energy Accelerator Research Organization, the spectrometer was a Si(111)2 crystal spectrometer, the absorption edge was the Ce L3 absorption edge, the detection method was the transmission method, and the detector was an ion chamber. The CeL3-edge XANES spectra are shown in FIGS. 1 and 2, respectively. The vertical axis was set by taking the ratio with the average value of the absorption in the range of -150 to -30 eV from E0 as 0 and the average value of the absorption in the range of +150 to +400 eV from E0 as 1, with 5724.4 eV of the spectrum as the absorption edge (E0). The cerium oxide nanoparticles prepared in Example 1 had maximum absorptions at 5727.990 eV and 5736.407 eV, and the cerium oxide nanoparticles prepared in Example 2 had maximum absorptions at 5727.990 eV and 5736.570 eV, respectively. From these results, it became clear that the cerium oxide nanoparticles of the present invention have maximum absorptions at 5726.0 - 5729.0 eV and 5735.0 - 5739.0 eV. On the other hand, for the solutions of cerium oxide nanoparticles prepared by post-adding a stabilizer in Comparative Examples 3 and 5, XAFS observations were also carried out under the same operations and conditions, and the obtained CeL3-edge XANES spectra are shown in FIGS. 1 and 2, respectively. The cerium oxide nanoparticles of Comparative Example 3 had maximum absorptions at 5729.285 eV and 5736.246 eV, and the cerium oxide nanoparticles of Comparative Example 5 had maximum absorptions at 5729.426 eV and 5736.407 eV, respectively. Although these cerium oxide nanoparticles have a maximum absorption between 5735.0 - 5739.0 eV, they do not have a maximum absorption between 5726.0 - 5729.0 eV, and it was found that they show spectra different from those of the cerium oxide nanoparticles of the present invention.

[0067] (Reference Example 1) XAFS Observation As cerium compounds that are not nanoparticles, cerium oxide crystals, cerium(III) carbonate, cerium(III) nitrate, and ammonium cerium(IV) nitrate were used, and XAFS observations were carried out under the same operations and conditions as in Example 12 above. The obtained CeL3-edge XANES spectra are shown in FIG. 3. The cerium oxide crystal had maximum absorptions at 5729.751 eV and 5736.582 eV, cerium(III) carbonate had a maximum absorption at 5725.161 eV, cerium(III) nitrate had a maximum absorption at 5725.316 eV, and ammonium cerium(IV) nitrate had maximum absorptions at 5725.796 eV and 5736.105 eV, respectively. It was found that none of these cerium compounds have a maximum absorption between 5726.0 - 5729.0 eV and 5735.0 - 5739.0 eV, which is different from the cerium oxide nanoparticles of the present invention.

Claims

1. Nanoparticles of cerium oxide produced by mixing a solution of an alicyclic amine represented by the following general formula (I) with a solution containing cerium(III) ions or a cerium(III) salt and adding an oxidizing agent. 【Chemical Formula 1】 (In the general formula (I), X represents NR 2 , O, S, and R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an aminoalkyl group having 1 to 4 carbon atoms, or a sulfonic acid alkyl group having 1 to 4 carbon atoms. R 1 and R 2 may be the same or different.)

2. The nanoparticles of cerium oxide according to Claim 1, wherein the pH is adjusted to 5 or more when adding the oxidizing agent.

3. Among the general formula (I), X represents NR ２ , O, and R 1 and R 2 represent a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 2 to 3 carbon atoms, an aminoalkyl group having 2 to 3 carbon atoms, or a sulfonic acid alkyl group having 2 to 3 carbon atoms. The nanoparticles of cerium oxide according to Claim 1 or 2, characterized in that.

4. The nano-particles of cerium oxide according to any one of claims 1 to 3, wherein the alicyclic amine represented by the general formula (I) is piperazine, 1-methylpiperazine, N,N'-dimethylpiperazine, 1-ethylpiperazine, N,N'-diethylpiperazine, 1-(2-hydroxyethyl)piperazine, 1,4-bis(2-hydroxyethyl)piperazine, N-(2-aminoethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid, piperazine-1,4-bis(2-ethanesulfonic acid), morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4-(2-aminoethyl)morpholine, 4-(2-hydroxyethyl)morpholine, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid.

5. Nano-particles of cerium oxide containing an alicyclic amine represented by the following general formula (I), wherein in the Ce L3-edge XANES spectrum obtained by X-ray absorption fine structure spectrum measurement, the nano-particles of cerium oxide having maximum absorption at 5726.0 to 5729.0 eV and 5735.0 to 5739.0 eV. 【Chemical formula 2】 (In the general formula (I), X represents NR2, O, S, and R1 and R2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an aminoalkyl group having 1 to 4 carbon atoms, a sulfonic acid alkyl group having 1 to 4 carbon atoms. R1 and R2 may be the same or different.)

6. A dispersion containing the nano-particles of cerium oxide according to any one of claims 1 to 5.

7. An oxidizing agent containing the nano-particles of cerium oxide according to any one of claims 1 to 5 or the dispersion according to claim 6.

8. An antioxidant containing the nano-particles of cerium oxide according to any one of claims 1 to 5 or the dispersion according to claim 6.

9. A method for producing cerium oxide nanoparticles, comprising mixing a solution of an alicyclic amine represented by the following general formula (I) with a solution containing cerium (III) ions or a cerium (III) salt, and adding an oxidizing agent. 【Chemical Formula 3】 (In the general formula (I), X represents NR2, O, or S; R1 and R2 each represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, an aminoalkyl group having 1 to 4 carbon atoms, or a sulfonic acid alkyl group having 1 to 4 carbon atoms. R1 and R2 may be the same or different.)

10. The method for producing cerium oxide nanoparticles according to Claim 9, wherein the pH is adjusted to 5 or higher when adding the oxidizing agent.

11. Among the general formula (I), X represents NR2 or O, and R1 and R2 each represent a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 2 to 3 carbon atoms, an aminoalkyl group having 2 to 3 carbon atoms, or a sulfonic acid alkyl group having 2 to 3 carbon atoms. The method for producing cerium oxide nanoparticles according to Claim 9 or 10, characterized in that.

12. The alicyclic amine represented by the general formula (I) is piperazine, 1 - methylpiperazine, N,N'-dimethylpiperazine, 1 - ethylpiperazine, N,N'-diethylpiperazine, 1-(2 - hydroxyethyl)piperazine, 1,4 - bis(2 - hydroxyethyl)piperazine, N-(2 - aminoethyl)piperazine, 1,4 - bis(2 - aminoethyl)piperazine, 2-[4-(2 - hydroxyethyl)-1 - piperazinyl]ethanesulfonic acid, piperazine - 1,4 - bis(2 - ethanesulfonic acid), morpholine, 4 - methylmorpholine, 4 - ethylmorpholine, 4-(2 - aminoethyl)morpholine, 4-(2 - hydroxyethyl)morpholine, 2 - morpholinoethanesulfonic acid, 3 - morpholinopropanesulfonic acid. The method for producing cerium oxide nanoparticles according to any one of Claims 9 to 11.

13. A method for producing a dispersion, comprising including cerium oxide nanoparticles produced by the method for producing cerium oxide nanoparticles according to any one of Claims 9 to 12.

14. A method for producing an oxidizing agent, including cerium oxide nanoparticles produced by the method for producing cerium oxide nanoparticles according to any one of Claims 9 to 12 or a dispersion produced by the method for producing a dispersion according to Claim 13.

15. A method for producing an antioxidant, including cerium oxide nanoparticles produced by the method for producing cerium oxide nanoparticles according to any one of Claims 9 to 12 or a dispersion produced by the method for producing a dispersion according to Claim 13.

Images