JP2010046625A - Method of synthesizing metal/alloy nanoparticles by supercritical hydrothermal reaction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such problems wherein though nanoparticles showing various particular excellent aspects, characteristics, and functions can be synthesized advantageously using supercritical and subcritical water reaction fields, in the reaction field of supercritical water conditions, the synthesis is limited to metal-oxide system nanoparticles due to the oxidizing power of water. <P>SOLUTION: When nanoparticles are synthesized from nanoparticle precursors at the reaction field under elevated temperature and pressure, and wherein water is present at the reaction field an organic modifying agent and a reducing agent are present together, and a nanoparticle synthesis reaction and a nanoparticle surface modification reaction are carried out, to prepare metal or alloy nanoparticles, in which organic groups are combined on the surface of the produced nanoparticles. Thereby, surface-modified metal or alloy nanoparticles are prepared by a simple method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for synthesizing metal / alloy nanoparticles using a hydrothermal reaction in supercritical / subcritical water. In particular, the present invention relates to a method for synthesizing metal / alloy nanoparticles whose surface is modified with an organic group under supercritical / subcritical water conditions.

  Nanometer-sized particles (nanoparticles) exhibit various unique and excellent properties, characteristics, and functions, so they are more accurate, smaller, and lighter than all current materials and products. It is expected to realize a technology that satisfies the above requirements. In this way, nanoparticles are made from ceramic nanostructure modifiers, optical functional coating materials, electromagnetic shielding materials, secondary battery materials, fluorescent materials, electronic component materials, magnetic recording materials, polishing materials, and other industrial and industrial materials, It is attracting attention as a material for the 21st century because it enables high-performance, high-performance, high-density, and high-precision products such as pharmaceuticals and cosmetics. From the recent basic research on nanoparticles, the discovery of ultra-high functionality, new physical properties, and the synthesis of new materials by the quantum size effect of nanoparticles has attracted a great deal of interest from industry.

Various methods have been proposed for the nanoparticle synthesis method. However, in many cases, since the surface energy of the nanoparticles is extremely high, the nanoparticles are likely to aggregate, and the original function of the nanoparticles is often not expressed. Once agglomerated nanoparticles cannot be redispersed, even if a surfactant or the like is used at that stage, the nanoparticles cannot be dispersed.
As a technology to solve these problems, Ajiri et al. Paid attention to the fact that the supercritical hydrothermal synthesis field forms a homogeneous phase between the organic modifier and the raw material aqueous solution. It has been shown that nanoparticle synthesis is possible. According to this method, a high-temperature stable phase can also be synthesized, and not only an organic modifier is adsorbed but also a chemical bond is generated due to a high-temperature reaction [Patent No. 3959332 (Patent Document 1) and Patent No. 3925936 (Patent Document 2)]. However, nanoparticle systems capable of supercritical synthesis have been limited to metal oxide systems due to the oxidizing power of water.
Magnetic nanoparticles are expected to have many applications such as magnetic fluids, high-density recording materials, and medical diagnostic materials, and extensive research has been conducted. So far, various synthetic means including synthesis in an organic solvent have been studied, but it has been difficult to synthesize metal nanoparticles that are easily oxidized such as iron in water.

Japanese Patent No. 3959332 Patent No. 3925936

Our group provides a technique for synthesizing various metal oxide nanocrystals in a supercritical water (SCW) field batch reactor in the presence of an organic modifier. However, although the nanoparticle synthesis method in the supercritical water (SCW) field is a technology that uses an elegant and environmentally friendly reaction medium, a metal that is easily oxidized in water, such as iron, is a metal oxide. Although it is possible to obtain nanoparticles, it has been difficult to obtain nanoparticles made of metals or alloys.

The present inventor has conducted intensive research with the aim of developing and utilizing a technology utilizing a fine particle synthesis system in a batch reactor of a supercritical water (SCW) field coexisting with an organic modifier. As a result, by using water, which is a low environmental load medium, the nanoparticle precursor is subjected to high-temperature and high-pressure water in the presence of a reducing agent and a surface modifier, for example, under supercritical water or subcritical water conditions. , Especially supercritical water (SCW
) The present invention was completed by successfully synthesizing metal or alloy nanoparticles by placing them under conditions. For example, the present invention has succeeded in realizing the synthesis of iron or iron-based alloy nanoparticles in the presence of a reducing agent and a surface modifier using water which is a low environmental load medium.

The present invention provides the following.
[1] A nanoparticle synthesis method in a reaction field in the presence of high-temperature and high-pressure water, in which a nanoparticle synthesis reaction is performed by coexisting an organic modifier and a reducing agent in a reaction field for synthesizing nanoparticles from a nanoparticle precursor. A method for synthesizing surface-modified metal or alloy nanoparticles, comprising performing a surface modification reaction of nanoparticles to obtain metal or alloy nanoparticles having an organic group bonded to the surface of the produced nanoparticles.
[2] The method for synthesizing surface-modified metal or alloy nanoparticles according to [1] above, wherein the reaction field in the presence of high-temperature and high-pressure water is subcritical or supercritical water.
[3] The method for synthesizing surface-modified metal or alloy nanoparticles according to the above [1] or [2], wherein the reducing agent is in a gas state.
[4] The above-mentioned [1] to [3], wherein the reducing agent is selected from the group consisting of formic acid, hydrogen gas, carbon monoxide gas, synthesis gas, water gas and mixtures thereof. A method for synthesizing surface-modified metal or alloy nanoparticles according to any one of the above.
[5] The surface-modified metal according to any one of the above [1] to [4], wherein the nanoparticle synthesis reaction is carried out at a temperature and / or pressure at or above the binary critical point or in the vicinity thereof. Or the synthesis method of alloy nanoparticles.
[6] The above-mentioned [1] to [1], wherein the organic modifier is allowed to coexist in the synthesis reaction field of the metal or alloy nanoparticles or the organic modifier is introduced into the reaction field immediately after the synthesis of the metal or alloy nanoparticles. [5] The method for synthesizing the surface-modified metal or alloy nanoparticles according to any one of [5].
[7] The surface modified metal or alloy nano of any one of the above [1] to [6], wherein the nanoparticle surface modification reaction is performed at a temperature of 200 ° C. or higher, preferably 250 ° C. or higher. Particle synthesis method.
[8] The organic modifier is selected from carboxylic acids, amines, thiols, phosphonic acid and derivatives thereof, as described in any one of [1] to [7] above Synthesis method of surface modified metal or alloy nanoparticles.
[9] The method for synthesizing surface-modified metal or alloy nanoparticles according to any one of [1] to [8], wherein the organic modifier is selected from carboxylic acids.
[10] A surface synthesized by the synthesis method according to any one of [1] to [9], wherein the surface is a metal or alloy nanoparticle having an organic group chemically bonded to the surface of the nanoparticle. Modified metal or alloy nanoparticles.
[11] The surface-modified metal or alloy nanostructure according to [10], wherein the bond between the surface of the nanoparticle and the modified organic group is a stable and strong bond at a temperature higher than the boiling point of the organic modifier. particle. [12] The surface modified metal according to [10] or [11] above, wherein the average particle diameter of the surface modified metal or alloy nanoparticles based on TEM and / or XRD data is about 1 to 50 nm. Or alloy nanoparticles.
[13] A magnetic material composition comprising the surface-modified metal or alloy nanoparticles according to any one of [10] to [12] as a magnetic material.

In the present invention, metal / alloy nanoparticles can be synthesized using hydrothermal reaction in supercritical / subcritical water, so that metal / alloy nanoparticles suitable for industrial use can be obtained by a simple method. Is possible. In the present invention, metal / alloy nanoparticles whose surface is modified with an organic group can be synthesized at low cost under supercritical / subcritical water conditions. The obtained metal / alloy nanoparticles can be used for various applications.
Other objects, features, excellence and aspects of the present invention will be apparent to those skilled in the art from the following description. However, it is understood that the description of the present specification, including the following description and the description of specific examples and the like, show preferred embodiments of the present invention and are presented only for explanation. I want. Various changes and / or modifications (or modifications) within the spirit and scope of the present invention disclosed herein will occur to those skilled in the art based on the following description and knowledge from other parts of the present specification. Will be readily apparent. All patent documents and references cited herein are cited for illustrative purposes and are not to be construed as a part of this specification. is there.

  The present invention provides a technique for synthesizing nanoparticles from a nanoparticle precursor in the presence of a reducing agent in a reaction field under high-temperature and high-pressure conditions, for example, subcritical or supercritical water conditions. In the nanoparticle synthesis method of the present invention, nanoparticle synthesis is performed using subcritical or supercritical water as a reaction field. By making the reaction field coexist with a reducing agent or an organic modifier, dispersibility in the medium is improved. Excellent metal nanoparticles and alloy nanoparticles can be efficiently synthesized by an extremely simple method. By allowing a reducing agent to be present in the reaction field, nanoparticles that are substantially composed of metal and whose surface is modified with an organic group, or that are composed essentially of alloy metal. Nanoparticles whose surfaces are modified with organic groups can be synthesized on an industrially available scale.

  In the present invention, a reaction field for forming nanometer-sized particles from an aqueous liquid mixed system containing nanoparticle precursors, and nanometer-sized particles from an aqueous liquid mixed system containing nanoparticle precursors and a reducing agent. The reaction field for forming is usually performed under high temperature and high pressure, and a typical state is a system using water in a supercritical state or a subcritical state as a solvent. The supercritical state refers to a state in a region at a temperature or pressure above the critical point of a substance, and it means that the boundary between gas and liquid disappears and is indistinguishable. ing. In the supercritical state, the viscosity is generally low and it diffuses more easily than the liquid, but has the same solvating power as the liquid. The subcritical state refers to a liquid state having a density substantially equal to the critical density near the critical temperature. For example, after the raw material is filled in a sealed container, the supercritical state is set, the raw material is dissolved, a homogeneous phase is formed, and then the temperature is changed so that the nanoparticle nuclei are formed and the subcritical state is reached. It is also possible to perform nanoparticle formation / growth using the difference in solubility between the critical and subcritical materials.

In order to produce nanoparticles in a supercritical state, the temperature is generally kept higher than the critical point of water as a solvent. In the case of supercritical water, the critical point is a critical temperature of 647 K (374 ° C.) and a critical pressure of 22.064 MPa (218 atm), but there are situations where the pressure far exceeds the critical pressure even at temperatures below the critical temperature. For example, if the filling rate into an autoclave (pressure vessel) is high, the pressure far exceeds the critical pressure even at a temperature below the critical temperature. The supercritical state here may include a state exceeding the critical pressure. Since the reaction mixture is enclosed within a constant volume (container volume), an increase in temperature increases the pressure of the fluid. In general, the temperature T is in a supercritical state if T> Tc (Tc: critical temperature of solvent) and pressure P> Pc (Pc: critical pressure of solvent). The reaction mixture may be pressurized to some extent and then enclosed in a fixed volume (container volume) and then allowed to increase in temperature to increase the pressure of the fluid. Actually, the solubility of the raw material introduced into the solvent is very different between the subcritical condition and the supercritical condition, so that a sufficient growth rate of the nanoparticles can be obtained under the supercritical condition. The reaction time depends in particular on the reactivity of the raw nanoparticle precursor, the reactivity of the organic modifier and the thermodynamic parameters, ie the temperature and pressure values.

The nanoparticle formation field can be obtained in an apparatus capable of achieving the conditions of high temperature and high pressure, and is not particularly limited as long as it is such an apparatus, and can be selected and used from apparatuses widely known to those skilled in the art in the art. For example, a batch type apparatus (batch type apparatus) can be used. Usually, an autoclave (pressure-resistant reactor) or the like can be used. In the present invention, an autoclave reactor can be preferably used. Such a reactor may be capable of temperature control. For example, the temperature of the reaction field may be different after the introduction of the nanoparticle precursor and before the generation of the generated nanoparticles, and by changing the temperature of the reaction field, It may be possible to control the growth stage of the fine particles by the reaction of the organic modifier. Furthermore, the temperature change of the reaction field in the reactor may be kept constant after the temperature rise, or may be continuously changed, or after the temperature is discontinuously increased to a high temperature and a low temperature lower than that. Any of these may be used, next to a high temperature.

The temperature range of the reaction field such as in an autoclave can be selected appropriately depending on the packing rate.For example, the lower limit is usually about 150 ° C., preferably about 200 ° C., more preferably about 250 ° C. It is about 275 ° C, more preferably about 300 ° C, more preferably about 350 ° C, and the upper limit is usually about 800 ° C, preferably about 650 ° C, more preferably about 550 ° C, more preferably about 500 ° C. C., in some cases about 450.degree. C., and the temperature range of the reaction field is preferably within the upper and lower limits as described above. In a typical case, the temperature range in the autoclave is about 200-475 ° C. and good results can be obtained, and in another case about 250-450 ° C., good results can be obtained, Furthermore, suitable results can be obtained at about 350 to 425 ° C. The temperature range can be selected according to the type and composition of the target nanoparticles. The temperature range in the autoclave is, for example, about 250 to 450 ° C., preferably about 250 to 425 ° C., more preferably about 270 to 400 ° C. when obtaining single metal nanoparticles, and when obtaining semiconductor nanoparticles. For example, when obtaining magnetic nanoparticles at about 200 to 450 ° C., preferably about 250 to 400 ° C., more preferably about 275 to 375 ° C., more preferably about 300 to 375 ° C., for example, about 200 ˜475 ° C., preferably about 225 ° C. to 450 ° C., more preferably about 250 ° C. to 425 ° C., more preferably about 275 ° C. to 400 ° C. Then, it can be set to a higher temperature range, for example, about 300 to 550 ° C, preferably about 325 to 525 ° C, more preferably about 340 to 500 ° C, and more preferably about 350 to 475 ° C.

The pressure range of the reaction field such as in the autoclave can be selected as appropriate depending on the raw materials used.For example, after the liquid reaction mixture is usually placed in the reactor and sealed in the autoclave, the pressure is adjusted to the above predetermined temperature. Those obtained by raising the temperature can be mentioned. The pressure range of the reaction field such as in an autoclave can be maintained, for example, at a pressure in the range of about 4 MPa to 600 MPa.For example, the lower limit is usually 5 MPa, preferably 7 MPa, particularly preferably 10 MPa, and the upper limit is usually 500 MPa. Can be maintained at 400 MPa, particularly preferably 200 MPa, but is not limited thereto, and is obtained by raising the temperature to a predetermined temperature under the above-mentioned sealing conditions, and the desired reaction occurs. If it is a thing, it will not specifically limit.

The injection ratio of water, nanoparticle precursor, reducing agent, organic modifier, etc. for achieving the above temperature range and pressure range in the reactor such as in the autoclave, that is, the filling rate is the free volume inside the container, That is, the volume of the aqueous solution containing the nanoparticle precursor to be placed in the autoclave is subtracted from the total volume of the autoclave and is usually 10 to 98%, preferably based on the volume of the aqueous solution containing the raw material with respect to the remaining volume. Can be 20 to 95%, more preferably 10 to 85%, but can be appropriately selected without particular limitation as long as the predetermined purpose can be achieved.
The ratio of the nanoparticle precursor to the reducing agent in the starting mixture for reaction can be determined by performing experiments or the like as appropriate to obtain a desired nanoparticle product, and is not particularly limited. The particle precursor: reducing agent ratio is about 1: 1,000 to about 1,000: 1, preferably about 1: 250 to about 250: 1, more preferably about 1: 100 to about 100: 1, in molar ratio. In case it is about 1:50 to about 50: 1,
More preferably, it can be about 1:25 to about 25: 1, more preferably about 1:15 to about 15: 1, and more preferably about 1: 5 to about 5: 1. The ratio of the nanoparticle precursor to the organic modifier in the reaction starting mixture can be determined by performing experiments or the like as appropriate to obtain the desired nanoparticle product, and is not particularly limited. The ratio of nanoparticle precursor: organic modifier is about 1: 1,000 to about 1,000: 1, about 1: 100 to about 100: 1, or about 1:50 to about 50: 1 in molar ratio. Or
About 1:25 to about 25: 1, about 1:10 to about 10: 1, about 1: 5 to about 5: 1, about 1: 2 to about 2: 1 Good.

In the production method of the present invention, a preliminarily heated aqueous solution of the nanoparticle precursor can be supplied to the reaction field, and a preliminarily heated reducing agent aqueous liquid or gaseous reducing agent can be introduced thereto.
The reaction time after reaching a predetermined temperature varies depending on the type of target nanoparticles, the raw materials used, the reducing agent, the type of organic modifier, and the size and amount of nanoparticles to be produced, but usually several minutes. From a few months. During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered. After a reaction time for producing desired nanoparticles, the temperature is lowered. The method for lowering the temperature is not particularly limited, but the heating of the heater may be stopped and the autoclave may be allowed to cool as it is installed in the furnace, or the autoclave may be removed from the electric furnace and air cooled. If necessary, it can be rapidly cooled using a refrigerant. In the method of the present invention, nanoparticles having a particle size of 100 nm or less are obtained by changing parameters such as the reaction time, the ratio of precursor: reducing agent, the length of the carbon chain present in the modifying group, and the reaction temperature. be able to. Rod-shaped nanoparticles and wire-shaped nanoparticles having a width of 5 to 50 nm can be obtained, and cube-shaped nanoparticles having a uniform size can also be obtained.

  The nanoparticle precursor that is a raw material can be preferably used as an aqueous solvent to be used, for example, water and / or a material that dissolves in a mixture of water and an organic modifier. A liquid material can be preferably used. The raw material may be an aqueous solution or a solution of a mixture of an appropriate organic solvent and water if necessary, but may be used as it is if the raw material is liquid at room temperature. In the present invention, a nanoparticle precursor that can form a homogeneous system in a reaction field can be suitably used. Moreover, in this invention, a homogeneous system can be formed in a reaction field and a water-soluble raw material precursor can be used conveniently.

  As the nanoparticle precursor, those giving desired nanoparticles can be suitably used, and any substance can be used as long as the desired nanoparticles can be obtained. Therefore, it is possible to arbitrarily select and use an appropriate one from simple substances or compounds containing elements contained in the nanoparticles to be produced. Preferably, those which are commercially available and can be easily obtained, or those which can be easily derived therefrom are used. For example, in the case of nanoparticles containing a metal element, examples of the precursor of metal nanoparticles (including alloy nanoparticles) include metal halides, metal carbonates, metal carboxylates, metal alkoxides, metal alkyls. Examples thereof include metal complex compounds such as xanthates and metal carbonyl compounds, and metal hydroxides. Representative metal nanoparticle precursors include, for example, metal alkoxide, metal hydroxide, metal acetate, metal citrate, metal glycolate, metal oxalate, metal glyoxalate, metal glycerate, Metal amine complexes, metal acetone complexes, metal acetylacetonates and the like are preferably used. The precursors may be used alone or in combination of two or more in any combination and ratio. The precursor may exist in any state in the reaction solution, but usually the precursor exists in a dissolved state in the reaction system. Furthermore, it can be used as a constituent element donor of a desired nanoparticle so that a compound containing the constituent element coexists.

In one exemplary embodiment of the present invention, a water-soluble salt can be suitably used as the nanoparticle precursor, such as iron halide (iron chloride, iron bromide, etc.), iron nitrate, iron carbonate, iron Carboxylate (iron acetate, iron citrate, etc.), iron acetylacetonate, iron hydroxide, platinum halide (platinum chloride, platinum bromide, etc.), platinum nitrate, platinum carbonate, platinum carboxylate ( Platinum acetate, platinum citrate, etc.), platinum acetylacetonate, platinum hydroxide and the like can be used. Preferably, an iron acetate aqueous solution, an iron nitrate aqueous solution, an iron hydroxide aqueous solution, an iron acetylacetonate aqueous solution, a platinum acetate aqueous solution, a platinum citrate aqueous solution, a platinum acetylacetonate aqueous solution, or a mixture thereof can be used. When an acidic salt is used, the pH can be adjusted to about 7 to 10 by treatment with an aqueous alkali solution such as sodium hydroxide or potassium hydroxide. The solution containing the nanoparticle precursor can be adjusted to the pH of the solution as appropriate so that desired nanoparticle synthesis is possible, and is preferred in some cases. It is allowed to contain other inevitable impurity elements derived from the raw material.

The “metal” constituting the nanoparticles of the present invention is not particularly limited as long as it can typically produce nanoparticles, and can be selected and used from those known to those skilled in the art. Typical metals include the group 13 boron (B) -group 14 silicon (Si) -group 15 arsenic (As) -group 16 tellurium (Te) lines in the periodic table of elements. As the boundary, elements on the line and those on the left side or the lower side of the long-period periodic table from the boundary can be mentioned.For example, Fe, Co, Ni, Ru, Rh , Pd, Os, Ir, Pt, etc., Group 11 elements such as Cu, Ag, Au, etc., Group 12 elements such as Zn, Cd, Hg, etc., Group 13 elements such as B, Al, Ga, In, Group 14 elements such as Tl, Si, Ge, Sn, Pb, Group 15 elements As, Sb, Bi, Group 16 elements Te, Po, etc., and Group 1-7 elements Etc. Mn, Tc, Re, etc. for Group 7 elements, Cr, Mo, W, etc. for Group 6 elements, V, Nb, Ta, etc. for Group 5 elements, Ti for Group 4 elements, etc. Sc, Y, lanthanides (eg, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, etc.) and actinoids (Ac, Th, etc.), Misch metal, etc. for Group 2 elements, such as Be, Mg, Ca, Sr, Ba, etc., for Group 1 elements, Li, Na,
K, Rb, Cs etc. are mentioned. The periodic table of elements is IUPC (International Union of
Pure and Applied Chemistry) Based on revised inorganic chemistry nomenclature (1989).

The nanoparticles of the present invention are: (a) a metal nanoparticle, (b) an alloy nanoparticle composed of at least two metals, (c) a metal oxide or a composite metal oxide (D) nanoparticles in which a metal oxide or composite metal oxide is dispersed in a metal or alloy; (e) a metal or alloy dispersed in a metal oxide or composite metal oxide; (F) nanoparticles that are semiconductor compounds containing Group 15 elements of the periodic table, (g) nanoparticles that are semiconductor compounds containing Group 16 elements of the periodic table, and the like. The nanoparticles of the present invention also include those that are crystalline nanoparticles.

In the present invention, the reducing agent and the organic modifier can coexist in a reaction field for synthesizing (forming) nanometer-sized particles from a liquid mixed system containing a nanoparticle precursor and water.
The reducing agent is capable of reducing metal oxides under subcritical water or supercritical water conditions, and / or forming nanoparticles made of metal or alloys under subcritical water or supercritical water conditions. Are listed. As the reducing agent, an aqueous solution and / or a gaseous substance can be preferably introduced into the reaction field, but a mixture of gas and liquid can also be used. Typical reducing agents include formic acid, hydrogen gas, carbon monoxide gas, synthesis gas, water gas, a mixture of hydrogen and carbon monoxide, a mixture thereof, and the like. In one preferred embodiment of the present invention, an aqueous formic acid solution, a gaseous mixture of hydrogen and carbon monoxide, and the like can be used. The reducing agent may be added to the nanoparticle precursor-containing aqueous medium in advance and then the resulting mixture is added to the reaction field, or the nanoparticle precursor-containing aqueous medium present in the reaction field. It may be added to the inside.

The organic modifier is not particularly limited as long as it can bond an organic molecular residue to the surface of the fine particle, and preferably the organic molecular residue can be chemically bonded to the surface of the fine particle. Therefore, it can be selected from organic substances (or organic molecules) widely known in fields where application of nanoparticles is expected, including the fields of organic chemistry, inorganic materials, and polymer chemistry. Examples of the organic modifier include a bond through an O atom including an ether bond and an ester bond, a bond through an N atom including an amino bond or an amide bond, a bond through an S atom, and metal-C-. Bond, metal -C = bond, metal-(C = O)-bond, P atom bond, -OP- bond, phosphate ester bond, phosphite bond , Phosphonic acid bonds, phosphinic acid bonds, phosphinic acid bonds, phosphinic acid bonds and the like that allow formation of chemical bonds. The organic residue (organic molecular residue) is not particularly limited, and examples thereof include those known in the art and / or those known in the field of organic synthesis. For example, a hydrocarbon group, or Examples thereof include a group containing the same.

  Examples of the organic residue include a linear or branched alkyl group that may be substituted, a linear or branched alkenyl group that may be substituted, and a linear or branched alkynyl group that may be substituted. An optionally substituted saturated or unsaturated cyclic alkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted saturated or unsaturated heterocyclic group Groups and the like. As the hydrocarbon, the number of carbon atoms is not particularly limited, and those having 1 or 2 carbon atoms can be used. From the viewpoint of taking advantage of the characteristics of the present invention, a long chain carbon chain having 3 or more carbon atoms is used. What is hydrogen is preferable, for example, a C3-C30 linear or branched or cyclic hydrocarbon etc. are mentioned. The hydrocarbon may be substituted or unsubstituted. The substituent may be selected from functional groups widely known in the fields of organic chemistry, inorganic materials, polymer chemistry, etc., and one or more substituents exist. May be the same or different from each other.

  Examples of the substituent include a linear or branched alkyl group, a linear or branched alkenyl group, a linear or branched alkynyl group, a cyclic alkyl group, an aryl group, an aralkyl group, a saturated or unsaturated heterocyclic group. Cyclic group, cyano group, nitro group, halogen, carboxy group, ester group, acyl group, amide group, imino group, acylamino group, ketone group, formyl group, ether group, hydroxyl group, acyloxy group, sulfhydryl group, amino group, Examples include a sulfonyl group, a sulfide group, a disulfide group, and an azide group. Examples of the substituent include those containing a bond such as —O—, —S—, —N—, and —P—.

Examples of organic modifiers include amines, alcohols, aldehydes, ketones, carboxylic acids, esters, amides, oximes, phosgene, enamines, amino acids, peptides, saccharides, phosphate esters, Phosphoric acid esters, phosphonic acid esters, phosphonic acid esters, phosphinic acid esters, phosphinic acid esters, phosphine, phosphine oxides and other organic phosphorus compounds, thiols, thiocarboxylic acids and their sulfur analogues, etc. Can be mentioned.
In the present invention, the organic modifier added to the reaction field for nanoparticle synthesis is a chemical bond to the produced nanoparticles and covering at least part of the surface of the metal (alloy) nanoparticles as an organic ligand. If there is, it will not specifically limit, For example, what was known in the said field | area can be used. Preferably, the modifier is an organic molecule, and those having an action of stabilizing the formed nanoparticles can be preferably used, and those that function as an organic modifier in a high-temperature and high-pressure aqueous phase are preferably used. it can.

Examples of the amines include organic amines. The organic amines may be any of primary amines, secondary amines, and tertiary amines, and preferably primary amines and secondary amines. Examples of the organic amines include aliphatic amines, and examples thereof include primary aliphatic amines and secondary aliphatic amines. The number of carbon atoms of the amines is not particularly limited as long as the objective effects of the present invention are not significantly impaired. For example, the number of carbons is usually 8 or more, preferably 14 or more, more preferably 16 or more, and usually 24 or less, preferably 20 Below, more preferably 18 or less. Typical aliphatic amines include, for example, oleylamine, laurylamine, myristylamine, palmitylamine, stearylamine, octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, dioctylamine and the like. Examples thereof include alkylamines, aromatic amines such as aniline, hydroxyl group-containing amines such as methylethanolamine and diethanolamine, and derivatives thereof.

  Examples of the carboxylic acids include organic carboxylic acids or sulfur analogs thereof. The organic carboxylic acids are not particularly limited as long as the object and effects of the present invention are not significantly impaired. Examples thereof include aliphatic carboxylic acids, alicyclic carboxylic acids, aromatic carboxylic acids, and the like, and preferably aliphatic carboxylic acids. Can be selected and used. The number of carbon atoms of the carboxylic acids is arbitrary as long as the objective effect of the present invention is not significantly impaired, but is usually 5 or more, in some cases 8 or more, or 14 or more, in other cases 16 or more, and usually 24 or less. , Preferably 20 or less, more preferably 18 or less. Examples of carboxylic acids include hexanoic acid, oleic acid, linoleic acid, linolenic acid, caprylic acid (octanoic acid), capric acid, lauric acid, behenic acid, stearic acid, myristic acid, palmitic acid, arachidic acid, lignoceric acid, Examples include myristoleic acid, palmitoleic acid, vaccenic acid, eicosenoic acid, stearidonic acid, eicosapentaenoic acid, docosahexaenoic acid, arachidonic acid, erucic acid and the like.

  Examples of the alcohols include those corresponding to the above organic carboxylic acids. Similarly, aldehydes, ketones, esters, amides, and the like can be exemplified by those corresponding to the above organic carboxylic acids. Those sulfur analogs such as thiols may also correspond to, for example, the above organic carboxylic acids.

  Examples of the organic phosphorus compounds include phosphate esters, phosphine, phosphine oxides, trialkylphosphine, phosphite esters, phosphonate esters, phosphinate esters, phosphinic acid. Esters, phosphinic acid esters and the like may be included. Examples of the organic phosphorus compounds include those containing, as an organic group, one selected from the hydrocarbon groups described above. Typical organic phosphorus compounds include, for example, trialkylphosphine such as tributylphosphine, trihexylphosphine, trioctylphosphine, tributylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide ( TOPO), and trialkylphosphine oxides such as tridecylphosphine oxide. As the organophosphorus compounds, compounds having a carbon-phosphorus single bond in the molecule can also be suitably used.

  Typical organic modifiers include, for example, pentanol, pentanal, pentanoic acid, pentanamide, pentanethiol, hexanol, hexanal, hexanoic acid, hexanamide, hexanethiol, heptanol, heptanal, heptanoic acid, heptaneamide, heptanethiol. Octanol, octanal, octanoic acid, octatanamide, octanethiol, decanol, decanal, decanoic acid, decanamide, decanethiol and the like. As the organic modifier (organic molecule) used as a raw material, a water-soluble one can be suitably used. The organic modifier is used as an aqueous solution, but may be used as a mixed solvent solution of an organic solvent and water, if necessary.

In the case where an organic solvent is allowed to coexist in an aqueous solution containing an organic molecule that is introduced into a reaction field as an organic modifier and an aqueous solution containing a nanoparticle precursor introduced into a reaction field as a raw material, the organic solvent is miscible with water, Alternatively, hydrophilic ones can be suitably used. For example, alcohols, ketones, aldehydes, nitriles, lactams, oximes, amides, ureas, amines, sulfides, sulfoxides, phosphate esters , Esters which are carboxylic acids or carboxylic acid derivatives, carbonic acid or carbonic acid esters, ethers and the like. Examples of alcohols include methanol, ethanol, propanol, isopropanol, butanol, pentanol, cyclopentanol, hexanol, cyclohexanol, heptanol, cycloheptanol, octanol, cyclooctanol, nonanol, decanol, dodecanol, tridecanol, tetradecanol, Examples include heptadecanol, cycloheptanol, methoxyethanol, chloroethanol, trifluoroethanol, hexafluoropropanol, phenol, benzyl alcohol, ethylene glycol, and triethylene glycol.

Examples of ketones or aldehydes include acetone, 2-butanone, 3-pentanone, diethyl ketone, methyl ethyl ketone, methyl propyl ketone, butyl methyl ketone, cyclohexanone, acetophenone, and the like. Examples of nitriles include acetonitrile and benzonitrile. Examples of lactams include ε-caprolactam. Examples of oximes include cyclohexanone oxime. Examples of amides or ureas include formamide, N-methylformamide, N, N-dimethylformamide (DMF), N, N′-dimethylacetamide, pyrrolidone, N-methylpyrrolidone, N, N′-dimethylethyleneurea, N, N′-dimethylpropyleneurea, N, N-dimethylformamide, tetrahydrofuran and the like can be mentioned. Examples of amines include quinoline, triethylamine, tributylamine and the like. Examples of the sulfoxides include sulfolane. Examples of phosphate esters include hexamethylene phosphonic acid. Examples of carboxylic acids or esters include ethyl acetate, methyl acetate, acetic acid, dimethyl carbonate, diethyl carbonate, and propylene carbonate. Formic acid which is a reducing agent may be used as an organic solvent. Examples of ethers include diglyme, diethyl ether, and anisole.

  The reaction product synthesized with nanoparticles according to the present invention is usually cooled to room temperature after the reaction. Separation of the produced nanoparticles from the reaction mixture can be performed by applying a method known in the art, and can be performed using a physical method or a chemical method. Since the surface of the nanoparticle is modified with an organic group, various physical properties can be imparted by the modifying group, and the nanoparticle can be isolated using the property of the modifying group. In general, it is possible to separate from impurities and raw materials by performing phase separation or phase partitioning using water and an organic solvent such as hydrophilic or hydrophobic. Preferably, solvent extraction, chromatography and the like can also be used.

  The metal / alloy nanoparticle product obtained in the present invention can be maintained in a stably dispersed state. For example, an appropriate organic solvent (for example, aromatic hydrocarbon such as benzene, toluene, xylene, naphthalene, n -Alkanes including long-chain alkanes such as hexane, n-heptane, n-octane, isooctane, nonane, decane, dodecane, and octadecane, cyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclohexane)) As a dispersed liquid, it can be maintained stably. Therefore, the nanoparticle dispersion of the present invention can form a uniform magnetic layer even when various industrial materials such as a coating type magnetic recording medium material are blended with a binder. Furthermore, an extremely thin layer can be formed, which is excellent.

In the present specification, the term “nanoparticle” refers to a nanometer-sized particle as described above, for example, an average particle diameter of 1 μm (1,000 nm) or less. The average particle diameter is preferably a size of 200 nm or less, and preferably a size of 150 nm or less. In some cases, the nanoparticles may have an average particle size of 100 nm or less, and in other cases the average particle size may be 50 nm or less. In a preferred case, the nanoparticles have an average particle size of 20 nm or less, and in other cases, the average particle size is 10 nm or less, or 5 nm or less. It may be a thing. The nanoparticles are 0.1-50 nm particles, 1-50 nm particles,
Preferably they are 1-25 nm particles, more preferably 1-20 nm particles, more preferably 5-20 nm particles, and even more preferably 5-10 nm particles.

In a preferred case, the nanoparticles preferably have a uniform particle size, but may have a mixture of particles having different particle sizes at a certain ratio. In the technology of the present invention, those having a particle size of 5 nm, those having a particle size of 2 to 7 nm, particles having a particle size of 2 to 2.5 nm, and even 70% or more, 80% or more of the nanoparticle population 90% or more, 95% or more of 5 nm particle size, 2 to 7 nm particle size, or 2 to 2.5 nm particle size is obtained . The nanoparticle population obtained by the method of the present invention includes 1-5 nm particles, 5-10 nm particles, 10-15 nm particles, 15-20 nm particles, 20-30 nm particles, 30-50 nm particles, 1 ~ 3nm particles, 3-5nm particles, 5-7nm particles, 7-10nm particles, 10-13nm particles, 13-16nm particles, 16-20nm particles, or 20-25nm particles And 70% or more, 80% or more, 90% or more, 95% or more of the nanoparticle population includes those of that size.

The metal / alloy nanoparticles are those having an average particle size of 9 to 50 nm or less, preferably 10 to 40 nm, as measured by dynamic light scattering (DLS), for example. Or an average particle size measured by X-ray diffraction (XRD) of 25 nm or less, or 15 nm or less. What you have is fine. Furthermore, the average particle diameter of the metal / alloy nanoparticles based on XRD data is about 5 to 25 nm, preferably about 7 to 25 nm, and more preferably about 8 to 25 nm. Or more preferably about 8-15 nm. In some cases, the nanoparticles may have an average particle size of 15 nm or less, and in other cases, the average particle size may be 10 nm or less.

When the nanoparticle shape is a rod, cylinder, cuboid, elliptic cylinder, etc., the size of the short axis is a small value of the particle size, and the size of the long axis is smaller than the size of the short axis. It may be a large value. Nanoparticles are spheres, cubes, hexahedrons, octahedrons and other polygonal cubes, rods, cylinders, oval shapes, tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, triclinic, wurtz It may be in the form of ore-type crystals, single-walled or multi-walled nanotubes, or other nanoscale shapes. They exhibit very interesting magnetic, electrical and optical properties.
The particle size can be measured by methods known in the art, such as TEM,
It can be measured by adsorption method, light scattering method (including DLS), SAXS, etc. In TEM, observation is performed with an electron microscope. When the particle size distribution is wide, it is necessary to pay attention to whether or not the particles entering the field of view represent all particles. In the adsorption method, the BET surface area is evaluated by N ₂ adsorption or the like.

  In the synthesis method of the present invention, nanoparticles composed of simple metals, alloy nanoparticles composed of two or more kinds of metal elements (for example, binary alloy nanoparticles, ternary alloy nanoparticles, quaternary alloy nanoparticles, multiple elements) Alloy nanoparticles, etc.), semiconductor nanoparticles, magnetic nanoparticles, phosphor nanoparticles, conductor nanoparticles, pigment nanoparticles, etc., in a simple manner, advantageously, in large quantities and / or inexpensively, And it is possible to manufacture a high quality product such as a uniform dispersion or a homogeneous product. Thus, the nanoparticles can be used to produce products with high performance.

The metal nanoparticles and alloy nanoparticles produced by the synthesis method of the present invention are selected from the above metals, for example, elements of Group 11 of the long-period periodic table such as Cu, Ag, Au (copper) Group elements), Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, etc.
Or platinum group elements), Zn, Cd, Hg and other periodic group 12 elements (zinc group elements), Mn, Tc, Re and other periodic group 7 elements (manganese group elements), Cr, Mo, Periodic Table Group 6 elements (chromium group elements) such as W, Periodic Table Group 5 elements (earth metal elements) such as V, Nb, Ta, and Periodic Table Group 4 elements such as Ti, Zr, Hf Elements (titanium group elements), Sc, Y, lanthanides (eg, La, Ce, Pr, Nd,
Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, etc.), actinoids (Ac, Th, etc.), Misch metal and other periodic group 3 elements (including rare earth elements), B, Al, Periodic table group 13 elements such as Ga, In, Tl (aluminum group elements), periodic table group 14 elements such as Si, Ge, Sn, Pb (carbon group elements), periodic periods such as As, Sb, Bi, etc. Examples include elements selected from Group 15 elements, Group 16 elements such as Te and Po, and Group 2 elements such as Mg, Ca, Sr and Ba. The nanoparticles may be used alone or may contain a plurality of elements. Moreover, in an alloy, what contains 2 or more types selected from said element may be mentioned.

Semiconductor nanoparticles produced by the synthesis method of the present invention include simple elements of Group 14 elements of the periodic table, such as carbon (C) (for example, diamond), silicon (Si), germanium (Ge), tin (Sn ) [
For example, α-Sn, etc.), lead (Pb), etc., a simple substance of Group 15 element of the periodic table, for example, phosphorus (black phosphorus),
Arsenic (As), antimony (Sb), etc., for example, selenium (Se), tellurium (Te), the compound comprising a plurality of periodic table group 14 element, for example, SiC, etc. Si _1-x Ge _x, the periodic table Compounds of Group 14 elements and Group 15 elements of the periodic table, for example, Si ₃ N ₄ ; compounds of Group 14 elements of the periodic table and S, Se, Te, etc., for example, tin (II) sulfide (SnS) , Tin (IV) sulfide (SnS ₂ ), tin (II, IV) (Sn (II) Sn (IV) S ₃ ), tin selenide (SnSe), tin telluride (SnTe) , Lead sulfide (PbS), lead selenide (PbSe), lead telluride (PbTe), etc., compounds of group 13 elements of the periodic table and group 15 elements of the periodic table, such as boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), aluminum nitride (AlN), Al _x Ga _1-x N, Al _x Ga _1-x As, aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb) ), Gallium nitride (GaN), gallium phosphide (GaP), GaInP ₂ , gallium arsenide (GaAs), antimony Periodic table such as gallium (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), In _x Ga _1-x As, indium antimonide (InSb), Ga-Al-In-As, etc. Compounds of Group 13 elements with S, Se, Te, etc., for example, aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ga ₂ Se ₃ ), gallium telluride (Ga ₂ Te ₃ ), indium sulfide (In ₂ S ₃ ), indium selenide (In ₂ Se ₃ ), indium telluride (In ₂ Te ₃ ), etc.

Compounds of Group 12 elements of Periodic Table and Group 15 elements of Periodic Table, for example, Cd ₃ P _2, etc., compounds of Group 12 elements of Periodic Table and S, Se, Te, etc., for example, zinc sulfide (ZnS), Zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS), mercury selenide (HgSe), mercury telluride (HgTe) and other compounds of group 15 elements of the periodic table with S, Se, Te, etc., for example, antimony (III) sulfide (Sb ₂ S ₃ ), antimony selenide (III) (Sb ₂ Se ₃ ), tellurium Antimony (III) iodide (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se ₃ ), bismuth telluride (III) (Bi ₂ Te ₃ ), etc. , Compounds of Group 11 elements of the periodic table with S, Se, Te, etc., for example, Cu ₂ S, Ag ₂ S, Group 4 elements of the periodic table, Group 5 elements of the periodic table, Group 6 elements of the periodic table, Periodic table group 7 element and periodic table group 8-10 element (iron group element and Those selected from the group consisting of containing a platinum group element) and S, Se, compounds and the like Te, for example, molybdenum sulfide (IV) (MoS _2), cobalt sulfide (II) (CoS), iron sulfide (II ) (FeS), Fe ₂ S, etc., compounds of Group 2 elements of the periodic table and S, Se, Te, etc., for example, magnesium sulfide (MgS), magnesium selenide (MgSe), and further, chalcogen spinels, For example, CdCr ₂ Se _4, like _{CuCr 2 S 4, CuIn 2 S} 2, CuIn 2 Se 2, HgCr 2 Se 4, and the like YSi _2.

Among these, as important semiconductors, for example, Si, Ge, SnS ₂ , SnS, SnSe, SnTe, PbS, PbSe, PbTe, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb , Al ₂ S ₃ , Al ₂ Se ₃ , Ga ₂ S ₃ , Ga ₂ Se ₃ , Ga ₂ Te ₃ , In ₂ S ₃ , In ₂ Se ₃ , In ₂ Te ₃ , ZnS, ZnSe, ZnTe, CdS, CdSe CdTe, HgS, HgSe, HgTe, Sb ₂ S ₃ , Sb ₂ Se ₃ , Sb ₂ Te ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , Bi ₂ Te ₃ , MgS, MgSe, and the like.
The semiconductor nanoparticles obtained by the production method of the present invention may be doped (meaning that they are intentionally added) with any activator for the main nanoparticle constituents. Examples of such active materials include alkaline earth metals such as magnesium, aluminum group elements such as manganese, boron, aluminum, gallium, indium and thallium, carbon group elements such as carbon, tin and germanium, phosphorus, arsenic and antimony , Nitrogen group elements such as bismuth, copper group elements such as copper and silver, rare earth elements including lanthanoids such as yttrium, cerium, europium, terbium, erbium and thulium, and halogen elements such as chlorine and fluorine, etc. However, the present invention is not limited thereto and is selected from those used in the field.

Examples of the magnetic nanoparticles produced by the synthesis method of the present invention include those composed of nano-sized particles containing metals or alloys containing iron group or manganese group elements as essential components. Exemplary magnetic, Fe, Co, metals Ni, FePt, CoPt, FePd, M 1 nAl, FePtM 1, CoPtM 1
, FePdM ¹ , alloys selected from the group consisting of M ¹ nAlM ¹ (in the chemical formula, M ¹ represents a metal element, and M ¹ is, for example, Li, Mg, Al, Si, P, S, Mn, Ni, Cu, Zn, Ga, Ge, As, Se, Ag, Cd, In, Sn, Sb, Te, I, Au, Tl, Bi, Po, and At). Typical examples are FeNi, FePd, FePt, FeRh, CoNi, CoPt, CoPd, CoRh, CoAu, Ni ₃ Fe, FePd ₃ , Fe ₃ Pt
, FePt ₃ , CoPt ₃ , Ni ₃ Pt, CrPt ₃ , Ni ₃ Mn, FeNiPt, FeCoPt, CoNiPt, FeCoPd, FeNiPd, FePtCu, FePtIn, FePtPb, FePtBi, FePtCu, FePtCu, FePdCu, FeCoPCu, FePdCu, FeCoPg, etc. May be included. Magnetic materials include Ni-Fe alloys (Permalloy), Fe or Fe-Co alloys, Fe-Cr-Co alloys, Alnico magnet alloys, rare earth cobalt intermetallic compounds, Nd-Fe-B intermetallic compounds, etc. Good.

By utilizing the technique of the present invention, highly crystalline nanoparticles can be obtained, and organically modified nanoparticles can be obtained.
High crystallinity includes electron diffraction method, transmission electron microscope (TEM), field emission transmission electron microscope (FE-TEM), scanning electron microscope (SEM), scanning transmission electron microscope. This can be confirmed by analysis of an electron micrograph such as (Scanning Transmission Electron Microscope: STEM), X-ray diffraction (XRD), or thermogravimetric analysis. For example, in electron diffraction, a dot is obtained as a diffraction interference image for a single crystal, a ring for a polycrystal, and a halo for an amorphous. In the electron micrograph, the crystal plane is solid if it is a single crystal, and it is polycrystalline if it has such a shape that crystals further appear from above the particles. When polycrystalline primary particles are small and many particles aggregate to form secondary particles, they become spherical. If it is amorphous, it must be spherical. In X-ray diffraction, a sharp peak is obtained if it is a single crystal. The crystallite size can be evaluated from the width of 1/2 height of the X-ray peak using the Sherre equation. If the crystallite size obtained by the evaluation is the same as the particle diameter evaluated from the electron microscope image, it is evaluated as a single crystal.

In thermogravimetric analysis, when heated in a dry inert gas with a thermobalance, the weight decreased due to the evaporation of water adsorbed at around 100 ° C, and further decreased to about 250 ° C due to dehydration from within the particles. Is seen. When organic materials are included, even greater weight loss is observed at 250-400 ° C. In the case of particles obtained by the technique of the present invention, even when the temperature is raised to 400 ° C., the weight loss due to dehydration from the inside of the crystal is 10% or less at maximum, which is greatly different from the case of nanoparticles synthesized at low temperature. Thus, the characteristics of the organic modified metal fine particles obtained according to the present invention are characterized by high crystallinity, for example, a sharp peak in X-ray diffraction, dots or rings observed in electron diffraction, For example, dehydration of crystal water is 10% or less per dry particle by thermogravimetric analysis, and / or primary particles have a crystal plane in an electron micrograph. The nanoparticle of the present invention has a bond strength higher than the boiling point of the organic molecule in thermogravimetric analysis and is equal to or higher than the thermal decomposition temperature.

Nanoparticles are, for example, Cu, Ag, and Al for applications such as electrodes and catalyst materials, Ni for applications such as electrodes, magnetic materials, and catalyst materials, Co and Fe for applications such as magnetic materials and catalyst materials, and Ag / Cu is used for applications such as electrodes and catalyst materials, and B ₄ C, AlN, TiB ₂ etc. are used for applications such as high-temperature materials and high-strength materials.
Nanoparticles and thin films having nanoparticles in a specific arrangement are recognized to exhibit unique and excellent characteristics. For example, a single-layered array of nanoparticles is known to be capable of being densely packed like magnetic nanoparticles and exhibit excellent functions as a near-field memory element, and is applied to magnetic tapes and the like. It exhibits excellent properties and is useful. In addition, since the quantum size effect can be obtained, for example, in the case of nano phosphors arranged in a dispersion pattern, products such as quantum effect phosphors, quantum effect light emitters, and LSI high-density mounting bases can be provided. . Nanoparticles that are arranged in multiple layers simultaneously exhibit excellent functions such as low light scattering and a photocatalytic effect, such as wet photoelectric conversion elements and highly functional photocatalytic coatings. A particle-dispersed film can be provided with excellent functions such as a reinforcing effect and a flame-retardant effect, and can be used as a semiconductor sealing agent.
The nanoparticles obtained by the present invention function as particles that meet user needs. For example, it is useful as a high-concentration nanoparticle-dispersed resin for semiconductor packaging, a nanoparticle-dispersed ink for inkjet, battery materials, catalyst materials, lubricants, and the like.

The metal / alloy nanoparticles obtained in the present invention can be a product mixed with a binder such as plastic or rubber, for example, a bonded magnet. The present invention further includes a coated magnetic recording medium having a magnetic layer in which the nanoparticles, which are magnetic materials, are dispersed in a binder. Examples of the binder usually include polyamide resins such as NBR rubber, polyethylene, polypropylene, polyethylene chloride, nylon 6 and nylon 12. The metal / alloy nanoparticles of the present invention can be kneaded with various binders such as resin, metal, rubber and the like and molded in a magnetic field or in the absence of a magnetic field. If necessary, the molded product may be cured to form a bonded magnet. Alternatively, the metal / alloy nanoparticles may be kneaded with a binder to form a coating material, which may be applied to a substrate made of a plastic resin or the like, and cured as necessary to form a magnetic layer to form a coating type magnetic recording medium. . Furthermore, the metal / alloy nanoparticles can also be used for the production of sintered magnets and ceramics.
The present invention also includes a magnetic recording medium having a thin film magnetic layer. This thin film magnetic layer may contain a conventionally known oxide magnetic material in addition to the metal / alloy nanoparticles of the present invention described above.

A product using the metal / alloy nanoparticle material of the present invention is appropriately processed as required into a predetermined shape and used for a wide range of applications as described below. For example, automotive motors for fuel pumps, power windows, ABS, fans, wipers, power steering, active suspension, starters, door locks, electric mirrors, etc .; FDD spindle, VTR capstan, VTR rotating head, VTR reel, OA for VTR loading, VTR camera capstan, VTR camera rotating head, VTR camera zoom, VTR camera focus, radio cassette etc. Capstan, CD, LD, MD spindle, CD, LD, MD loading, CD, LD optical pickup, etc. Motors for AV equipment; motors for home appliances for air conditioner compressors, refrigerator compressors, electric tool drives, fans, microwave fans, microwave plate rotation, mixer drives, dryer fans, shaver drives, electric toothbrushes, etc .; robot shafts, Joint drive, robot main drive, work Motors for factory automation equipment for machine table drive, machine tool belt drive, etc .; motorbike generators, magnets for speakers and headphones, magnetron tubes, magnetic field generators for MRI, CD-ROM clampers, distributor sensors, ABS It is suitably used for various electric / electronic machines and parts / devices such as sensors for fuel, oil / oil level sensors and magnet latches, optical equipment / instruments, parts / devices, various circuits / wirings, etc.
When the metal / alloy nanoparticle of the present invention is a magnetic material, it can be used for magnetic disks, magnetic cards, magnetic tapes, memory cards, and is useful for applications such as credit cards, identification cards, and information recording media. Even if used, it is useful.

The present invention will be described in detail with reference to the following examples, which are provided merely for the purpose of illustrating the present invention and for reference to specific embodiments thereof. These exemplifications are for explaining specific specific embodiments of the present invention, but are not intended to limit or limit the scope of the invention disclosed in the present application. In the present invention, it should be understood that various embodiments based on the idea of the present specification are possible.
All examples were performed or can be performed using standard techniques, except as otherwise described in detail, and are well known and routine to those skilled in the art. .

(1) In a glove box, in a pressure-resistant reactor with an internal volume of 5 mL, an aqueous iron (II) acetate solution as a raw material, formic acid used as a reducing agent, and hexane, an organic modifier that is expected to modify the surface of synthesized particles. Acid was added. This was heated to 400 ° C. in a shaking electric furnace and reacted. After the reaction
The product was evaluated with an X-ray diffractometer (XRD), a transmission electron microscope (TEM), and the like. In this example, the time when heating was started in the electric furnace was defined as a reaction time of 0 minutes.
(2) The effect of adding 0.1M hexanoic acid was evaluated under the conditions of iron acetate 0.01M, formic acid 0.4M, and water density 0.523g / mL. From the XRD pattern of the product, only magnetite was produced when hexanoic acid was not added, whereas when hexanoic acid was added, an iron peak was confirmed in addition to magnetite (FIG. 1).
(2) Based on the results of (2) above, an attempt was made to optimize the formic acid concentration and water density. As a result, it was revealed that the most iron nanoparticles can be synthesized when the water density is 0.167 g / mL and the formic acid concentration is 3.0 M. Under this condition, the composition ratio of magnetite and iron was 9: 1.
Judging from the Ellingham diagram used to discuss the stability of metal oxides, it was expected that iron nanoparticles would not be produced under the conditions used here, but they were actually produced. One reason for this is thought to be because the surface of the nanoparticles produced by hexanoic acid is capped.

(3) Subsequently, in order to clarify the synthesis mechanism of iron particles, the reaction time was changed to 1, 2, 3, 5, 10, 60 minutes, and the product was identified. When the water density was 0.167 g / mL, which is below the critical density (0.315 g / mL), magnetite and iron particles were formed when the reaction time was 2 minutes and 3 minutes, respectively. The amount of iron produced increased as the reaction time increased to 5 and 10 minutes. On the other hand, when the water density was 0.523 g / mL, magnetite and iron particles were formed when the reaction time was 3 minutes and 10 minutes, respectively. As a result of separate investigations, when the water density is 0.167 g / mL, all the water is evaporated at the reaction time of 3 minutes, and 99% of the formic acid decomposes to generate hydrogen. Therefore, it is considered that the iron nanoparticles were produced by reducing the iron acetate left unreacted with the evaporation of water with hydrogen.
On the other hand, when the water density is 0.523 g / mL, it reaches the critical temperature of water in 5 minutes after the start of the reaction and becomes a supercritical state, so iron acetate in the liquid phase is not reduced until 5 minutes, and iron nanoparticles Is not generated. After becoming uniform in the supercritical state, it is considered that unreacted iron acetate is reduced to produce iron.

In this example, in addition to the synthesis of the iron nanoparticles in Example 1, the present inventors also worked on the synthesis of FePt nanoparticles. Based on the synthesis of iron nanoparticles described so far, we attempted to synthesize FePt particles using iron (II) acetate, platinum acetylacetonate (II), and formic acid as raw materials. In the glove box, an aqueous raw material solution, a reducing agent, and oleic acid as an organic modifier were added to a pressure resistant reactor having an internal volume of 5 mL. This was heated to 400 ° C. in a shaking electric furnace and reacted. After the reaction, the product was evaluated with an X-ray diffractometer (XRD), a transmission electron microscope (TEM) or the like.
As a result, it was shown that FePt was synthesized in the presence of oleic acid added in anticipation of surface modification. The average particle size of the particles was 4.9 nm. Figure 2 shows the FePt synthesized in the presence of the modifier.
The TEM image of a nanoparticle is shown. Moreover, since the synthesized particles are well dispersed in the solvent, it is considered that oleic acid is bonded to the particle surface to protect the FePt phase and to impart hydrophobicity.
From the above, it has been clarified that iron nanoparticles and FePt nanoparticles can be synthesized in a hydrothermal synthesis field using hydrogen as a reducing agent in the presence of a surface modifier.

According to the present invention, it is possible to synthesize metal / alloy nanoparticles that are simple, low-cost, and highly useful. Therefore, application and application are expected as industrial materials such as electric / electronic materials, magnetic materials, and optical materials. . The metal / alloy nanoparticles obtained by the present invention have a modified surface, excellent dispersibility in the medium, a wide range of applications, and use their unique properties in various applications. Since it is convenient to do, it is also excellent as an industrial material. The method of the present invention is applied to industrial / industrial materials such as ceramic nanostructure modifiers, optical functional coating materials, electromagnetic shielding materials, secondary battery materials, fluorescent materials, electronic component materials, magnetic recording materials, polishing materials, pharmaceuticals・ This nanoparticle synthesis method is useful as a high-performance, high-performance, high-density, and highly precise material for cosmetic materials.
It will be apparent that the invention may be practiced otherwise than as particularly described in the foregoing description and examples. Many modifications and variations of the present invention are possible in light of the above teachings, and thus are within the scope of the claims appended hereto.

The XRD pattern of the particle | grains obtained by the supercritical hydrothermal synthesis in the presence / absence of an organic modifier (hexanoic acid) is shown. A TEM image (drawing substitute photograph) of FePt nanoparticles obtained by supercritical hydrothermal synthesis in the presence of an organic modifier (oleic acid) is shown.

Claims (13)

This is a nanoparticle synthesis method in a reaction field in the presence of high-temperature and high-pressure water. The organic field and the surface of the nanoparticle are synthesized by coexisting an organic modifier and a reducing agent in the reaction field for synthesizing nanoparticles from a nanoparticle precursor. A method for synthesizing surface-modified metal or alloy nanoparticles, wherein a modification reaction is performed to obtain metal or alloy nanoparticles having organic groups bonded to the surface of the produced nanoparticles. The method for synthesizing surface-modified metal or alloy nanoparticles according to claim 1, wherein the reaction field in the presence of high-temperature and high-pressure water is subcritical or supercritical water. The method for synthesizing surface-modified metal or alloy nanoparticles according to claim 1 or 2, wherein the reducing agent is in a gas state. The reducing agent is selected from the group consisting of formic acid, hydrogen gas, carbon monoxide gas, synthesis gas, water gas, and a mixture thereof. Synthesis method of surface modified metal or alloy nanoparticles. The synthesis of the surface modified metal or alloy nanoparticles according to any one of claims 1 to 4, wherein the nanoparticle synthesis reaction is performed at a temperature and / or pressure at or above the binary critical point or in the vicinity thereof. Law. The organic modifier is coexistent in the synthetic reaction field of the metal or alloy nanoparticles or the organic modifier is introduced into the reaction field immediately after the synthesis of the metal or alloy nanoparticles. A method for synthesizing surface-modified metal or alloy nanoparticles according to 1. The method for synthesizing surface-modified metal or alloy nanoparticles according to any one of claims 1 to 6, wherein the nanoparticle surface modification reaction is performed at a temperature of 200 ° C or higher, preferably 250 ° C or higher. The surface modified metal or alloy nano according to any one of claims 1 to 7, wherein the organic modifier is selected from carboxylic acids, amines, thiols, phosphonic acid and derivatives thereof. Particle synthesis method. The method for synthesizing surface-modified metal or alloy nanoparticles according to any one of claims 1 to 8, wherein the organic modifier is selected from carboxylic acids. A surface-modified metal or alloy nanoparticle synthesized by the synthesis method according to any one of claims 1 to 9, wherein the metal or alloy nanoparticle has an organic group chemically bonded to the surface of the nanoparticle. . The surface-modified metal or alloy nanoparticles according to claim 10, wherein the bond between the surface of the nanoparticle and the modified organic group is a stable and strong bond at a temperature higher than the boiling point of the organic modifier. The average particle size of surface-modified metal or alloy nanoparticles based on TEM and / or XRD data is about 1
The surface-modified metal or alloy nanoparticles according to claim 10 or 11, wherein the surface-modified metal or alloy nanoparticles are -50 nm. A magnetic material composition comprising the surface-modified metal or alloy nanoparticles according to any one of claims 10 to 12 as a magnetic substance.