Method for producing amino group-modified nanodiamond and amino group-modified nanocarbon particles

Abstract

To provide nanodiamond particles in which a large amount of amino groups are introduced onto the particle surface, and provide a method for producing the nanocarbon particles in which a large amount of amino groups are introduced onto the particle surface.SOLUTION: An amino group-modified nanodiamond has nanodiamond particles and primary amino groups and / or ammonium ions directly bonded to carbon atoms on a surface of the nanodiamond particles, and has an amino group bonding amount of 200 μmol / g or more. The isoelectric point of the amino group-modified nanodiamond is preferably in the range of 3 to 5.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for producing amino-group-modified nanodiamonds and amino-group-modified nanocarbon particles. [Background technology]

[0002] Nanodiamonds have high mechanical strength, excellent physical and chemical stability, and excellent biocompatibility. In addition, their particle diameter is several nm to several hundred nm, which is a size that allows them to pass through gaps in blood vessel walls. Therefore, they are applied to DDS (drug delivery systems) and are used to form composites with resins to give the resins toughness.

[0003] Nanodiamonds have a large proportion of surface atoms, and various functional groups are present on these surface atoms. Therefore, by utilizing these functional groups to bind or adsorb functional elements or molecules through covalent bonds, ionic bonds, or other interactions, or by binding polymerizable monomers, it is possible to impart high functionality to nanodiamonds.

[0004] Nanodiamonds usually have surface functional groups that contain oxygen, such as hydroxyl groups, carbonyl groups, carboxyl groups, and carboxylic acid derivatives, and various chemical modification reactions are carried out using these oxygen-containing functional groups as a base to impart functionality.

[0005] On the other hand, nanodiamonds have almost no amino groups as surface functional groups. However, amino groups have a positive charge, are highly nucleophilic, and therefore easily undergo amidation and alkylation reactions to form strong bonds, and have a high coordination ability for metals, etc., so there is a demand for them to be introduced onto the surface of nanodiamonds.

[0006] For example, the amino groups on the surface of nanodiamonds can be used to immobilize biological substances (e.g., proteins such as antibodies, sugar chains such as gangliosides, nucleotides such as DNA, etc.) on the surface of nanodiamonds for use in DDS and other biomedical applications.

[0007] Therefore, the introduction of amino groups onto the nanodiamond surface has been considered. For example, Patent Document 1 describes a method of introducing amino groups by reacting ammonia gas in the gas phase under a high-temperature environment. However, it was difficult to introduce a sufficient amount of amino groups to enhance functionality. Another problem was that the manufacturing process was complicated and involved many steps.

[0008] In addition, Non-Patent Document 1 describes a method of introducing an amino group using a silane coupling agent having an amino group, a method of graphitizing the surface by annealing and then modifying it with an aminomethylphenyl group, and a method of reducing a carboxyl group on the surface to obtain a hydroxyl group, replacing it with a cyano group via the introduction of a leaving group, and reducing this with a metal hydride to obtain an amino group. However, in all of these methods, the amino group introduced is not directly bonded to the surface carbon of the nanodiamond, but is bonded via a linker, and the introduction of the linker may change the properties and dispersibility of the nanodiamond. In addition, all of these methods have the problem that the introduction of the amino group requires a complex and multi-step reaction process.

[0009] Patent Document 2 discloses nanodiamonds having 10 μmol / g or more of amino groups directly bonded to the particle surface, and a method for producing the same. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2015 / 192142 [Patent Document 2] JP 2019-167255 A [Patent Document 3] JP 2017-186234 A [Non-patent literature]

[0011] [Non-Patent Document 1] A. Krueger, Advanced Functional Materials, 22(5), p890-906. Summary of the Invention [Problem to be solved by the invention]

[0012] The amino group content of the amino group-modified nanodiamond particles specifically disclosed in Patent Document 2 is about 30 μmol / g at most, but it is thought that in the future, nanodiamond particles with more amino groups introduced on the particle surface will be required. Note that Patent Document 3 discloses a surface-modified nanodiamond with amide groups introduced on the surface, but does not disclose the use of the surface-modified nanodiamond to obtain amino group-modified nanodiamond.

[0013] Therefore, an object of the present disclosure is to provide nanodiamond particles having a large amount of amino groups introduced on the particle surface. Another object of the present disclosure is to provide a method for producing nanocarbon particles having a large amount of amino groups introduced on the particle surface. [Means for solving the problem]

[0014] The present disclosure provides an amino-modified nanodiamond having nanodiamond particles and primary amino groups and / or ammonium ions directly bonded to carbon atoms on the surface of the nanodiamond particles, the amino group binding amount being 200 μmol / g or more.

[0015] The amino group-modified nanodiamond preferably has an isoelectric point within the range of 3-5.

[0016] The amino group-modified nanodiamond preferably has a maximum zeta potential of 10 mV or more at pH 0-4.

[0017] The present disclosure also provides a method for producing amino-group-modified nanocarbon particles, comprising: a condensation step of reacting nanocarbon particles with an amino compound represented by the following formula (1) in an aqueous solvent; and an amination step of, after the condensation step, eliminating a leaving group bonded to the amino group to obtain amino-group-modified nanocarbon particles having primary amino groups and / or ammonium ions on the surface thereof. RNH2(1) [In formula (1), R represents a leaving group.] Effect of the Invention

[0018] The amino group-modified nanodiamond of the present disclosure has a large amount of primary amino groups and / or their salts on the surface. Nanodiamonds having a structure in which an amino group is bonded to a carbon atom on the surface via a linker may have reduced nanodiamond properties or reduced dispersibility due to the linker, but the amino group-modified nanodiamond of the present disclosure has a structure in which a primary amino group, an ammonium ion, or a salt thereof is directly bonded to a carbon atom on the surface of the nanodiamond, so that the properties of the nanodiamond (such as high mechanical strength, excellent physical and chemical stability, and excellent biocompatibility) and dispersibility can be maintained at a high level without being impaired.

[0019] Therefore, the amino group-modified nanodiamond of the present disclosure can be preferably used for nanocomposite applications and DDS applications. For example, the composite in which a biologically relevant substance is bound to the amino group of the amino group-modified nanodiamond of the present disclosure can be preferably used as a DDS preparation, etc. In addition, the composite (nanocomposite) in which fibers are bound to the amino group of the amino group-modified nanodiamond of the present disclosure can be preferably used as reinforcing fibers, etc. [Brief description of the drawings]

[0020] [Figure 1]FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 1. [Diagram 2] FIG. 1 shows the FT-IR spectrum of the amino group-modified nanodiamond hydrochloride obtained in Example 1. [Diagram 3] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 2. [Figure 4] FIG. 1 shows the FT-IR spectrum of the amino group-modified nanodiamond obtained in Example 2. [Diagram 5] FIG. 1 shows the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 3. [Figure 6] FIG. 2 shows an isoelectric point titration graph of the amino group-modified nanodiamond hydrochloride obtained in Example 1. [Figure 7] FIG. 2 shows an isoelectric point titration graph of the amino group-modified nanodiamond obtained in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [Amino group modified nanodiamond] The amino group modified nanodiamond according to one embodiment of the present disclosure comprises a nanodiamond particle and a primary amino group (-NH2) and / or an ammonium ion (-NH3) bonded directly to a carbon atom on the surface of the nanodiamond particle. + That is, the amino group-modified nanodiamond has a structure in which at least one of a primary amino group and an ammonium ion is directly bonded to a carbon atom on the surface of the nanodiamond. The ammonium ion may be in the form of a salt with an anion.

[0022] The amount of amino group bonded in the amino group-modified nanodiamond is 200 μmol / g or more, preferably 205 μmol / g or more. The upper limit of the amount of amino group bonded is, for example, 700 μmol / g, and may be 500 μmol / g, 400 μmol / g, or 350 μmol / g.

[0023] The amino group binding amount is the binding amount including the primary amino group, ammonium ion, and its salt in the amino group modified nanodiamond. The amino group content may be difficult to directly quantify because the amino group is directly bonded to the carbon atom on the surface of the nanodiamond. In such a case, for example, the primary amino group or ammonium ion is reacted with an amino acid (e.g., Boc-alanine-hydroxysuccinimide ester, etc.), and the amino acid reacted with the primary amino group and ammonium ion is quantified (e.g., a colorimetric method such as the Kaiser test using ninhydrin, or a method of performing amino acid analysis after hydrolysis, etc.) to indirectly measure the content.

[0024] The amino group-modified nanodiamond may have functional groups other than primary amino groups and ammonium ions (eg, carboxy groups, hydroxy groups, etc.) on the surface of the nanodiamond.

[0025] The amino group-modified nanodiamond preferably has an isoelectric point in the range of 3 to 5, more preferably 3.5 to 4.5. If the isoelectric point is in the above range, it is presumed that the proportion of primary amino groups and ammonium ions in all functional groups present on the surface of the amino group-modified nanodiamond particles is high. As a result, the amino group-modified nanodiamond tends to have excellent water dispersibility.

[0026] The amino group-modified nanodiamond preferably has a maximum zeta potential of 10 mV or more at pH 0 to 4. The maximum zeta potential may be, for example, 50 mV, 40 mV, or 30 mV. If the maximum zeta potential is 10 mV or more, it is presumed that the proportion of primary amino groups and ammonium ions in all functional groups present on the amino group-modified nanodiamond particle surface is high, and the amino group-modified nanodiamond tends to have high acidity and excellent water dispersibility.

[0027] In the amino group modified nanodiamond, the mass ratio of nanodiamond to the surface modification group containing amino group and ammonium salt [nanodiamond / surface modification group] is not particularly limited, but is preferably 5.0 or more, more preferably 7.0 or more. The mass ratio is preferably 15.0 or less, more preferably 10.0 or less. If the mass ratio is 5.0 or more, the properties as a nanodiamond material are not easily impaired. If the mass ratio is 15.0 or less, the degree of modification of the amino group is sufficient. The mass ratio is calculated based on the weight loss rate from 200°C to 450°C measured by thermogravimetric analysis, and the reduced weight is taken as the mass of the surface modification group.

[0028] The amino group-modified nanodiamond has excellent dispersibility. The dispersed particle diameter D50 (median diameter; 50 volume % diameter) of the amino group-modified nanodiamond in a 0.1 to 5 mass % water suspension is, for example, 500 nm or less, preferably 100 nm or less, and more preferably 40 nm or less. The lower limit of the dispersed particle diameter D50 is, for example, 3 nm. The dispersed particle diameter is measured by a dynamic light scattering method.

[0029] The amino group-modified nanodiamonds described above can bind various compounds (e.g., small molecule drugs, biopharmaceuticals, antibodies, cytokines, amino acids, proteins, DNA, RNA, sugars, fibers, etc.) to the primary amino groups and ammonium ions on the surface of the nanodiamonds. Note that "biopharmaceuticals" are drugs whose active ingredients are derived from proteins (growth hormones, insulin, antibodies, etc.), or drugs derived from substances produced by living organisms such as cells, viruses, and bacteria. Therefore, the amino group-modified nanodiamonds described above can be preferably used for nanocomposite applications and as raw materials for DDS preparations.

[0030] [Method of manufacturing amino group-modified nanocarbon particles] A method for producing amino group-modified nanocarbon particles according to an embodiment of the present disclosure includes a condensation step of reacting nanocarbon particles with an amino compound represented by the following formula (1) in an aqueous solvent, and a reaction step of removing a leaving group bonded to the amino group to produce a primary amino group (-NH2) and / or an ammonium ion (-NH3 + and an amination step of obtaining amino group-modified nanocarbon particles having an ammonium ion on the surface thereof. The ammonium ion may be in the form of a salt with an anion. RNH2(1) [In formula (1), R represents a leaving group.]

[0031] (condensation process) In the condensation step, nanocarbon particles having hydroxy groups on the surface are nano-dispersed in water and reacted with the amino compound represented by formula (1) above, and as shown in the formula below, the hydroxy groups in the nanocarbon particles and the H of -NH2 in the amino compound represented by formula (1) are dehydrated and condensed to obtain amino group-modified nanocarbon particles to which the leaving group R is bonded. Thereafter, as shown in the formula below, the leaving group R is eliminated in the amination step to obtain amino group-modified nanocarbon particles. In the formula below, "ND" represents nanodiamond, and "X - " indicates an anion that forms a salt with ammonium ion. [ka]

[0032] The nanocarbon particles are not particularly limited, and particles of known or commonly used nano-order carbon materials (nanocarbon materials) can be used. Examples of the nanocarbon materials in the nanocarbon particles include nanodiamond, fullerene, graphene oxide, nanographite, carbon nanotubes, carbon nanofilaments, onion-like carbon, diamond-like carbon, amorphous carbon, carbon black, carbon nanohorns, and carbon nanocoils. As the nanocarbon particles, nanodiamond particles are preferred. The nanocarbon particles may be used in combination of one type or two or more types.

[0033] The above-mentioned nanodiamond particles are not particularly limited, and known or conventional nanodiamond particles can be used. The nanodiamond particles have hydroxyl groups that are inherently generated during the manufacturing process. The nanodiamond particles may be used in one type or in two or more types.

[0034] As the above-mentioned nanodiamond particles, for example, detonation nanodiamond (i.e., nanodiamond produced by detonation method) or high-temperature high-pressure nanodiamond (i.e., nanodiamond produced by high-temperature high-pressure method) can be used. Among them, detonation nanodiamond is preferred because it has better dispersibility in the dispersion medium, that is, the particle size of the primary particle is one digit nanometer.

[0035] The detonation nanodiamond includes air-cooled detonation nanodiamond (i.e., nanodiamond produced by air-cooled detonation method) and water-cooled detonation nanodiamond (i.e., nanodiamond produced by water-cooled detonation method). Among them, air-cooled detonation nanodiamond is preferred because it has smaller primary particles than water-cooled detonation nanodiamond.

[0036] The detonation may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen atmosphere, argon atmosphere, or carbon dioxide atmosphere.

[0037] R in the above formula (1) represents a leaving group, and examples thereof include -OS(=O)2-R' group, -OC(=O)-R' group, -C(=O)-R' group, -S(=O)2-R' group, -C(=O)-O-R' group, -(C=O)-NH-R' group, and -R' group (R' represents a hydrogen atom or a monovalent organic group which may have a substituent). The leaving group is appropriately selected according to the type of the leaving agent used in the amination step. As the above R, among others, -C(=O)-R' group and -R' group are preferable.

[0038] Examples of the monovalent organic group in R' include substituted or unsubstituted hydrocarbon groups (monovalent hydrocarbon groups), substituted or unsubstituted heterocyclic groups (monovalent heterocyclic groups), organic group-substituted amino groups, and groups in which two or more of these are bonded. The bonded groups may be directly bonded or may be bonded via a linking group. Examples of the linking group include amino groups, ether bonds, ester bonds, phosphinic acid groups, sulfide bonds, carbonyl groups, sulfonyl groups, organic group-substituted silyl groups, organic group-substituted amide groups, organic group-substituted urethane bonds, organic group-substituted imide bonds, thiocarbonyl groups, siloxane bonds, and groups in which two or more of these are bonded.

[0039] Examples of the hydrocarbon group in the monovalent organic group include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups in which two or more of these are bonded together.

[0040] Examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group. The alkenyl group and the alkynyl group may have an unsaturated carbon-carbon bond inside or at the end. Examples of the alkyl group include C groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl group, an isooctyl group, a decyl group, and a dodecyl group. 1-30 Alkyl groups are preferred, and C 10-25 Alkyl groups, more preferably C 12-20 The alkyl group. The alkenyl group is C such as oleyl. 2-30Alkenyl groups are preferred, and C 10-25 Alkenyl groups, more preferably C 12-20 The alkynyl group is C 2-30 Alkynyl groups are preferred, and C 10-25 Alkynyl groups, more preferably C 12-20 It is an alkynyl group.

[0041] Examples of the alicyclic hydrocarbon group include C cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclododecyl groups. 3-12 Cycloalkyl groups; cyclohexenyl groups, etc. 3-12 Cycloalkenyl groups; bicycloheptanyl groups, bicycloheptenyl groups, etc. 4-15 and bridged cyclic hydrocarbon groups.

[0042] Examples of the aromatic hydrocarbon group include C phenyl, naphthyl, and fluorenyl groups. 6-14 Aryl groups (especially C 6-10 Aryl groups).

[0043] Examples of the heterocyclic ring forming the heterocyclic group include aromatic heterocyclic rings and non-aromatic heterocyclic rings. Examples of such heterocyclic rings include 3- to 10-membered rings (preferably 4- to 6-membered rings) having carbon atoms and at least one heteroatom (e.g., oxygen atom, sulfur atom, nitrogen atom, etc.) as atoms constituting the ring, and condensed rings thereof. Specifically, heterocyclic rings containing an oxygen atom as a heteroatom (e.g., 3-membered rings such as oxirane ring; 4-membered rings such as oxetane ring; 5-membered rings such as furan ring, tetrahydrofuran ring, oxazole ring, isoxazole ring, γ-butyrolactone ring; 6-membered rings such as 4-oxo-4H-pyran ring, tetrahydropyran ring, morpholine ring; condensed rings such as benzofuran ring, isobenzofuran ring, 4-oxo-4H-chromene ring, chroman ring, isochroman ring; 3-oxatricyclo[4.3.1.1 4,8 ]Undecane-2-one ring, 3-oxatricyclo[4.2.1.0 4,8]nonan-2-one ring and the like), heterocycles containing a sulfur atom as a heteroatom (for example, 5-membered rings such as a thiophene ring, a thiazole ring, an isothiazole ring, a thiadiazole ring, and the like; 6-membered rings such as a 4-oxo-4H-thiopyran ring, and the like; condensed rings such as a benzothiophene ring, and the like), heterocycles containing a nitrogen atom as a heteroatom (for example, 5-membered rings such as a pyrrole ring, a pyrrolidine ring, a pyrazole ring, an imidazole ring, and a triazole ring, and the like; 6-membered rings such as an isocyanuric ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a piperidine ring, and the like; condensed rings such as an indole ring, an indoline ring, a quinoline ring, an acridine ring, a naphthyridine ring, a quinazoline ring, and a purine ring, and the like).

[0044] Examples of the group having two or more hydrocarbon groups bonded thereto include the above-mentioned aliphatic hydrocarbon group and aromatic hydrocarbon group bonded thereto. Examples of the group having an aliphatic hydrocarbon group and an aromatic hydrocarbon group bonded thereto include aralkyl groups such as a benzyl group, and C groups such as a phenethyl group. 7-18 Aralkyl groups (especially C 7-10 aralkyl group), cinnamyl group, etc. 6-10 Aryl-C 2-6 Alkenyl group, tolyl group, etc. 1-4 C such as alkyl-substituted aryl groups and styryl groups 2-4 Among them, an aralkyl group is preferable, and a benzyl group is more preferable.

[0045] Examples of the group in which two or more of the monovalent hydrocarbon groups and / or monovalent heterocyclic groups are bonded via a linking group include a group in which the monovalent hydrocarbon group and / or the monovalent heterocyclic group is bonded to an alkoxy group, an alkenyloxy group, an alkynyloxy group, an aryloxy group, an aralkyloxy group, an acyloxy group, an alkylthio group, an alkenylthio group, an arylthio group, an aralkylthio group, an acyl group, an alkenylcarbonyl group, an arylcarbonyl group, an aralkylcarbonyl group, an alkoxycarbonyl group, an alkenyloxycarbonyl group, an aryloxycarbonyl group, an aralkyloxycarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, a dialkylamino group, an acylamino group, an oxetanyl group-containing group, a carbamoyl group, a trialkylsilyl group, an arylamide group, or a group in which two or more of these are bonded to each other.

[0046] Examples of the substituent that the monovalent organic group in R' may have include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; a nitro group; a cyano group; an isocyanate group; and an isothiocyanate group.

[0047] When R is a -C(=O)-R' group, R' is an alkenyl group such as 3-butenyl group or oleyl group; a haloalkyl group such as chloromethyl group, trichloromethyl group or trifluoromethyl group (particularly, a haloC 1-4 alkyl group; benzyl group, 3-phenylpropyl group, 1-(N-benzoylamino)phenethyl group, and other aralkyl groups (especially C 1-4 alkyl-aryl skeleton)-containing groups; aryl groups such as 2-anilyl group, 3-anilyl group, phenyl group, and 4-phenylphenyl group (particularly, anilyl group, phenyl group, and p-biphenyl group) are preferred. Among these, C 2-30 Alkenyl groups are preferred, more preferably C 10-25 Alkenyl groups, more preferably C 12-20 It is an alkenyl group.

[0048] When R is a -S(=O)2-R' group, R' is an alkyl group such as a methyl group (particularly, 1-4 alkyl group; dialkylamino group such as dimethylamino group (especially diC 1-4 Alkylamino groups; phenyl groups; alkoxy-substituted phenyl groups such as 3-methoxyphenyl groups (especially C 1-4 Alkoxy-substituted phenyl group: alkyl-substituted phenyl group such as 3-methylphenyl group and 1,3,5-trimethylphenyl group (especially C 1-4 Alkyl-substituted phenyl groups are preferred.

[0049] When R is a -C(=O)-O-R' group, R' is an aralkyl skeleton-containing group such as a benzyl group, a 9-fluorenylmethyl group, or a 2,7-di-t-butyl[9-(10,10-dioxo-10,10,10,10-tetrahydrothioxanthyl)]methyl group (particularly, 1-4 Alkyl-aryl skeleton-containing groups; haloalkyl groups such as 2,2,2-trichloroethyl group, 1-chloroethyl group, and 1-(1,1-dimethyl-2,2,2-trichloro)ethyl group (particularly haloC 1-4 Preferred are alkyl groups; branched-chain alkyl groups such as t-butyl and (2,4-dimethyl)pent-3-yl groups; alicyclic hydrocarbon groups such as cyclohexyl, 1-adamantyl and 2-adamantyl groups; organic group-substituted silyl-substituted alkyl groups such as 2-(trimethylsilyl)ethyl groups; and 2-(4-trifluoromethylphenylsulfonyl)ethyl groups.

[0050] When R is an -R' group, R' is preferably a group containing an aromatic hydrocarbon (particularly, a benzene ring) from the viewpoint of high fat solubility, dispersibility in aqueous solvents, and higher reactivity with the nanocarbon particle surface. Furthermore, R' is preferably a group containing a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group (particularly, a phenyl group) are bonded, from the viewpoint of excellent dispersibility in aqueous solvents due to a melting point below the boiling point of water. Examples of the aliphatic hydrocarbon group include alkyl groups (particularly C 1-10 alkyl group) is preferred.

[0051] Preferred examples of the group containing a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded include benzyl skeleton-containing groups such as a benzyl group, a 3,4-dimethoxybenzyl group, a 3-methoxybenzyl group, a 4-methoxybenzyl group, a 3,5-dimethoxybenzyl group, a 2-nitrobenzyl group, a triphenylmethyl group, a diphenylmethyl group, and a diphenyl-4-pyridylmethyl group; and aralkyl skeleton-containing groups such as a phenethyl skeleton-containing group such as a 4-nitrophenethyl group and a phenylacyl group.

[0052] In addition, when the above R is a -R' group, R' may be a 2,4-dinitrophenyl group, a 2-(phenylsulfonyl)ethyl group, an allyl group, or the like.

[0053] The amino compound represented by the formula (1) preferably has a melting point of 100° C. or less, from the viewpoint of excellent dispersibility in an aqueous solvent and higher reactivity with the hydroxyl group on the surface of the nanocarbon particles. In addition, the amino compound represented by the formula (1) preferably has solubility or dispersibility in water in the presence or absence of an acid catalyst described below. When the amino compound has poor solubility or dispersibility in water, it is possible to dissolve or disperse the amino compound in an organic solvent and carry out the reaction in a mixed solvent system of water and an organic solvent. Examples of the organic solvent include those that can be used in the amination step described below.

[0054] The condensation step is carried out in a state where the nanocarbon particles are nano-dispersed in water, i.e., in an aqueous dispersion composition of nanocarbon particles. The median diameter (D50) of the nanocarbon particles in the aqueous dispersion composition is preferably 1 to 100 nm, more preferably 1 to 50 nm, and even more preferably 1 to 10 nm. When the median diameter is within the above range, the amount of hydroxyl groups on the nanocarbon particle surface is large, and the reaction with the amino compound represented by the above formula (1) proceeds more. In addition, the dispersibility of the obtained amino group-modified nanocarbon particles is excellent.

[0055] The condensation step is preferably carried out in the presence of an acid catalyst. The acid catalyst may be a known or conventional acid catalyst used in the esterification of carboxylic acid and alcohol, the dehydration condensation reaction of alcohol and amine, the dehydration condensation reaction of alcohol and thiol, etc. Examples of the acid catalyst include sulfonic acid group-containing compounds, hydrochloric acid, nitric acid, sulfuric acid, sulfuric anhydride, phosphoric acid, boric acid, trihaloacetic acid (trichloroacetic acid, trifluoroacetic acid, etc.), their salts (ammonium salts, etc.), inorganic solid acids, etc. The acid catalyst may be used alone or in combination of two or more.

[0056] The acid catalyst may be in the form of either a homogeneous catalyst that can be dissolved in a solvent or a substrate during the reaction, or a heterogeneous catalyst that cannot be dissolved during the reaction. Examples of heterogeneous catalysts include supported catalysts in which an acid component is supported on a carrier.

[0057] Examples of the sulfonic acid group-containing compound include aliphatic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, dodecanesulfonic acid, hexadecanesulfonic acid, trifluoromethanesulfonic acid, and heptadecafluorooctanesulfonic acid; alicyclic sulfonic acids such as 10-camphorsulfonic acid; benzenesulfonic acid, p-toluenesulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, hexylbenzenesulfonic acid, and octylbenzenesulfonic acid. aromatic sulfonic acids such as sulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid (DBSA), octadecylbenzenesulfonic acid, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, and butyl-2-naphthalenesulfonic acid; sulfonic acid-type ion exchange resins, 3-[trioctylammonio]propane-1-sulfonic acid-triflimide, 4-[trioctylammonio]butane-1-sulfonic acid-triflimide, and compounds represented by the following formula (A).

[0058] [ka]

[0059] Examples of the inorganic solid acid include silica, silica alumina, alumina, zeolites, activated clay, and montmorillonite.

[0060] Examples of the ammonium salt as the acid catalyst include an ammonium ion salt represented by the following formula (B-1), an ammonium ion salt represented by the following formula (B-2), an ammonium ion salt represented by the following formula (B-3), and an ammonium ion salt represented by the following formula (B-4). [ka]

[0061] In the above formula (B-1), R I ~R III are the same or different and each represents a group containing a hydrogen atom, an aliphatic hydrocarbon group, or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is a linear or branched C 1-22 Hydrocarbon groups are preferred. Examples of the group containing an aromatic hydrocarbon group include aromatic hydrocarbon groups such as a phenyl group; and groups in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded, such as a 4-t-butylphenyl group and a mesityl group. Among these, the above R I ~R III It is preferable that two or more of the above groups contain an aromatic hydrocarbon group.

[0062] The acid anion serving as a counter anion to the ammonium ions represented by the above formulas (B-1) to (B-3) is preferably a sulfonate ion, more preferably an aromatic sulfonate ion, and particularly preferably a p-dodecylbenzenesulfonate ion.

[0063] In the above formula (B-4), R i and R ii are the same or different and each represents a group containing a hydrogen atom, an aliphatic hydrocarbon group, or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is a linear or branched C 1-4Hydrocarbon groups are preferred. Examples of the group containing an aromatic hydrocarbon group include aromatic hydrocarbon groups such as a phenyl group, and groups in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded. Among these, a hydrogen atom, a methyl group, an isopropyl group, and a phenyl group are preferred.

[0064] The acid anion serving as a counter anion to the ammonium ion represented by the above formula (B-4) is preferably a sulfonate ion or a sulfate ion, and particularly preferably a trifluoromethanesulfonate ion, a 10-camphorsulfonate ion, a benzenesulfonate ion, or a sulfate ion.

[0065] The acid anion serving as the counter anion of the ammonium ion represented by the above formulae (B-1) to (B-4) may form a complex salt by forming a hydrogen bond between an oxygen atom forming an acid group and a hydrogen atom on a nitrogen atom in the above formulae (B-1) to (B-4). The above complex salt may form one salt with one ammonium cation and one acid anion, or may form one salt with two ammonium cations and two acid anions, and the number of ammonium cations and acid anions forming one salt is not particularly limited. In one salt, the acid anion may form a polymer. For example, sulfuric acid forming a sulfate ion is [H2SO4(SO3) X An example of the complex salt formed between the acid anion and the above formula (B-4) is a compound represented by the following formula (C). [ka]

[0066] In the above formula (C), R i and R ii is the same as in the above formula (B-4).

[0067] As the acid catalyst, from the viewpoint of further accelerating the reaction in the condensation step, a sulfonic acid group-containing compound or an ammonium salt of a sulfonic acid group-containing compound is preferred.

[0068] The ratio (former:latter, mass ratio) of the nanocarbon particles to be reacted to the amino compound represented by the formula (1) is, for example, 1:1 to 1:25. The concentration of the nanocarbon particles in the water-dispersed composition is, for example, 1 to 10 mass%, and the concentration of the amino compound represented by the formula (1) in the water-dispersed composition is, for example, 1 to 60 mass%.

[0069] The reaction conditions for the reaction between the nanocarbon particles and the amino compound represented by the formula (1) can be appropriately selected within the ranges of, for example, a temperature of 0 to 100° C., a reaction time of 1 to 48 hours, and a pressure of 1 to 5 atm.

[0070] The surface-modified nanocarbon particles obtained by the condensation step are nanocarbon particles having a group represented by the following formula (2) directly bonded to a carbon atom on the surface of the nanocarbon particles, where R in the following formula (2) is the same as R in the amino compound represented by the above formula (1). -NH-R (2) [In formula (2), R represents a leaving group, and the bond extending to the left is bonded to a carbon atom on the surface of the nanocarbon particle.]

[0071] In the surface-modified nanocarbon particles, the mass ratio of the nanocarbon particles to the surface-modifying groups [nanocarbon particles / surface-modifying groups] is not particularly limited, but is preferably 5.0 or more, more preferably 7.0 or more. The mass ratio is preferably 15.0 or less, more preferably 10.0 or less. When the mass ratio is 5.0 or more, the properties of the nanocarbon particle material are unlikely to be impaired. When the mass ratio is 15.0 or less, the degree of modification by the surface-modifying groups is sufficient. The mass ratio is determined based on the weight loss rate from 200°C to 450°C measured by thermogravimetric analysis, with the reduced weight being the mass of the surface-modifying groups.

[0072] The surface-modified nanocarbon particles have a dispersed particle diameter D50 (median diameter; 50 volume % diameter) in a 0.1 to 5 mass % solvent of, for example, 500 nm or less, preferably 100 nm or less, and more preferably 40 nm or less. The lower limit of the dispersed particle diameter D50 is, for example, 3 nm. The dispersed particle diameter is measured by a dynamic light scattering method.

[0073] (Amination step) After the condensation step, the leaving group (-R) attached to the amino group is removed to give a primary amino group (-NH2) and / or an ammonium ion (-NH3 + ) on the surface of the amino group-modified nanocarbon particles.

[0074] For the elimination, a elimination agent according to the elimination group, or an elimination treatment such as active energy rays or heating can be used. When R is an -OC(=O)-R' group, examples of the elimination agent include known or conventional hydrolysis acids (e.g., mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid) and bases (e.g., sodium hydroxide and potassium carbonate). When R is an -R' group, examples of the elimination agent include 2,3-dichloro-5,6-dicyano-p-benzoquinone, Pd-C, hydrochloric acid, methanol, and hydrogen; Pd(OH)2 and hydrogen; 1-chloroethyl chloroformate; or ammonium cerium(IV) nitrate.

[0075] Examples of combinations of the above amino compounds with the above desorption agents or desorption treatments are shown in Tables 1 and 2. [Table 1] [Table 2]

[0076] The amination step is preferably carried out in the presence of a solvent. The solvent is preferably an organic solvent. Examples of the organic solvent include aliphatic hydrocarbons such as hexane, heptane, and octane (particularly, linear saturated aliphatic hydrocarbons); aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aprotic polar solvents such as dimethylformamide (DMF), dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide; alcohols such as methanol; halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, and trifluoromethylbenzene; chain or cyclic ethers such as diethyl ether, diisopropyl ether, dimethoxyethane, tetrahydrofuran (THF), and dioxane; esters such as ethyl acetate and butyl acetate; chain ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone; and nitriles such as acetonitrile. The solvents may be used alone or in combination.

[0077] The amount of the solvent used is, for example, 5 to 100 times by mass relative to the total amount of the nanocarbon particles and the amino compound represented by the formula (1). When the amount of the solvent used is within the above range, the concentration of the reaction components becomes appropriate, and a decrease in the reaction rate can be suppressed.

[0078] The reaction atmosphere in the amination step is not particularly limited as long as it does not inhibit the reaction, and may be, for example, any of an air atmosphere, a nitrogen atmosphere, an argon atmosphere, etc. The reaction temperature in the amination step is, for example, 20 to 150° C. The reaction time is, for example, 1 to 96 hours. The reaction can be carried out by any method such as a batch method, a semi-batch method, or a continuous method.

[0079] The above-mentioned production method may have other steps in addition to the above-mentioned condensation step and the above-mentioned amination step. After the above-mentioned condensation step or the above-mentioned amination step, the obtained product is preferably purified by, for example, filtration, centrifugation, extraction, water washing, neutralization, or a combination of these. In addition, for example, a crushing step may be performed before the above-mentioned condensation step in order to obtain a water-dispersed composition in which the above-mentioned nanocarbon particles are nano-dispersed in water.

[0080] As described above, the above-mentioned manufacturing method, which includes at least the above-mentioned condensation step and the above-mentioned amination step, can produce nanocarbon particles and amino group-modified nanocarbon particles having primary amino groups and / or ammonium ions directly bonded to the carbon atoms on the surface of the nanocarbon particles. In particular, the above-mentioned manufacturing method can produce the above-mentioned amino group-modified nanodiamonds having an amino group bond amount of 200 μmol / g or more.

[0081] According to the above-mentioned manufacturing method, since there is no need to use nanocarbon particle powder, there is no need to obtain nanocarbon particle powder by disintegrating the nanocarbon particles by bead milling or the like and then drying or removing the solvent, and amino group-modified nanocarbon particles can be easily manufactured. In addition, since disintegration and condensation reaction are not performed simultaneously by bead milling, the disintegration treatment time can be minimized, so that zirconia is less likely to be mixed in and side reactions due to the generation of radicals can be suppressed.

[0082] [Nanocarbon particle dispersion composition] By dispersing the amino group-modified nanodiamond or the amino group-modified nanocarbon particles obtained by the above manufacturing method in a dispersion medium, a nanocarbon particle dispersion composition containing the dispersion medium and the amino group-modified nanocarbon particles dispersed in the dispersion medium can be obtained. If the nanocarbon particles remain aggregated after the amination process, the liquid after the amination process can be left to stand and the supernatant liquid can be collected and used as the nanocarbon particle dispersion composition. In addition, after obtaining the reaction composition obtained by the above manufacturing method, before or after distilling off the solvent in the dispersion composition with an evaporator, the nanocarbon particle dispersion composition can also be produced by mixing and stirring a new dispersion medium, i.e., by exchanging the solvent.

[0083] [Complex] In one embodiment of the composite of the present disclosure, a compound having a group reactive with the amino group is bonded to the amino group of the amino group-modified nanocarbon particle (such as the amino group-modified nanodiamond) at the reactive group portion.

[0084] Examples of the group reactive with the amino group include a carboxy group, a carboxamide group (=aminocarbonyl group), a phosphate group, an alkyl group, and a vinyl group.

[0085] The above-mentioned complex can be produced, for example, by stirring and mixing in a solvent a compound that is desired to be formed into a complex with the nanocarbon particles and that has a reactive group with the amino group or to which a reactive group has been added (e.g., a low molecular weight drug, an antibody, a cytokine, an amino acid, a protein, DNA, RNA, sugars, fibers, etc.) with the above-mentioned amino group-modified nanocarbon particles.

[0086] For example, a composite (=nanocomposite) in which fibers or the like are bound to the amino groups of the amino group-modified nanocarbon particles can be preferably used as a reinforcing fiber, etc. Furthermore, a composite in which, for example, a low molecular weight drug, an antibody, a cytokine, an amino acid, a protein, DNA, RNA or the like is bound to the amino groups of the amino group-modified nanocarbon particles can be preferably used as a DDS preparation.

[0087] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration in each embodiment and their combinations are merely examples, and addition, omission, substitution, and other modifications of the configuration are possible as appropriate within the scope of the present disclosure. In addition, each invention according to this disclosure is not limited by the embodiments or the following examples, but is limited only by the claims. EXAMPLES

[0088] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0089] Example 1 (condensation process) 163 mg (0.5 mmol) of dodecylbenzenesulfonic acid, 4 mL of water, 744.0 mg of detonation nanodiamond aqueous dispersion (solid content concentration about 4% by mass), and 1.3 g (active ingredient 3 mmol) of oleamide (purity 65% ​​by mass) were added in sequence and reacted at 100 ° C for 30 hours. After the reaction was completed, 5 mL of water and 15 mL of toluene were added, cooled to room temperature, and 2 mL of saturated saline was added to remove the aqueous phase. The obtained toluene phase was centrifuged (20000 G, 10 minutes) to obtain a toluene dispersion of nanodiamond particles modified with oleamide groups. The median diameter (D50) of the obtained surface-modified nanodiamond particles was about 24 nm. The same amount of acetone was added to the obtained dispersion and centrifuged (20000 G, 10 minutes) to obtain a solid surface-modified nanodiamond. It was washed with acetone several times, and the mass ratio [nanodiamond / surface modification group] obtained by thermogravimetric analysis of the solid obtained after drying was 8.1.

[0090] (Amination step) 13 mL of concentrated hydrochloric acid was added to 90 mg of the solid obtained as described above, and the mixture was stirred at 50°C for 8 hours. After the reaction was completed, the solid was precipitated by centrifugation (7000G, 30 seconds). After washing multiple times with water and acetone, the solid was dried to obtain 60 g of deprotected amino group-modified nanodiamond hydrochloride. The amino group binding amount of the obtained amino group-modified nanodiamond hydrochloride was 211 μmol / g, and the isoelectric point was 3.58.

[0091] Example 2 (condensation process) 163 mg (0.5 mmol) of dodecylbenzenesulfonic acid, 3 mL of water, 610 mg of detonation nanodiamond aqueous dispersion (solid content concentration about 5% by mass), and 0.4 mL (3 mmol) of p-methoxybenzylamine were added in sequence and reacted at 100 ° C for 24 hours. After the reaction was completed, 5 mL of water and 15 mL of toluene were added, cooled to room temperature, and the aqueous phase was removed. The mixture was washed again with 5 mL of water, and the resulting toluene phase was centrifuged (20000 G, 10 minutes) to obtain a toluene dispersion of nanodiamond particles modified with p-methoxybenzylamino groups. The median diameter (D50) of the obtained surface-modified nanodiamond particles was about 31 nm. The same amount of 2-propanol was added to the obtained dispersion, and the surface-modified nanodiamond solid was obtained by centrifuging (20000 G, 10 minutes). The solid was washed several times with acetone and THF / acetone (1 / 1), and the mass ratio [nanodiamond / surface modifying group] of the solid obtained after drying was determined by thermogravimetric analysis to be 8.5.

[0092] (Amination step) To 190 mg of the solid obtained as described above, 5 mL of toluene, 1 mL of water, and 2,3-dichloro-5,6-dicyano-p-benzoquinone were added in that order, and the mixture was stirred at 30°C for 10 hours. After the reaction was completed, 4 mL of toluene was added and the solid was precipitated by centrifugation (7000G, 1 minute). After washing multiple times with toluene, THF, and acetone, the solid was dried to obtain 171 mg of deprotected amino-modified nanodiamonds. The amino group binding amount of the obtained amino-modified nanodiamonds was 334 μmol / g, and the isoelectric point was 4.22.

[0093] Example 3 (Reaction of amino group-modified nanodiamond with acid halides) 60 mg of the amino group-modified nanodiamond obtained in Example 2, 1 mL of toluene, 0.17 mL (1 mmol) of diisopropylethylamine, and 303 mg (1 mmol) of stearoyl chloride were added in sequence and reacted at 100°C for 16 hours. After the reaction was completed, 2 mL of toluene was added, and the mixture was cooled to room temperature, and then the entire mixture was centrifuged (7000G, 1 minute) to obtain a toluene dispersion and a precipitated solid. The precipitated solid was separated and collected, 3 mL of THF was added, and the mixture was centrifuged again (7000G, 30 seconds) to obtain a THF dispersion. 3 mL of water was gently added to the liquid obtained by combining this THF dispersion and the above toluene dispersion, and the water was removed after a while to obtain an organic phase. 5 mL of 2-propanol was added to the organic phase, and the mixture was further centrifuged (7000G, 2 minutes) to precipitate the nanodiamond, and a surface-modified nanodiamond was obtained. The solid was washed with toluene / acetone (1 / 1) and acetone, and then dried. The mass ratio [nanodiamond / surface modifying group] of the solid obtained was determined by thermogravimetric analysis to be 5.3.

[0094] <Particle size D50> The median diameter (particle size D50) of the nanodiamond particles in the nanodiamond dispersion of the example obtained as described above is a volume-based value measured from the particle size distribution of the nanodiamonds obtained by the dynamic light scattering method. Specifically, the above particle size distribution was measured by the dynamic light scattering method (non-contact backscattering method) using an apparatus manufactured by Malvern (trade name "Zetasizer Nano ZS").

[0095] <Thermogravimetric analysis> Using a TG / DTA (thermogravimetric measurement / differential thermal analysis) apparatus (trade name "EXSTAR6300", manufactured by SII NanoTechnology Inc.), a sample (about 3 mg) was heated at a heating rate of 20 °C / min in an air atmosphere to measure the weight loss. Alumina was used as the reference substance.

[0096] <FT-IR analysis> Regarding the surface-modified nanodiamonds and amino group-modified nanodiamonds (or their hydrochlorides) obtained in the examples, FT-IR measurements were performed using an apparatus equipped with a Fourier transform infrared spectrophotometer "IRTracer" (manufactured by Shimadzu Corporation) and a heating vacuum stirring reflection "Heat Chamber Type-1000 °C" (manufactured by S.T. Japan Co., Ltd.). In order to remove the adsorbed water of the nanodiamond particles, after heating at 150 °C for 10 minutes under a vacuum of 2 × 10 -3 Pa, FT-IR measurements were carried out.

[0097] The FT-IR spectrum of the surface-modified nanodiamond obtained in Example 1 is shown in Figure 1, the FT-IR spectrum of the amino group-modified nanodiamond hydrochloride obtained in Example 1 is shown in Figure 2, the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 2 is shown in Figure 3, the FT-IR spectrum of the amino group-modified nanodiamond obtained in Example 2 is shown in Figure 4, and the FT-IR spectrum of the surface-modified nanodiamond obtained in Example 3 is shown in Figure 5, respectively.

[0098] In the surface-modified nanodiamond of Example 1, around 2928 cm -1 near, 2857 cm-1 Near and 1460cm -1 A peak due to the alkyl group in the oleyl group is found near 1651 cm -1 The peak due to the olefin in the oleyl group is around 1537 cm -1 In the case of the amino group-modified nanodiamond hydrochloride of Example 1, a peak derived from the amide group was observed at 1537 cm -1 Since the peak derived from the nearby amide group disappeared, it was confirmed that the leaving group was deprotected.

[0099] For the surface-modified nanodiamond of Example 2, 2928 cm -1 Near, 2857cm -1 Near, and 1458 cm -1 A peak due to alkyl groups is observed near 1609 cm -1 Near, 1514cm -1 Near, and 831 cm -1 A peak due to the benzene ring is observed near 1248 cm -1 In addition, the amino group-modified nanodiamond of Example 2 had a peak at 1609 cm compared to that of FIG. -1 Near, 1514cm -1 Near, and 831 cm -1 The peaks due to the benzene ring near 1248 cm -1 Since the nearby peak derived from the ether disappeared, it was confirmed that the leaving group had been deprotected.

[0100] For the surface-modified nanodiamond of Example 3, 2926 cm -1 Near, 2855cm -1 Near, and 1456 cm -1 The peak due to the stearyl group is around 1539 cm -1 Peaks derived from amide groups were confirmed near the peaks. Amides are formed by reacting nanodiamonds with amino groups with acid chlorides, and it was confirmed that amides were prepared by the reaction in Example 3, which confirmed that the nanodiamonds obtained in Example 2 have amino groups.

[0101] <Zeta potential> The amino group-modified nanodiamond hydrochloride obtained in Example 1 was used as it was for zeta potential measurement. On the other hand, for the amino group-modified nanodiamond obtained in Example 2, amino group-modified nanodiamond hydrochloride was prepared as follows and used for zeta potential measurement. 3 mL of concentrated hydrochloric acid was added to 64.3 mg of amino group-modified nanodiamond obtained in Example 2 at 0°C, stirred at room temperature for 40 minutes, and then centrifuged (7000G, 5 minutes). The precipitated solid was washed with acetone and dried to obtain 66.5 mg of amino group-modified nanodiamond hydrochloride. The pH at which the zeta potential of the obtained sample solution becomes 0 was defined as the isoelectric point.

[0102] Then, ultrapure water was added to the amino group modified nanodiamond hydrochloride prepared as above so that the concentration was 0.1% by mass. After thorough stirring, ultrasonic treatment was performed for 10 minutes to prepare a sample solution. The measurement range was from the pH of the sample solution to pH1 on the acidic side, and from the pH of the sample solution to pH12 on the alkaline side. When changing the pH of the sample solution to pH1, a 1M aqueous hydrochloric acid solution was used, and when changing it to pH12, a 1M aqueous sodium hydroxide solution was used. The pH was also measured using a pH meter (trade name "Lacom Tester PH110", manufactured by Nikko Hansen Co., Ltd.).

[0103] The isoelectric point titration graph of the amino group-modified nanodiamond hydrochloride obtained in Example 1 is shown in Figure 6, and the isoelectric point titration graph of the amino group-modified nanodiamond obtained in Example 2 is shown in Figure 7. The maximum value of the zeta potential at pH 0 to 4 was 10 mV or more in both cases.

[0104] <Amino group binding amount> 50 mg of the amino group modified nanodiamond (or its hydrochloride) obtained in the examples was suspended in 10 mL of acetonitrile, 60 mg of Nt-butoxycarbonyl-L-alanine hydroxysuccinimide ester (Boc-L-Ala-OSu) and 50 μL of triethylamine were added, and the reaction was carried out at room temperature for about 20 hours. The reaction mixture was centrifuged to remove the supernatant, and then acetonitrile (20 mL) was added to the sediment layer, which was mixed uniformly and then centrifuged to remove the supernatant and wash the layer. The sediment layer was further washed with 30 mL of aqueous sodium bicarbonate solution, and then washed with water. The resulting sediment layer was dried under reduced pressure to obtain a gray nanodiamond solid (yield: 42 mg).

[0105] The obtained nanodiamond solid (3-5 mg) was weighed into a test tube, 100 μL of trifluoroacetic acid was added, and ultrasonic irradiation was performed to obtain a uniform suspension. After heating at 60 °C for 1 minute, the trifluoroacetic acid was removed by blowing nitrogen gas. The residue was suspended in 200 μL of water, to which 200 μL of ethanol solution of phenol (20 g of phenol dissolved in 5 mL of ethanol) and 200 μL of pyridine solution of potassium cyanide (21.6 mg of potassium cyanide dissolved in 30 mL of water, and 1 mL of this solution diluted with 50 mL of pyridine) were added, and the mixture was heated in an oil bath at 120 °C for 10 minutes. The test tube was once removed from the oil bath, and 200 μL of ethanol solution of ninhydrin (2.5 g of ninhydrin dissolved in 50 mL of ethanol) was added, and the mixture was heated again in an oil bath at 120 °C for 10 minutes. The test tube was removed from the oil bath, left to cool for 30 minutes, and then a 60% ethanol solution was added to adjust the volume to 3 mL. The diluted solution was centrifuged to remove the precipitate. The absorbance of the resulting supernatant was measured at 570 nm. Amino groups were quantified by colorimetry using DL-alanine as a standard sample (Kaiser test).

[0106] Variations of the invention according to the present disclosure are described below. [Appendix 1] An amino-group-modified nanodiamond having nanodiamond particles and primary amino groups and / or ammonium ions directly bonded to carbon atoms on the surface of the nanodiamond particles, and having an amino group binding amount of 200 μmol / g or more (or 205 μmol / g or more). [Appendix 2] The amino group-modified nanodiamond described in Appendix 1, wherein the amount of amino group bonded is 700 μmol / g or less (500 μmol / g or less, 400 μmol / g or less, or 350 μmol / g or less). [Appendix 3] An amino group-modified nanodiamond according to appendix 1 or 2, having an isoelectric point in the range of 3 to 5 (or 3.5 to 4.5). [Appendix 4] An amino group-modified nanodiamond according to any one of Appendices 1 to 3, having a maximum zeta potential of 10 mV or more at pH 0 to 4. [Appendix 5] An amino group-modified nanodiamond according to Appendix 4, wherein the zeta potential is 50 mV or less (40 mV or less, or 30 mV or less). [Appendix 6] An amino-group-modified nanodiamond described in any one of Appendices 1 to 5, wherein the mass ratio of nanodiamond to surface-modifying group containing an amino group and an ammonium salt [nanodiamond / surface-modifying group] in the amino-group-modified nanodiamond is 5.0 or more (or 7.0 or more). [Appendix 7] An amino-group-modified nanodiamond as described in Appendix 6, wherein the mass ratio of nanodiamond to surface-modifying group containing an amino group and an ammonium salt [nanodiamond / surface-modifying group] in the amino-group-modified nanodiamond is 15.0 or less (or 10.0 or less).

[0107] [Appendix 8] A method for producing amino-group-modified nanocarbon particles, comprising: a condensation step of reacting nanocarbon particles with an amino compound represented by the following formula (1) in an aqueous solvent; and an amination step of eliminating a leaving group bonded to the amino group after the condensation step to obtain amino-group-modified nanocarbon particles having primary amino groups and / or ammonium ions on the surface thereof. RNH2(1) [In formula (1), R represents a leaving group.] [Appendix 9] A method for producing amino group-modified nanocarbon particles according to Appendix 8, wherein the nanocarbon particles contain nanodiamond particles. [Appendix 10] A method for producing amino-group-modified nanocarbon particles described in Appendix 9, wherein the nanodiamond particles include detonation nanodiamonds. [Appendix 11] A method for producing amino group-modified nanocarbon particles according to any one of Appendices 8 to 10, wherein R in the formula (1) represents an -OS(=O)2-R' group, an -OC(=O)-R' group, a -C(=O)-R' group, a -S(=O)2-R' group, a -C(=O)-O-R' group, a -(C=O)-NH-R' group, or a -R' group [wherein R' represents a hydrogen atom or a monovalent organic group which may have a substituent] (preferably a -C(=O)-R' group or a -R' group). [Appendix 12] The R represents a -C(=O)-R' group, and the R' is an alkenyl group, a haloalkyl group (particularly, a haloC 1-4 Alkyl group), aralkyl skeleton (especially C 1-4 12. A method for producing amino group-modified nanocarbon particles according to claim 11, wherein the amino group-modified nanocarbon particles have an alkyl-aryl skeleton-containing group or an aryl group (particularly, an allyl group, a phenyl group, or a p-biphenyl group). [Appendix 13] The R' is C 2-30 Alkenyl group (preferably C 10-25 Alkenyl groups, more preferably C 12-20 A method for producing amino group-modified nanocarbon particles according to Appendix 12, wherein the amino group is an alkenyl group). [Appendix 14] The R represents a -S(=O)2-R' group, and the R' is an alkyl group (particularly, 1-4 alkyl groups), dialkylamino groups (especially diC 1-4 alkylamino groups), alkoxy-substituted phenyl groups (especially C 1-4 alkoxy-substituted phenyl groups), or alkyl-substituted phenyl groups (especially C 1-4 12. A method for producing amino group-modified nanocarbon particles according to claim 11, wherein the amino group is an alkyl-substituted phenyl group. [Appendix 15] The R represents a -C(=O)-O-R' group, and the R' is an aralkyl skeleton-containing group (particularly, 1-4 Alkyl-aryl skeleton-containing groups), haloalkyl groups (especially haloC 1-412. A method for producing amino group-modified nanocarbon particles according to claim 11, wherein the amino group represents an alkyl group, a branched alkyl group, an alicyclic hydrocarbon group, an organic group-substituted silyl-substituted alkyl group, or a 2-(4-trifluoromethylphenylsulfonyl)ethyl group. [Appendix 16] A method for producing amino group-modified nanocarbon particles according to Appendix 11, wherein R represents an -R' group, and R' is a group containing an aromatic hydrocarbon (particularly, a benzene ring) (preferably a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded). [Appendix 17] A method for producing amino group-modified nanocarbon particles according to Appendix 16, wherein the group containing a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded is an aralkyl skeleton-containing group (preferably a benzyl skeleton-containing group or a phenethyl skeleton-containing group). [Appendix 18] The method for producing amino group-modified nanocarbon particles according to any one of Appendices 8 to 17, wherein the amino compound represented by formula (1) has a melting point of 100° C. or lower. [Appendix 19] A method for producing amino group-modified nanocarbon particles described in any one of Appendices 8 to 18, wherein the amino compound represented by formula (1) has solubility or dispersibility in water in the presence or absence of the acid catalyst. [Appendix 20] The method for producing amino group-modified nanocarbon particles according to any one of Appendices 8 to 19, wherein the condensation step is carried out in a state in which the nanocarbon particles are nano-dispersed in water. [Appendix 21] A method for producing amino group-modified nanocarbon particles according to Appendix 20, wherein the nanocarbon particles have a median diameter (D50) of 1 to 100 nm (1 to 50 nm, or 1 to 10 nm) when nanocarbon particles are nano-dispersed in water. [Appendix 22] A method for producing amino group-modified nanocarbon particles described in any one of Appendices 8 to 21, wherein the condensation step is carried out in a mixed solvent system of water and an organic solvent with the amino compound represented by formula (1) dissolved or dispersed in the organic solvent.

[0108] [Appendix 23] A surface-modified nanocarbon particle comprising a nanocarbon particle and a group represented by the following formula (2) directly bonded to a carbon atom on the surface of the nanocarbon particle: -NH-R (2) [In formula (2), R represents a leaving group, and the bond extending to the left is bonded to a carbon atom on the surface of the nanocarbon particle.] [Appendix 24] Surface-modified nanocarbon particles according to Appendix 23, wherein the mass ratio of the nanocarbon particles to the surface-modifying groups in the surface-modified nanocarbon particles [nanocarbon particles / surface-modifying groups] is 5.0 or more (or 7.0 or more). [Appendix 25] Surface-modified nanocarbon particles according to Appendix 23 or 24, wherein the mass ratio of the nanocarbon particles to the surface-modifying groups in the surface-modified nanocarbon particles [nanocarbon particles / surface-modifying groups] is 15.0 or less (10.0 or less). [Appendix 26] The surface-modified nanocarbon particles according to any one of Appendices 23 to 25, wherein the surface-modified nanocarbon particles have a dispersed particle diameter D50 of 500 nm or less (100 nm or less, or 40 nm or less) in a 0.1 to 5 mass % solvent. [Appendix 27] The surface-modified nanocarbon particles according to any one of Appendices 23 to 26, wherein the nanocarbon particles contain nanodiamond particles. [Appendix 28] The surface-modified nanocarbon particles described in Appendix 27, wherein the nanodiamond particles include detonation nanodiamonds. [Appendix 29] The surface-modified nanocarbon particle according to any one of Appendices 23 to 28, wherein R in the formula (2) represents an -OS(=O)2-R' group, an -OC(=O)-R' group, a -C(=O)-R' group, a -S(=O)2-R' group, a -C(=O)-O-R' group, a -(C=O)-NH-R' group, or a -R' group [wherein R' represents a hydrogen atom or a monovalent organic group which may have a substituent] (preferably a -C(=O)-R' group or a -R' group). [Appendix 30] The R represents a -C(=O)-R' group, and the R' is an alkenyl group, a haloalkyl group (particularly, a haloC 1-4 Alkyl group), aralkyl skeleton (especially C 1-4 29. The surface-modified nanocarbon particles according to claim 29, which exhibit an alkyl-aryl skeleton-containing group or an aryl group (particularly an aryl group, a phenyl group, a p-biphenyl group). [Appendix 31] The R' is C 2-30 Alkenyl group (preferably C 10-25 Alkenyl groups, more preferably C 12-2031. The surface-modified nanocarbon particles of claim 30, wherein the carbon atom is an alkenyl group. [Appendix 32] The R represents a -S(=O)2-R' group, and the R' is an alkyl group (particularly, 1-4 alkyl groups), dialkylamino groups (especially diC 1-4 alkylamino groups), alkoxy-substituted phenyl groups (especially C 1-4 alkoxy-substituted phenyl groups), or alkyl-substituted phenyl groups (especially C 1-4 30. The surface-modified nanocarbon particles according to claim 29, wherein the carbon atom is an alkyl-substituted phenyl group. [Appendix 33] The R represents a -C(=O)-O-R' group, and the R' is an aralkyl skeleton-containing group (particularly, 1-4 Alkyl-aryl skeleton-containing groups), haloalkyl groups (especially haloC 1-4 30. The surface-modified nanocarbon particle according to claim 29, wherein the alkyl group is a silyl-substituted alkyl group, a branched alkyl group, an alicyclic hydrocarbon group, an organic group-substituted silyl-substituted alkyl group, or a 2-(4-trifluoromethylphenylsulfonyl)ethyl group. [Appendix 34] The surface-modified nanocarbon particles according to Appendix 29, wherein R represents an -R' group, and R' is a group containing an aromatic hydrocarbon (particularly, a benzene ring) (preferably a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded). [Appendix 35] The surface-modified nanocarbon particles according to Appendix 34, wherein the group containing a group in which an aliphatic hydrocarbon group and an aromatic hydrocarbon group are bonded is an aralkyl skeleton-containing group (preferably a benzyl skeleton-containing group or a phenethyl skeleton-containing group).

Claims

1. A method for producing amino-group-modified nanodiamond particles, comprising: a condensation step in which nanodiamond particles having hydroxyl groups are reacted with an amino compound represented by the following formula (1) in an aqueous solvent; and an amination step in which, after the condensation step, a leaving group bonded to the amino group is removed to obtain amino-group-modified nanodiamond particles having primary amino groups and / or ammonium ions on the surface. 100 ２ (1) [In formula (1), R represents a leaving group.]

2. The method for producing amino-group-modified nanodiamond particles according to claim 1, wherein the amount of amino groups bound to the amino-group-modified nanodiamond is 200 μmol / g or more.

3. The method for producing amino-modified nanodiamond particles according to claim 2, wherein the isoelectric point of the amino-modified nanodiamond is in the range of 3 to 5.

4. The method for producing amino-group-modified nanodiamond particles according to claim 1 or 2, wherein the maximum zeta potential of the amino-group-modified nanodiamond at pH 0 to 4 is 10 mV or more.

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