JP2018127595A - Highly dispersible metal nano particles and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly dispersible metal nano particles which hardly cause peeling of a surfactant which coats metal nano particles and have extremely excellent dispersibility and to provide a method capable of easily producing such highly dispersible metal nano particles.SOLUTION: There is provided a method for producing highly dispersible metal nano particles, which comprises: a step of mixing a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group and raw material metal nano particles to coat the raw material metal nano particles with the polymerizable surfactant; and a step of polymerizing the polymerizable surfactant.SELECTED DRAWING: None

Description

  The present invention relates to a highly dispersible metal nanoparticle having extremely excellent dispersibility and a method capable of easily producing the highly dispersible metal nanoparticle.

  Metal nanoparticles exhibit unique properties of nanoparticles that are not found in bulk. For example, gold nanoparticles (AuNPs) are known to have optical properties and specific thermal, electrical, and magnetic properties such as vivid red to blue colors depending on particle size and particle shape. In addition, the quantum dots (QDs) exhibit a fluorescent color depending on the particle diameter, have high light stability, and have optical characteristics different from those of organic fluorescent materials such as a wide wavelength band of excitation light. In addition, iron oxide nanoparticles exhibit superparamagnetism. Thus, the metal nanoparticles have various properties depending on the metal species. In recent years, attempts have been made to apply these properties to biotechnology, medical treatment, etc. by combining with biomolecules or polymer materials.

  However, the surface of the metal nanoparticles generally exhibits strong hydrophobicity and lyophobic properties, so that it aggregates in the solvent during the application process, has poor compatibility with biomolecules, and has limited reaction points. There's a problem. That is, in order to combine the metal nanoparticles with other materials, it is necessary to chemically modify the surface of the metal nanoparticles and perform surface modification.

  As a surface modification method for metal nanoparticles, a method using a thiol compound is known. Specifically, gold, in particular, has a high affinity with thiol groups and disulfide groups, and the subsequent chain structure interacts by van der Waals force, and a film called a self-assembled monolayer (SAM) is formed. Formed on the gold surface. Various groups such as a reactive group can be introduced at the opposite end of the chain structure.

  However, the surface modification method using a thiol compound has a problem that the affinity between the thiol compound and the metal surface varies depending on the metal species, and the applicable metal is limited. Moreover, it is not clear what kind of bond the interaction between the thiol compound and the metal surface is, and the thiol compound may peel from the metal surface. Furthermore, since the thiol compound is toxic, there is a problem that even if the metal surface can be modified using the thiol compound, it is difficult to apply to a living body.

  In addition, a method for modifying the surface of metal nanoparticles using a surfactant is also known. In the surface modification method using a surfactant, the surface modification is performed by utilizing the property that the surfactant is adsorbed on the material surface and regularly arranged. For example, Patent Document 1 discloses a phase change magnetic ink containing surfactant-coated magnetic nanoparticles. Patent Document 2 discloses an inorganic nanoparticle-polymer composite in which the surface of an inorganic nanoparticle is coated with a surfactant.

  By the way, the research group of the present inventors has developed a technique for improving the dispersibility of carbon materials such as carbon nanotubes using a polymerizable surfactant. However, although the surface properties of the carbon material and the metal nanoparticles are both hydrophobic, it can be said that they are completely different. For example, it is known that an aromatic hydrophobic group has a high affinity for the surface of a carbon material, but there is no finding that an aromatic hydrophobic group has an affinity for the surface of a metal nanoparticle.

JP 2012-193356 A International Publication No. 2009/096365 Pamphlet JP 2013-1212431 A JP 2014-176844 A

  As described above, conventionally, a technique for modifying the surface of metal nanoparticles by coating with a surfactant has been known. However, since the adsorption of the surfactant to the metal nanoparticle surface is governed by physical adsorption equilibrium, there is a problem that the surfactant is desorbed from the material surface. Not only the particles eventually aggregate due to the desorption of the surfactant, but the free surfactant may inhibit the function of the biomolecule.

  Therefore, the present invention makes it possible to easily produce highly dispersible metal nanoparticles and highly dispersible metal nanoparticles having excellent dispersibility, in which the surfactant that coats the metal nanoparticles is difficult to peel off. It aims to provide a method.

The inventors of the present invention have made extensive studies to solve the above problems. As a result, by polymerizing specific polymerizable surfactants on the surface of the metal nanoparticles, it is possible to produce highly dispersible metal nanoparticles that are extremely excellent in dispersibility because the surfactant layer is difficult to peel off from the surface of the metal nanoparticles. And the present invention was completed.
Hereinafter, the present invention will be described.

[1] A method for producing highly dispersible metal nanoparticles,
Mixing a raw material metal nanoparticle with a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group, and coating the raw material metal nanoparticle with the polymerizable surfactant; and
A method comprising polymerizing the polymerizable surfactant.

[2] The method according to [1] above, wherein a polymerizable surfactant represented by the following formula (I) or a salt thereof is used as the polymerizable surfactant.
[Wherein, R ¹ represents a C _6-20 alkyl group; R ² represents a C _1-4 alkylene group which may have a hydroxyl group; and R ³ represents a C _1- group which may have a hydroxyl group. _{4 represents an} alkylene group; X represents N, N ⁺
One or more groups selected from the group consisting of —R ⁴ , S ⁺ and P ⁺ —R ⁴ (R ⁴ represents a C _1-4 alkyl group); Y represents a radically polymerizable group; Shows hydrophilic group]

[3] The method according to [1] or [2], wherein the ratio of the polymerizable surfactant to the raw metal nanoparticles is 0.1 mass times or more and 10 × 10 ⁸ mass times or less.

  [4] The method according to any one of [1] to [3], wherein in addition to the polymerizable surfactant and the raw material metal nanoparticles, a crosslinking agent having two or more radical polymerizable groups is further mixed.

[5] Highly dispersible metal nanoparticles, wherein the raw metal nanoparticles are coated with a polymer of a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group.

  [6] The highly dispersible metal nanoparticles according to [5], wherein the hydrophilic group includes a polyalkylene glycol group.

  [7] The above [5] or [6], wherein the hydrophilic group includes one or more reactive functional groups selected from the group consisting of epoxy groups, amino groups, carboxy groups, active ester groups, thiol groups, and disulfide groups. ] Highly dispersible metal nanoparticles described in the above.

In the present invention, the “C _6-20 alkyl group” refers to a linear or branched monovalent saturated aliphatic hydrocarbon group having 6 to 20 carbon atoms. Examples include hexyl, octyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, icosyl and the like. Preferably it is a C _8-16 alkyl group, more preferably C _10-14.
It is an alkyl group.
The “C _1-4 alkylene group” refers to a linear or branched divalent saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. For example, methylene, ethylene, propylene, methylethylene, dimethylmethylene, butylene, methylpropylene and the like can be mentioned. A C _1-3 alkyl group or a C _2-4 alkyl group is preferred.
The “C _1-4 alkyl group” refers to a linear or branched monovalent saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. For example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl. A C _1-2 alkyl group is preferable, and methyl is more preferable.

  The highly dispersible metal nanoparticles according to the present invention are safe because the surfactant layer on the surface is difficult to peel off and are extremely excellent in dispersibility. Moreover, since it is also possible to introduce a reactive functional group into the surfactant layer, it can be expected that the application range of metal nanoparticles will be further expanded.

FIG. 1 is a ¹ H-NMR spectrum and a MALDI-TOF / MS spectrum of a polymerizable surfactant produced in Examples described later. FIG. 2 is a MALDI-TOF / MS spectrum after the polymerization operation of the polymerizable surfactant produced in the examples described later. FIG. 3 is a MALDI-TOF / MS spectrum after a polymerization operation of a dispersion liquid containing a polymerizable surfactant and gold nanoparticles produced in Examples described later. FIG. 4 shows an untreated gold nanoparticle, a gold nanoparticle coated with a polymerizable surfactant, and a dispersion of gold nanoparticles coated with a polymerizable surfactant and subjected to a polymerization operation under acidic conditions. It is a graph which shows the result of an absorption spectrum measurement. FIG. 5 shows a dynamic light scattering method of a dispersion of untreated gold nanoparticles, gold nanoparticles coated with a polymerizable surfactant, and gold nanoparticles coated with a polymerizable surfactant and subjected to a polymerization operation. It is a graph which shows a (DLS) measurement result. FIG. 6 shows the absorbance after extraction of untreated gold nanoparticles, gold nanoparticles coated with a polymerizable surfactant, and gold nanoparticles coated with a polymerizable surfactant and subjected to a polymerization operation into a dichloromethane layer. It is the photograph which shows the graph which shows a measurement result, and a visual observation result. FIG. 7 shows the number of times that untreated gold nanoparticles, gold nanoparticles coated with a polymerizable surfactant, and gold nanoparticles coated with a polymerizable surfactant and subjected to a polymerization operation were washed with ultrapure water. It is a graph which shows the relationship with a particle size. FIG. 8 is an absorption spectrum and a photograph of the appearance of an untreated gold nanoparticle dispersion and a gold nanoparticle dispersion coated with a polymerizable surfactant and subjected to a polymerization operation at 40 ° C. before and after pH adjustment. . FIG. 9 is an extinction spectrum and a photograph of the appearance of an untreated gold nanoparticle dispersion and a gold nanoparticle dispersion coated with a polymerizable surfactant and subjected to a polymerization operation at 45 ° C. before and after pH adjustment. . FIG. 10 is an absorption spectrum before and after pH adjustment and a photograph of the appearance of an untreated gold nanoparticle dispersion and a gold nanoparticle dispersion coated with a polymerizable surfactant and subjected to a polymerization operation at 50 ° C. .

First, a method for producing highly dispersible metal nanoparticles according to the present invention will be described.
1. Coating step In this step, a raw material metal nanoparticle is mixed with a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group, and the raw material metal nanoparticle is coated with the polymerizable surfactant. To do.

The polymerizable surfactant used in the present invention has a hydrocarbon group, a hydrophilic group, and a radical polymerizable group.
The hydrocarbon group corresponds to a hydrophobic portion in the polymerizable surfactant, and exhibits an action of binding to the hydrophobic surface of the raw metal nanoparticles by hydrophobic interaction. The carbon number is preferably 6 or more and 20 or less. If the said carbon number is 6 or more, the coupling | bonding to the hydrophobic surface of a raw material metal nanoparticle can be made more reliable. Moreover, if the said carbon number is 20 or less, when an aqueous solvent is used, the solubility and dispersibility with respect to an aqueous solvent will be ensured more reliably. Furthermore, when the number of carbon atoms is 6 or more and 20 or less, the function as a surfactant is more reliably exhibited when an aqueous solvent is used. As said carbon number, 8 or more are more preferable, 10 or more are more preferable, 18 or less or 16 or less are more preferable, and 15 or less are more preferable. Moreover, since it is easy to align with the surface of raw material metal nanoparticles, the hydrocarbon group is preferably an alkyl group, and more preferably a linear alkyl group.

  The hydrophilic part of the polymerizable surfactant is not particularly limited as long as it exhibits hydrophilicity. For example, in addition to a nonionic hydrophilic group such as a polyalkylene glycol group or a polyvinyl alcohol group, an amino group, a carboxy group, etc. The ionic hydrophilic group can be mentioned.

Examples of the polyalkylene glycol group include a polyethylene glycol group, a polypropylene glycol group, and a polybutylene glycol group. A polyethylene glycol group or a polypropylene glycol group is preferable, and a polyethylene glycol group is more preferable from the viewpoint of water solubility. . Moreover, the terminal of the polyalkylene glycol group may remain as a hydroxyl group or may be C _1-4 alkyl etherified with a methyl group or the like. The terminal hydroxyl group can further bind other molecules as a reactive functional group.

The polymerization numbers m and n of the polyalkylene glycol group (— [C—C—O—] _m —) and the polyvinyl alcohol group (— [C—C (OH) —] _n —) are not particularly limited and may be adjusted as appropriate. For example, it may be 4 or more and 20 or less. When the number of polymerization is 4 or more, the effect of the hydrophilic group such as the effect of improving the dispersibility of the nanoparticles can be more reliably exhibited. On the other hand, when the number of polymerizations is 20 or less, the bonding of the polymerizable surfactant to the hydrophobic surface of the raw metal nanoparticles can be made more reliable. The number of polymerization is more preferably 5 or more, further preferably 6 or more, more preferably 16 or less or 14 or less, and further preferably 12 or less or 10 or less.

A reactive functional group may be further bonded to the ends of the hydrophilic portion, particularly the polyalkylene glycol group and the polyvinyl alcohol group. As described above, since the hydrocarbon group of the polymerizable surfactant is bonded to the hydrophobic surface of the raw metal nanoparticles, the hydrophilic portion is relatively directed to the outside of the particle. Therefore, if a reactive functional group is introduced into the hydrophilic portion, useful molecules such as biomolecules can be covalently bonded to the outside of the metal nanoparticles exhibiting excellent dispersibility.

Examples of the reactive functional group include one or more selected from the group consisting of an epoxy group, an amino group, a carboxy group, an active ester group, a thiol group, and a disulfide group. These reactive functional groups make it possible to introduce molecules such as biomolecules such as peptides, DNA, RNA and sugar chains to the outside of the highly dispersible metal nanoparticles. Examples of the active ester group include succinimide ester, sulfosuccinimide ester, 1-hydroxybenzotriazole ester, 1-hydroxy-7-azabenzotriazole ester, pentafluorophenol ester and the like. In addition, examples of the disulfide group include —S—S—C _1-4 alkyl group such as —S—S—CH ₃ group.

The radical polymerizable group of the polymerizable surfactant is not particularly limited as long as radical polymerization is possible, and may be a vinyl group (—CH═CH ₂ ) itself, or at least one C _1-4 alkyl. It may be a vinyl group substituted with a group. As the substituent, a C _1-2 alkyl group is preferable, and a methyl group is more preferable. The radical polymerizable group may be a vinyl group such as an acrylate group (—OC (═O) —CH═CH ₂ ) or a methacrylate group (—OC (═O) —C (CH ₃ ) ═CH ₂ ) or a derivative thereof. In addition to the group, it may include a group that facilitates the synthesis of a radical polymerizable group by facilitating introduction of a vinyl group or a derivative group thereof.
Specific examples of the radical polymerizable group include a vinyl group, allyl group, vinyl ether group, allyl ether group, acrylate group, methacrylate group, acryloyl group, and methacryloyl group.

In the polymerizable surfactant, the hydrocarbon group, the hydrophilic portion, and the vinyl polymerizable group may be directly bonded to each other, or at least two of these may be bonded via a linker group. . The linker group is not particularly limited, and examples thereof include a C _1-6 alkylene group, an amino group, an ether group, a thioether group, a carbonyl group, a thionyl group, an ester group, an amide group, a urea group, a thiourea group, and these groups. And a group in which two or more groups selected from the group are linked linearly. When two or more groups are linked in a straight chain to form a linker group, the same type of group may be used twice or more, and the upper limit of the total number of groups is not particularly limited. 8 or less is preferable, and 5 or less is more preferable. Moreover, you may have a functional group which arises as a result of coupling | bonding reaction, such as a hydroxyl group.

In the polymerizable surfactant, it is preferable that a hydrocarbon group, a hydrophilic group and a radical polymerizable group are bonded via a linker group. With this structure, the hydrocarbon group and the hydrophilic group are located at the respective terminals, the hydrocarbon group is easily bonded to the metal nanoparticle, the hydrophilic group is easily aligned outward, and a radical is formed. Since the polymerizable group is located in the middle, the polymerizable surfactant can be strongly polymerized on the surface of the nanoparticle. Examples of such a structure include a polymerizable surfactant represented by the above formula (I) and a salt thereof. Examples of the salt include halide salts such as chloride and bromide. In the above formula (I), when X is ∋N ⁺ -R ⁴ ,> S ⁺ -or ∋P ⁺ -R ⁴ and the hydrophilic group contains an anionic group such as a carboxy group, so-called Become betaine.

In the polymerizable surfactant of the above formula (I) and a salt thereof, a linker group that binds a hydrocarbon group, a hydrophilic group, and a radical polymerizable group exhibits hydrophilicity. According to the experimental findings of the present inventors, it has been clarified that the hydrophilicity of the linker moiety contributes to good coating with a polymerizable surfactant on the metal nanoparticles.

  The material of the raw metal nanoparticles used in the present invention is not particularly limited, for example, gold, silver, copper, platinum, palladium, iron, ruthenium, cobalt, nickel, molybdenum, indium, iridium, titanium, aluminum, alloys thereof, And oxides thereof. In this invention, a metal nanoparticle means the metal particle whose average particle diameter is less than 1 micrometer. The average particle size is preferably 500 nm or less, and more preferably 100 nm or less. On the other hand, the lower limit of the average particle diameter is not particularly limited, but is preferably 5 nm or more. If the average particle diameter is 5 nm or more, aggregation of raw material metal nanoparticles can be more effectively suppressed.

The amount of the raw material metal nanoparticles and the polymerizable surfactant used may be adjusted as appropriate as long as the surface of the raw material metal nanoparticles is sufficiently covered with the polymerizable surfactant. It is preferable that the usage-amount of a surface active agent shall be 0.1 mass times or more and 1.0 * 10 < ⁸ > mass times or less. From the viewpoint of further improving the dispersibility of the metal nanoparticles, the amount used is more preferably 0.8 mass times or more, and even more preferably 1.0 mass times or more.

In this step, it is preferable to use a solvent in order to facilitate at least mixing of the raw metal nanoparticles and the polymerizable surfactant. The solvent used in the present invention is not particularly limited as long as it can dissolve the polymerizable surfactant and can well disperse the raw metal nanoparticles, and examples thereof include an aqueous solvent and an organic solvent.
In the present invention, the aqueous solvent refers to water itself or a mixed solvent of water and a water-miscible organic solvent. Examples of water include pure water, distilled water, ion exchange water, and buffer solution. The water-miscible organic solvent refers to an organic solvent that is miscible with water without limitation, such as lower alcohol solvents such as methanol, ethanol, and isopropanol; lower nitrile solvents such as acetonitrile; lower ketone solvents such as acetone; dimethylformamide, Examples thereof include amide solvents such as dimethylacetamide; sulfoxide solvents such as dimethylsulfoxide.
Examples of the organic solvent include a water-miscible organic solvent, a halogenated hydrocarbon solvent such as dichloromethane and chloroform; an aromatic hydrocarbon solvent such as benzene, toluene and chlorobenzene; and an ester solvent such as ethyl acetate.

In the case of using a solvent, the concentration of the raw metal nanoparticles and the polymerizable surfactant may be appropriately adjusted. For example, the concentration of the raw metal nanoparticles with respect to the entire mixed solution is 1.0 × 10 ⁻¹¹ M.
As mentioned above, it can be set to 1.0 × 10 ⁻⁶ M or less. If it is in the said range, raw material metal nanoparticles can be disperse | distributed more easily in a liquid mixture. Moreover, as a density | concentration of the polymerizable surfactant with respect to the whole liquid mixture, 0.01 mM or more and 1 M or less are preferable. When the concentration is 0.01 mM or more, the raw metal nanoparticles can be sufficiently covered with the polymerizable surfactant. On the other hand, if the said density | concentration is 1 M or less, the discard amount of polymeric surfactant can be suppressed.

  In addition to the raw material metal nanoparticles and the polymerizable surfactant, the order of addition of the optional component solvent, the crosslinking agent and the polymerization accelerator described later is not particularly limited. Alternatively, two or more components may be added simultaneously.

  The raw metal nanoparticles can be coated with the polymerizable surfactant only by mixing with the polymerizable surfactant. The temperature at that time is sufficient at room temperature, but it may be heated at about 30 ° C. or more and 60 ° C. or less. What is necessary is just to adjust mixing time suitably, for example, an absorption spectrum can be measured timely and it can be carried out until the peak derived from an aggregate is no longer confirmed.

2. Polymerization reaction step In this step, the polymerizable metallurgy that coats the raw metal nanoparticles is subjected to a polymerization reaction and polymerized, so that the raw metal nanoparticles are firmly coated with the surfactant and highly dispersed. Metal nanoparticles are obtained.

In the polymerization reaction, a crosslinking agent may be added to the mixed solution in order to promote polymerization of the polymerizable surfactant. The crosslinking agent has a structure in which two or more vinyl-based polymerizable groups are connected by the same linker group as the linker group of the polymerizable surfactant. The number of vinyl polymerizable groups in the crosslinking agent is preferably 2 or 3.
Although the usage-amount of a crosslinking agent should just be adjusted suitably, it can be about 0.01 times mole or more and 1 time mole or less with respect to 1 mol of polymeric surfactants, for example.

In the polymerization reaction, a polymerization accelerator may be used. Examples of the polymerization accelerator include N, N, N ′, N′-tetramethylethylenediamine (TEMED).
Although the usage-amount of a polymerization accelerator should just be adjusted suitably, it can be 0.01 times mole or more and about 1 time mole or less with respect to 1 mol of polymeric surfactants, for example.

The polymerization reaction can be initiated by adding a polymerization initiator. As the polymerization initiator, water-soluble ones are preferable. For example, persulfates such as ammonium persulfate (APS), sodium persulfate, and potassium persulfate, and peroxides such as hydrogen peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide. Oxides can be mentioned.
Although the usage-amount of a polymerization initiator should just be adjusted suitably, it can be 0.01 times mole or more and about 1 time mole or less with respect to 1 mol of polymeric surfactants, for example.

  The polymerization reaction proceeds even at room temperature, but it may be heated at about 30 ° C. or more and 60 ° C. or less. In particular, when the amount of the polymerizable surfactant used for the metal nanoparticles is small, the polymerization of the particles can be more effectively suppressed by setting the reaction temperature relatively low. Preferably, 42 degrees C or less is more preferable. The reaction time may be appropriately adjusted. For example, it may be about 1 hour or more and 30 hours or less.

  In addition, although the said coating process and a polymerization reaction process may be performed continuously, you may perform substantially simultaneously. For example, raw material metal nanoparticles, a polymerizable surfactant, a polymerization initiator and, if necessary, a crosslinking agent and / or a polymerization accelerator are added to a solvent and stirred, and the raw material metal nanoparticles by the polymerizable surfactant are used. The polymerization reaction of the coating and the polymerizable surfactant may proceed simultaneously.

3. Useful molecule binding step The highly dispersible metal nanoparticles produced through the coating step and the polymerization reaction step have a surface coated with a polymer of a polymerizable surfactant, and the hydrophilic portions facing each other. High dispersibility due to electrostatic repulsion. In addition, the implementation of this step is optional, but when a reactive functional group is introduced into the hydrophilic portion, various molecules such as biomolecules can be bonded through the reactive functional group. Is possible.

  For example, since a peptide which is a biomolecule has various reactive functional groups at the terminal or side chain, it can form a covalent bond with the reactive functional group. For example, when an epoxy group, an active ester group, a thiol group, a disulfide group or the like is introduced into the hydrophilic portion as the reactive functional group, an ordinary peptide has an amino group or a thiol group at its terminal or side chain. Therefore, the peptide can be easily bound to the outside of the metal nanoparticles.

In addition, since metal nanoparticles have been studied for use in drug delivery systems and the like, for example, a drug is bound to a highly dispersible metal nanoparticle according to the present invention, and the drug is selectively delivered to a specific position. It may also be possible to do.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Example 1: Preparation of gold nanoparticles according to the present invention (1) Synthesis of polymerizable surfactant C ₁₂ -GMA-EG ₇ m-PEG (8) -amine (1 mmol) and potassium carbonate (3 mmol) were mixed with dichloromethane (3 mmol). 7 mL). Separately, lauroyl chloride dissolved in dichloromethane (3 mL) was added dropwise and reacted at room temperature for 24 hours. After completion of the reaction, the solid component was filtered off with a membrane filter, and the solvent was distilled off from the filtrate. Thereafter, freeze-drying, C ₁₁ -CONH-EG _7: to obtain a crude product of (Mw 565.4).

Super dehydrated THF (45 mL) was added to lithium aluminum hydride (6.5 mmol). Using the three-necked flask, the above C ₁₁ -CONH-EG ₇ (1 mmol) dissolved in ultra-dehydrated THF (10 mL) was added and reacted at 60 ° C. for 4 hours under a nitrogen atmosphere. Ultrapure water (2m
After the reaction was completed by adding L) little by little, the solid component was filtered off, and the solvent was distilled off from the filtrate under reduced pressure. Thereafter, the solid was recrystallized with diethyl _{ether, C 12 -EG 7 (Mw:} 551.4
) Was obtained.

Glycidyl methacrylate (GMA) (0.6 mmol) was mixed with ultrapure water (2 mL), and hydroquinone (0.015 m) as the above-mentioned C ₁₂ -EG ₇ (0.3 mmol) and a polymerization inhibitor.
mol) was added dropwise to a solution in which ultrapure water (3 mL) was dissolved, and the mixture was reacted at 80 ° C. for 3 hours. After completion of the reaction, the solvent was distilled off under reduced pressure and freeze-dried to obtain C ₁₂ -GMA-EG ₇ (M
w: 693.5) was obtained.

^The product was identified by ¹ H-NMR and MALDI-TOF / MS. In FIG.
The results of ¹ H-NMR spectrum and MALDI-TOF / MS spectrum of the product are shown. From the result of MALDI-TOF / MS, a peak derived from C ₁₂ -GMA-EG _{7 as} the target product was confirmed. In addition, a slight amount of unreacted C ₁₂ -EG ₇ (Mw: 551.4
), And a peak of C ₁₂ -2GMA-EG ₇ (Mw: 837.6) as a by-product was also confirmed. ^From the result of ¹ H-NMR, a peak derived from the target product, C ₁₂ -GMA-EG ₇ , was confirmed, and from the integration ratio, it was considered that there were few unreacted products and by-products.

(2) Polymerization test of polymerizable surfactant C ₁₂ -GMA-EG ₇ C ₁₂ -GMA-EG ₇ (15 mg) was dissolved in ultrapure water. N, N'-methylenebisacrylamide (MBAA) as a crosslinking agent, ammonium peroxodisulfate (APS) as a polymerization initiator, and N, N, N ', N'-tetramethylethylenediamine (TEMED) are dissolved in ultrapure water. And added with a syringe so that the molar ratio of polymerizable surfactant: MBAA: APS: TEMED = 4: 1: 1: 1. The reaction was stirred for 17 hours at room temperature. After completion of the reaction, analysis was performed by MALDI-TOF / MS.
FIG. 2 shows a MALDI-TOF / MS spectrum after the polymerization operation. Since a regular peak derived from the molecular weight of C ₁₂ -GMA-EG ₇ was observed, it was confirmed that the polymerization reaction of C ₁₂ -GMA-EG ₇ was in progress.

(3) Polymerization of the polymerizable surfactant C ₁₂ -GMA-EG _{7 on} the gold nanoparticle surface 4 × 10 ⁻⁹ M gold nanoparticle aqueous dispersion (1 mL) (hereinafter referred to as “AuNPs”) C ₁₂ -GMA-EG ₇ was dissolved to 50 mM. N as a crosslinking agent
, N′-methylenebisacrylamide (MBAA), ammonium peroxodisulfate (APS) as a polymerization initiator, and N, N, N ′, N′-tetramethylethylenediamine (TEMED) are dissolved in ultrapure water, and a molar ratio The polymerizable surfactant: MBAA: APS: TEMED = 4: 1: 1: 1 was added by a syringe. The reaction was stirred for 17 hours at room temperature. After completion of the reaction, analysis by MALDI-TOF / MS was performed. Absorption spectrum measurement was performed after adding 1M HCl to the solution so that pH might be set to 1.
FIG. 3 shows a MALDI-TOF / MS spectrum of the AuNPs dispersion after the polymerization operation. Since a regular peak derived from the molecular weight of C ₁₂ -GMA-EG ₇ was observed, AuN
It was confirmed that the polymerization reaction of C ₁₂ -GMA-EG ₇ was proceeding even in the system where Ps was present.
FIG. 4 shows the result of the absorption spectrum measurement of the AuNPs dispersion under acidic conditions. From the results of the absorption spectrum measurement, when AuNPs alone was used, no peak was observed at 520 nm, and AuNPs aggregated when the solution was brought to acidic conditions. When C ₁₂ -GMA-EG ₇ was coated and polymerized, there was no change in the peak position of the absorption spectrum even after the solution was acidified, and AuNPs kept in a dispersed state.
FIG. 5 shows the results of dynamic light scattering (DLS) measurement of AuNPs dispersion under acidic conditions. The results of DLS measurements, although the particle diameter when the solution is acidified after polymerization operation of C ₁₂ -GMA-EG ₇ is large, no big as aggregates, the C ₁₂ -GMA-EG ₇ AuN
It was suggested that the Ps surface was dispersed. From these results, it is clear that when C ₁₂ -GMA-EG ₇ is added and polymerized, C ₁₂ -GMA-EG ₇ protects the AuNPs surface and can maintain a dispersed state even under acidic conditions. Became.

(4) Extraction of AuNPs into organic solvent AuNPs dispersion, C ₁₂ -GMA-EG ₇ coated AuNPs dispersion, or C ₁₂ -GMA
Place -EG ₇ polymerization AuNPs dispersion (1 mL) in an upper layer of each dichloromethane (1 mL), and centrifuged 20 minutes at 14,000 rpm. After removing the aqueous layer, the dichloromethane layer was stirred and the absorption spectrum was measured.
FIG. 6 shows the absorbance measurement and visual observation results after extracting AuNPs into the dichloromethane layer. From the visual observation, in the case of AuNPs alone, AuNPs stayed at the interface between dichloromethane and ultrapure water and could not be extracted into the dichloromethane layer. In contrast, C ₁₂ -GMA-EG ₇ coated AuNPs and C ₁₂ -GMA-EG ₇ polymerized AuNPs could be extracted into the dichloromethane layer. From the results of the absorption spectrum measurement of the dichloromethane layer, the C ₁₂ -GMA-EG ₇ coated AuNPs partially aggregated, whereas the C ₁₂ -GMA
It was revealed that -EG ₇ polymerized AuNPs were maintained in a dispersed state. C ₁₂ -GM
By polymerizing the A-EG _7, considered with resistance to organic solvents is improved.

(5) Washing of AuNPs The AuNPs dispersion, the C ₁₂ -GMA-EG _7- coated AuNPs dispersion, and the C ₁₂ -GMA-EG ₇ polymerized AuNPs dispersion are each centrifuged at 14,000 rpm for 20 minutes, and the supernatant is obtained. After removing 800 μL of the solution, 800 μL of ultrapure water was added. This operation was repeated twice as one washing operation. The dispersibility of AuNPs was evaluated by DLS measurement for each washing operation.
FIG. 7 shows the particle size with respect to the number of washing times of the AuNPs dispersion. From FIG. 7, it was confirmed that the C ₁₂ -GMA-EG ₇ polymerized AuNPs could suppress aggregation and prevent aggregation compared to AuNPs alone and C ₁₂ -GMA-EG ₇ coated AuNPs.

Example 2: Effect of temperature on the polymerization reaction A C ₁₂ -GMA-EG ₇ aqueous solution (200 μL) in 4 × 10 ⁻⁹ M AuNPs aqueous dispersion (8
00 μL) was added. The concentration of C ₁₂ -GMA-EG ₇ was adjusted to 1 mM, 0.5 mM, or 0.3 mM at the final concentration. N, N'-methylenebisacrylamide (MBAA) as a crosslinking agent, ammonium peroxodisulfate (APS) as a polymerization initiator, and N, N, N ', N'-tetramethylethylenediamine (TEMED) are dissolved in ultrapure water. And added in a molar ratio such that polymerizable surfactant: MBAA: APS: TEMED = 40: 1: 1: 1. The mixture was stirred at 40 ° C., 45 ° C. or 50 ° C. for 24 hours to be reacted. After completion of the reaction, analysis by ¹ H-NMR and measurement of absorption spectrum were performed. Further, the reaction solution was transferred to another container, and 1M HCl was added to the solution so that the pH was 1, and then the absorption spectrum measurement was performed again.
The AuNPs dispersion absorption spectra and external appearance photographs before and after pH adjustment at reaction temperatures of 40 ° C., 45 ° C., and 50 ° C. are shown in FIGS. As shown in FIGS. 8 to 10, in the AuNPs dispersion, when the pH was adjusted to 1, Au particles aggregated and became colorless and transparent. In contrast, in the C ₁₂ -GMA-EG ₇ polymerized AuNPs dispersion, even when the pH was 1, the color and the absorption spectrum hardly changed, and the Au particles maintained dispersibility. As described above, according to the present invention, it was revealed that the dispersion of metal particles can be remarkably improved.

Claims (7)

A method for producing highly dispersible metal nanoparticles comprising:
Mixing a raw material metal nanoparticle with a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group, and coating the raw material metal nanoparticle with the polymerizable surfactant; and
A method comprising polymerizing the polymerizable surfactant. The method according to claim 1, wherein a polymerizable surfactant represented by the following formula (I) or a salt thereof is used as the polymerizable surfactant.
[Wherein, R ¹ represents a C _6-20 alkyl group; R ² represents a C _1-4 alkylene group which may have a hydroxyl group; and R ³ represents a C _1- group which may have a hydroxyl group. _{4 represents an} alkylene group; X represents N, N ⁺
One or more groups selected from the group consisting of —R ⁴ , S ⁺ and P ⁺ —R ⁴ (R ⁴ represents a C _1-4 alkyl group); Y represents a radically polymerizable group; Shows hydrophilic group] The method according to claim 1 or 2, wherein the ratio of the polymerizable surfactant to the raw metal nanoparticles is 0.1 mass times or more and 10 x 10 ⁸ mass times or less.   The method according to any one of claims 1 to 3, wherein a crosslinking agent having two or more radical polymerizable groups is further mixed in addition to the polymerizable surfactant and the raw metal nanoparticles.   A highly dispersible metal nanoparticle, wherein the raw metal nanoparticle is coated with a polymer of a polymerizable surfactant having a hydrocarbon group, a hydrophilic group and a radical polymerizable group.   The highly dispersible metal nanoparticles according to claim 5, wherein the hydrophilic group includes a polyalkylene glycol group.   The high dispersion according to claim 5 or 6, wherein the hydrophilic group includes one or more reactive functional groups selected from the group consisting of an epoxy group, an amino group, a carboxy group, an active ester group, a thiol group, and a disulfide group. Metal nanoparticles.