JP4112945B2 - Core-shell type metal nano colloidal fine particles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a core-shell type metal-based nanocolloid.
[0002]
[Prior art]
Conventionally, as described in Non-Patent Document 1, for example, a metal nanocolloid fine particle is prepared by preparing an aqueous solution of a metal salt in the presence of a surfactant and adding a reducing agent to the metal ion to convert the metal ion into a metal. It has been produced by a reduction method. Surfactant adsorbs to the generated metal nanocolloid fine particles and prevents sedimentation of the metal nanocolloid fine particles, but the original function is to use a surfactant with the opposite charge to the metal ions. Since ions are taken in, it is known that the particle diameter of the obtained metal nanocolloid fine particles can be controlled. In this case, the concentration of the surfactant is set to be equal to or higher than the critical concentration necessary for forming micelles, and the obtained metal nanocolloid fine particles are fine particles made of one component metal.
[0003]
On the other hand, when a reducing agent is added to an aqueous solution containing two kinds of metal ions, both of these metal ions are reduced to become metals. At this time, as described in Non-Patent Documents 2 and 3, a metal having a core-shell structure is obtained by using a noble metal as a core and a base metal as a shell.
[0004]
Furthermore, Non-Patent Document 4 discloses that when a base metal nanocolloid fine particle is treated with hydrogen in the presence of a dispersant and a noble metal ion is added thereto, a base metal nanocolloid fine particle is added. It is described that metal nanocolloid fine particles with a reverse core shell structure in which a noble metal ion is reduced to a metal on the surface, a base metal is a core, and a noble metal is a shell are obtained. Yes.
[0005]
[Non-Patent Document 1]
Mikijiro Torigoe and Kunio Esumi, “Chemical production of gold colloid”, Chemical Industry, Chemical Industry, April 1998, pages 21-29
[Non-Patent Document 2]
N. Toshima and K.K. Hirakawa, Polym. J. et al. 31, 1127-1132 (1999)
[Non-Patent Document 3]
N. Toshima and 4 others; Phys. Chem. 95, 7448-7453 (1991)
[Non-Patent Document 4]
Y. Wang and N.W. Toshima, J .; Phys. Chem. B, 101, 5301-5306 (1997)
[0006]
[Problems to be solved by the invention]
As described above, many studies on metal nanocolloids have been reported, but the core-shell-structured metal-based nanocolloids in which the core component containing the ions of the base metal is coated with the shell containing the noble metal are reported. I can't see the report.
[0007]
Therefore, an object of the present invention is to provide a metal-based nanocolloid fine particle having a core-shell structure in which a core component containing a base metal ion is covered with a shell containing a more noble metal.
[0008]
[Means for Solving the Problems]
  According to the present invention for achieving the above object, a core-shell type nanocolloid fine particle having a core component containing a base metal component and a shell containing a noble metal coating the core component.A manufacturing method of
Adding a surfactant to a more complex metal-ligand ion to form a premicelle;
Adding a noble metal ion to the premicelle to oxidize the base metal ion and simultaneously reducing the noble metal ion to the noble metal;
The surfactant concentration is lower than the minimum concentration required to form micelles
Method for producing core-shell nano colloidal fine particlesIs provided.
[0009]
The nanocolloid fine particles mean fine particles contained in a colloidal state in the nanocolloid.
[0011]
The core-shell type metal nanocolloid fine particles obtained as described above have a core-shell structure in which a core (core) component containing ions of a base metal is covered with a shell (shell) containing a noble metal. Therefore, for example, there are the following advantages.
[0012]
(A) Since the core of the base metal component is covered with the shell of the noble metal, it is inexpensive. For this reason, in the field of application of the conventional nanocolloid fine particles made of a noble metal, if the surface of the nanocolloid fine particles only needs to be a noble metal, the core-shell type nanocolloid fine particles of the present invention can be substituted.
[0013]
(A) Nano colloidal fine particles made of iron, copper, aluminum or the like are useful as a conductive agent, but the surface of these nano colloidal fine particles is easily oxidized and the conductivity may be lowered. However, if the method of the present invention is used, these conductive agent metal components can be coated with a noble metal. As a result, sufficient conductivity can be maintained even in an oxidative environment.
[0014]
(C) Furthermore, in the present invention, since the core component reduces the shell component, conduction is maintained even if the shell component is not a noble metal.
[0015]
(D) Since the core-shell nanocolloid fine particles of the present invention have a structure having many hydrophobic portions, extraction into a hydrophobic environment is easy. For this reason, it is easy to make ink.
[0016]
(E) In the premicelle region, the core (core) component can be efficiently concentrated, so that nanocolloid fine particles are easily generated.
[0017]
(F) Since the more complex metal ions are concentrated in the premicel, the oxidation of the base metal ions and the reduction of the more noble metal ions proceed efficiently. Further, when a surfactant having a charge opposite to that of a base metal complex ion is used, a concentration effect equal to or higher than that in the case of micelles can be expected.
[0018]
(G) The amount of the surfactant used is smaller when the nanocolloid particles are produced in the premicelle state than when the nanocolloid particles are produced in the micelle state. For this reason, the raw material cost is low, and purification is easy.
[0019]
(H) In the case where the core component is a complex ion of a more basic metal and a ligand, the complex ion is bulky, so that the volume can be increased.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0021]
(Core-shell nano colloidal particles)
The core-shell nanocolloid fine particles of the present invention have a core-shell structure in which a core component containing a more basic metal ion is coated with a shell containing a more noble metal. The core-shell nanocolloid fine particles can be confirmed with an electron microscope or the like, and the number average particle diameter can be calculated by measuring and averaging the diameters of the core-shell nanocolloid fine particles in the image obtained with the electron microscope. Further, the volume average particle diameter can be measured by utilizing a light scattering method or the like. The average particle diameter of the core-shell nanocolloid fine particles measured in this manner is usually 1 nm or more and sometimes 5 nm or more, while it is usually 50 nm or less and sometimes 20 nm or less.
[0022]
It should be noted that the core-shell nanocolloid fine particles of the present invention can be confirmed by various spectroscopic techniques to have a core component containing ions of a more basic metal coated with a shell containing a more noble metal. However, when the obtained core-shell nanocolloid fine particles are exposed to further reducing conditions, it can be easily confirmed that the reduction reaction does not proceed further.
[0023]
In addition, there is a difference in the appearance of ultraviolet absorption peaks (derived from a ligand) of nanocolloid fine particles prepared using premicelle as a core and nanocolloid fine particles prepared in a micelle region and diluted to a premicelle state. Since the latter peak is larger than the former, it can be predicted that premicelle is incorporated in the core portion.
[0024]
(Shell formation in premicelle state)
FIG. 1 shows the relationship between the concentration of the metal (lower base metal) M forming the core in the core-shell nanocolloid fine particles and the concentration of the surfactant. In the region (I) where the surfactant is low in concentration, complex ions composed of the metal ions 10 and the ligands 20 are dissolved. In the region (II), the concentration of the surfactant 30 increases, and the surfactant 30 binds to the complex ions to cause precipitation. Further, when the concentration of the surfactant is increased, the precipitate formed in the region (II) is dissolved again as shown in the region (III).
[0025]
In addition, when the formation and re-dissolution of the precipitate is not clear, the regions (I) to (III) can be confirmed by measuring the conductivity of the system. In the region (II), the conductivity decreases or decreases drastically.
[0026]
However, when adding a surfactant to solubilize complex ions to form micelles, the surfactant concentration is usually higher than the surfactant concentration in region (III), as shown in region (VI). . In the region (VI), the complex ions are solubilized by the action of the fine particles made of the surfactant, and the complex ions are considered to exist in the vicinity of the fine particles made of the surfactant.
[0027]
In region (III), the concentration of surfactant is lower than the typical concentration required to form micelles in region (VI). That is, although the concentration of the surfactant is lower than the minimum concentration (critical micelle concentration) necessary for forming micelles, the complex ions are dissolved, and the state before the formation of micelles, that is, the premicelle state It is thought that it is formed. In the premicelle state, it is considered that the excess hydrophobic part of the surfactant is bound to the hydrophobic part of the surfactant generated in the region (II), and the precipitate is redissolved.
[0028]
When a noble metal ion is supplied to a system in which such a premicelle is formed, the noble metal ion is reduced to form a shell. This is shown in FIG. In FIG. 2, the less basic metal M_BIons form a premicel state, and the more precious metal M_NIons are supplied, and as shown in FIG._BOn the surface of the premicelle microparticles containing ions, M_NIons are being reduced. As a result, as shown in FIG._BMetal M on the surface of the core containing ions_NIs formed, and M is formed._BThe core containing ions is metal M_NIt is considered that a structure covered with a shell containing is formed.
[0029]
In the case of such a structure, it is considered that the base metal component is present in the core as a complex ion of the base metal and the ligand.
[0030]
In the above reaction, as a base metal, aluminum (Al), titanium (Ti), vanadium (for example, it is easy to form stable complex ions and premicelles and is highly useful for coating the surface with a noble metal. V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), cadmium (Cd), tin ( Sn), lead (Pb), bismuth (Bi), and the like are used, and iron (Fe), cobalt (Co), palladium (Pd), and the like are preferable from the viewpoints of redox potential, toxicity, price, and the like.
[0031]
Further, the concentration of the more complex metal ions in the shell formation reaction is 0.01 mmol / L from the viewpoint of forming stable complex ions and premicelles, and the shell formation reaction proceeds sufficiently. The above is preferable, 0.05 mmol / L or more is more preferable, 0.1 mmol / L or more is further preferable, while 10 mmol / L or less is preferable, and 5 mmol / L or less is more preferable.
[0032]
More precious metals include gold (Au), platinum (Pt), silver (Ag), palladium (Pd), rhodium (Rh), iridium (Ir), and osmium because the shell can be easily formed. (Os), ruthenium (Ru), or the like is used.
[0033]
In addition, the concentration of the noble metal ions during the shell formation reaction is preferably 0.01 mmol / L or more from the viewpoint of sufficient progress of the shell formation reaction without destroying the premicelle. 0.05 mmol / L or more is more preferable, 0.1 mmol / L or more is more preferable, and 10 mmol / L or less is preferable and 5 mmol / L or less is more preferable.
[0034]
Ligands that form complex ions with lower-grade metals include those that easily form stable complex ions and premicelles, and that do not inhibit the formation of shells, such as cationic ligands, anionic ligands, and amphoteric ligands. A ligand and a nonionic ligand are carefully selected, and among them, a cationic ligand is preferable from the viewpoint of stability of complex ions and premicelles and reaction efficiency.
[0035]
Examples of cationic ligands include pyridine and derivatives thereof, 2,2′-bipyridine and derivatives thereof, 1,10-phenanthroline and derivatives thereof, ethylenediamine and derivatives thereof, propylenediamine and derivatives thereof, triethylenetetramine and derivatives thereof, and the like. Among them, 1,10-phenanthroline, 2,2′-bipyridine and the like are preferable from the viewpoints of stability of complex ions and premicelles and reaction efficiency.
[0036]
From the viewpoint of the stability of complex ions and premicelles and the reaction efficiency, anionic ligands are also preferred.
[0037]
Among them, from the viewpoint of the stability and reaction efficiency of complex ions and premicelles, ethylenediaminetetraacetic acid (EDTA) and its derivatives, dimethylglyoxime and its derivatives, 1,10-phenanthroline carboxyl group-substituted products, 1,10-phenanthroline A sulfonyl group substitution product or the like is used.
[0038]
Further, glycine and its derivatives are used as amphoteric ligands.
[0039]
As the nonionic ligand, acetylacetone and its derivatives are used.
[0040]
On the other hand, as surfactants, those that easily form stable premicelles and do not inhibit the formation of shells can be selected from anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants. Although carefully selected, anionic surfactants are preferred.
[0041]
Examples of the anionic surfactant include fatty acid soap, N-acyl amino acid, N-acyl amino acid salt, polyoxyethylene alkyl ether carboxylate, carboxylate such as acylated peptide; alkyl sulfonate, alkyl benzene sulfonate, Alkyl naphthalene sulfonate, Naphthalene sulfonic acid salt Formalin polycondensate, Melamine sulfonic acid salt Formalin polycondensate, Dialkyl sulfosuccinic acid ester salt, Sulfosuccinic acid alkyl disalt, Polyoxyethylene alkyl sulfosuccinic acid disalt, Alkyl sulfoacetic acid Sulfonates such as salts, α-olefin sulfonates, N-acyl-N-methyltaurine salts, dimethyl-5-sulfoisophthalate sodium salts; sulfated oils, higher alcohol sulfates, secondary higher alcohol sulfates Stealth salts, polyoxyethylene alkyl ether sulfates, secondary higher alcohol ethoxy sulfates, monoglyculates, sulfate esters such as sulfates of fatty acid alkylol amides; sulfates such as alkyl sulfates; polyoxyethylene alkyl ethers Phosphate esters such as phosphates, polyoxyethylene alkylphenyl ether phosphates, alkyl phosphates; partial hydrolysis of poly and oligo (meth) acrylic acid, styrene-maleic anhydride copolymers and oligomers Ring product (ring opening rate is preferably 30 to 80%), styrene-maleic anhydride copolymer polymer and oligomer completely hydrolyzed ring-opened product, ethylene-maleic anhydride copolymer polymer and oligomer partially hydrolyzed Rings (opening rate is 30-80% Preferred), fully hydrolyzed ring-opened products of ethylene-maleic anhydride copolymer and oligomer, isobutylene-maleic anhydride copolymer polymer and oligomer (opening rate is 30 to 80%) Preferred), fully hydrolyzed ring-opened products of copolymer and oligomer of isobutylene-maleic anhydride, poly and oligo vinyl acetate, poly and oligo vinyl alcohol, oligomer derived from hexaethyl cellulose, oligomer derived from methyl cellulose, oligomer derived from carboxymethyl cellulose Among them, alkyl sulfates such as sodium dodecyl sulfate (SDS), alkyl sulfonates, alkyl benzene sulfonates, salt formalin polycondensates of melamine sulfonate, and polyvinyl acetate are preferable.
[0042]
The concentration of the anionic surfactant during the shell formation reaction is in a range lower than the critical micelle concentration, from the viewpoint of forming a stable premicelle and not inhibiting the shell formation reaction without forming a micelle. , Carefully optimize. In particular, as shown in FIG. 1, since the concentration of the anionic surfactant in the region III where the premicelle state is formed is affected by the concentration of complex ions of the base metal, prior to the production of the nanocolloid fine particles, Understand the range of the concentration of the more complex metal ions and the concentration of the anionic surfactant in which the region III is realized.
[0043]
For example, if the concentration of the complex ion of the base metal is in the range of 0.01 to 10 mmol, the concentration of the anionic surfactant such as SDS is used when the anionic surfactant has a low molecular weight of 1,000 or less. Is preferably 0.5 mmol / L or more, more preferably 0.8 mmol / L or more, still more preferably 1 mmol / L or more, on the other hand, preferably 15 mmol / L or less, more preferably 10 mmol / L or less, and 8 mmol / L or less. Is more preferable.
[0044]
The concentration of the anionic surfactant is generally preferably 0.01% by mass or more, more preferably 0.02% by mass or more, on the other hand, preferably 5% by mass or less, and more preferably 2% by mass or less. .
[0045]
In the case of an anionic surfactant having a molecular weight higher than 1,000, such as a polymer, the concentration of the anionic surfactant is preferably 0.01 to 1% by mass.
[0046]
Regardless of the molecular weight, if the amount of the anionic surfactant added is too small, the dispersion may be unstable or precipitation may occur, so 0.1% by mass or more is usually preferable.
[0047]
On the other hand, cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and (meth) acrylates containing quaternary ammonium bases. Polymers, quaternary ammonium base-containing maleimide copolymers, quaternary ammonium base-containing methacrylimide copolymers, etc. are used, among which aliphatic such as alkylammonium bromide (the alkyl group has 10 to 14 carbon atoms) Polymeric quaternary ammonium salts such as quaternary ammonium salts and quaternary ammonium base-containing (meth) acrylate copolymers are preferred.
[0048]
The concentration of the cationic surfactant in the shell formation reaction is in a range lower than the critical micelle concentration, from the viewpoint of forming a stable premicelle and not inhibiting the shell formation reaction without forming a micelle. , Carefully optimize. In particular, as shown in FIG. 1, since the concentration of the cationic surfactant in the region III where the premicelle state is formed is affected by the concentration of the more complex metal ions, prior to the production of the nanocolloid fine particles, Understand the range of the concentration of the more complex metal ions and the concentration of the cationic surfactant in which region III is realized.
[0049]
Generally, the concentration of the cationic surfactant is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, while 1% by mass or less. Preferably, 0.5 mass% or less is more preferable.
[0050]
As the amphoteric surfactant, carboxybetaines, aminocarboxylates, imidazolinium betaines, lecithin, alkylamine oxides and the like are used.
[0051]
In the shell formation reaction, the concentration of the amphoteric surfactant is in a range lower than the critical micelle concentration, from the viewpoint of forming a stable premicelle, not forming a micelle, and not inhibiting the shell formation reaction. Optimize carefully. In particular, as shown in FIG. 1, the concentration of the amphoteric surfactant in the region III where the premicelle state is formed is influenced by the concentration of the complex ions of the base metal. Understand the range of the concentration of the more complex metal ions and the concentration of the amphoteric surfactant, where III is realized.
[0052]
Generally, the concentration of the amphoteric surfactant is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, still more preferably 0.01% by mass or more, while preferably 1% by mass or less. 0.5 mass% or less is more preferable.
[0053]
Nonionic surfactants include polyoxyethylene alkyl ether, single chain length polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative , Ethers such as ethylene oxide derivatives of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene alkyl ether; polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene Ester ethers such as sorbitol fatty acid ester and polyoxyethylene fatty acid alkanolamide sulfate; polyethylene glycol Esters such as fatty acid esters, ethylene glycol fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters; fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyls Nitrogen-containing compounds such as amines are preferred, with polyoxyethylene alkyl ethers being particularly preferred.
[0054]
The concentration of the nonionic surfactant in the shell formation reaction is in a range lower than the critical micelle concentration, from the viewpoint of forming a stable premicelle and not inhibiting the shell formation reaction without forming a micelle. , Carefully optimize. In particular, as shown in FIG. 1, since the concentration of the nonionic surfactant in the region III where the premicelle state is formed is affected by the concentration of complex ions of the base metal, prior to the production of the nanocolloid fine particles, The range of the concentration of the more complex metal ions and the concentration of the nonionic surfactant, in which the region III is realized, is grasped.
[0055]
Generally, the concentration of the nonionic surfactant is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, further preferably 0.01% by mass or more, while 1% by mass or less. Preferably, 0.5 mass% or less is more preferable.
[0056]
The combination of the ligand and the surfactant described above takes into consideration the charge of the complex ion and the charge of the surfactant from the viewpoint of the stability of the premicelle and the progress of the shell formation reaction. decide. For example, when a cationic ligand is used as the ligand and the complex ion is a cation, an anionic surfactant having a charge opposite to that of the complex ion, a high molecular weight amphoteric surfactant, and a high molecular weight nonionic surfactant Is preferred. When an anionic ligand is used as the ligand and the complex ion is an anion, a cationic surfactant having a charge opposite to that of the complex ion, a high molecular weight amphoteric surfactant, and a high molecular weight nonionic surfactant Is preferred. Among these combinations, from the viewpoint of premicelle stability and reaction efficiency, a system in which the complex ion is a cation and an anionic surfactant is used is preferable.
[0057]
In addition, two or more kinds of surfactants can be used in combination as required. In particular, at least one of an anionic surfactant and a cationic surfactant, an amphoteric surfactant and a nonionic surfactant are used. It is preferable to use at least one of these in combination from the viewpoint of the stability of the premicelle and the reaction efficiency. In particular, a high molecular weight amphoteric surfactant (amphoteric surfactant polymer) and a high molecular weight nonionic surfactant (nonionic surfactant polymer) are preferable because the premicelle is stabilized by the inclusion effect.
[0058]
The reaction temperature for forming the shell is about 0 to 30 ° C. The reaction time for forming the shell is about 5 to 60 minutes.
[0059]
(Application field)
The core-shell nanocolloid fine particles obtained as described above are catalysts, particularly heterogeneous catalysts in oxidation-reduction reactions, organic synthesis reactions, photopolymerization reactions, combustion reactions, etc .; microspherical supports; highly conductive conductivity Material: Conductive ink; Optical material; Transparent conductive material; Antistatic material; Electromagnetic wave shielding material; Useful as a coloring material utilizing the color of metal colloid liquid.
[0060]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not restrict | limited to a following example. Unless otherwise specified, commercially available high-purity products are used for reagents and the like.
[0061]
(Reference Example 1) micelle method (cationic surfactant)
Chloroauric acid (HAuCl_FourAnd an aqueous solution containing hexadecyltrimethylammonium bromide (CTAB, concentration at the time of reduction reaction: 2.2 mmol / L) and a hydrazine (N concentration at the time of the reduction reaction: 0.5 mmol / L).₂H_FourThe concentration during the reduction reaction: 1 mmol / L) was added to reduce the gold ions to obtain a colloidal gold having an average particle diameter of 20 nm.
[0062]
(Reference Example 2) Micelle method (anionic surfactant)
Chloroauric acid (HAuCl_FourAnd an aqueous solution containing sodium dodecyl sulfate (SDS, concentration at the time of the reduction reaction: 20 mmol / L) and a hydrazine (N concentration at the time of the reduction reaction: 0.5 mmol / L).₂H_FourThe concentration during the reduction reaction: 1 mmol / L) was added to reduce the gold ions to obtain a colloidal gold having an average particle diameter of 20 nm.
[0063]
(Reference Example 3) Micelle method (nonionic surfactant)
Chloroauric acid (HAuCl_Four, An aqueous solution containing a reduction reaction concentration: 0.5 mmol / L) and polyoxyethylene nonylphenyl ether (NP-X, a reduction reaction concentration: 20 mmol / L) was stirred, and hydrazine (N₂H_Four, Concentration during reduction reaction: 1 mmol / L) is added to reduce gold ions to obtain a colloidal gold having an average particle diameter of 20 nm.
[0064]
(Reference Example 4) Core-shell method
0.033 mmol palladium chloride (PdCl₂) Containing 25 mL of ethanol and 0.033 mmol of chloroplatinic acid (H₂PtCl₆) Containing 25 mL of water, and 151 mg of poly (N-vinyl-2-pyrrolidone) (PVP) having a weight average molecular weight of 40,000 was added. This was refluxed at 100 ° C. for 90 minutes to obtain platinum colloid (Pt core / Pd shell colloid) coated with palladium having an average particle diameter of 2 nm.
[0065]
(Reference Example 5) Reverse core shell method
50 mL of water, 50 mL of ethylene glycol, and 50 mL of ethanol were mixed to disperse 0.2 mmol of palladium colloid. Hydrogen gas was supplied thereto for 2 hours, and the surface of the palladium colloid was treated with hydrogen. Thereafter, 0.4 mmol of potassium chloroplatinate (K₂PtCl_Four) Containing 100 mL of water was added dropwise over 6 hours to obtain a palladium colloid (Pd core / Pt shell-colloid) coated with platinum having an average particle diameter of 3 nm.
[0066]
(Reference Example 6) Conditions under which premicelles are formed
Tris-1,10-phenanthroline iron chloride ([Fe (C₁₂H₈N₂)_Three] Cl₂) And an aqueous solution containing sodium dodecyl sulfate (SDS) are mixed to maintain the concentration of tris-1,10-phenanthroline iron chloride at 0.5 mmol / L and the concentration of sodium dodecyl sulfate at 0.1 mmol. An experimental system for increasing from / L to 10 mmol / L was constructed. If the concentration of sodium dodecyl sulfate was lower than 0.2 mmol / L, no precipitation occurred. Precipitation occurred when the concentration of sodium dodecyl sulfate was 0.2 mmol / L or higher and lower than 2.2 mmol / L. If the concentration of sodium dodecyl sulfate was 2.2 mmol / L or higher and lower than 8 mmol / L, the precipitate was redissolved and premicelles were formed. And when the concentration of sodium dodecyl sulfate was 8 mmol / L or more, micelles were formed.
[0067]
Further, the same experiment was performed by changing the concentration of tris-1,10-phenanthroline iron chloride, and the concentration of tris-1,10-phenanthroline iron chloride and sodium dodecyl sulfate was within the region indicated by the oblique lines in FIG. It was confirmed that premicelles were formed.
[0068]
The above behavior can also be confirmed by measuring the conductivity.
[0069]
Example 1 Premicel-Reverse Core Shell Method 1
Tris-1,10-phenanthroline iron chloride ([Fe (C₁₂H₈N₂)_Three] Cl₂And a premicelle aqueous solution containing sodium dodecyl sulfate (SDS, shell formation concentration: 4 mmol / L). The obtained aqueous solution of premicelle has a deep red color, which is [Fe (C₁₂H₈N₂)_Three]²⁺It is thought that it is derived from (dark red).
[0070]
To this premicelle aqueous solution, chloroauric acid (HAuCl_FourThen, the concentration at the time of shell formation: 0.3 mmol / L) was added and the reaction was allowed to proceed at 25 ° C. for 10 minutes.₁₂H₈N₂)_Three]²⁺[Fe (C₁₂H₈N₂)_Three]³⁺Was oxidized, gold ions were reduced, and a gold shell was formed. At this time, the liquid color changes from dark red to light red.₁₂H₈N₂)_Three]²⁺(Dark red) is [Fe (C₁₂H₈N₂)_Three]³⁺This is probably because Au (light red) was generated at the same time. In addition, sodium borohydride (NaBH_Four, Concentration: 1 mmol / L) to make the system reductive, but [Fe (C₁₂H₈N₂)_Three]³⁺(Light red) is [Fe (C₁₂H₈N₂)_Three]²⁺It was confirmed that a shell made of Au was formed on the surface without being reduced to (dark red) and discolored.
[0071]
When the obtained reaction solution was dried and observed with an electron microscope, fine particles derived from nanocolloid fine particles could be confirmed, and the number average particle diameter was measured to be 10 nm.
[0072]
Further, it was confirmed from the ultraviolet absorption peak (derived from phen) that a shell made of Au was formed on the surface.
[0073]
Example 2 Premicel-Reverse Core Shell Method 2
Tris-1,10-phenanthroline iron chloride ([Fe (C₁₂H₈N₂)_Three] Cl₂) Instead of tris-1,10-phenanthroline chloride ([Co (C₁₂H₈N₂)_Three] Cl₂) Was used in the same manner as in Premicel-Reverse Core Shell Method 1 to obtain nanocolloid fine particles having an Au shell on the surface.
[0074]
(Comparative Example 1)
Tris-1,10-phenanthroline iron chloride ([Fe (C₁₂H₈N₂)_Three] Cl₂) Was changed to 5 mmol / L and the sodium dodecyl sulfate (SDS) shell formation concentration was changed to 10 mmol / L. Formation of colloidal fine particles could not be confirmed.
[0075]
【The invention's effect】
Under pre-micellar conditions, the core component containing the base metal ions is coated with the shell containing the noble metal by reducing the shell component by oxidation of the core component. Metal nano colloidal particles are prepared.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a premicel.
FIG. 2 is a schematic diagram for explaining shell formation.
FIG. 3 is an experimental result regarding the formation of a precipitate.
[Explanation of symbols]
10 Metal ions
20 Ligand
30 Surfactant

Claims (3)

A core-shell type nanocolloid fine particle production method comprising a core component containing a more base metal component and a shell containing a noble metal covering the core component ,
Adding a surfactant to a more complex metal-ligand ion to form a premicelle;
Adding a noble metal ion to the premicelle to oxidize the base metal ion and simultaneously reducing the noble metal ion to the noble metal;
The surfactant concentration is lower than the minimum concentration required to form micelles
A method for producing core-shell nano colloidal fine particles. The complex ion is a cation, the surfactant method for producing the core-shell nano-colloid particles of claim 1 further comprising an anionic surfactant. The concentration of complex ions of the base metal and ligand in the reaction system is 0.01 to 10 mmol / L, the surfactant is an anionic surfactant, and the reaction of the anionic surfactant The method for producing core-shell nanocolloid fine particles according to claim 1 or 2 , wherein the concentration in the system is 0.5 to 15 mmol / L.

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