JP2013040374A - Metal nanoparticle dispersion, metal nanoparticle aggregate, metal nanoparticle dispersed body, and method for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal nanoparticle dispersion, a metal nanoparticle aggregate, metal nanoparticle dispersed body and a method for producing them, which is capable of preparing nm level metal nanoparticles and is excellent in dispersion stability of particles.SOLUTION: A metal compound such as silver nitrate is reduced by adding water swellable clay mineral and/or reductant to an aqueous solution comprising specified nonionic surface active agent and anionic surface active agent and, thereby, the metal nanoparticles having uniform particle size are provided. The metal nanoparticles exist to be aggregated in the aqueous solution having a wormy micellar structure formed by the specified surface active agent around the micellar structure. Further, sol-gel transition of metal nanoparticle dispersion having a wormy micellar structure is reversibly caused and the aggregation of the metal nanoparticles is produced in a gel state. In addition, the dispersion is coated on a substrate and is applied, dried or is subjected to heat treatment and, thereby, the aggregate of metal nanoparticles for which the micelle is used as a template and a two-dimensional network of the metal nanoparticles can be formed.

Description

  The present invention relates to a dispersion of metal nanoparticles, a metal nanoparticle aggregate, a metal nanoparticle dispersion, and methods for producing them.

  Since metal nanoparticles exhibit many characteristics different from the bulk state due to their fine particle diameter, they are being studied for wide use in various fields including conductive materials. However, since the metal nanoparticles have a particle size as small as nm and can be synthesized as homogeneously and inexpensively as possible, and metal nanoparticles are very active and tend to cause non-uniform aggregation between particles. There has been a widespread need to prepare stable metal nanoparticle dispersions.

  For example, in the production of metal nanoparticles, the conventional generation method in which a reducing agent is added all at once to a metal salt solution makes it difficult to control the nucleation of metal particles and their growth, and the particle size of nm level is uniform. It was difficult to obtain uniform particles. On the other hand, a method of causing slow reduction, a production method by a continuous flow method, a method of reducing in the presence of halide ions, a method of coexisting different metals, and the like have been proposed.

  On the other hand, regarding the achievement of stable and uniform dispersion of metal nanoparticles in dispersion or redispersion liquid, the performance as nanoparticles cannot be fully exhibited when metal nanoparticles aggregate and precipitate unevenly. Is, for example, a method of coating the surface of metal nanoparticles with a specific organic compound (Patent Document 1), after forming a fatty acid metal salt, followed by two-stage substitution and derived from amines and raw materials of carbon chains 8 to 20 A method of coating the surface of metal nanoparticles with a fatty acid (Patent Document 2), a method of replacing an organic compound protected once with another organic compound protective agent (Patent Document 3), and a polymer compound containing polyethyleneimine and polyethylene glycol A method for producing silver nanoparticles by reducing silver compounds in the presence (Patent Document 4), and coating the surface of metal nanoparticles with a protective material comprising an organic compound having a carboxyl group And a method (Patent Document 5) it has been proposed.

  In addition to these, as a method for effectively utilizing the performance of metal nanoparticles, it is considered effective to aggregate metal nanoparticles at a microscopic level in a controlled form rather than uniformly dispersing them throughout the system. It is done. However, in general, metal nanoparticles having a nano-sized particle size are aggregated in a dispersion or on a coated substrate in a micro-controlled form, or there are no metal nanoparticles in other places. It was difficult to agglomerate the metal nanoparticles only at the target location. Up to now, for example, a method of producing silver nanowires by irradiating a metal ion carrier with an electron beam, in a photoexcited state, a metal complex or metal hydroxide ion having higher electron affinity than halide ions is dissolved. UV or visible light is applied to a two-phase structure of an aqueous phase-organic phase consisting of an aqueous phase and an organic phase obtained by dissolving a fat-soluble organic salt (for example, a tetraalkylammonium salt) in an organic solvent (for example, chloroform). A method of producing metal nanowires by irradiation, a method of collecting nanoparticles in a ring shape by convection by laser light irradiation, a method of aggregating metal nanoparticles using a liquid crystal form (Non-Patent Document 1), etc. have been proposed. However, it was limited to minute metal nanowires and annular forms, or only metal nanoparticle aggregates in very limited shapes and regionsIn addition, a method of creating a patterning wiring circuit by a normal printing method using a dispersion containing metal nanoparticles, a method of drawing a wiring circuit with a writing instrument using conductive aqueous ink (Patent Document 6), and the like have been reported. However, it was not the control of the micro-aggregation form of the metal nanoparticles spontaneously by the dispersion itself, but normal pattern formation.

JP 2006-089786 A JP 2008-150701 A JP 2008-297580 A Japanese Patent No. 4573138 JP 2011-38128 A JP 2010-269516 A

Martin Andersson, Viveka Alfredsson, Per Kjellin, and Anders E. C. Palmqvist, Nanoletters, vol. 2, No. 12, Page 1403-1407.

  The problem to be solved by the present invention is to produce metal nanoparticles at the nanometer level, a metal nanoparticle dispersion having excellent particle dispersion stability, and a metal nanoparticle aggregate and metal nanoparticle with controlled micro morphology The object is to provide particle dispersions and methods for their production.

  As a result of diligent research to solve the above problems, the present inventor reduced a metal compound such as silver nitrate in an aqueous solution composed of a specific nonionic surfactant and an anionic surfactant by addition of a water-swellable clay mineral. It is possible to obtain metal nanoparticles with uniform particle size, and to form an aggregate structure in which metal nanoparticles are selectively arranged around a worm-like micelle structure consisting of a specific nonionic surfactant and an anionic surfactant. By discovering that Furthermore, the present invention provides that the sol-gel transition of the metal nanoparticle dispersion having worm-like micelles occurs reversibly and the aggregation of the metal nanoparticles occurs in a gel state. The present invention is completed based on the discovery that an aggregate of metal nanoparticles having a worm-like micelle structure as a template and a two-dimensional network thereof can be formed on a substrate by applying to the substrate and drying or heat treatment. It came to.

  That is, the present invention provides a metal nanoparticle dispersion comprising an aqueous solution containing an anionic surfactant, a nonionic surfactant, and metal nanoparticles.

  Further, the present invention includes an anionic surfactant, a nonionic surfactant, and metal nanoparticles, and the metal nanoparticles have a structure in which the metal nanoparticles are aggregated in a ribbon shape having a (length / width) ratio of 1 or more. Provided are metal nanoparticle aggregates.

  Moreover, this invention provides the base material characterized by having the metal nanoparticle aggregate aggregated in said ribbon shape on the surface.

  The present invention also provides a substrate in which a metal nanoparticle dispersion containing an anionic surfactant, a nonionic surfactant and metal nanoparticles is uniformly dispersed and adhered to the surface.

  Further, the present invention is characterized in that an anionic surfactant and a nonionic surfactant are mixed with water, and after adding a metal compound, an aqueous dispersion and / or a reducing agent of a layered exfoliated clay mineral is added. A method for producing a metal nanoparticle dispersion is provided.

  In addition, the present invention provides a metal nanoparticle aggregate, or a metal nanoparticle aggregate or dispersion obtained by applying the above metal nanoparticle dispersion onto a substrate, followed by drying and / or heat treatment. A method for producing a substrate having a surface is provided.

  According to the present invention, homogeneous and fine metal nanoparticles can be obtained, a dispersion of metal nanoparticles with excellent stability can be obtained, and metal nanoparticles having a particle aggregation structure reflecting the micelle structure made by a surfactant. A particle dispersion can be obtained, a sol-gel transition can be reversibly generated, and a metal nanoparticle dispersion in which dispersion and aggregation change accordingly can be obtained, and these metal nanoparticle dispersions can be applied onto a substrate. By carrying out drying and heat treatment, it is possible to prepare a ribbon-like metal nanoparticle aggregate reflecting the worm-like micelle structure created by the surfactant on the substrate and its two-dimensional network, or a metal dispersed without agglomeration Nanoparticle dispersions can be prepared.For example, it can be used as a material having excellent electrical conductivity, surface antistatic properties, and electromagnetic wave shielding properties, Door used as such.

Viscoelastic properties (G 'and G "frequency dependence) of the silver nanoparticle dispersion obtained in Example 1. The inset is a silver nanoparticle dispersion (gel). The ultraviolet visible spectrum of the silver nanoparticle dispersion liquid obtained in Example 1. 4 shows a TEM observation result of the silver nanoparticle aggregate obtained in Example 1. FIG. The STEM-EDM measurement result of the silver nanoparticle aggregate obtained in Example 1.

  As the anionic surfactant in the present invention, an anionic surfactant that forms a micelle structure in an aqueous solution is used. Specifically, sodium dodecyl sulfate (SDS), sodium trioxyethylene sulfate (SDES), sodium dodecyl benzene sulfate (SDBS), disodium 2,3-didodecyl-1,2,3,4- Butanetetracarboxylate (GB), sodium oleate (NaOA), sodium 4- (8-methacryloyloxyoctyl) oxybenzene sulfate (MOBS), sodium cholate, sodium dioxycholate, and the like, more preferably Those that form worm-like micelles when combined with a nonionic surfactant are particularly preferably SDS, GB, and SDES. In the present invention, the worm-like micelle is a string-like micelle formed by a surfactant and has a length / width ratio of 1 or more, and the width of the string-like micelle is generally 10 to 200 nm. Is. More preferably, the length / width is 5 or more, particularly preferably the length / width is 10 or more, and the worm-like micelles are entangled with each other and the system (dispersion) is gelled.

  As the nonionic surfactant used in the present invention, those which form a micelle structure, particularly a worm-like micelle, when used together with an anionic surfactant are preferably used. More preferably, it is a nonionic surfactant that cannot be dissolved in water alone and can be dispersed in water by using with an anionic surfactant. Specific examples include polyoxyethylene alkyl ether (formula 1) and polyoxyethylene cholesteryl ether (formula 2: m = 10, 15, 20).

（式１）

(Formula 1)

（式２）

(Formula 2)

  More preferably, it is a nonionic surfactant represented by the formula 1, and n = 5 to 20, m = 2 to 6, and n / m = 2 to 5, particularly preferably n = 12 to 14 and n / m = 3.

  The metal nanoparticles of the present invention are obtained by reducing a metal compound in a dispersion, and are applied to metal nanoparticles in general, and the type thereof is not particularly limited. For example, one or two selected from gold, silver, copper, nickel, platinum, palladium, aluminum, zinc, chromium, iron, cobalt, molybdenum, zirconium, ruthenium, iridium, tantalum, mercury, indium, tin, lead, tungsten An alloy composed of more than seeds or metal nanoparticles composed of a mixture is used. More preferred are silver, gold, platinum, palladium, nickel, copper, and cobalt. Particularly preferred are silver, gold, platinum and copper from the viewpoints of high functionality, ease of reduction reaction, ease of handling, and the like.

  The particle size of the metal nanoparticles constituting the metal nanoparticle dispersion is not particularly limited as long as it has the characteristics of nanoparticles, but the metal nanoparticle dispersion has good dispersion stability. The average particle diameter of the metal nanoparticles of the present invention is preferably in the range of 0.5 to 50 nm, more preferably 1 to 30 nm, and particularly preferably 1 to 10 nm.

  As the metal compound in the present invention, a water-soluble metal compound that can obtain metal nanoparticles by a reduction reaction is used. For example, a salt of a metal cation and a counter anion, or one in which a metal is contained in the counter anion is used. As the metal in the metal compound, the metals described in the above-mentioned metal nanoparticles, such as silver, gold, platinum, palladium, nickel, copper, and cobalt, are used. As the metal compound, for example, in the case of silver, silver nitrate, silver oxide, silver acetate, silver fluoride, silver acetylacetonate, silver benzoate, silver citrate, silver hexafluorophosphate, silver lactate, silver nitrite, For example, silver pentafluoropropionate is used. Of these, silver nitrate, silver oxide, and silver lactate are preferably used from the viewpoint of ease of handling, box office availability, and the like, and silver nitrate is particularly preferably used. In addition, a metal complex is used as the metal compound. For example, in the case of a silver complex (containing aqueous solution), a compound produced by adding aqueous ammonia, ammonium salt, chelate compound, or the like to the aqueous silver nitrate solution is used. In particular, an ammine complex aqueous solution obtained using aqueous ammonia is preferably used. Among the above metal compounds, a metal compound having a metal species (eg, silver, gold, platinum, palladium) such as a transition metal is particularly preferably used because the reduction proceeds smoothly and has high functionality.

  The clay mineral in the present invention is required to be capable of being peeled in layers, and is preferably required to swell and finely disperse in water or an aqueous solution, more preferably an anion. It does not aggregate macroscopically in an aqueous solution in the presence of a surfactant but is finely dispersed. As the dispersion state, it is preferable that the layer is peeled to 10 layers or less, more preferably 3 layers or less, and particularly preferably 1 layer or 2 layers. Furthermore, as the clay mineral, those having a property of reducing or promoting reduction of a metal compound in an aqueous medium are particularly preferable. As such a clay mineral, for example, an inorganic clay mineral having a negative surface charge, which can swell in water such as water-swellable smectites and water-swellable mica and finely disperse in a layered state, is used. Specific examples include water-swellable hectorite, water-swellable montmorillonite, water-swellable saponite, and water-swellable synthetic mica. Also, a clay mineral partially organicized with a surfactant or the like can be used as long as it does not aggregate in the presence of an anionic surfactant and can be separated into layers in water or an aqueous solution.

  Various reducing agents can be used as the reducing agent in the present invention, and the reducing agent is not particularly limited. The reducing agent depends on the intended use of the obtained metal nanoparticle dispersion and metal nanoparticle aggregate, the metal species used, and the like. Can be selected. Examples of the reducing agent used include boron compounds such as hydrogen, sodium borohydride, and ammonium borohydride, alcohols such as methanol, ethanol, propanol, isopropyl alcohol, ethylene glycol, and propylene glycol, formaldehyde, acetaldehyde, and propionaldehyde. Aldehydes such as, acids such as ascorbic acid, citric acid, sodium citrate, propylamine, butylamine, diethylamine, dipropylamine, dimethylethylamine, triethylamine, ethylenediamine, triethylenetetramine, methylaminoethanol, dimethylaminoethanol, triethanol Amines such as amines, hydrazines such as hydrazine and hydrazine carbonate, sodium hydroxide, hydroxide Umm, and the like alkali such as. Among these, sodium borohydride and alkali are preferable, and sodium borohydride is particularly preferable in view of reducing properties and handling properties.

  The metal nanoparticle dispersion obtained in the present invention is a gel in a stationary state due to the action of an anionic surfactant and a nonionic surfactant, and preferably in a gel state in a stationary state, a stress above a certain level. In a field, for example, in a stirred state, the gel is reversibly changed to a sol state, and particularly preferably, a gel is formed by forming worm-like micelles in a stationary state. Furthermore, the metal nanoparticle dispersion in the present invention includes those that cause a change in sol-gel state or formation-disappearance of worm-like micelles even when an organic solvent is included in or removed from the liquid. Such an organic solvent is not particularly limited as long as it is a water-miscible organic solvent that affects the formation of worm-like micelles, and is preferably a highly volatile organic solvent. Specific examples include methanol, ethanol, acetone, tetrahydrofuran and the like.

  The metal nanoparticle dispersion liquid in the present invention stably contains metal nanoparticles in a dispersed or aggregated state. For example, the metal nanoparticle dispersion in the present invention is stable for several days or more, preferably for several months or more, and does not cause uneven aggregation or precipitation. This is due to the effect of anionic and nonionic surfactants and / or layered exfoliated clay minerals that make up the metal nanoparticle dispersion. In addition, the metal nanoparticle dispersion liquid is preferably used in a gel state so that the metal nanoparticles can form a stable micro-aggregated structure, and more preferably, the metal nanoparticle dispersion has an aggregated structure along the surface of the micelle formed by the surfactant. What is formed, particularly preferably one that forms an aggregate structure along the surface of the worm-like micelle.

  The metal nanoparticle aggregate in the present invention is obtained by applying a metal nanoparticle dispersion on a substrate, and the metal nanoparticles are aggregated along the surfactant micelles on the substrate. More preferably, it is a metal nanoparticle aggregate formed in a ribbon shape having a (length / width) ratio of 1 or more along the worm-like micelle on the substrate. Specifically, the width is in the range of 10 to 200 nm, and the (length / width) ratio is 1 or more, preferably 10 or more. Particularly preferably, the metal nanoparticle aggregates aggregated in a ribbon form form a two-dimensional network on the substrate.

  As the substrate in the present invention, polymers, nonwoven fabrics, paper, glass, ceramics, metals and the like are not particularly limited and are preferably used by applying metal nanoparticle dispersion or subsequent drying, heat treatment, etc. Those in which particles and / or metal nanoparticle aggregates closely adhere to the substrate are used. In order to increase the adhesion between the metal nanoparticles and the aggregate, a component that enhances the adhesion with the substrate, specifically, a water-soluble polymer, a silane coupling agent, or the like is added to the metal nanoparticle dispersion.

  In the production of the metal nanoparticle dispersion liquid in the present invention, the final product containing an anionic surfactant, nonionic surfactant and metal nanoparticles, or anionic surfactant, nonionic surfactant, metal nanoparticles and delamination However, it is not necessarily limited, but preferably, an anionic surfactant and a nonionic surfactant are mixed with water, then a metal compound is added, and then a clay mineral dispersion is added. A method of preparing a metal nanoparticle dispersion by reducing metal ions, or after mixing an anionic surfactant and a nonionic surfactant with water, and then adding a metal compound, a clay mineral dispersion and A method of preparing a metal nanoparticle dispersion by reducing metal ions by adding a reducing agent is used. Here, the metal compound is reduced by the action of the oxyethylene group in the clay mineral and the nonionic surfactant or by the action of the reducing agent and / or the clay mineral to obtain metal nanoparticles.

  In the production of the metal nanoparticle aggregate or metal nanoparticle dispersion on the substrate in the present invention, it is prepared by applying the metal nanoparticle dispersion on a substrate. The application method is not particularly limited, and all conventionally known application methods are used. Specifically, the sol solution is cast so as to have a constant thickness, spin-coated, or gel solution is applied. The method of apply | coating is used.

  The concentration of the anionic surfactant and the nonionic surfactant used in the present invention can be arbitrarily selected from the concentration at which they form a micelle structure, particularly preferably the concentration at which worm-like micelles are formed. For example, in the case of SDS (anionic surfactant), 3 to 15% by mass is preferably used with respect to water, and particularly preferably 4 to 14% by mass. On the other hand, in the case of trioxyethylene dodecyl ether (nonionic surfactant), when used together with SDS, 2 to 8% by mass is preferably used with respect to water, more preferably 3 to 7% by mass, and particularly preferably 5 to 5%. 7% by mass.

  The metal nanoparticle content in the metal nanoparticle dispersion in the present invention is not particularly limited as long as a uniform metal nanoparticle dispersion, metal nanoparticle aggregate or metal nanoparticle dispersion can be obtained.

  In the present invention, the clay mineral in the metal nanoparticle dispersion serves to reduce or accelerate the reduction of metal ions in the metal compound. The amount of the clay mineral to be used is not particularly limited as long as it is more than the amount necessary for reducing metal ions in the metal compound, and the upper limit is not particularly defined. Further, the method of adding the clay mineral is not limited. For example, the clay mineral can be mixed as it is or dissolved or dispersed in water or an aqueous solution, and preferably a dilute concentration (for example, 0.1 to 0.1). 4 wt%) of the clay mineral aqueous solution prepared. The clay mineral can be used alone or in combination with the reducing agent shown below.

  The amount of the reducing agent used in the present invention is not particularly limited as long as it is more than the amount necessary for reducing the metal ion in the metal compound, and the upper limit is not particularly defined. The molar ratio is preferably not more than 2 times, and more preferably not more than 2 times. Moreover, the addition method of a reducing agent is not limited, either, For example, a reducing agent can be mixed as it is, or it melt | dissolves and disperses in aqueous solution or another solvent. The reducing agent can be used alone or in combination with the clay mineral.

  In the present invention, the metal nanoparticle aggregate and the metal nanoparticle dispersion are produced by a method of applying and drying the metal nanoparticle dispersion, followed by heat treatment, baking, dry etching (plasma treatment, etc.), etc. In addition, removal of part or all of the organic component or promotion of fusion of metal nanoparticles is used in combination.

  EXAMPLES Next, although an Example demonstrates this invention more concretely, this invention is not limited only to the Example shown below from the first.

Example 1
5 g of an aqueous solution of sodium dodecyl sulfate (SDS) (SDS concentration = 4.5% by mass)
Then, 0.35 g of 7% by mass of trioxyethylene monododecyl ether (C ₁₂ EO ₃ ) with respect to water was added to prepare a uniform colorless and transparent aqueous solution. The obtained aqueous solution was a gel, which was a sol in a stirred state and a gel state in a stationary state. To the above aqueous solution, 20 μl of a 1M silver nitrate (A _g NO ₃ ) aqueous solution was added with stirring to obtain a homogeneous aqueous solution composed of SDS-C ₁₂ EO ₃ -AgNO ₃ . In this state, there was no significant change in transparency and viscosity, and it was a colorless and transparent gel (standing) and sol (stirring). Next, a uniform transparent clay mineral water dispersion containing 2% by mass of synthetic hectorite (Laponite XLG: Rockwood), which is a kind of smectites that are water-swellable clay minerals, was prepared, and the resulting clay mineral water dispersion was obtained. Was added to the homogeneous transparent aqueous solution of SDS-C ₁₂ EO ₃ —AgNO ₃ with stirring so that the content of clay mineral in the entire system was 0.15% by mass. As a result, a uniform transparent dispersion that became a gel and a sol upon stirring was obtained in a transparent and ocher-colored standing state (inset photograph in FIG. 1). Even if the obtained dispersion was kept at room temperature for 3 months, no heterogeneous aggregation or precipitation was observed and it was stable. The viscoelastic properties of the obtained dispersion are shown in FIG. The ultraviolet-visible spectrum of the obtained dispersion is shown in FIG. A maximum peak was observed in the vicinity of 405 nm, indicating that _Ag nanoparticles were formed. The obtained silver nanoparticle dispersion was dropped on a carbon film for a transmission electron microscope (TEM), and the solvent (water) was removed by drying, and then TEM measurement was performed. The results are shown in FIG. As a result, silver ions are reduced in the aqueous solution to form silver nanoparticles having a particle size of about ₃ to 5 nm, and the silver nanoparticles are formed on the base material from SDS and C ₁₂ EO _3. The silver nanoparticle aggregates aggregated in a ribbon shape reflecting the worm-like micelle structure formed, and the silver nanoparticle aggregates aggregated in a ribbon shape on the substrate form a two-dimensional network. It became clear that it was spreading. On the other hand, the formation of silver nanoparticles was also confirmed by mapping by STEM-EDS measurement (FIG. 4).

(Example 2)
An experiment was performed in the same manner as in Example 1 except that 100 μl of sodium borohydride (NaBH ₄ ) (0.01 M) was used instead of the clay mineral aqueous dispersion. A stable dispersion of silver nanoparticles and ribbon-like silver nanoparticle aggregates and their two-dimensional networks were obtained.

(Example 3)
A silver nanoparticle dispersion was prepared in the same manner as in Example 1 except that the concentration of trioxyethylene monododecyl ether (C ₁₂ EO ₃ ) used was 4.5% by mass. As a result of TEM measurement, a structure in which many silver nanoparticles (particle size 2 to 6 nm) were aggregated in a ribbon shape was observed. However, the ribbon-like aggregates include those having a short length, and a network of ribbon-like aggregates spreading over the entire system as in Example 1 was not observed.

Example 4
A silver nanoparticle dispersion was prepared in the same manner as in Example 1 except that the concentration of trioxyethylene monododecyl ether (C ₁₂ EO ₃ ) used was 3% by mass. As a result of performing the TEM measurement result in the same manner as in Example 1, a silver nanoparticle dispersion in which silver nanoparticles (particle size: 3 to 10 nm) were dispersed without aggregation was obtained.

(Example 7-9)
Instead of AgNO ₃ , the metal was used in the same manner as in Example 2 except that Na (AuCl ₄ ) 2 H ₂ O was used in Example 7, K ₂ (PtCl ₄ ) was used in Example 8, and PdCl ₂ was used in Example 9. A nanoparticle dispersion was obtained. Each dispersion was stable and no change was seen after 3 months. The ultraviolet-visible spectrum of the metal nanoparticle dispersion is shown in FIG. From the spectral results, TEM observation, and STEM-EDS measurement, it was confirmed that nanoparticles of Au (Example 7), Pt (Example 8), and Pd (Example 9) were formed, respectively.

(Comparative Example 1-3)
In Comparative Example 1, neither an anionic surfactant nor a nonionic surfactant was used. In Comparative Example 2, only an anionic surfactant was used. In Comparative Example 3, only a nonionic surfactant was used. The experiment was conducted in the same manner as in 2. As a result, in all of Comparative Examples 1-3, macroscopic aggregation precipitation of Ag occurred. In Comparative Example 3, the nonionic surfactant coexisted in a state insoluble in water.

Claims (19)

A metal nanoparticle dispersion comprising an aqueous solution containing an anionic surfactant, a nonionic surfactant and metal nanoparticles. The metal nanoparticle dispersion liquid according to claim 1, comprising a layered exfoliated clay mineral. The metal nanoparticle dispersion liquid according to claim 1 or 2, wherein the anionic surfactant and the nonionic surfactant form worm-like micelles. The metal nanoparticle dispersion liquid according to claim 3, wherein the metal nanoparticles are aggregated around the worm-like micelle. The sol state at the time of stirring and the gel state at the time of standing, they change reversibly, and the metal nanoparticles have a micro aggregated structure in the gel state. Metal nanoparticle dispersion liquid. The metal nanoparticle dispersion liquid according to claim 1 or 2, wherein the metal nanoparticles are dispersed without aggregation. The metal nanoparticle dispersion liquid according to any one of claims 1 to 6, wherein the nonionic surfactant is hydrophobic so as not to dissolve in water alone. The nonionic surfactant is represented by the general formula C _n H _{2n + 1} — (OCH ₂ CH ₂ ) _m —OH, and n = 5 to 20, m = 2 to 6, and n / m = 3 to 5 It exists, The metal nanoparticle dispersion liquid as described in any one of Claims 1-7 characterized by the above-mentioned. The metal nanoparticle dispersion liquid according to any one of claims 2 to 8, wherein the clay mineral is a water-swellable clay mineral. A metal nanoparticle comprising an anionic surfactant, a nonionic surfactant, and a metal nanoparticle, wherein the metal nanoparticle is aggregated in a ribbon shape having a (length / width) ratio of 1 or more Aggregates. The metal nanoparticle aggregate according to claim 10, comprising a layered exfoliated clay mineral. A base material comprising the metal nanoparticle aggregate aggregated in a ribbon shape according to claim 10 on the surface. The substrate according to claim 12, wherein the ribbon-like metal nanoparticle aggregates form a two-dimensional network. The substrate according to claim 12 or 13, wherein the shape of the metal nanoparticle aggregate is formed using worm-like micelles formed by the anionic surfactant and the nonionic surfactant as a template. A base material in which a metal nanoparticle dispersion containing an anionic surfactant, a nonionic surfactant, a layered exfoliated clay mineral, and metal nanoparticles is uniformly attached to the surface. An anionic surfactant and a nonionic surfactant are mixed with water, then a metal compound is added, and then a layered exfoliated clay mineral dispersion and / or a reducing agent is added. Production method. A method for producing a metal nanoparticle aggregate, wherein the metal nanoparticle dispersion liquid according to any one of claims 1 to 9 is applied on a substrate and then dried and / or heat-treated. A method for producing a metal nanoparticle dispersion, wherein the metal nanoparticle dispersion liquid according to any one of claims 1 to 9 is applied on a substrate, followed by drying and / or heat treatment. After applying the metal nanoparticle dispersion liquid according to any one of claims 1 to 9 on a substrate, drying and / or heat treatment is performed on the surface of the metal nanoparticle aggregate or dispersion. The manufacturing method of the base material which has.

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