KR101599104B1 - Method for manufacturing metal particles with core-shell structure - Google Patents

Abstract

The present invention relates to a method for producing core-shell metal particles. (1) obtaining a first metal particle dispersion solution containing first metal particles and a solvent; And (2) mixing a second metal precursor solution and a reducing agent solution in the first metal particle dispersion solution, wherein the reducing agent is mixed at a molar ratio of 1.5 to 2.0 times the mole of the second metal precursor, A method for producing particles is provided. According to the present invention, a second metal (shell) such as silver (Ag) is uniformly coated on the surface of the first metal particle (core) by an efficient process. In addition, the second metal (shell) is evenly coated on the surface of the first metal particles (core) in a thin film even with a low content of the second metal (shell), and excellent dispersibility is maintained without agglomeration among the particles after coating.

Description

[0001] METHOD FOR MANUFACTURING METAL PARTICLES WITH CORE-SHELL STRUCTURE [0002]

The present invention relates to a method for producing core-shell metal particles, and more particularly, to a method for manufacturing a core-shell metal particle which can uniformly coat a metal (shell) Shell metal particles.

Metals such as silver (Ag) and copper (Cu) have excellent thermal and electrical properties. Among them, silver (Ag) has excellent electrical properties and antibacterial properties. Accordingly, silver (Ag) has been applied to various uses such as a conductive material, an electromagnetic wave shielding material, and an antibacterial material. Silver (Ag) particles are usefully used as electrodes for circuit substrates, display devices, transistors, and batteries (solar cells) of various electronic products, for example.

However, silver (Ag) is expensive and its strength is weak. In addition, metals such as copper (Cu) have a disadvantage of being weak in oxidation. Accordingly, metal particles having a core-shell structure complementary to the disadvantages of these metals have attracted attention.

The metal particles having the core-shell structure as described above are mainly produced through electroplating, electroless plating and vapor phase reaction. However, methods such as electroplating and gas phase reaction are difficult to commercialize because of difficulty in coating with dense and uniform thickness. On the other hand, the electroless plating method enables a dense and uniform thickness coating. In addition, the electroless plating method is advantageous in that the manufacturing cost is low and mass production is possible from the industrial aspect. At this time, most of the metal particles of the core-shell structure are manufactured by using a metal such as copper (Cu) as a core and a metal such as silver (Ag) as a shell.

For example, Korean Patent Laid-Open Nos. 10-2004-0016097, 10-2007-0104802 and 10-2011-0059946 disclose a technique related to the above, (Ag) is coated on the surface of copper (Cu).

However, in the manufacturing method according to the prior art, there is a problem that coating layers such as silver (Ag) constituting the shell are not uniformly coated, and coating amount is small. Particularly, when metal particles of a small size are used as the core, there is a problem that the dispersibility of the coating particles is lowered and coagulates with each other, and the particle size becomes larger.

In addition, the manufacturing method according to the prior art has a problem that the reduced silver (Ag) is coated (deposited) on the wall surface of the reaction vessel or the like. Accordingly, the silver (Ag) loss is large, so that a silver nitrate (AgNO ₃ ) solution must be further injected, which is troublesome and costly to wash the reaction vessel.

Korean Patent Publication No. 10-2004-0016097 Korean Patent Publication No. 10-2007-0104802 Korean Patent Publication No. 10-2011-0059946

Accordingly, an object of the present invention is to provide a method for producing core-shell metal particles which can uniformly coat a metal (shell) such as silver (Ag) or the like on the surface of metal particles (cores) with an efficient process .

According to an aspect of the present invention,

(1) obtaining a first metal particle dispersion solution containing first metal particles and a solvent; And

(2) mixing the second metal precursor solution and the reducing agent solution in the first metal particle dispersion solution so that the reducing agent is in a molar ratio of 1.5 to 2.0 times the mole of the second metal precursor, Of the present invention.

In the step (2), the reducing agent solution may be added to the first metal particle dispersion solution, and then the second metal precursor solution may be added in small amounts over a period of 9 to 12 hours.

Also, it is preferable that the oxide film on the surface of the first metal particles is removed, and the oxide film can be removed by, for example, an acid treatment.

The first metal particle dispersion solution may further comprise at least one salt component selected from the group consisting of tartaric acid salts and carboxylate salts. The salt component may be included in an amount of 100 to 200 parts by weight based on 100 parts by weight of the first metal particles .

The second metal precursor solution may include a second metal precursor having at least one metal element selected from silver (Ag), gold (Au), platinum (Pt), and palladium (Pd) The bimetallic precursor may be selected from silver (Ag) precursors.

According to the present invention, a second metal (shell) such as silver (Ag) is uniformly coated on the surface of the first metal particle (core) by an efficient process.

In addition, the second metal (shell) is evenly coated on the surface of the first metal particles (core) in a thin film even with a low content, and maintains excellent dispersibility without microgravity between the particles after coating and has a fine size . In addition, the amount of coating on the wall surface of the reaction vessel is minimized or minimized.

FIG. 1 and FIG. 2 are FESEM (Field Emission Scanning Electron Microscope) photographs of silver (Ag) coated nickel (Ni) particles prepared according to Examples and Comparative Examples of the present invention.
FIGS. 3 and 4 are graphs showing particle size distribution (PSD) of silver (Ag) coated nickel (Ni) particles prepared according to Examples and Comparative Examples of the present invention.

The present invention provides metal particles having a core-shell structure, wherein a surface of a first metal particle (core) is coated with a second metal (shell).

The method for producing a core-shell metal particle according to the present invention comprises:

(1) obtaining a first metal particle dispersion solution; And

(2) mixing the second metal precursor solution and the reducing agent solution in the first metal particle dispersion solution.

In the step (2), the reducing agent is mixed to a molar ratio of 1.5 to 2.0 times the mole of the second metal precursor. According to the present invention, the reducing agent and the second metal precursor are mixed in an appropriate molar range to improve the coating property of the second metal, and at the same time, the second metal is formed in the form of a thin film Uniformly coated. In addition, the core-shell metal particles after coating do not agglomerate with each other but maintain excellent dispersibility and have a fine size.

Hereinafter, an exemplary embodiment of the present invention will be described.

The first metal particles constitute a core. Such first metal particles are not particularly limited, and may be selected from various metals (single metal or two or more alloys). The first metal particles may be selected from, for example, nickel (Ni), copper (Cu), tungsten (W), aluminum (Al) The first metal particles are preferably selected from nickel (Ni) particles, for example.

In addition, the first metal particles may have various shapes and sizes. The first metal particles may have, for example, a spherical shape or the like. In the present invention, a spherical shape does not mean a complete spherical shape. In addition, the first metal particles may have an average size (diameter) of, for example, 1.5 mu m (micrometer) to 20 mu m. At this time, if the size of the first metal particles is less than 1.5 mu m, a large amount of a second metal precursor (e.g., silver nitrate, etc.) may be added to obtain a coating thickness of a desired second metal And the particle size is small, so that the dispersibility in the solution phase may be deteriorated. If the size of the first metal particles is more than 20 mu m, the size of the produced core-shell metal particles may become too large, which may be difficult to apply to electrodes or the like. If the shape of the prepared core- As shown in Fig. In addition, when the first metal particles having the above-mentioned size range are used, the application fields of the core-shell metal particles are various and are effective for exhibiting the properties of the core-shell metal particles.

According to a preferred embodiment, it is preferable that the first metal particles have an oxide film (for example, NiO film or the like) present on the surface thereof removed. When an oxide film is formed on the surface of the first metal particles, the coating property of the second metal may be deteriorated. The removal of the oxide film can be realized, for example, by etching. The etching may be selected from an acid treatment, a plasma treatment, and a laser irradiation.

According to an exemplary embodiment of the present invention, the removal of the surface oxide film of the first metal particles is preferably performed through an acid treatment, wherein the acid treatment is performed by etching the first metal particles with an acidic solution, And then dispersed and left in an acidic solution for 10 minutes to 2 hours to etch the first metal particles.

The acidic solution may be selected from a solution containing at least one selected from, for example, sulfuric acid, nitric acid, hydrochloric acid, and the like. In the acid treatment, more specifically, 3 to 30 parts by weight of the first metal particles (for example, Ni particles) are dispersed in 100 parts by weight of water, and then an acidic solution (for example, 60 to 98 wt% Sulfuric acid aqueous solution), and the mixture is subjected to an etching treatment for 10 minutes to 2 hours. In the case of the acid treatment in this way, the oxide film (NiO film or the like) present on the surface of the first metal particles (for example, Ni particles) is effectively removed and the coating amount of the second metal is increased, have. At this time, it is preferable to use a sulfuric acid solution for the acid treatment. The sulfuric acid solution is useful for the present invention because it can selectively remove the oxide film (NiO film, etc.) without damaging the first metal particles, particularly the nickel (Ni) particles, as compared with other acidic solutions.

The first metal particle dispersion solution is obtained by dispersing the first metal particles as described above in a solvent. At this time, the solvent may be selected from water and the like. It is preferable that the first metal particle dispersion solution further comprises a salt component according to a preferred form. That is, it is preferable that the first metal particle dispersion solution is obtained by mixing and dispersing the first metal particle (preferably, the oxide film on the surface is removed by an acid treatment), a salt component and a solvent (water or the like).

In addition, stirring and ultrasonic waves may be applied to the first metal particle dispersion solution. That is, when the first metal particles, the salt component, and the solvent are mixed, for example, ultrasonic waves may be applied while stirring at 600 to 800 rpm.

The salt component is selected from a tartrate salt and a carboxylate salt. At this time, the tartaric acid salt and the carboxylic acid salt may contain at least one element selected from Na, K, Ca and Mg in the molecule. For example, the tartaric acid salt may be at least one selected from the group consisting of sodium tartrate, potassium tartrate and potassium tartarate. The carboxylic acid salt may be selected from ethylenediamine tetraacetate (EDTA-salt) having two amine groups in the molecule, and more specific examples thereof include sodium ethylenediaminetetraacetate (Na-EDTA), ethylenediamine tetra At least one selected from potassium acetate (K-EDTA), calcium ethylenediamine tetraacetate (Ca-EDTA) and magnesium ethylenediamine tetraacetate (Mg-EDTA).

The salt component effectively improves the coating property of the second metal (Ag, etc.). The salt component improves the reaction efficiency by, for example, activating the surface of the first metal particle while stabilizing the first metal particle dispersion solution. In addition, the salt component may serve as a pH adjusting agent favorable for reduction reaction, for example. In addition, the salt component can also act as a dispersant, for example. As a result, the coating amount of the second metal is increased and uniformly coated.

The salt component may be used in an amount of 100 to 200 parts by weight based on 100 parts by weight of the first metal particles. That is, it is preferable that the first metal particles (for example, Ni particles) and the salt components are mixed at a weight ratio of 1: 1 to 2: 1. If the content of the salt component is less than 100 parts by weight based on 100 parts by weight of the first metal particles, an increase in the coating amount of the second metal, a surface stabilization of the first metal particle, a change in the pH of the solution, And the like may be negligible. If the content of the salt component exceeds 200 parts by weight, the synergistic effect with excess use is not so large, and the viscosity of the solution becomes high and the coating amount of the second metal can be reduced. In preparing the first metal particle dispersion solution, the solvent (water, etc.) is not particularly limited, but may be used in an amount of 2 to 20 times the weight of the first metal particle.

The first metal particle dispersion solution described above is mixed with the second metal precursor solution and the reducing agent solution to produce metal particles of a core-shell structure of good quality and to process efficiently. At this time, in the present invention, the second metal precursor solution and the reducing agent solution are not particularly limited.

The second metal precursor solution may include at least one second metal precursor. The second metal precursor solution may comprise, for example, from 5 to 30 parts by weight of the second metal precursor relative to 100 parts by weight of water. The second metal precursor is not particularly limited as long as it can produce a second metal by a reduction reaction. At this time, the second metal is coated (plated) on the surface of the first metal particle (core) in its production process to form a shell. The second metal may be at least one selected from, for example, silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)

Specifically, the second metal precursor may include at least one second metal selected from the group consisting of silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) Is not limited. The second metal precursor may be selected from, for example, a silver (Ag) precursor containing silver (Ag) in the molecule or a palladium (Pd) precursor containing palladium (Pd). More specifically, for example, the second metal precursor may be a silver (Ag) salt such as AgNO ₃ , AgBF ₄ , AgCF ₃ SO ₃ , AgClO ₄ , AgOAc and AgPF ₆ ; And palladium (Pd) salts such as palladium chloride, tetraamine palladium nitrate and palladium sulfamate.

Further, the reducing agent solution may be any one containing at least a reducing agent. The reducing agent solution may include, for example, 0.05 to 10.0 parts by weight of a reducing agent relative to 100 parts by weight of water. At this time, the reducing agent is not particularly limited as far as it can reduce the second metal precursor. Reducing agent, for example, hydrazine _{(N 2 H 4), Ag} (NH 3) 2 NO 3, NaBH 4, LiBH 4, tetrabutyl ammonium borohydride, dimethylformamide, tannic acid, glycolic, chelyeom as glycerol, glucose, (Rochelle salt), stearate, formaldehyde, and formalin. Also, in the present invention, the reducing agent includes a hydrate of the above listed materials, for example, hydrazine monohydrate (N ₂ H ₄ .H ₂ O) and the like.

When the second metal precursor solution and the reducing agent solution are mixed in the first metal particle dispersion solution, the reducing agent is mixed at a mole ratio of 1.5 to 2.0 times the mole of the second metal precursor. use. For example, at the time of mixing, the second metal precursor solution and the reducing agent solution may be mixed at a molar concentration (M) ratio of 1: 1.5 to 2.0 based on a solution. When the molar ratio is adjusted to such a range, the coating property of the second metal is improved. In addition, the second metal can be uniformly coated on the surface of the first metal particle even in a low content. In addition, the coated particles, that is, the metal particles of the core-shell structure do not agglomerate, maintain excellent dispersibility, and prevent the particle size from becoming large, and have a fine size. In addition, the amount of coating on the wall surface of the reaction vessel is minimized or minimized.

If the amount of the reducing agent is less than 1.5 mol based on 1 mol of the second metal precursor, uniform coating in the form of a thin film is difficult and the unreacted second metal precursor remains, resulting in a coating amount of the second metal relative to the usage amount. When the amount of the reducing agent is more than 2.0 mol, the dispersibility of the core-shell structure particles after the coating is lowered, and the particles agglomerate and become larger in size.

For example, when the first metal particle is nickel (Ni) and the second metal is silver (Ag), the silver (Ag) precursor solution (for example, AgNO ₃ aqueous solution) M), a reducing agent solution (for example, a hydrazine aqueous solution) is used at a concentration of 1.5 to 2.0 molar (M). At this time, the silver (Ag) content may be 20 wt% or more based on the total weight of the metal particles of the core-shell (Ni-Ag) structure. In addition, even when the amount of silver (Ag) reduced in the reaction vessel is low, silver (Ag) is uniformly coated on the surface of the nickel (Ni) particles. And the coated particles, that is, the Ag-coated Ni particles of the core-shell structure, maintain good dispersibility without mutual agglomeration, and have a fine size without enlarging the particle size.

Further, in the course of the mixing, the second metal precursor solution and the reducing agent solution are mixed with each other, and then the mixed solution is added to the first metal particle dispersion solution, or the second metal precursor solution and the reducing agent solution are separately added to the first It can be added and mixed into the metal particle dispersion solution. At this time, when the solution is mixed, stirring may be performed at 400 to 800 rpm, more specifically, 500 to 600 rpm. The total amount of the second metal precursor solution and the reducing agent solution injected to the first metal particle dispersion solution is not particularly limited, but the second metal precursor solution may be, for example, 30 To 80 parts by weight, and the reducing agent solution may be, for example, 30 to 80 parts by weight.

According to a preferred embodiment, it is preferable that the mixing is performed by adding the reducing agent solution to the first metal particle dispersion solution, then pumping the second metal precursor solution by small amount over 9 to 12 hours. That is, the total amount of the reducing agent solution is added to the first metal particle dispersion solution at a time, and then, when adding the second metal precursor solution, a small amount of the reducing agent solution is added by 9 to 12 hours It is good to do. In this way, when the second metal precursor solution is added in small portions over 9 to 12 hours, the second metal is uniformly coated on the surface of the first metal particles in a uniform thickness as a thin film, The effect can be prevented.

According to the present invention described above, metal particles having a core-shell structure having a uniform coating layer can be easily produced by an efficient process. That is, even if the reduced amount of the second metal (Ag or the like) is small while the coating layer (shell) of the second metal is coated on the surface of the first metal particles (core) Lt; / RTI > Also, the content of the second metal accounts for a high content of not less than 20 wt%, preferably not less than 25 wt%, of the total weight of the metal particles of the core-shell structure. In addition, as described above, the coated product, that is, the metal particles of the core-shell structure, maintains excellent dispersibility without aggregation, and has a fine size without enlarging the particle size.

As described above, when the coating amount (content) of the second metal is large and has a fine size, the characteristics of the second metal can be effectively imparted. For example, when the second metal is silver (Ag), the amount of silver (Ag) coating is large, and it has a fine size and excellent electrical conductivity and antibacterial property. Additionally, according to the present invention, a second metal such as silver (Ag) is not coated or minimized on the wall surface of the reaction vessel, so that a precursor solution such as silver nitrate (AgNO ₃ ) It can save hassle and cost.

Meanwhile, the metal particles of the core-shell structure manufactured according to the present invention can be applied to various fields, and their application fields are not limited. For example, it can be applied to various applications such as a conductive material of various electronic products, an electromagnetic wave shielding material and an antibacterial material, and more specifically, it can be used as an electrode material for a solar cell or the like.

Hereinafter, examples and comparative examples of the present invention will be exemplified. The following examples are provided to illustrate the present invention in order to facilitate understanding of the present invention, and thus the technical scope of the present invention is not limited thereto. In the following Examples and Comparative Examples, approximately spherical Ni particles were used as the first metal particles (cores). And D _{0 .5} In the following Examples and Comparative Examples is a median diameter of the total particles.

[Example 1]

90 g of Ni particle powder (D _{0 .5} = 1.7 탆) was added to 1 L (liter) of water and stirred and dispersed. Then, a sulfuric acid solution (95 wt% aqueous solution) was injected thereinto and subjected to an etching treatment for 30 minutes to remove the oxide film on the surface of the Ni particles. Thereafter, the filtrate was removed, Ni particles were separated, and the separated Ni particles were washed with distilled water three times.

Subsequently, 90 g of the Ni particles from which the oxide film had been removed was added to 200 g of water, 180 g of potassium potassium tartrate (C ₆ H ₄ O ₆ KNa ₄ H ₂ O) was added thereto, and then stirred at about 700 rpm Followed by mixing and dispersing with ultrasonic waves. (Preparation of Ni particle dispersion)

30 g of AgNO ₃ was dissolved in 300 g of water, and 0.49 mol of AgNO ₃ solution (360 ml) was prepared. Further, 1.2 g of hydrazine monohydrate (N ₂ H ₄ .H ₂ O) was dissolved in a solution in which Ni particles were dispersed over a total of three times (total of 3.6 g), and the molar amount was 1.5 times the molar amount of AgNO ₃ .

In the reaction vessel, the hydrazine-added Ni particle dispersion solution was added, and the AgNO ₃ solution was added in small amounts over 9 hours while stirring at about 500 rpm to react. After the reaction, it was found that the Ag thin film was coated on the surface of the Ni particles. At this time, the AgNO ₃ solution was pumped in three times (total 9 hours) by using a syringe pump (Model Pump 11 Elite) for 3 hours to inject 10 g of AgNO ₃ in small amounts Respectively.

[Example 2]

The same procedure as in Example 1 was carried out except that the molar ratio of hydrazine to AgNO ₃ and the time of addition of AgNO ₃ solution were different. Specifically, the hydrazine was mixed at a molar ratio of 2.0 times the molar amount of AgNO ₃ adjusted by the molar ratio. Further, In was carried out over the AgNO ₃ solution in a small amount of 12 hours a solution as followed by the addition of hydrazine to the Ni particle dispersion solution, the AgNO ₃ solution was added.

[Comparative Examples 1 to 3]

The same procedure as in Example 1 was carried out except that the molar ratio of hydrazine to AgNO ₃ was varied. Specifically, the hydrazine was changed to 1.2 times (Comparative Example 1), 2.2 times (Comparative Example 2), and 4.0 times (Comparative Example 3) to 1 mole of AgNO ₃ .

Coating particles (Ag-coated Ni particles) prepared according to each of the above Examples and Comparative Examples were evaluated for particle size distribution. The results are shown in Table 1 below.

≪ Particle size distribution of Ag-coated Ni particles > Remarks
Comparative Example 1 Example 1 Example 2 Comparative Example 2 Comparative Example 3 Mole ratio
(AgNO ₃ : hydrazine) 1: 1.2 1: 1.5 1: 2.0 1: 2.2 1: 4.0 Particle size distribution
(D _{0 .5)} 2.1 4.5 4.8 14-16 20 ~ 22

1 and 2 show the results according to Example 1 (molar ratio 1: 1.5). FIG. 1 is a graph showing the results of FESEM (Field Emission Scanning Electron (Scanning Electron Microscope) photograph, and Figure 2 is a graph showing the Particle Size Distribution (PSD).

3 and 4 show the results according to Comparative Example 2 (ratio of solution molar concentration (M): 1: 2.2). FIG. 3 is a graph showing the results of FESEM And Fig. 4 is a graph showing the PSD.

1 and FIG. 3, when AgNO ₃ and hydrazine were used in an appropriate molar ratio of 1: 1.5 (FIG. 1) according to Example 1 of the present invention, particles after coating (Ag-coated Ni particles) Are uniformly dispersed without being agglomerated with each other, and Ag is uniformly coated in the form of a thin film. However, as in Comparative Example 2, when the molar ratio of hydrazine is high (FIG. 3), it can be seen that the particles after coating (Ag-coated Ni particles) cohere to each other and the size is uneven and large.

In addition, as shown in Table 1, Ni particles of D _{0 .5} = 1.7 탆 were D _{0 .5} = 4.5 and 4.8 탆 after Ag coating in Examples 1 and 2 according to the present invention, It can be seen that it has a fine size without being enlarged.

Further, as shown in Table 1, when the molar ratio of hydrazine is small as in Comparative Example 1, it can be seen that the particles after coating are too small, which means that the coating amount of Ag is small. As in Comparative Examples 2 and 3, when the molar ratio of hydrazine is large, the particles after coating become too large, which is due to the agglomeration of the particles rather than the coating amount of Ag.

On the other hand, compared to Fig. 4 and the accompanying Fig. 2, not become enlarged in the case of Example 1 (Fig. 2) in accordance with the present invention, D _{0 .5} = 1.7 ㎛ of Ni Ag mouth after coating D = _{0 .5} as 4.5 ㎛ And it can be seen that it is uniform as a fine size. However, in the case of Comparative Example 2 (Fig. 4), the Ni particles having D _{0 .5} = 1.7 탆 were D _{0 .5} = 14 ~ 15 탆 after Ag coating and the particles became largely enlarged due to agglomeration and had an uneven distribution Able to know.

As can be seen from the above Examples and Comparative Examples, it can be seen that the molar ratio of the Ag precursor (AgNO ₃ ) to the reducing agent (hydrazine) acts as an important factor in the dispersibility and coatability of the coating particles. That is, when the molar ratio is in the range of 1: 1.5 to 2.0, it is possible to easily produce metal particles having a core-shell structure having fine dispersibility and coatability, .

Claims (15)

(1) obtaining a first metal particle dispersion solution comprising a first metal particle and at least one solvent selected from the group consisting of nickel (Ni), copper (Cu), tungsten (W), aluminum (Al) And
(2) adding a second metal precursor solution and at least one of hydrazine (N ₂ H ₄ ), hydrazine monohydrate (N ₂ H ₄ .H ₂ O), NaBH ₄ , LiBH ₄ , borohydride and form And mixing the reducing agent with a reducing agent solution containing at least one reducing agent selected from aldehyde so that the reducing agent is in a molar ratio of 1.5 to 2.0 times the molar amount of the second metal precursor.
delete The method according to claim 1,
Wherein the first metal particles have an average size of from 1.5 mu m to 20 mu m.
The method according to claim 1,
Wherein the first metal particles have a surface oxide film removed.
5. The method of claim 4,
Wherein the surface of the first metal particle is removed by an acid treatment to remove the oxide film on the surface of the first metal particle.
6. The method of claim 5,
Wherein the first metal particles are nickel (Ni) particles and the acid treatment is a sulfuric acid solution.
The method according to claim 1,
Wherein the first metal particle dispersion solution further comprises at least one salt component selected from among tartaric acid salts and carboxylate salts.
8. The method of claim 7,
Wherein the salt component comprises at least one element selected from Na, K, Ca and Mg in the molecule.
8. The method of claim 7,
Wherein the salt component is at least one selected from sodium tartrate, potassium tartrate, sodium potassium tartrate, sodium ethylenediamine tetraacetate, potassium ethylenediamine tetraacetate, calcium ethylenediamine tetraacetate, and magnesium ethylenediamine tetraacetate. ≪ / RTI >
8. The method of claim 7,
Wherein the first metal particle dispersion solution comprises 100 to 200 parts by weight of a salt component based on 100 parts by weight of the first metal particles.
The method according to claim 1,
Wherein the second metal precursor solution comprises a second metal precursor having at least one metal element selected from silver (Ag), gold (Au), platinum (Pt) and palladium (Pd) Gt;
The method according to claim 1,
Wherein the second metal precursor solution comprises a silver (Ag) precursor.
13. The method of claim 12,
Wherein the silver (Ag) precursor is at least one selected from AgNO ₃ , AgBF ₄ , AgCF ₃ SO ₃ , AgClO ₄ , AgOAc and AgPF ₆ .
delete The method according to claim 1,
Wherein the step (2) comprises adding a reducing agent solution to the first metal particle dispersion solution, and then introducing the second metal precursor solution over a period of 9 to 12 hours.

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