WO2011155473A1 - Method for producing fine metal particles and fine metal particle dispersion solution - Google Patents

Abstract

Plasma is generated by a glow discharge between a pair of discharge electrodes (1) and (1) that are disposed in a solution (5) into which no dispersing/dissolving agent is added, so that the discharge electrodes (1) and (1) are melted, thereby forming fine metal particles which are formed from the metal that constitutes the discharge electrodes (1) and (1). Consequently, metal fine particles that are not agglomerated (a fine metal particle dispersion liquid) can be easily produced despite the fact that no dispersing/dissolving agent is added in a method for producing fine metal particles using solution plasma.

Description

Method for producing metal fine particles and metal fine particle dispersion

The present invention relates to a method for producing metal fine particles and a metal fine particle dispersion. More specifically, in the method for producing metal fine particles using solution plasma, the production of metal fine particles that can easily produce non-aggregated metal fine particles (dispersed metal fine particles) without adding a dispersion solubilizer. The present invention relates to a fine metal particle dispersion solution stably dispersed in a solution to which a method and a dispersion solubilizer are not added.

Conventionally, as a method for producing various fine particles including metal fine particles or metal oxide fine particles, a gas phase method such as a flame method and a plasma method, a liquid phase method such as a sol-gel method, and the like are known.

For example, Patent Document 1 describes a method for producing metal oxide nanoparticles using vapor phase plasma as a method for producing metal oxide using a vapor phase method. However, in the vapor phase method, (1) the equipment is large and the cost is high, (2) the synthesis speed is slow and unsuitable for mass production, (3) it is necessary to consider scattering because it handles fine particles in the air, etc. There is a problem.

On the other hand, Patent Document 2 describes a method for producing metal nanoparticles in which a metal wire is vaporized in a solution as a method for producing metal fine particles using a liquid phase method. However, even in the liquid phase method, (1) the raw materials used are limited, (2) the raw materials used are generally expensive, (3) the raw materials used are toxic, etc., and handling is often necessary. There are problems such as.

Thus, both the gas phase method and the liquid phase method have problems in industrially producing metal fine particles.

Therefore, in recent years, as a method for producing metal fine particles, a method for producing metal fine particles by generating plasma by submerged discharge and reducing the same has attracted attention. Such plasma in liquid is called “solution plasma” because it is mainly used in solution.

Solution plasma is plasma generated between discharge electrodes by applying a voltage (high electric field) between two discharge electrodes arranged opposite to each other in a solution. Bubbles are generated around the generated plasma, the bubbles surround the plasma, and the solution surrounds the bubbles. In other words, the solution plasma is characterized by two interfaces: plasma / gas phase and gas phase / liquid phase. As described above, the solution plasma realizes a state in which the “high energy state” due to the plasma is confined in the solution. As a result, various chemical reactions are promoted in the gas phase, the liquid phase or the interface around the plasma.

For example, Patent Document 3 describes a method for producing metal nanoparticles using solution plasma. Specifically, metal ions contained in the aqueous metal salt solution are reduced by applying a high voltage between a pair of discharge electrodes provided in the aqueous metal salt solution with adjusted conductivity to generate plasma. Metal nanoparticles have been manufactured.

Patent Document 5 discloses a method for producing fine metal particles by causing a strong arc discharge (several tens of volts, several hundred amperes) intermittently between consumable electrodes arranged in water to evaporate the consumable electrodes. Is described. Further, Patent Document 6 discloses that metal powder is produced by bringing metal ion vapor generated by discharge in plasma water between an elemental metal electrode and a counter electrode into high pressure water by bringing it into contact with water and pulverizing. A method of manufacturing is described.

Japanese Patent Publication “JP 2006-55839 A (published March 2, 2006)” Japanese Patent Gazette "Special Table 2009-506205 Gazette (published on February 12, 2009)" Japanese Patent Publication “Japanese Unexamined Patent Application Publication No. 2008-013810 (published January 24, 2008)” Japanese Patent Publication “Japanese Patent Laid-Open No. 2010-9993 (published on Jan. 14, 2010)” Japanese Patent Publication “JP-A-2-166202 (published on June 26, 1990)” WO2003 / 37553 (released on May 8, 2003)

However, in order to produce metal fine particles by the method described in Patent Document 3, there is a problem that a complicated process is required to remove the dispersion-dissolving agent. Further, the methods described in Patent Documents 4 and 5 are not suitable as a method for producing metal fine particles.

Specifically, when the particle diameter of the metal fine particles is small, the metal fine particles are likely to aggregate. In particular, so-called metal nanoparticles having a particle diameter of 100 nm or less are remarkably easily aggregated. For this reason, in the method described in Patent Document 3, it is necessary to add a dispersion solubilizing agent such as gelatin to the metal salt aqueous solution in order to prevent the formed fine metal particles (metal nanoparticles) from aggregating with time. It is essential.

However, when a dispersion solubilizer is added to the metal salt aqueous solution, the dispersion solubilizer remains as an impurity in the metal salt aqueous solution. For this reason, a treatment for removing the dispersion-dissolving agent is finally required, but it is difficult to remove the dispersion-dissolving agent without agglomerating the metal fine particles. Further, when a dispersion solubilizer is added, the dispersion solubilizer is adsorbed on the metal fine particles. For this reason, the dispersion | dissolution solubilizer adsorbed | sucked to the metal microparticle cannot be removed completely. As described above, when the dispersion solubilizer is added, aggregation of the metal fine particles can be avoided, but a complicated process (step) for removing the dispersion solubilizer is required. Therefore, the method described in Patent Document 3 cannot be said to be a simple method for producing fine metal particles.

The methods described in Patent Documents 5 and 6 are all based on the premise that plasma is generated by arc discharge. However, in arc discharge, a very large current flows between the discharge electrodes, so that the discharge electrodes are significantly consumed. For this reason, it is unlikely that the plasma state can be maintained for a long time (several tens of minutes) and the metal fine particles can be stably produced. Therefore, the methods described in Patent Documents 5 and 6 are inappropriate as a method for producing metal fine particles.

The present invention has been made in view of the above-described conventional problems, and the object thereof is a metal fine particle that is not aggregated without adding a dispersion-dissolving agent in a method for producing metal fine particles using a solution plasma. An object of the present invention is to provide a method for producing metal fine particles, which can easily produce (metal fine particle dispersion). Another object of the present invention is to provide a metal fine particle dispersion solution that is stably dispersed in a solution to which a dispersion solubilizer is not added.

In order to solve the above-described problems, the method for producing fine metal particles of the present invention melts a discharge electrode by generating plasma by glow discharge between a pair of discharge electrodes made of the same material arranged in a solution. And a step of forming metal fine particles made of a metal constituting the discharge electrode, wherein the dispersion solution for suppressing aggregation of the metal fine particles is not added to the solution.

According to the above invention, when a voltage is applied between the discharge electrodes provided in the solution to cause discharge, plasma is generated between the discharge electrodes. As a result, the discharge electrode is melted by the plasma, and metal fine particles made of metal constituting the discharge electrode are formed. In addition, the aggregation of the metal fine particles is suppressed despite the fact that no dispersing and dissolving agent is added to the solution. For this reason, a dispersion | distribution solubilizer does not remain as an impurity and the complicated process for removing a dispersion | distribution solubilizer is also unnecessary. Therefore, it is possible to easily produce non-aggregated metal fine particles (metal fine particles dispersed in a solution, that is, a metal fine particle dispersion solution) without adding a dispersion solubilizer. Further, since the dispersion solubilizer does not remain as an impurity in the solution, the metal fine particles dispersed in the solution can be directly used as the metal fine particle dispersion solution. Moreover, according to said invention, since plasma is generated by glow discharge, the current flowing between the discharge electrodes is significantly smaller than in the case of arc discharge. For this reason, the discharge electrode is not easily consumed. Accordingly, the plasma state can be maintained for a long time (several tens of minutes), and the metal fine particles can be stably produced.

In addition, the manufacturing method of the metal microparticle of this invention forms the metal microparticle which consists of the metal which comprises a discharge electrode by melting a discharge electrode. That is, the raw material for the metal fine particles is supplied from the discharge electrode. For this reason, the discharge electrode is made of a metal that is easily melted by plasma. On the other hand, the method described in Patent Document 3 forms metal fine particles constituting the metal salt by reducing metal ions in the metal salt aqueous solution. That is, the raw material for the metal fine particles is supplied from the metal salt aqueous solution. For this reason, the discharge electrode is made of a metal that is not easily melted by plasma.

Moreover, in the method for producing metal fine particles of the present invention, aggregation of the metal fine particles is suppressed without adding a dispersion solubilizer. On the other hand, in the method described in Patent Document 3, it is essential to add a dispersion solubilizer in order to suppress aggregation of metal fine particles.

Thus, the method for producing metal fine particles of the present invention is patented in that the origin of the metal fine particles, the metal constituting the discharge electrode, and the aggregation of metal fine particles can be suppressed without the addition of a dispersing and dissolving agent. This is greatly different from the method described in Document 3.

In the method for producing metal fine particles of the present invention, the discharge electrode is melted to form metal fine particles, and the discharge electrode is not vaporized in the solution. Therefore, it is different from the method described in Patent Document 2 in which the metal wire is vaporized in the solution. Further, the method described in Patent Document 2 is not a method using the solution plasma method.

Furthermore, not only the current flowing between the discharge electrodes but also the electric field strength (kV / m), temperature (K), and electron density (m ⁻³ ) differ greatly between glow discharge and arc discharge. That is, the electric field strength of glow discharge (low temperature plasma) is larger than the electric field strength of arc discharge (thermal plasma), and the temperature and electron density of glow discharge are lower (smaller) than the temperature and electron density of arc discharge. For this reason, the chemical action of the plasma is also different. Accordingly, the particle diameter of the metal fine particles, the dispersibility of the metal fine particles, and the like are also different. Thus, the plasma state is completely different between the plasma generated by glow discharge as in the present invention and the plasma generated by arc discharge as in Patent Documents 5 and 6.

In order to solve the above problems, the metal fine particle dispersion solution of the present invention has metal fine particles dispersed in a solution in which plasma is generated by glow discharge, and suppresses aggregation of the metal fine particles in the solution. It is characterized in that no dispersing solubilizer is added.

According to the above invention, since the metal fine particles are dispersed in the solution in which the plasma is generated by glow discharge, the aggregation of the metal fine particles is suppressed even though the dispersion solution is not added to the solution. Is done. Accordingly, it is possible to provide a metal fine particle dispersion solution that is stably dispersed in a solution to which a dispersion solubilizer is not added.

As described above, the method for producing fine metal particles of the present invention uses the metal constituting the discharge electrode by generating plasma between a pair of discharge electrodes made of the same material arranged in a solution to melt the discharge electrode. And forming a fine metal particle, and the dispersion solution for suppressing the aggregation of the fine metal particle is not added to the solution. Therefore, in a method for producing metal fine particles using solution plasma, metal particles that are not aggregated (metal fine particles dispersed in a solution, that is, a metal fine particle dispersion solution) are simply produced without adding a dispersion solubilizer. There is an effect that can be.

As described above, the metal fine particle dispersion solution of the present invention is a dispersion solution in which metal fine particles are dispersed in a solution in which plasma is generated by glow discharge, and the aggregation of the metal fine particles is suppressed in the solution. Is a structure in which is not added. Therefore, there is an effect that it is possible to provide a metal fine particle dispersion solution that is stably dispersed in a solution to which a dispersion solubilizer is not added.

Further objects, features, and superior points of the present invention will be fully understood from the following description. The advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

It is the schematic which shows the solution plasma discharge apparatus used for the manufacturing method of the metal microparticles of this invention. It is a figure which shows the state after one month progress of the gold nanoparticle dispersion liquid manufactured in Example 1. FIG. It is a figure which shows the result of having observed the gold nanoparticle manufactured in Example 1 with the atomic force microscope. It is a figure which shows the state after one month progress of the platinum nanoparticle dispersion liquid manufactured in Example 2. FIG. It is a figure which shows the state after one month progress of the gold nanoparticle dispersion liquid manufactured in Example 3. FIG. It is a figure which shows the state after one month progress of the gold nanoparticle dispersion liquid manufactured in Example 4, (a) shows the gold nanoparticle dispersion liquid using 7.0 w / w% hydrogen peroxide aqueous solution. (B) shows a gold nanoparticle dispersion using a 17.5 w / w% aqueous hydrogen peroxide solution. In Example 4, it is a figure which shows the TEM image of the gold nanoparticle manufactured using 17.5 w / w% hydrogen peroxide aqueous solution. In Example 4, it is a figure which shows the elemental-analysis result by EDS of the gold nanoparticle manufactured using 17.5 w / w% hydrogen peroxide aqueous solution. It is a figure which shows the state after one month progress of the platinum nanoparticle dispersion liquid manufactured in Example 5, (a) shows the platinum nanoparticle dispersion liquid using 7.0 w / w% hydrogen peroxide aqueous solution. (B) shows a platinum nanoparticle dispersion using a 17.5 w / w% aqueous hydrogen peroxide solution. In Example 5, it is a figure which shows the TEM image of the platinum nanoparticle manufactured using 7.0 w / w% hydrogen peroxide aqueous solution. In Example 5, it is a figure which shows the elemental-analysis result by EDS of the platinum nanoparticle manufactured using 7.0 w / w% hydrogen peroxide aqueous solution. It is a figure which shows the state after one month progress of the silver nanoparticle dispersion liquid manufactured in Example 6, (a) shows the silver nanoparticle dispersion liquid using 0.44 w / w% hydrogen peroxide aqueous solution. , (B) shows a silver nanoparticle dispersion using a 0.88 w / w% aqueous hydrogen peroxide solution, and (c) shows a silver nanoparticle dispersion using a 1.75 w / w% aqueous hydrogen peroxide solution. Indicates. In Example 6, it is a figure which shows the TEM image of the silver nanoparticle manufactured using 0.88 w / w% hydrogen peroxide aqueous solution. In Example 6, it is a figure which shows the elemental-analysis result by EDS of the silver nanoparticle manufactured using 0.88 w / w% hydrogen peroxide aqueous solution. It is a figure which shows the state after one month progress of the gold nanoparticle dispersion liquid manufactured in Example 7, (a) shows the gold nanoparticle dispersion liquid using 0.1 mM sodium hydroxide aqueous solution, (b ) Shows a gold nanoparticle dispersion using a 0.5 mM sodium hydroxide aqueous solution, and (c) shows a gold nanoparticle dispersion using a 3.0 mM sodium hydroxide aqueous solution. It is a figure which shows the state after one month progress of the gold nanoparticle dispersion liquid manufactured in Example 8. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. However, the scope of the present invention is not limited to the following description, and other than the following examples, the scope of the present invention can be appropriately modified and implemented without departing from the spirit of the present invention. That is, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

<The manufacturing method of the metal microparticle of this invention>
The metal fine particle production method of the present invention is a metal fine particle production method using solution plasma, wherein plasma is generated by glow discharge between a pair of discharge electrodes arranged in a solution to melt the discharge electrode, It is a method including a step of forming metal fine particles made of a metal constituting the discharge electrode. However, the dispersion solution which suppresses aggregation of metal fine particles is not added to the solution.

In the method for producing fine metal particles of the present invention, when glow discharge is performed in a solution, plasma is generated and the discharge electrode is melted by the plasma. As a result, colloidal metal fine particles are formed in the solution. The metal fine particles can be taken out (isolated) through steps such as precipitation, filtration, and drying. In addition, in the manufacturing method of the metal fine particle of this invention, in order to adjust the crystal | crystallization and particle size of the obtained metal fine particle, you may add heat processing.

<Solution Plasma Discharge Device Used in the Present Invention>
The metal fine particle production method of the present invention can be performed using, for example, a solution plasma discharge apparatus 10 as shown in FIG. FIG. 1 is a schematic view showing a solution plasma discharge apparatus used in the method for producing fine metal particles of the present invention. As shown in FIG. 1, a solution plasma discharge apparatus 10 is configured to apply a voltage to a pair of discharge electrodes 1 provided in a solution 5 in a container 6, a ceramic tube 2 that covers the discharge electrodes 1, and the discharge electrodes 1. A plasma generating power source 3 to be applied and a ground 4 connected to the plasma generating power source 3 are provided.

The discharge electrodes 1 are each made of a metal that constitutes the target metal fine particles. That is, the pair of discharge electrodes 1 and 1 are made of the same material. Each discharge electrode 1 is covered with a ceramic tube 2 so as to have a portion exposed in the solution 5. The ceramic tube 2 plays a role of fixing the discharge electrode 1, but the ceramic tube 2 may not be used. Instead of the ceramic tube 2, a material that can withstand the temperature of bubbles generated by plasma (for example, a silicone rubber tube) can be used. The heat-resistant temperature of the ceramic is about 1500 to 1900 ° C., although it varies depending on the contained components. Moreover, the heat-resistant temperature of typical silicon rubber is about 200 degreeC. The distance between electrodes, size, etc. of the discharge electrodes 1 and 1 are not particularly limited. Details of the discharge electrode 1 will be described later.

The plasma generating power source 3 supplies the discharge electrode 1 with a voltage for causing glow discharge. As a result, plasma is generated in the region A between the discharge electrodes 1 and 1 by glow discharge. The conditions of the plasma generation power source 3 are not particularly limited as long as plasma is generated by glow discharge. That is, the voltage value, pulse width, pulse frequency, pulse waveform, etc. of the plasma generation power source 3 are not particularly limited as long as glow discharge can be caused.

Solution 5 is not particularly limited as long as plasma can be generated by glow discharge. The solution 5 may contain an electrolyte or the like for adjusting the conductivity of the solution 5. That is, the solution 5 may be a single solution, a mixed solution of a plurality of solutions, or various additives such as an electrolyte may be added. However, as described above, a dispersion solubilizer that suppresses aggregation of metal fine particles is not added to the solution 5. Details of the solution 5 will be described later.

The solution plasma discharge device 10 generates plasma in the region A between the discharge electrodes 1 and 1 by glow discharge when a voltage (preferably 800 V or more) is applied between the plasma generation power source 3 and the discharge electrode 1. Further, during the glow discharge, the solution 5 is heated by the current flowing between the discharge electrodes 1 and 1. As a result, bubbles are generated in the solution 5, particularly around the plasma. Bubbles generated during voltage application surround the plasma, and the plasma state is stabilized and maintained inside the bubbles. The region A, which is a plasma generation region, includes plasma and a gas phase that contains the plasma. Thus, the gas phase surrounds the plasma (plasma phase), and the liquid phase surrounds the gas phase. Such a plasma state promotes melting of the discharge electrode 1, and metal fine particles are formed in the solution 5.

It should be noted that if a plurality of pairs of discharge electrodes 1 are provided in the container 6, the synthesis rate of the metal fine particles can be increased. Further, in order to stably produce the metal fine particles over a long period of time, it is desirable to add a device for adjusting the temperature and concentration of the solution 5. In addition, the method for producing fine metal particles of the present invention is not limited to the solution plasma discharge device 10, and a known solution plasma discharge device can be used. For example, the solution plasma discharge device described in Patent Document 4 disclosed by the present inventors can be applied.

<Discharge electrode 1>
The discharge electrode 1 is an electrode material (conductive material) that melts by plasma generated by glow discharge, and is not particularly limited as long as it is made of a metal that forms the target metal fine particles. For example, as the metal constituting the discharge electrode 1, Au (gold), Pt (platinum), Ag (silver), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os) ), Mo (molybdenum) Cu (copper), Zn (zinc), and the like. Thereby, the single metal microparticle according to the metal material which comprises the discharge electrode 1 can be manufactured. Gold, platinum, and silver are particularly easily melted by plasma. For this reason, it is preferable that the discharge electrode 1 is comprised from gold | metal | money, platinum, or silver. Thereby, gold fine particles, platinum fine particles, and silver fine particles can be efficiently produced.

<Solution 5>
The solution 5 is not particularly limited as long as the solution 5 can generate plasma by glow discharge. However, in the conventional method for producing metal fine particles using solution plasma (see Patent Document 3), the dispersion / dissolving agent that is essential for suppressing aggregation of metal fine particles is not added to the solution 5.

In the method for producing fine metal particles of the present invention, when a voltage is applied between the discharge electrodes 1 and 1 provided in the solution 5 to cause discharge, plasma is generated in the region A between the discharge electrodes 1 and 1. As a result, the discharge electrode 1 is melted by the plasma, and metal fine particles made of the metal constituting the discharge electrode 1 are formed. In addition, the aggregation of the metal fine particles is suppressed even though the dispersing and dissolving agent is not added to the solution 5. For this reason, a dispersion | dissolution solubilizer does not remain as an impurity in the solution 5, and the complicated process for removing a dispersion | distribution solubilizer is also unnecessary. Accordingly, it is possible to easily produce non-aggregated metal fine particles (metal fine particles dispersed in the solution 5, that is, metal fine particle dispersion solution) without adding a dispersion solubilizer. Further, since the dispersion solubilizer does not remain as an impurity in the solution 5, the metal fine particles dispersed in the solution 5 can be directly used as a metal fine particle dispersion solution. Furthermore, in the method for producing fine metal particles of the present invention, plasma is generated by glow discharge, so that the current flowing between the discharge electrodes 1 and 1 is significantly smaller than in the case of arc discharge. For this reason, the discharge electrode 1 is hardly consumed. Accordingly, the plasma state can be maintained for a long time (several tens of minutes), and the metal fine particles can be stably produced.

The reason why the metal fine particles produced according to the present invention do not aggregate is that the metal fine particles or metal colloids dispersed in the solution are positively or negatively charged, and the surrounding particles are oppositely charged. It is considered that this is because (for example, cations, anions, radicals, solvated electrons, hydroxide ions, etc.) surround and are in thermal motion (Brownian motion).

By the way, the metal fine particles produced by the method for producing metal fine particles of the present invention are given various functions to the metal fine particles by subjecting the metal fine particles to surface modification. For example, it is used as functional metal fine particles by introducing a specific functional group or molecule into the surface of the metal fine particles.

For this reason, it is preferable that the solution 5 does not contain a specific component that interferes with the surface modification of the metal fine particles. For example, the solution 5 preferably does not contain fluorine, chlorine, bromine, iodine, and sulfur atoms, molecules, and ions. In this case, halogen and sulfur atoms, molecules, or ions that are easily chemisorbed or physically adsorbed on the surface of the formed fine metal particles do not exist in the solution. That is, there is no component in the solution that interferes with the surface modification (surface treatment) of the metal fine particles. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced.

More specifically, the solution 5 can be exemplified by a peroxide solution. Here, the “peroxide solution” refers to a liquid in which a peroxide is dissolved or dispersed in a solvent. “Peroxide” means, for example, a peroxide structure (—O—O—), a hydroperoxide structure (—O—O—H), or a percarboxylic acid structure (—C (═O) —O—O—). It is an organic compound having in the molecule, or an inorganic compound having a peroxide ion (O ₂ ²⁻ ) or a hydroperoxide structure (—O—O—H) in the molecule. “Peroxide” is also referred to as a salt or derivative of a peracid. The “peroxide” is preferably an ionic peroxide. “Ionic peroxide” refers to a peroxide that is decomposed into hydrogen peroxide by water or acid.

Note that hydrogen peroxide (H—O—O—H) is included in the category of “peroxide”. That is, the “peroxide solution” refers to a liquid in which peroxide or hydrogen peroxide is dissolved or dispersed in a solvent.

The solvent for dispersing or dissolving the peroxide is generally water, but an organic solvent, an inorganic acid, or the like can also be used as long as the peroxide can be dispersed or dissolved.

Such a peroxide solution does not contain impurities such as components (halogen, sulfur, etc.) that adsorb on the surface of the metal fine particles and interfere with the surface modification of the metal fine particles. That is, even if it is adsorbed on the surface of the metal fine particles, the surface modification of the metal fine particles is not easily disturbed. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced. In particular, an aqueous hydrogen peroxide solution is a simple molecule composed of hydrogen and oxygen. Therefore, highly versatile metal fine particles that can be easily surface-modified can be produced. Furthermore, even when hydrogen peroxide is decomposed, only water and oxygen are generated, so that safety is high.

When the solution 5 is a peroxide solution, the peroxide content (peroxide solution concentration) in the solution 5 is not particularly limited. However, since the synthesis rate and efficiency generally increase as the concentration increases, it is desirable that the concentration of the solution 5 (peroxide concentration) be as high as possible without reaching the saturation concentration. However, if the concentration is too high, it may become unstable and may cause agglomeration, so the content of peroxide in the solution 5 is within the range of 0.01 w / w% or more and 35.5 w / w% or less. Preferably there is. Thereby, metal microparticles can be produced without causing aggregation in the peroxide solution.

Further, as the solution 5, an alkaline solution can also be used. “Alkaline solution” refers to an ionic solution exhibiting alkalinity, such as a solution in which an alkali metal hydroxide or an alkaline earth metal hydroxide is dispersed or dissolved in a solvent (sodium hydroxide solution, potassium hydroxide). Solution, barium hydroxide solution, calcium hydroxide solution, etc.) or sodium carbonate aqueous solution. The concentration of the alkaline solution may be as low as the metal fine particles do not aggregate. For example, the alkaline solution is preferably an aqueous solution of 0.01 mM or more and 50 mM or less. The alkaline solution is preferably a low concentration sodium hydroxide aqueous solution. Such a low-concentration alkaline solution does not cause electrostatic shielding to the formed metal fine particles, so that the metal fine particles do not aggregate. Further, components (halogen, sulfur) that adsorb on the surface of the metal fine particles and interfere with the surface modification of the metal fine particles are not present in the solution 5. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced.

The solution 5 may contain various additives such as an electrolyte for adjusting the conductivity of the solution 5 in addition to the peroxide solution. However, when the solution 5 contains an additive, a process (step) for finally removing the additive from the solution 5 becomes necessary, or the additive component is chemically or physically adsorbed on the surface of the metal fine particles. There is a possibility of doing. In addition, the properties as metal fine particles (particularly metal nanoparticles) may be significantly impaired. For this reason, in order to obtain metal fine particles easily, it is preferable to avoid the addition of the additive to the solution 5 as much as possible.

As described above, the solution 5 may be any solution that can generate plasma by glow discharge, but preferably does not contain a specific component that interferes with the surface modification of the metal fine particles. In other words, an aqueous solution of simple molecules composed only of atoms (for example, atoms selected from C, H, O, and metals) that do not interfere with the surface modification of the metal fine particles is preferable. Specifically, the solution 5 is preferably a hydrogen peroxide solution, a sodium carbonate solution, a sodium hydroxide solution, a potassium hydroxide solution, a barium hydroxide solution, a calcium hydroxide solution, or the like. Furthermore, the solution 5 is more preferably a peroxide solution or a low-concentration alkaline solution, and particularly preferably an aqueous hydrogen peroxide solution.

It should be noted that the combination of the solute and the solvent constituting the solution 5, the concentration, conductivity, pH, etc. of the solution 5 may be set according to the purpose and are not particularly limited. Note that the ease of generating plasma may vary depending on the type of the solution 5, and the dispersibility in the solution 5 may vary depending on the type of metal fine particles. For this reason, the concentration of the solution 5 may be set in consideration of the ease of generating plasma, the type of metal fine particles, and the dispersibility of the metal fine particles in the solution 5. Further, the temperature of the solution 5 is not limited, but generally, the higher the temperature of the solution 5, the higher the synthesis rate and efficiency. Therefore, the temperature is preferably within the range of 25 ° C. or more and the boiling point or less.

<Metal fine particle dispersion of the present invention>
The metal fine particle dispersion solution of the present invention is a solution in which metal fine particles are dispersed in a solution in which plasma (solution plasma) is generated by glow discharge. However, the dispersion solution which suppresses aggregation of metal fine particles is not added to the solution.

The method for producing the metal fine particle dispersion of the present invention is not particularly limited, but can be produced by the above-described metal fine particle production method or the solution plasma discharge apparatus 10 of the present invention.

That is, the metal fine particle dispersion solution of the present invention melts the discharge electrode by generating plasma by a glow discharge between a pair of discharge electrodes made of the same material arranged in the solution, and from the metal constituting the discharge electrode. And a step of dispersing the fine metal particles in the solution, and a method in which the dispersion solution for suppressing the aggregation of the fine metal particles is not added to the solution.

In addition, in the metal fine particle dispersion solution of the present invention, the solution in which the metal fine particles are dispersed is the same as the solution 5 described above, and thus the description thereof is omitted. Hereinafter, the solution in which the metal fine particles are dispersed will be described as the solution 5.

In the fine metal particle dispersion solution of the present invention, since the fine metal particles are dispersed in the solution 5 in which plasma is generated by glow discharge, the dispersion of the fine metal particles is not added to the solution even though the dispersion solution is not added to the solution. Aggregation is suppressed. Accordingly, it is possible to provide a metal fine particle dispersion solution that is stably dispersed in the solution 5 to which no dispersion solubilizer is added.

In order to disperse the metal fine particles in the solution 5, the metal fine particles are positively or negatively charged, and the surroundings are particles having an opposite charge (for example, cation, anion, radical, solvated electron, hydroxylation) It is preferable that product ions and the like are surrounded. In other words, it is preferable that particles having the opposite charge to the surface of the metal fine particles are attracted near the surface of the metal fine particles. Usually, the surface of the metal fine particles is positively charged. Therefore, it is more preferable that the surface of the metal fine particles is positively charged, and the negatively charged particles are attracted around the metal fine particles.

In this case, the negatively charged particles are attracted around the surface of the positively charged metal fine particles. That is, a fixed layer (Stern layer: also referred to as a Stern layer) is formed around the metal fine particles. Thereby, the metal fine particles and the fixed layer move together in the solution 5. Therefore, the metal fine particles can be stably dispersed in the solution 5 that does not contain the dispersing and dissolving agent.

On the other hand, as an index for evaluating the dispersibility (dispersion stability) of the metal fine particles in the solution 5, there is a zeta potential. The zeta potential is related to the surface charge at the particle interface, and is the potential difference between the electric double layer surface (slip surface) and the bulk portion of the solution sufficiently away from the interface. As the absolute value of the zeta potential increases, the repulsion between the metal fine particles in the solution 5 becomes stronger. That is, the dispersion stability of the metal fine particles in the solution 5 is increased. On the other hand, as the absolute value of the zeta potential is closer to zero, the metal fine particles are more likely to aggregate. 1
Therefore, in the metal fine particle dispersion of the present invention, the absolute value of the zeta potential of the solution 5 is preferably as large as possible. Specifically, the absolute value of the zeta potential is preferably 25 mV or more, more preferably 30 mV or more, and particularly preferably 30 mV to 80 mV.

Thus, it is preferable that the absolute value of the zeta potential indicating the dispersion stability of the metal fine particles is 25 mV or more. Thereby, the repulsion between metal fine particles becomes strong, and the dispersion stability of the metal fine particles in the solution 5 becomes high. Therefore, the metal fine particles can be stably dispersed in the solution 5 to which no dispersion solubilizer is added.

As described above, the metal fine particle dispersion solution of the present invention has the advantage that the dispersion of the metal fine particles is suppressed and stably dispersed in the solution even though the dispersion solubilizer is not added to the solution. It has the characteristics of

<Metal fine particles produced by the present invention>
The fine metal particles obtained by the method for producing fine metal particles of the present invention preferably have an average particle size of 500 nm or less, and more preferably 100 nm or less. On the other hand, the lower limit of the average particle diameter of the metal fine particles is preferably 50 nm or more, and more preferably 10 nm or more. Thereby, the metal fine particle which has a specific property different from a bulk metal can be manufactured. Such metal fine particles (metal nanoparticles) can be suitably used in chemical and bio-related fields such as pharmaceuticals, cosmetics, catalysts, electronic materials, and optical materials. The average particle diameter of the metal fine particles can be confirmed by observation with a transmission electron microscope (TEM). The average particle diameter of the metal fine particles can also be confirmed by an AFM image obtained by an atomic force microscope (AFM). Furthermore, depending on the type of the solution 5 and the metal fine particles, the particle diameter of the metal fine particles can be confirmed from the color of the solution 5 in which the metal fine particles are dispersed. For example, in Examples 1 and 3 to be described later, the average particle diameter of the gold particles was also confirmed from the color of the gold nanoparticle dispersion after discharge.

The present invention can also be expressed as follows.

In the method for producing fine metal particles of the present invention, the solution preferably does not contain fluorine, chlorine, bromine, iodine, and sulfur atoms, molecules, and ions.

According to the above invention, halogen and sulfur atoms, molecules, or ions that are easily chemically or physically adsorbed on the surface of the formed metal fine particles are not present in the solution. That is, there is no component in the solution that interferes with the surface modification (surface treatment) of the metal fine particles. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced.

In the method for producing fine metal particles of the present invention, the solution is preferably a peroxide solution.

According to the above invention, a peroxide solution is used as the solution. Even if the peroxide solution is adsorbed on the surface of the metal fine particles, the surface modification of the metal fine particles is not easily disturbed. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced.

In the method for producing metal fine particles of the present invention, the peroxide content in the peroxide solution is preferably 0.01 w / w% or more and 35.5 w / w% or less.

According to the above invention, the peroxide content in the peroxide solution is in the range of 0.01 w / w% to 35.5 w / w%. Thereby, metal microparticles can be produced without causing aggregation in the peroxide solution.

In the method for producing fine metal particles of the present invention, the peroxide solution is preferably an aqueous hydrogen peroxide solution.

According to the above invention, a simple molecular hydrogen peroxide solution composed of hydrogen and oxygen is used as the solution. That is, impurities such as components (halogen, sulfur, etc.), metal, and metal oxide that adsorb on the surface of the metal fine particles and interfere with the surface modification of the metal fine particles are not present in the solution. Therefore, highly versatile metal fine particles that can be easily surface-modified can be produced. Furthermore, even if hydrogen peroxide is decomposed, since only water and oxygen are generated, a highly safe method for producing fine metal particles can be realized.

In the method for producing fine metal particles of the present invention, the solution is preferably an alkaline solution of 0.01 mM or more and 50 mM or less. The alkaline solution is more preferably a sodium hydroxide aqueous solution.

According to the above invention, a low concentration alkaline solution of 0.01 mM or more and 50 mM or less is used as the solution. That is, there are no components (halogen, sulfur, etc.) that adsorb on the surface of the metal fine particles and interfere with the surface modification of the metal fine particles in the solution. This facilitates surface modification of the metal fine particles. Therefore, highly versatile metal fine particles can be produced.

In the method for producing fine metal particles of the present invention, the average particle size of the fine metal particles is preferably 500 nm or less. Thereby, the metal fine particle which has a specific property different from a bulk metal can be manufactured. Such metal fine particles can be suitably used in chemical and bio fields such as pharmaceuticals, cosmetics, catalysts, electronic materials and optical materials.

In the metal fine particle dispersion of the present invention, it is preferable that the surface of the metal fine particles is positively charged, and the negatively charged particles are attracted around the metal fine particles.

According to the above invention, the negatively charged particles are attracted around the surface of the positively charged metal fine particles. That is, a fixed layer (Stern layer: also referred to as a Stern layer) is formed around the metal fine particles. As a result, the metal fine particles and the fixed layer move together in the solution. Therefore, the metal fine particles can be stably dispersed in a solution that does not contain the dispersing and dissolving agent.

In the metal fine particle dispersion of the present invention, the absolute value of the zeta potential of the solution is preferably 25 mV or more.

According to the above invention, the absolute value of the zeta potential indicating the dispersion stability of the metal fine particles is 25 mV or more. Thereby, the repulsion between metal fine particles becomes strong, and the stability of the metal fine particles in a solution becomes high. Therefore, the metal fine particles can be stably dispersed in the solution to which the dispersion solubilizer is not added.

Hereinafter, the method for producing metal fine particles of the present invention will be described more specifically with reference to examples. However, the method for producing metal fine particles of the present invention is not limited to the following examples.

[Example 1]
Gold fine particles were produced using the solution plasma discharge apparatus 10 of FIG. Specifically, a gold electrode having a purity of 99.9% and a diameter of 1 mm is used as each discharge electrode 1, the distance between the discharge electrodes 1 and 1 is 0.5 mm, and the solution 5 is 3.5 w / w% peroxide. Only aqueous hydrogen solution was used. The solution 5 contains no additives such as a dispersion solubilizer other than the hydrogen peroxide solution. In order to generate plasma by glow discharge between the discharge electrodes 1 and 1 of such a solution plasma discharge apparatus 10, the discharge start voltage applied between the discharge electrodes 1 and 1 is set to 800 V, and a voltage is applied for 4 minutes. . The maximum current flowing between the discharge electrodes 1 and 1 was 4.7A. FIG. 2 is a view showing a state after one month of the gold nanoparticle dispersion produced in Example 1. FIG. As shown in the figure, since the gold nanoparticle dispersion has a transparent feeling, it was confirmed that the gold nanoparticles were not aggregated even after one month had elapsed since the production of the gold fine particles. In addition, when a gold nanoparticle aggregates, an aggregate precipitates. Since the aqueous hydrogen peroxide solution was transparent, dissolution of the gold electrode was observed immediately after the start of discharge. Furthermore, since the gold nanoparticle dispersion liquid after the voltage application was finished was red and the gold nanoparticle dispersion liquid after one month was slightly purple, it was confirmed that gold nanoparticles of 100 nm or less were produced. It was. Further, the gold nanoparticle dispersion was naturally evaporated and dried on a thin glass plate and observed with an atomic microscope. FIG. 3 is a diagram showing the results of observation of the gold nanoparticles produced in Example 1 with an atomic force microscope. In the figure, the horizontal axis indicates the particle size (0 to 1.0 μm), and the vertical axis indicates the thickness from the glass plate in color. As shown in FIG. 3, it was confirmed that gold nanoparticles of 100 nm or less were formed. Note that the atomic force microscope cannot confirm the formed particle component (element). However, under the conditions of this example, there is no metal element contained in the hydrogen peroxide solution other than gold derived from the gold electrode. It was also confirmed that the residue on the glass substrate after evaporation and drying was visually similar to gold. Furthermore, as described above, the color of the dispersion is the same as that of the gold solution. Therefore, the particles produced according to this example are gold nanoparticles.

[Example 2]
Platinum fine particles were produced under the same conditions as in Example 1 except that a platinum electrode having a purity of 99.9% and a diameter of 1 mm was used as the discharge electrode 1. 4 is a view showing a state after one month of the platinum nanoparticle dispersion produced in Example 2. FIG. As shown in the figure, since the platinum nanoparticle dispersion liquid is transparent, it was confirmed that the platinum nanoparticles were not aggregated even after one month from the production of the platinum fine particles. In addition, dissolution of the platinum electrode was observed immediately after the start of discharge, and the platinum nanoparticle dispersion after application of the voltage exhibited a light brown color, confirming the production of platinum nanoparticles.

Example 3
Gold fine particles were produced under the same conditions as in Example 1 except that 5 mM sodium hydroxide aqueous solution was used as the solution 5. FIG. 5 is a view showing a state after one month of the gold nanoparticle dispersion liquid produced in Example 3. FIG. As shown in the figure, since the gold nanoparticle dispersion has a transparent feeling, it was confirmed that the gold nanoparticles were not aggregated even after one month had elapsed since the production of the gold fine particles. In addition, dissolution of the gold electrode was observed immediately after the start of discharge, the gold nanoparticle dispersion after application of voltage was red, and the gold nanoparticle dispersion after one month was slightly purple. It was confirmed that the gold nanoparticles were produced.

Example 4
Gold fine particles were produced under the same conditions as in Example 1 except that 7.0 w / w% and 17.5 w / w% aqueous hydrogen peroxide solution was used as Solution 5. FIG. 6 is a diagram showing a state after one month of the gold nanoparticle dispersion produced in Example 4, wherein (a) is a gold nanoparticle using a 7.0 w / w% aqueous hydrogen peroxide solution. A dispersion liquid is shown, and (b) shows a gold nanoparticle dispersion liquid using a 17.5 w / w% aqueous hydrogen peroxide solution. As shown in the figure, since the gold nanoparticle dispersion has a transparent feeling, it was confirmed that the gold nanoparticles were not aggregated even after one month had elapsed since the production of the gold fine particles. In addition, dissolution of the gold electrode was observed immediately after the start of discharge, the gold nanoparticle dispersion after application of voltage was red, and the gold nanoparticle dispersion after one month was slightly purple. It was confirmed that the gold nanoparticles were produced. 7 is a diagram showing a TEM image of gold nanoparticles produced using a 17.5 w / w% aqueous hydrogen peroxide solution in Example 4. FIG. As shown in the figure, it was confirmed that gold nanoparticles of 10 nm to 100 nm were produced. FIG. 8 is an elemental analysis by EDS (Energy Dispersive X-ray Spectrometer) of gold nanoparticles produced using a 17.5 w / w% aqueous hydrogen peroxide solution in Example 4. It is a figure which shows a result. EDS irradiates a sample with an electron beam, decomposes the energy of X-rays generated from the sample, and analyzes elements contained in the sample from the spectrum. It is mounted on a transmission electron microscope (TEM), a scanning electron microscope (SEM), etc., and used for elemental analysis of a minute region. As shown in FIG. 8, as a result of elemental analysis by EDS, it was confirmed that the produced nanoparticles were gold.

Example 5
Example 1 except that a platinum electrode having a purity of 99.9% and a diameter of 1 mm was used as the discharge electrode 1 and a 7.0 w / w% and 17.5 w / w% aqueous hydrogen peroxide solution was used as the solution 5. Platinum fine particles were produced under the same conditions. FIG. 9 is a diagram showing a state after one month of the platinum nanoparticle dispersion produced in Example 5, wherein (a) is a platinum nanoparticle using a 7.0 w / w% aqueous hydrogen peroxide solution. A dispersion liquid is shown, and (b) shows a platinum nanoparticle dispersion liquid using a 17.5 w / w% aqueous hydrogen peroxide solution. As shown in the figure, since the platinum nanoparticle dispersion liquid is transparent, it was confirmed that the platinum nanoparticles were not aggregated even after one month from the production of the platinum fine particles. Moreover, dissolution of the platinum electrode was observed immediately after the start of discharge, and the platinum nanoparticle dispersion liquid after the voltage application was finished showed a light brown color, confirming the production of platinum nanoparticles. FIG. 10 is a diagram showing a TEM image of platinum nanoparticles produced in Example 5 using a 7.0 w / w% aqueous hydrogen peroxide solution. As shown in the figure, it was confirmed that platinum nanoparticles of 1 nm to 100 nm were produced. FIG. 11 is a diagram showing an elemental analysis result by EDS of platinum nanoparticles produced in Example 5 using a 7.0 w / w% aqueous hydrogen peroxide solution. As shown in FIG. 11, as a result of elemental analysis by EDS, it was confirmed that the produced nanoparticles were platinum.

Example 6
A silver electrode having a purity of 99.9% and a diameter of 1 mm is used as the discharge electrode 1, and 0.44 w / w%, 0.88 w / w%, and 1.75 w / w% aqueous hydrogen peroxide solution is used as the solution 5. Except for the above, fine platinum particles were produced under the same conditions as in Example 1. FIG. 12 is a view showing a state after one month of the silver nanoparticle dispersion produced in Example 6, wherein (a) is a silver nanoparticle using a 0.44 w / w% aqueous hydrogen peroxide solution. 1 shows a dispersion, (b) shows a silver nanoparticle dispersion using a 0.88 w / w% aqueous hydrogen peroxide solution, and (c) shows a silver using a 1.75 w / w% aqueous hydrogen peroxide solution. A nanoparticle dispersion is shown. As shown in the figure, since the silver nanoparticle dispersion has a transparent feeling, it was confirmed that the silver nanoparticles were not aggregated even after one month had elapsed since the production of the silver fine particles. FIG. 13 is a diagram showing a TEM image of silver nanoparticles produced using a 0.88 w / w% aqueous hydrogen peroxide solution in Example 6. FIG. As shown in the figure, it was confirmed that silver nanoparticles of 10 nm to 100 nm were produced. FIG. 14 is a diagram showing an elemental analysis result by EDS of silver nanoparticles produced in Example 6 using a 0.88 w / w% aqueous hydrogen peroxide solution. As shown in FIG. 14, as a result of elemental analysis by EDS, it was confirmed that the produced nanoparticles were silver.

Example 7
Gold fine particles were produced under the same conditions as in Example 1 except that 0.1 mM, 0.5 mM, and 3 mM sodium hydroxide aqueous solutions were used as the solution 5. FIG. 15 is a view showing a state after one month of the gold nanoparticle dispersion produced in Example 7, wherein (a) shows a gold nanoparticle dispersion using a 0.1 mM sodium hydroxide aqueous solution. (B) shows a gold nanoparticle dispersion using a 0.5 mM aqueous sodium hydroxide solution, and (c) shows a gold nanoparticle dispersion using a 3.0 mM aqueous sodium hydroxide solution. As shown in the figure, since the gold nanoparticle dispersion has a transparent feeling, it was confirmed that the gold nanoparticles were not aggregated even after one month had elapsed since the production of the gold fine particles. In addition, dissolution of the gold electrode was observed immediately after the start of discharge, the gold nanoparticle dispersion after application of voltage was red, and the gold nanoparticle dispersion after one month was slightly purple. It was confirmed that the gold nanoparticles were produced.

Example 8
Gold fine particles were produced under the same conditions as in Example 1 except that 7.0 w / w% aqueous hydrogen peroxide solution was used as Solution 5. FIG. 16 is a diagram showing a state after one month of the gold nanoparticle dispersion liquid produced in Example 8. As shown in the figure, since the gold nanoparticle dispersion has a transparent feeling, it was confirmed that the gold nanoparticles were not aggregated even after one month had elapsed since the production of the gold fine particles. In addition, dissolution of the gold electrode was observed immediately after the start of discharge, the gold nanoparticle dispersion after application of voltage was red, and the gold nanoparticle dispersion after one month was slightly purple. It was confirmed that the gold nanoparticles were produced. In FIG. 16, “160 V”, “180 V”, and “220 V” indicate supply average voltages, and do not indicate discharge start voltages.

Next, the zeta potential of the gold nanoparticle dispersion after half a month passed was measured by electrophoretic light scattering measurement using a zeta potential measuring device. As a result, the zeta potential when the supply average voltage is 160 V is −38.9 mV (repetitive standard deviation is 1.1 mV), and the zeta potential when the supply average voltage is 180 V is −31.9 mV (repetitive standard). The deviation was 2.2 mV), and the zeta potential when the supply average voltage was 220 V was −32.9 mV (repetitive standard deviation was 1.1 mV). In addition, the measurement result of zeta potential has shown the average value measured 3 times. Thus, the absolute value of the zeta potential of the solution was 30 mV or more, and it was confirmed that the gold nanoparticles were stably dispersed in the solution to which no dispersion solubilizer was added.

Specific embodiments or examples made in the section of the detailed description of the invention are merely to clarify the technical contents of the present invention, and are limited to such specific examples and interpreted in a narrow sense. It should be understood that various modifications may be made within the spirit of the invention and the scope of the following claims.

The metal fine particles obtained by the present invention have specific properties different from those of bulk metals. Therefore, it can be suitably used in chemical and bio fields such as pharmaceuticals, cosmetics, catalysts, electronic materials, optical materials and the like.

DESCRIPTION OF SYMBOLS 1 Discharge electrode 2 Ceramic tube 3 Plasma generation power source 4 Ground 5 Solution 6 Container 10 Solution plasma discharge device

Claims (11)

A step of generating plasma by glow discharge to melt the discharge electrode between a pair of discharge electrodes made of the same material disposed in the solution, and forming metal fine particles made of metal constituting the discharge electrode;
A method for producing metal fine particles, characterized in that a dispersion-dissolving agent that suppresses aggregation of the metal fine particles is not added to the solution. The method for producing fine metal particles according to claim 1, wherein the solution does not contain fluorine, chlorine, bromine, iodine, and sulfur atoms, molecules, and ions. The method for producing fine metal particles according to claim 1 or 2, wherein the solution is a peroxide solution. The method for producing metal fine particles according to claim 3, wherein the peroxide content in the peroxide solution is 0.01 w / w% or more and 35.5 w / w% or less. 5. The method for producing fine metal particles according to claim 3, wherein the peroxide solution is an aqueous hydrogen peroxide solution. The method for producing fine metal particles according to claim 1 or 2, wherein the solution is an alkaline solution of 0.01 mM or more and 50 mM or less. The method for producing fine metal particles according to claim 6, wherein the alkaline solution is an aqueous sodium hydroxide solution. The method for producing metal fine particles according to any one of claims 1 to 7, wherein an average particle diameter of the metal fine particles is 500 nm or less. Metal fine particles are dispersed in the solution in which plasma is generated by glow discharge.
A metal fine particle dispersion solution, wherein a dispersion solubilizing agent that suppresses aggregation of the metal fine particles is not added to the solution. The surface of the metal fine particles is positively charged,
The metal fine particle dispersion solution according to claim 9, wherein negatively charged particles are attracted around the metal fine particles. The metal fine particle dispersion solution according to claim 9 or 10, wherein the absolute value of the zeta potential of the solution is 25 mV or more.

Images