JP2009062570A - Method for producing dispersion of high concentration of metal nanoparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover a dispersion with a high concentration of metal nanoparticles while lowering a centrifugal force. <P>SOLUTION: The method for producing the dispersion with the high concentration of the metal nanoparticles includes increasing the concentration of the metal nanoparticles by removing a part of a dispersion medium from the dispersion of the metal nanoparticles with a centrifuge, in which the metal nanoparticles are dispersed in the dispersion medium. The metal nanoparticles comprise 100 wt.% silver nanoparticles, or comprise 75 wt.% silver nanoparticles and the balance that includes particles of one element selected from among gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese, or particles of a mixture composition or an alloy composition of two or more elements selected from among the above elements. The production method also includes adding a dispersibility-lowering agent for decreasing the dispersibility of the metal nanoparticles to the dispersion with the high concentration of the metal nanoparticles, which is to be centrifuged. It is preferable to add pure water to the dispersion of the metal nanoparticles, from which the part of the dispersion medium has been removed with a centrifuge, and to further remove the part of the dispersion medium together with the pure water by centrifuging the dispersion again. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a production method for obtaining a high-concentration metal nanoparticle dispersion by removing a part of a dispersion medium from a metal nanoparticle dispersion in which metal nanoparticles are dispersed in a dispersion medium by centrifugation. .

Conventionally, so-called metal nanoparticle dispersions in which metal nanoparticles of several nm are uniformly dispersed in a solvent have been used in various fields by taking advantage of the characteristics thereof, for example, as a thin film having a metallic luster, Alternatively, it is used in various electronic devices, electronic components, electronic circuits, and the like as conductive films in electrode materials for capacitors and chip resistors, conductor circuits on ceramic substrates, and the like. As a method for producing such a high-concentration metal nanoparticle dispersion, a reducing agent solution in which a reducing agent is dissolved is added to and mixed with a metal salt solution, and the metal salt is reduced to disperse the metal nanoparticles in the dispersion medium. After the obtained metal nanoparticle dispersion is obtained, a method for producing a highly concentrated metal nanoparticle dispersion by removing a part of the dispersion medium from the obtained metal nanoparticle dispersion by centrifugation is proposed. (For example, refer to Patent Document 1).
WO 02/094954 pamphlet (claims)

  However, when a reducing agent solution is added to the metal salt solution, a protective agent that protects and modifies the surface of the metal nanoparticles is often added in order to ensure dispersibility of the resulting metal nanoparticles in the dispersion medium. For this reason, in the conventional manufacturing method described above, excess protective agent, reducing agent, and other ions derived from the raw material of the metal nanoparticle dispersion are added to the metal nanoparticle dispersion obtained by reducing the metal salt solution. included. These protective agents, reducing agents, and miscellaneous ions may affect the long-term stability of the metal nanoparticles and the sinterability when used as a conductive material, and are desirably removed.

  Further, when metal nanoparticles are used as a paste for wiring materials, it is necessary to increase the metal concentration as much as possible in order to suppress shrinkage after firing. Considering the case of forming a thick film, it is preferable to achieve a predetermined film thickness by one application, and it is also desirable to increase the metal concentration in such a case. Then, in the above-described manufacturing method in which a part of the dispersion medium is removed by centrifugation from the metal nanoparticle dispersion liquid, when the dispersion stability of the metal nanoparticles is high, the centrifugal separation method is used to precipitate this. Power is required. In general, the smaller the particle size, the lower the sedimentation rate and the lower the recovery rate by the centrifugal separation method.

The objective of this invention is providing the manufacturing method of the high concentration metal nanoparticle dispersion liquid which can reduce a protective agent, a reducing agent, and a miscellaneous ion.
Another object of the present invention is to disperse high-concentration metal nanoparticles capable of recovering a dispersion with a high concentration of metal nanoparticles in a relatively high yield despite reducing centrifugal force to remove a part of the dispersion medium. It is in providing the manufacturing method of a liquid.

In the invention according to claim 1, as shown in FIG. 1, a part of the dispersion medium is removed by centrifugation from the metal nanoparticle dispersion in which the metal nanoparticles are dispersed in the dispersion medium to increase the concentration of the metal nanoparticles. It is an improvement of the manufacturing method of a high concentration metal nanoparticle dispersion.
The characteristic point is that the metal nanoparticles are 100% by weight of silver nanoparticles, or 75% by weight or more of silver nanoparticles and the balance is gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, Metal nano-dispersion, which is composed of one type of particles selected from the group consisting of iron, chromium and manganese, or a mixed composition or alloy composition of two or more types, and reduces the dispersibility of the metal nanoparticles before centrifugation. It is added to the particle dispersion.

  100% by weight of silver nanoparticles, or 75% by weight or more of silver nanoparticles and the balance are selected from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese. In addition, a dispersion liquid in which metal nanoparticles composed of one kind of particle or two or more kinds of mixed composition or alloy composition are dispersed has a relatively high so-called electrostatic repulsion force and stable dispersibility. Even in such a dispersion having a stable dispersibility, in the method for producing a high concentration metal nanoparticle dispersion described in claim 1, the dispersibility reducing agent is dispersed in the metal nanoparticles before centrifugation. Since it is added to the liquid, the dispersion stability of the metal nanoparticles is lowered, which makes it possible to centrifugally precipitate the metal nanoparticles with a low centrifugal force. For this reason, by performing centrifugation on the metal nanoparticle dispersion whose dispersion stability has been reduced by adding a dispersibility reducing agent in this manner, a high recovery rate can be achieved with a lower centrifugal force and a shorter processing time. Centrifugation is possible.

  Moreover, the dispersion liquid in which the metal nanoparticles are dispersed shows a tendency that the metal nanoparticles are strongly aggregated as the centrifugal force increases during the centrifugation. By reducing the centrifugal force in the centrifugal separation, aggregation of the metal nanoparticles can be suppressed.

The invention according to claim 2 is the invention according to claim 1, wherein pure water is added to the metal nanoparticle dispersion liquid after part of the dispersion medium is removed by centrifugation, and then centrifuged again. And a part of the dispersion medium is further removed together with pure water.
In the method for producing a high-concentration metal nanoparticle dispersion according to claim 2, pure water is added to the metal nanoparticle concentrate after centrifugation, and the precipitate is dispersed again in the solvent. The concentration of the protective agent, reducing agent, miscellaneous ions, etc. present therein can be reduced. By centrifuging this again, the centrifugal force that removes part of the dispersion medium is removed with low centrifugal force by removing the protective agent, reducing agent, and miscellaneous ions contained in the solvent during the synthesis of the metal nanoparticles. Nevertheless, a dispersion having a high concentration of metal nanoparticles can be recovered with a relatively high yield.

The invention according to claim 3 is the invention according to claim 1 or 2, characterized in that the dispersibility reducing agent is any one of hydrochloric acid, nitric acid, ammonia, amines, and salts using these. .
The invention according to claim 4 is characterized in that the dispersibility reducing agent is a salt containing the same metal element as the element constituting the metal nanoparticle.
In the method for producing a high-concentration metal nanoparticle dispersion described in claims 3 and 4, since the salt concentration is increased or the pH is adjusted, the dispersion stability of the metal nanoparticles in the metal nanoparticle dispersion is improved. It can be reliably lowered.
In addition, the dispersibility reducing agent described in claims 3 and 4 is easily volatilized or decomposed during firing, and affects long-term stability and sinterability when used as a conductive material. There is nothing.

The invention according to claim 5 is a high-concentration metal nanoparticle dispersion obtained by the production method according to any one of claims 1 to 4.
In this specification, “pure water” means water from which impurities and ionic components have been removed. For this reason, this “pure water” includes either “purified water” from which impurities have been removed by filtration or distillation, “deionized water” deionized by an ion exchange resin, etc., or “distilled water” from which impurities have been removed by distillation. Is also included.

  In the method for producing a high-concentration metal nanoparticle dispersion of the present invention, a dispersibility reducing agent for reducing the dispersibility of metal nanoparticles is added to the metal nanoparticle dispersion before centrifuging. Even if it has high dispersibility, the dispersion stability of the metal nanoparticles is lowered, and the metal nanoparticles can be centrifugally settled with a lower centrifugal force. For this reason, by performing centrifugation on the metal nanoparticle dispersion whose dispersion stability has been reduced by adding a dispersibility reducing agent in this manner, a high recovery rate can be achieved with a lower centrifugal force and a shorter processing time. Centrifugation is possible. In addition, although the metal nanoparticle dispersion shows a tendency for the metal nanoparticles to strongly aggregate during the centrifugation, the aggregation of the metal nanoparticles can also be suppressed by reducing the centrifugal force in the centrifugation. .

In addition, pure water is added to the metal nanoparticle dispersion liquid after part of the dispersion medium is removed by centrifugation, and then centrifugal separation is performed again to further remove part of the dispersion medium together with pure water. For example, the protective agent contained in the solvent at the time of synthesizing the metal nanoparticles with low centrifugal force will be centrifuged in a state where the concentration of the protective agent, reducing agent, miscellaneous ions, etc. present in the dispersion is reduced. In addition, it is possible to recover a dispersion liquid having a high concentration of metal nanoparticles with a relatively high yield, although the reducing agent and miscellaneous ions are removed and the centrifugal force for removing a part of the dispersion medium is reduced.
On the other hand, although the dispersibility reducing agent may remain in the high-concentration metal nanoparticle dispersion, the dispersibility reducing agent is any one of hydrochloric acid, nitric acid, ammonia, amines, and salts using these. Or, if the dispersibility reducing agent is a salt containing the same metal element as the element constituting the metal nanoparticles, it is easy to volatilize or decompose during firing, so it was used as a long-term stability or conductive material The influence on the sinterability at the time can be reduced.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, in the method for producing a high concentration metal nanoparticle dispersion of the present invention, a part of the dispersion medium is removed by centrifugation from the metal nanoparticle dispersion in which the metal nanoparticles are dispersed in the dispersion medium. It increases the concentration of metal nanoparticles. A metal nanoparticle dispersion liquid in which metal nanoparticles are dispersed in a dispersion medium can be obtained by reducing the metal in the metal salt solution. The metal salt solution is a solution in which a metal compound is dissolved in a solvent, and metal ions are generated by dissolving the metal compound in the solvent, and the metal ions are reduced to supply metal nanoparticles. It is preferable that the metal used as the said metal nanoparticle is silver. Or the metal used as the metal nanoparticle is one kind of particles selected from gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium, and manganese with 75% by weight or more of silver. Or it consists of 2 or more types of mixed compositions or alloy compositions.

  The solvent is not particularly limited as long as it can dissolve the metal compound, and examples thereof include water and organic solvents. It does not specifically limit as said organic solvent etc., For example, C1-C4 alcohol, such as ethanol and ethylene glycol; Ketones, such as acetone; Esters, such as ethyl acetate, etc. are mentioned. As the solvent, one type or two or more types can be used. When the solvent is a mixture of water and an organic solvent, the organic solvent is preferably water-soluble, and examples thereof include acetone, methanol, ethanol, ethylene glycol, and the like. In the present invention, water, alcohol, and a mixed solution of water and alcohol are particularly preferable. However, it is not limited to these, and organic solvents that are not water-soluble can also be used. And a metal salt solution is prepared by dissolving the metal compound mentioned above in such a solvent.

  On the other hand, as a reducing agent for reducing the metal in the metal salt solution, alkali metal borohydride salts such as ferrous sulfate and sodium borohydride; hydrazine compound; citric acid; tartaric acid; ascorbic acid; formic acid; formaldehyde; Nithionate, sulfoxylate derivatives and the like can be used. Of these, ferrous sulfate, citric acid; tartaric acid; ascorbic acid; formic acid are preferable. These can each be used in the form of a salt, thereby enabling a reaction at a pH close to neutrality.

  The protective agent is preferably included in the reducing agent solution. The protective agent functions to increase the dispersion stability of the metal nanoparticles obtained by reducing the metal in the metal salt solution in the solvent, and a commercially available one can be used as such. What is marketed may be used independently and may use 2 or more types together. Specifically, as the functional group, any one of hydroxyl group (—OH), carboxyl group (—COOH), carbonyl group (—C═O), amino group, mercapto group (—SH), or two or more thereof is used. The contained organic molecule can be used as a protective agent.

  Here, the case where the metal in a metal salt solution is reduced using sodium citrate as a protective agent and ferrous iron as a reducing agent will be specifically described. First, a sodium citrate, which is a protective agent, is dissolved in water such as deionized water, and the aqueous solution of sodium citrate having a concentration of 10 to 40% is granular or powdery in an inert gas stream such as nitrogen gas. A reducing agent comprising ferrous sulfate is directly added and dissolved to prepare an aqueous reducing agent solution containing citrate ions and ferrous ions in a molar ratio of 3: 2. Next, the aqueous metal salt solution is added dropwise to and mixed with the reducing agent aqueous solution while stirring the reducing agent aqueous solution in the inert gas stream. Here, by adjusting the concentration of each solution so that the addition amount of the metal salt aqueous solution is 1/10 or less of the amount of the reducing agent aqueous solution, the reaction temperature is 30 to 30 even when the metal salt aqueous solution at room temperature is dropped. It is preferable to keep the temperature at 60 ° C. The mixing ratio of the two aqueous solutions is such that the molar ratio of the citrate ions and the ferrous ions in the reducing agent aqueous solution is 3 times the total valence of the metal ions in the metal salt aqueous solution. . After the dropping of the aqueous metal salt solution is completed, the mixed solution is further stirred for 10 to 300 minutes to reduce the metal in the metal salt solution to obtain a metal nanoparticle dispersion in which the metal nanoparticles are dispersed in the dispersion medium.

  The metal nanoparticle dispersion obtained in this way is in a state where the metal nanoparticles can be visually recognized dispersed in a solvent. In the present invention, the metal nanoparticles obtained by reduction are 100% by weight of silver nanoparticles, or 75% by weight or more of silver nanoparticles and the balance is gold, platinum, palladium, ruthenium, nickel, copper, tin. It is intended to be composed of one kind of particles selected from Indium, Zinc, Iron, Chromium and Manganese, or a mixed composition or alloy composition of two or more kinds. Such a dispersion in which metal nanoparticles are dispersed in a solvent contains miscellaneous ions such as nitrate ions derived from the raw material of the metal colloid solution and an excess reducing agent in addition to the metal nanoparticles and the protective agent. It becomes.

  In the method for producing a high-concentration metal nanoparticle dispersion of the present invention, a part of the solvent is removed by centrifugation, but a dispersibility reducing agent for reducing the dispersibility of the metal nanoparticles before centrifugation is added to the metal. It is added to the nanoparticle dispersion liquid. There are two methods for reducing the dispersibility. One is to increase the electrolyte concentration in the dispersion medium to reduce the thickness of the electric double layer formed around the particles. The other is to reduce the zeta potential. Is to bring the potential near the particle surface close to zero. The dispersibility reducing agent is preferably any one of hydrochloric acid, nitric acid, ammonia, amines, and salts using these. When such a compound is added to the metal nanoparticle dispersion as a dispersibility reducing agent, the salt concentration (electrolyte concentration) increases, so that the dispersion stability of the metal nanoparticles can be reliably reduced. Furthermore, by adding a dispersibility reducing agent in this way, the dispersion stability of the nanoparticles is reduced by bringing the pH of the dispersion closer to the equipotential point characterized by the zero zeta potential of the nanoparticles. Can be made. Examples of amines include, but are not limited to, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, methylethylamine, triethanolamine, and ethylenediamine.

  On the other hand, the dispersibility reducing agent may be a salt containing the same metal element as the element constituting the metal nanoparticle. When a dispersibility reducing agent composed of such a salt is added to the metal nanoparticle dispersion, the dispersion stability of the metal nanoparticles can be reliably lowered by increasing the salt concentration. In the present invention, after adding such a dispersibility reducing agent, the metal nanoparticle dispersion is centrifuged, and the concentration of the metal nanoparticles is increased by removing the dispersion medium that is the supernatant separated by centrifugal force. It is a manufacturing method.

  Thus, in the production method of the present invention in which centrifugation is performed after adding the dispersibility reducing agent, the metal nanoparticles are precipitated by adding the dispersibility reducing agent, and the concentration of the metal nanoparticles in this portion is increased. Can do. On the other hand, unnecessary miscellaneous ions, salts and amines contained in the solvent and the polymer pigment protective agent are dissolved in the supernatant liquid, and these miscellaneous ions, salts and amines dissolved in the supernatant liquid are The stability of the resulting metal colloid solution may be adversely affected. However, in the present invention, since the supernatant is removed by centrifugation, a high-concentration metal nanoparticle dispersion from which these unnecessary components are removed can be obtained.

  Here, since the dispersibility of the metal nanoparticles is reduced by the addition of the dispersibility reducing agent, the production method of the present invention removes the unnecessary ions, salts, amines, and protective agents with a relatively low centrifugal force. The containing supernatant can be separated. The resulting high-concentration metal nanoparticle dispersion is composed of 100% by weight of silver nanoparticles, or 75% by weight or more of silver nanoparticles and the balance of gold, platinum, palladium, ruthenium, nickel. One type of particles selected from copper, tin, indium, zinc, iron, chromium and manganese, or a mixed composition or alloy composition of two or more types.

  In the production method of the present invention, as shown in FIG. 2, pure water is added as a dispersion medium to the metal nanoparticle dispersion liquid after a part of the dispersion medium is removed by centrifugation, and a dispersibility reducing agent is further added. May then be added, followed by centrifugation again to further remove a portion of the dispersion medium. By repeatedly adding pure water and a dispersibility reducing agent and centrifuging in this way, the concentration of the electrolyte in the liquid phase derived from the metal salt, protective agent, reducing agent, etc. used in the synthesis is reduced, and even in trace amounts, metal nanoparticles It becomes possible to separate these electrolytes that affect the sintering of the metal with a relatively low centrifugal force, and the recovery rate of the metal nanoparticles by the centrifugal separation operation can be significantly increased.

Next, examples of the present invention will be described in detail together with comparative examples.
<Comparative Example 1>
A metal salt forming Ag 100 wt% metal nanoparticles was dissolved in deionized water to prepare an aqueous metal salt solution. In addition, sodium citrate was dissolved in deionized water to prepare an aqueous sodium citrate solution having a concentration of 26% by weight. Reduction in which aqueous ferric sulfate is directly added and dissolved in this sodium citrate aqueous solution in a nitrogen gas stream maintained at 35 ° C. to contain citrate ions and ferrous ions in a molar ratio of 3: 2. An aqueous agent solution was prepared.

  Next, with the nitrogen gas stream maintained at 35 ° C., a magnetic stirrer stirrer is placed in the reducing agent aqueous solution, and the stirrer is rotated at a rotational speed of 100 rpm while stirring the reducing agent aqueous solution. The metal salt aqueous solution was added dropwise to the reducing agent aqueous solution and mixed. Here, the amount of the metal salt aqueous solution added to the reducing agent aqueous solution is adjusted so that the concentration of each solution is adjusted to 1/10 or less of the amount of the reducing agent aqueous solution. The reaction temperature was maintained at 40 ° C. The mixing ratio of the reducing agent aqueous solution to the metal salt aqueous solution is such that the molar ratio of citrate ions and ferrous ions in the reducing agent aqueous solution to the total valence of metal ions in the metal salt aqueous solution is 3 times the mole. It was made to become. After the dropping of the aqueous metal salt solution into the reducing agent aqueous solution is completed, the mixed solution is further stirred for 15 minutes to generate metal nanoparticles inside the mixed solution, and the metal nanoparticle dispersion in which the metal nanoparticles are dispersed. Got.

  The obtained metal nanoparticle dispersion (Ag 100 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Since this separated into a concentrate and a supernatant, the supernatant was separated, 100 mL of deionized water was added to the concentrate, and the mixture was stirred with a spatula to obtain a uniform metal nanoparticle dispersion. This dispersion was again centrifuged at 1000 G for 10 minutes to remove a part of the dispersion medium to obtain a high concentration metal nanoparticle dispersion in which the concentration of metal nanoparticles was increased. The high-concentration metal nanoparticle dispersion thus obtained was used as Comparative Example 1.

<Comparative example 2>
An aqueous metal salt solution was prepared by dissolving a metal salt forming 95% by weight of Ag and 5% by weight of Cu to form metal nanoparticles in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 95 wt%, Cu 5 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion. This dispersion was centrifuged at 1000 G for 10 minutes to remove a part of the dispersion medium, thereby obtaining a high concentration metal nanoparticle dispersion in which the concentration of metal nanoparticles was increased. The high-concentration metal nanoparticle dispersion liquid thus obtained was used as Comparative Example 2.

<Comparative Example 3>
A mixed water solvent of silver sulfate and chloroauric acid was prepared to be Ag: Au = 75: 25, boiled, trisodium citrate aqueous solvent was added to this, and the mixture was refluxed for 10 minutes with vigorous stirring. Was synthesized. Thereafter, this was cooled to room temperature to obtain a metal nanoparticle dispersion having a pH of 3.
The obtained metal nanoparticle dispersion (Ag 75 wt%, Au 25 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thereby, the supernatant separated into the concentrate and the supernatant was separated, 100 mL of deionized water was added to the concentrate, and the mixture was stirred with a spatula to obtain a uniform metal nanoparticle dispersion. This dispersion was centrifuged at 1000 G for 10 minutes to remove a part of the dispersion medium, thereby obtaining a high concentration metal nanoparticle dispersion in which the concentration of metal nanoparticles was increased. The high-concentration metal nanoparticle dispersion liquid thus obtained was used as Comparative Example 3.

<Example 1>
The same metal nanoparticle dispersion as in Comparative Example 1 was obtained under the same conditions and procedures as in Comparative Example 1.

The metal nanoparticle dispersion (Ag 100 wt%) 1000 mL thus obtained was centrifuged at 500 G for 1 minute using a centrifuge, and the supernatant was separated. Thereafter, 100 mL of deionized water was added to the metal nanoparticle dispersion in the same manner as in Comparative Example 1, and the mixture was stirred with a spatula to obtain a uniform dispersion.
To this dispersion, a 10 molar aqueous nitric acid solvent, which is a dispersibility reducing agent, was added dropwise to adjust the dispersion to pH 4. Then, it centrifuged at 500G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 1.

<Example 2>
Under the same conditions and procedures as in Comparative Example 2, the same metal nanoparticle dispersion as in Comparative Example 2 was obtained.

The thus obtained metal nanoparticle dispersion (Ag 95 wt%, Cu 5 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge, and the supernatant was separated. Thereafter, 100 mL of deionized water was added to the metal nanoparticle dispersion in the same manner as in Comparative Example 2, and the mixture was stirred with a spatula to obtain a uniform dispersion.
To this dispersion, 10 mL of a 0.1 wt% aqueous copper nitrate solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 500G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 2.

<Example 3>
An aqueous metal salt solution was prepared by dissolving a metal salt forming Ag nanoparticles of 75 wt% and Pd of 25 wt% in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 75 wt%, Pd 25 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, a 10 molar aqueous nitric acid solvent, which is a dispersibility reducing agent, was added dropwise to adjust the dispersion to pH 4. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 3.

<Example 4>
An aqueous metal salt solution was prepared by dissolving a metal salt forming metal nanoparticles with 99.5 wt% Ag and 0.5 wt% Ru in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 99.5 wt%, Ru 0.5 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.1 wt% aqueous triammonium citrate solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 4.

<Example 5>
An aqueous metal salt solution was prepared by dissolving a metal salt forming 99% by weight of Ag and 1% by weight of Ni to form metal nanoparticles in a solvent. As the solvent, a mixed solution of 50% by weight of deionized water and 50% by weight of ethanol was used. Except for these, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 99 wt%, Ni 1 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after separating into a concentrated solution and a supernatant, and 100 mL of the above solvent was added to the concentrated solution, followed by stirring with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.1 wt% aqueous ammonium nitrate solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 5.

<Example 6>
A metal salt forming 99% by weight of Ag and 1% by weight of Cu forming metal nanoparticles was dissolved in deionized water to prepare a metal salt aqueous solution. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 99 wt%, Cu 1 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 5 mL of a 0.1% by weight copper nitrate aqueous solution, which is a dispersibility reducing agent, was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 6.

<Example 7>
An aqueous metal salt solution was prepared by dissolving a metal salt forming 99% by weight Ag and 1% by weight Sn metal nanoparticles in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 99 wt%, Sn 1 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.1 wt% aqueous silver nitrate solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 7.

<Example 8>
An aqueous metal salt solution was prepared by dissolving a metal salt forming 99.5 wt% Ag and 0.5 wt% In metal nanoparticles in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 99.5 wt%, In 0.5 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of 0.1 wt% indium nitrate aqueous solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 8.

<Example 9>
An aqueous metal salt solution was prepared by dissolving a metal salt that forms metal nanoparticles with 95 wt% Ag and 5 wt% Zn in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 95 wt%, Zn 5 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.02% by weight ammonium nitrate aqueous solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 9.

<Example 10>
An aqueous metal salt solution was prepared by dissolving a metal salt forming 95% by weight of Ag and 5% by weight of Fe to form metal nanoparticles in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 95 wt%, Fe 5 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of 0.1% by weight chromium acetate aqueous solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 800G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 10.

<Example 11>
An aqueous metal salt solution was prepared by dissolving a metal salt that forms metal nanoparticles with 95 wt% Ag and 5 wt% Cr in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 95 wt%, Cr 5 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.1 wt% aqueous solution of ammonium formate as a dispersibility reducing agent was dropped. Then, it centrifuged at 500G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 11.

<Example 12>
An aqueous metal salt solution was prepared by dissolving a metal salt that forms metal nanoparticles with 95 wt% Ag and 5 wt% Mn in deionized water. Except for this, a metal nanoparticle dispersion in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 1 was obtained.
The obtained metal nanoparticle dispersion (Ag 95 wt%, Mn 5 wt%) 1000 mL was centrifuged at 500 G for 1 minute using a centrifuge. Thus, the supernatant was separated after being separated into the concentrate and the supernatant, and 100 mL of deionized water was added to the concentrate and stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, 10 mL of a 0.1% by weight dimethylamine hydrochloride aqueous solution as a dispersibility reducing agent was dropped. Then, it centrifuged at 1000G for 1 minute, and isolate | separated the supernatant liquid. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 12.

<Example 13>
A metal nanoparticle dispersion liquid in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 3 was obtained.
The obtained metal nanoparticle dispersion (Ag 75 wt%, Au 25 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thereby, the supernatant separated into the concentrate and the supernatant was separated, 100 mL of deionized water was added to the concentrate, and the mixture was stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
Ammonia water, which is a dispersibility-lowering agent, was added dropwise to this dispersion to adjust the dispersion to pH 8. Thereafter, the mixture was centrifuged at 800 G for 10 minutes, and the supernatant was separated. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 13.

<Example 14>
A metal nanoparticle dispersion liquid in which metal nanoparticles were dispersed under the same conditions and procedures as in Comparative Example 3 was obtained.
The obtained metal nanoparticle dispersion (Ag 75 wt%, Au 25 wt%) (1000 mL) was centrifuged at 500 G for 1 minute using a centrifuge. Thereby, the supernatant separated into the concentrate and the supernatant was separated, 100 mL of deionized water was added to the concentrate, and the mixture was stirred with a spatula to obtain a uniform metal nanoparticle dispersion.
To this dispersion, sodium hydroxide water as a dispersibility reducing agent was added dropwise to adjust the dispersion to pH 8. Thereafter, the mixture was centrifuged at 800 G for 10 minutes, and the supernatant was separated. This operation was repeated twice to obtain a high concentration metal nanoparticle dispersion. The high-concentration metal nanoparticle dispersion liquid thus obtained was designated as Example 14.

<Comparison test and evaluation>
About the liquid which fractionated the recovery rate of the metal nanoparticles in each of the high-concentration metal nanoparticle dispersions in Comparative Examples 1 and 2 and Examples 1 to 12, the contained metal nanoparticles were dissolved with an acid or the like and further inductively coupled Evaluation was made by measuring the metal concentration by plasma emission analysis (ICP-AES method). The test conditions and results are shown in Table 1.

As is apparent from Table 1, in Comparative Examples 1 to 3 in which the dispersibility reducing agent was not added to the metal nanoparticle dispersion before centrifugation, the metal recovery rate was 15.1% at the maximum, It can be seen that the value is extremely low.
On the other hand, in Examples 1 to 13 in which the dispersibility reducing agent is added to the metal nanoparticle dispersion before centrifugation, the metal recovery rate is high even though the centrifugal force in the centrifugation is 1000 G or less. It can be seen that This is because the dispersibility-reducing agent is added to the metal nanoparticle dispersion before centrifuging, so that the dispersion stability of the metal nanoparticles is reduced, and the metal nanoparticles can be spun down with a low centrifugal force. This is thought to be due to this.

It is a figure which shows the manufacturing method of embodiment of this invention. It is a figure which shows another manufacturing method of this invention.

Claims (5)

In the method for producing a high-concentration metal nanoparticle dispersion in which a part of the dispersion medium is removed by centrifugation from the metal nanoparticle dispersion in which the metal nanoparticles are dispersed in the dispersion medium to increase the concentration of the metal nanoparticles,
Metal nanoparticles are 100 wt% silver nanoparticles, or 75 wt% or more silver nanoparticles and the balance is gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese It consists of one kind of particles selected from the group consisting of two or more kinds of mixed composition or alloy composition,
A method for producing a high-concentration metal nanoparticle dispersion, comprising adding a dispersibility reducing agent for reducing the dispersibility of the metal nanoparticles to the metal nanoparticle dispersion before centrifugation.   The pure water is added to the metal nanoparticle dispersion liquid from which a part of the dispersion medium has been removed by centrifugation, and then centrifuged again to further remove a part of the dispersion medium together with the pure water. The manufacturing method of the high concentration metal nanoparticle dispersion liquid of description.   The method for producing a high-concentration metal nanoparticle dispersion according to claim 1 or 2, wherein the dispersibility reducing agent is any one of hydrochloric acid, nitric acid, ammonia, amines, and salts using these.   The method for producing a high-concentration metal nanoparticle dispersion according to claim 1 or 2, wherein the dispersibility reducing agent is a salt containing the same metal element as the element constituting the metal nanoparticle.   A high-concentration metal nanoparticle dispersion obtained by the production method according to any one of claims 1 to 4.

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