Dispersion of metal nanoparticles, method for producing the same, and method for synthesizing metal nanoparticles

Patent metadata

Field	Value
Publication number	US-9580810-B2
Application number	US-52862508-A
Country	US
Kind code	B2
Filing date	Feb 27, 2008
Priority date	Feb 27, 2007
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

The present invention aims to provide a method for producing a dispersion of metal nanoparticles which enables to control the shape and the particle diameter over a wide range, a dispersion of metal nanoparticles having superior dispersion stability, and a method for producing the same. In addition, the present invention further aims to provide a dispersion of metal nanoparticles which has a volume resistivity of 2×10 −6 to 6×10 −6 Ω·cm and is suitable for use as an electrically conductive material, and a method for producing the same. Moreover, the present invention further aims to provide a method for synthesizing metal nanoparticles which can produce metal nanoparticles suitable for use as electrically conductive materials by synthesizing the metal nanoparticles from a insoluble metal salt which is free of corrosive materials.

First claim

The invention claimed is:

1. A method for synthesizing metal nanoparticles, comprising the steps of:
preparing an aqueous metal salt solution (A) by dissolving a metal salt, said aqueous metal salt solution (A) consisting essentially of the metal salt and a solvent;
preparing an aqueous carboxylic acid solution (B) by dissolving one type or two or more types of compounds selected from the group consisting of citric acid, maleic acid and salts thereof;
preparing an aqueous reducing agent solution (C) by dissolving one type or two or more types of compounds selected from the group consisting of oxalic acid and salts thereof;
mixing the aqueous carboxylic acid solution (B) with the aqueous metal salt solution (A) so as to obtain a suspension of a carboxylic acid salt in which poorly-soluble carboxylic acid salt precipitates; and
forming metal nanoparticles by adding and mixing the aqueous reducing agent solution (C) with the suspension of the carboxylic acid salt,
wherein the aqueous solutions (A), (B), and (C) are separately prepared,
metal elements contained in the metal salt comprise 75% by mass or more of silver, and
the mixing with the aqueous reducing agent solution is carried out by stirring at a temperature of 25 to 95° C.

2. The method for synthesizing metal nanoparticles according to claim 1 , wherein one type or two or more types of metals selected from the group consisting of gold, platinum, palladium, and ruthenium are included as the remainder of the metal elements contained in the metal salt of the aqueous metal salt solution (A) other than silver.

3. A method for producing a metal film, comprising the steps of:
obtaining a dispersion of metal nanoparticles by dispersing the metal nanoparticles which are obtained by the synthesis method according to claim 1 in a dispersion medium; and
forming a metal film by coating the dispersion of metal nanoparticles as a composition for producing a metal film on a base material by a wet coating process.

4. A dispersion of metal nanoparticles comprising metal nanoparticles which are dispersed in a dispersion medium,
wherein the metal nanoparticles are synthesized by adding and mixing a metal salt in which the proportion of silver to metal elements is 75% by mass or more, a carboxylic acid, a reducing agent, and an additive containing borate ions in a liquid phase, and stirring the resulting suspension at a temperature of 25 to 95° C.,
the concentration of the additive contained in the dispersion is within a range from 0.01 to 100 ppm,
the carboxylic acid is an aqueous carboxylic acid solution that is prepared by dissolving one type or two or more types of compounds selected from the group consisting of citric acid, maleic acid, and salts thereof,
the metal salt is an aqueous metal salt solution that is prepared by dissolving the metal salt therein, said aqueous metal salt solution consisting essentially of the metal salt and a solvent,
the additive is an aqueous additive solution,
the reducing agent is an aqueous reducing agent solution,
the aqueous metal salt solution, the aqueous carboxylic acid solution, and the aqueous reducing agent solution are separately prepared,
the aqueous carboxylic acid solution is mixed with the aqueous metal salt solution and the aqueous additive solution so as to obtain a suspension of a carboxylic acid salt in which poorly-soluble carboxylic acid salt precipitates, and
the suspension of the carboxylic acid salt is subsequently mixed with the aqueous reducing agent solution.

5. The dispersion according to claim 4 , wherein the dispersion medium contains 1% by mass or more of water and 2% by mass or more of alcohol.

6. The dispersion according to claim 5 , wherein the alcohol is one type or two or more types selected from the group consisting of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, isobornyl hexanol, glycerol, and erythritol.

7. A method for producing a dispersion of metal nanoparticles, comprising the steps of:
synthesizing metal nanoparticles by mixing a metal salt in which the proportion of silver to metal elements is 75% by mass or more, a carboxylic acid, and a reducing agent in a liquid phase;
dispersing the synthesized metal nanoparticles in a dispersion medium;
wherein the synthesizing of the metal nanoparticles is carried out by adding and mixing an additive containing borate ions together with the metal salt, the carboxylic acid, and the reducing agent in the liquid phase, and stirring the resulting suspension at a temperature of 25 to 95° C.;
preparing the carboxylic acid in the form of an aqueous carboxylic acid solution by dissolving one type or two or more types of compounds selected from the group consisting of citric acid, maleic acid, and salts thereof;
preparing the metal salt in the form of an aqueous metal salt solution by dissolving the metal salt, said aqueous metal salt solution consisting essentially of the metal salt and a solvent;
preparing the additive in the form of an aqueous additive solution;
preparing the reducing agent in the form of an aqueous reducing agent solution;
mixing the aqueous carboxylic acid solution with the aqueous metal salt solution and the aqueous additive solution so as to obtain a suspension of a carboxylic acid salt in which poorly-soluble carboxylic acid salt precipitates;
subsequently mixing the suspension of the carboxylic acid salt with the aqueous reducing agent solution; and
reducing the concentration of the additive contained in the prepared dispersion to be within a range from 0.01 to 100 ppm after the synthesizing of the metal nanoparticles, and
wherein the aqueous metal salt solution, the aqueous carboxylic acid solution, and the aqueous reducing agent solution are separately prepared.

8. The production method according to claim 7 , wherein the reducing agent is one type or two or more types selected from the group consisting of hydrazine, sodium borohydride, ascorbic acid, oxalic acid, formic acid, salts thereof, and salts of Fe(II).

9. The production method according to claim 7 , wherein metal nanoparticles which has a composition, a mixed composition, or an alloy composition composed of one type or two or more types selected from the group consisting of gold, platinum, palladium, and ruthenium, are contained at a content within a range from 0.02% by mass or more to less than 25% by mass.

10. The production method according to claim 7 , wherein the dispersion medium contains 1% by mass or more of water and 2% by mass or more of alcohol.

11. The production method according to claim 10 , wherein the alcohol is one type or two or more types selected from the group consisting of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, isobornyl hexanol, glycerol, and erythritol.

12. A dispersion of metal nanoparticles which is obtained by the production method according to claim 7 ,
wherein the concentration of the additive contained in the dispersion is within a range from 0.01 to 100 ppm.

13. A method for forming an electrode for a solar cell, comprising the steps of:
preparing an electrode-forming composition by using the dispersion of metal nanoparticles according to claim 4 , a dispersion of metal nanoparticles obtained by the method according to claim 7 , or the dispersion of metal nanoparticles according to claim 12 ; and
coating the electrode-forming composition on a base material by a wet coating process.

14. A method for forming an electrode of a solar cell according to claim 13 ,
wherein in the coating of the electrode-forming composition on the base materi

Assignees

• Yamasaki Kazuhiko
• Katagiri Airi
• Arai Masahide
• Takata Yoshiaki
• Hayashi Toshiharu
• Mitsubishi Materials Corp

Inventors

• Yamasaki Kazuhiko
• Katagiri Airi
• Arai Masahide
• Takata Yoshiaki
• Hayashi Toshiharu

Classifications

• B22F1/0545

  Dispersions or suspensions of nanosized particles · CPC title

• B22F1/0022

  Operations & Transport · mapped topic

• H01L31/022425

  Electricity · mapped topic

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• C23C18/54 Primary

  Contact plating, i.e. electroless electrochemical plating · CPC title