Process for producing metal nanoparticle and metal nanoparticle produced by the process

1. A method for producing metal nanoparticles, comprising:

(A) dissolving a salt and/or complex of a metal element and a coordinating organic protective agent in a solvent to produce a solution containing the salt and/or complex of a metal and the coordinating organic protective agent, followed immediately by

(B) irradiating the solution thus obtained with laser light, thereby decomposing and/or reducing the salt and/or complex within the solution and directly generating metal nanoparticles having an average particle size within a range from 0.3 to 3 nm within the solution wherein, during irradiation of the solution with the laser light, said coordinating organic protective agent coordinates with the generated metal nanoparticles and prevents aggregation thereof.

2. The method according to claim 1 , wherein the laser light is excimer pulsed laser light or Nd:YAG laser light.

3. The method according to claim 1 wherein a decomposition-reduction promoter that absorbs the laser light and promotes the decomposition and/or reduction of the salt and/or complex of the metal is added to the solution.

4. The method according to claim 3 , wherein the decomposition-reduction promoter is an oxygen-containing organic compound.

5. The method of claim 4 , wherein the decomposition-reduction promoter is an alcohol.

6. The method of claim 5 , wherein the alcohol is ethanol.

7. The method according to claim 1 , wherein the salt and/or complex of the metal element is a salt and/or complex of one metal element selected from the group consisting of platinum, palladium, gold, silver, rhodium, ruthenium and iridium.

8. The method according to claim 1 , wherein the coordinating organic protective agent is an organic compound having a R 4 -X structure wherein R 4 represents an alkyl group, alkenyl group, aralkyl group or aryl group, and X represents a NH 2 group, CN group, COOH group, OH group or SH group, an organic compound having a R 1 —Y—R 2 structure wherein R 1 and R 2 each represent, independently, an alkyl group, aralkyl group or aryl group, or alternatively, R 1 and R 2 are linked together to form a divalent group, and Y represents O, S, C═O, C═NH or NHCO, an organic compound having a ZR 1 R 2 R 3 structure wherein R 1 and R 2 and R 3 each represent independently an alkyl group, aralkyl group or aryl group, or alternatively, R 1 and R 2 , R 2 and R 3 , or R 3 and R 1 may be linked together to form a divalent group, and Z represents Nor P, a C6 to C1B long-chain alkylamine, carboxylic acid, ether, nitrile, tertiary amine polymer, polyether. polyester or polyamide, containing a coordinating functional group X, Y or Z wherein X, Y and Z are as defined above, or a combination of two or more of these compounds.

9. The method according to claim 1 , wherein the coordinating organic protective agent is citric acid monohydrate. poly-N-vinylpyrrolidone, oleic acid, oleylamine or a combination of two or more thereof.

10. The method according to claim 1 , wherein the metal nanoparticles have an average particle size within a range from 0.3 to 2.0 nm.

11. A method for producing metal nanoparticles, comprising:

(A) dissolving a salt and/or complex of a metal element and a coordinating organic protective agent in a solvent to produce a solution containing the salt and or complex of a metal and the coordinating organic protective agent, followed immediately by

(B) irradiating the solution thus obtained with laser light, thereby decomposing and/or reducing the salt and/or complex within the solution and directly generating metal nanoparticles having an average particle size within a range from 0.3 to 100 nm within the solution wherein, during irradiation of the solution with the laser light, said coordinating organic protective agent coordinates with the generated metal nanoparticles and prevents aggregation thereof,

wherein the salt and/or complex of the metal element comprises a salt and/or complex of at least one element selected from the group consisting of platinum, palladium, gold, silver, rhodium, ruthenium and iridium (group A), and a salt and/or complex of at least one element selected from the group consisting of iron, cobalt, nickel, copper and chromium (group B), and the obtained metal nanoparticles are composed of an alloy of these elements.

12. The method of claim 11 , wherein the average particle size of the metal nanoparticles is from 0.3 to 10 nm.

13. The method of claim 11 , wherein the average particle size of the metal nanoparticles is from 0.3 to 3 nm.

14. The method of claim 11 , wherein the alloy is a solid solution alloy of an element of the group A and an element of the group B.

15. The method of claim 11 , wherein the alloy is an ordered alloy of an element of the group A and an element of the group B.