Method for forming nano-scale metal particles

Abstract

A method for forming nano-scale metal particles by a novel reducing agent is described. The method can be carried out at room temperature and under an atmospheric environment by relatively simple processes to prepare nano-scale metal particles with a diameter less than 20 nm. This method comprises the following steps. At first, a first blending process is performed to blend a metal salt and a first solvent together to form a first solution. Then, a second blending process is performed to blend a reducing agent and a second solvent together to form a second solution. The reducing agent comprises one compound selected from the group consisting of the following or combination thereof: boron-containing hydride and boron-containing hydrocarbon. Following that, a third blending process is performed to blend the first solution and the second solution together to form a third solution. Finally, the reducing agent is used to reduce the metal salt in the third solution to form the nano-scale metal particles. In addition, if a dispersing agent is added after the nano-scale metal particles are formed, the nano-scale metal particles can have a particle diameter less than 10 nm.

1 . A method for forming nano-scale metal particles, comprising:
 performing a first blending process to blend a metal salt and a first solvent together to form a first solution;   performing a second blending process to blend a reducing agent and a second solvent together to form a second solution wherein said reducing agent comprises one compound selected from the group consisting of the following or combination thereof: boron-containing hydride and boron-containing hydrocarbon;   performing a third blending process to blend said first solution and said second solution together to form a third solution; and   using said reducing agent to reduce said metal salt in said third solution to form said nano-scale metal particles.   
     
     
         2 . The method according to  claim 1 , wherein the temperature in said first, second, and third blending processes is less than or equal to 40° C. 
     
     
         3 . The method according to  claim 1 , wherein in said first solution the molar concentration of said metal salt is less than or equal to 10 −4 M. 
     
     
         4 . The method according to  claim 1 , wherein in said second solution the molar concentration of said reducing agent is less than or equal to 10 −4 M. 
     
     
         5 . The method according to  claim 1 , wherein said reducing agent is tetraethylammonium borohydride. 
     
     
         6 . The method according to  claim 1 , wherein said metal salt has a general formula: MX where M is selected from the group consisting of the following: tin, copper, silver, and gold; and X is selected from the group consisting of the following: halogen, sulfate ion, phosphate ion, sulfonate ion, nitrate ion, and carboxylate ion. 
     
     
         7 . The method according to  claim 1 , wherein said first solvent and said second solvent are independently selected from the group consisting of the following or combination thereof: water, alcohol, and a polar solvent. 
     
     
         8 . The method according to  claim 7 , wherein said nano-scale metal particles are dispersed in solution by a dispersing agent after formed where said dispersing agent is selected from the group consisting of the following: water, alcohol, n-hexane, toluene, and tetrahydrofuran. 
     
     
         9 . The method according to  claim 7 , wherein the molar ratio of said reducing agent to said metal salt is between 60 and 300. 
     
     
         10 . The method according to  claim 7 , wherein the particle diameter of said formed nano-scale metal particles is 5˜70 nm. 
     
     
         11 . The method according to  claim 1 , wherein said first solvent and said second solvent are independently selected from the group consisting of the following or combination thereof: N,N-dimethyl-acetamide (DMAC), dimethyl-sulfoxide (DMSO), and 1-methyl-2-pyrrolidinone (NMP). 
     
     
         12 . The method according to  claim 11 , wherein the molar ratio of said reducing agent to said metal salt is between 5 and 25. 
     
     
         13 . The method according to  claim 11 , wherein the particle diameter of said formed nano-scale metal particles is 15˜60 nm. 
     
     
         14 . A method for forming tin-containing nano-scale metal particles, comprising:
 performing a blending process to blend a tin salt, a reducing agent, and a solvent together to form a mixture solution wherein said mixture solution selectively comprises other metal salts and said reducing agent comprises one compound selected from the group consisting of the following or combination thereof: boron-containing hydride and boron-containing hydrocarbon; and   using said reducing agent to reduce said metal salt in said mixture solution to form said tin-containing nano-scale metal particles.   
     
     
         15 . The method according to  claim 14 , wherein the temperature in said blending processes is less than or equal to 40° C. 
     
     
         16 . The method according to  claim 14 , wherein said blending process is performed under an atmospheric environment. 
     
     
         17 . The method according to  claim 14 , wherein said reducing agent is tetraethylammonium borohydride. 
     
     
         18 . The method according to  claim 14 , wherein said solvent is selected from the group consisting of the following or combination thereof: water, alcohol, a polar solvent. 
     
     
         19 . The method according to  claim 14 , wherein said tin salt has a general formula: SnX where and X is selected from the group consisting of the following: halogen, sulfate ion, phosphate ion, sulfonate ion, nitrate ion, and carboxylate ion. 
     
     
         20 . The method according to  claim 14 , wherein said other metal salt is selected from the group consisting of the following or combination thereof: silver salt, copper salt, and gold salt. 
     
     
         21 . The method according to  claim 14 , wherein said nano-scale metal particles are dispersed in solution by a dispersing agent after formed where said dispersing agent is selected from the group consisting of the following: water, alcohol, n-hexane, toluene, and tetrahydrofuran. 
     
     
         22 . The method according to  claim 14 , wherein the molar ratio of said reducing agent to all of said metal salts is between 60 and 300. 
     
     
         23 . The method according to  claim 14 , wherein the particle diameter of said formed tin-containing nano-scale metal particles is 5˜70 nm. 
     
     
         24 . A method for forming copper nano-scale metal particles, comprising:
 performing a first blending process to blend a copper salt and a first solvent together to form a first solution;   performing a second blending process to blend a reducing agent and a second solvent together to form a second solution wherein said reducing agent comprises one compound selected from the group consisting of the following or combination thereof: boron-containing hydride and boron-containing hydrocarbon and said second solvent is selected from the group consisting of the following: N,N-dimethyl-acetamide (DMAC), dimethyl-sulfoxide (DMSO), and 1-methyl-2-pyrrolidinone (NMP);   performing a third blending process to blend said first solution and said second solution together to form a third solution and using said reducing agent to reduce said copper salt in said third solution to form dispersed copper nano-scale metal particles.   
     
     
         25 . The method according to  claim 24 , wherein the temperature of said first, second, and third blending processes is less than or equal to 40° C. 
     
     
         26 . The method according to  claim 24 , wherein said first, and second, and third blending processes are performed under a nitrogen environment. 
     
     
         27 . The method according to  claim 24 , wherein in said first solution the molar concentration of said metal salt is less than or equal to 10 −4 M. 
     
     
         28 . The method according to  claim 24 , wherein in said second solution the molar concentration of said reducing agent is less than or equal to 10 −4 M. 
     
     
         29 . The method according to  claim 24 , wherein said reducing agent is tetraethylammonium borohydride. 
     
     
         30 . The method according to  claim 24 , wherein said first solvent is independently selected from the group consisting of the following or combination thereof: N,N-dimethyl-acetamide (DMAC), dimethyl-sulfoxide (DMSO), and 1-methyl-2-pyrrolidinone (NMP). 
     
     
         31 . The method according to  claim 24 , wherein said first solvent is N,N-dimethyl-acetamide (DMAC) and said second solvent is dimethyl-sulfoxide (DMSO). 
     
     
         32 . The method according to  claim 24 , wherein said copper salt has a general formula: CuX where and X is selected from the group consisting of the following: halogen, sulfate ion, phosphate ion, sulfonate ion, nitrate ion, and carboxylate ion. 
     
     
         33 . The method according to  claim 24 , wherein the molar ratio of said reducing agent to said copper-containing metal salts is between 5 and 25. 
     
     
         34 . The method according to  claim 14 , wherein the particle diameter of said formed copper nano-scale metal particles is 15˜60 nm.