Stabilized metal nanoparticles and methods for production thereof
Processes for synthesizing metal nanoparticles, particularly copper nanoparticles, are described. The processes can involve reacting an insoluble complex of a metal salt with a reducing agent in a reaction mixture containing a primary amine first surfactant, a secondary amine second surfactant, and a diamine chelating agent third surfactant. More specifically, processes for forming copper nanoparticles can involve forming a first solution containing a copper salt, a primary amine first surfactant, a secondary amine second surfactant, and a diamine chelating agent third surfactant; allowing an insoluble complex of the copper salt to form from the first solution; combining a second solution containing a reducing agent with the insoluble complex; and forming copper nanoparticles from the insoluble complex. Such copper nanoparticles can be about 10 nm or smaller in size, more particularly about 3 nm to about 6 nm in size, and have a fusion temperature of about 200° C. or lower.
1. A process comprising:
reacting an insoluble complex of a metal salt with a reducing agent in a reaction mixture comprising a first surfactant, a second surfactant, and a third surfactant so as to form metal nanoparticles;
wherein the first surfactant comprises a primary amine, the second surfactant comprises a secondary amine, and the third surfactant comprises a chelating agent comprising an N,N′-diakylethylenediamine or N,N,N′,N′-tetraalkylethylenediamine.
2. The process of claim 1 , wherein the metal nanoparticles comprise copper nanoparticles.
3. The process of claim 1 , wherein the insoluble complex comprises a coordination compound of the metal salt with at least one of the first surfactant, the second surfactant, and the third surfactant.
4. The process of claim 1 , wherein the reaction mixture is substantially oxygen free.
5. The process of claim 1 , further comprising:
after forming the metal nanoparticles, quenching the reducing agent with a terminating agent that is reactive therewith.
6. The process of claim 5 , wherein the terminating agent is selected from the group consisting of an aldehyde, a nitrile, an organic acid, water, and combinations thereof.
7. The process of claim 1 , further comprising:
arresting the formation of the metal nanoparticles by performing an action selected from the group consisting of adding a terminating agent to the reaction mixture, cooling the reaction mixture to about −10° C. or below, centrifuging the reaction mixture, and combinations thereof.
8. The process of claim 1 , further comprising:
isolating the metal nanoparticles from the reaction mixture.
9. The process of claim 1 , wherein the reaction mixture further comprises an organic solvent.
10. The process of claim 9 , wherein the organic solvent comprises diglyme or triglyme.
11. The process of claim 1 , wherein reacting takes place at a temperature ranging between about 0° C. and about 50° C.
12. The process of claim 1 , wherein the insoluble complex is formed at a temperature of at most about 85° C.
13. The process of claim 1 , wherein the reducing agent comprises NaBH 4 .
14. The process of claim 1 , wherein the metal nanoparticles range from about 3 nm to about 6 nm in size.
15. The process of claim 1 , wherein the reaction mixture comprises about 1 part of the first surfactant, about 2 parts of the second surfactant, and about 1 part of the third surfactant.
16. A process comprising:
forming a first solution comprising a copper salt, a first surfactant, a second surfactant, and third surfactant;
wherein the first surfactant comprises a primary amine, the second surfactant comprises a secondary amine, and the third surfactant comprises a chelating agent comprising an N,N′-dialkylethylenediamine or N,N,N′,N′-tetraalkylethylenediamine;
allowing an insoluble complex of the copper salt to form from the first solution;
combining a second solution comprising a reducing agent with the insoluble complex, thereby forming a reaction mixture; and
forming copper nanoparticles from the insoluble complex.
17. The process of claim 16 , wherein the insoluble complex comprises a coordination compound of the copper salt and at least one of the first surfactant, the second surfactant, and the third surfactant.
18. The process of claim 16 , wherein the copper salt is selected from the group consisting of a copper halide, copper nitrate, copper acetate, copper sulfate, copper formate, copper oxide, and combinations thereof.
19. The process of claim 16 , wherein the first solution and the second solution are substantially oxygen free.
20. The process of claim 16 , further comprising:
isolating the insoluble complex from the first solution.
21. The process of claim 16 , wherein the primary amine comprises a C4 to C18 primary alkylamine.
22. The process of claim 21 , wherein the primary alkylamine comprises a branched alkyl group bound to its nitrogen atom.
23. The process of claim 22 , wherein the branching occurs on the carbon atom bound to the nitrogen atom.
24. The process of claim 16 , wherein the secondary amine comprises branched or cyclic C4 to C12 alkyl groups bound to its nitrogen atom.
25. The process of claim 24 , wherein the branching occurs on the carbon atom bound to the nitrogen atom.
26. The process of claim 16 , wherein the N,N′-dialkylethylenediamine or N,N,N′,N′-tetraalkylethylenediamine comprises C1 to C6 alkyl groups bound to its nitrogen atoms.
27. The process of claim 26 , wherein the alkyl groups comprise branched or cyclic C3 to C6 alkyl groups.
28. The process of claim 16 , wherein at least one of the first solution or the second solution comprises an organic solvent comprising diglyme or triglyme.
29. The process of claim 16 , wherein formation of the insoluble complex takes place at a temperature of at most about 85° C.
30. The process of claim 16 , wherein forming the copper nanoparticles takes place at a temperature between about 0° C. and about 50° C.
31. The process of claim 16 , further comprising:
heating the second solution prior to combining with the insoluble complex.
32. The process of claim 16 , further comprising:
after forming the copper nanoparticles, quenching the reducing agent with a terminating agent that is reactive therewith.
33. The process of claim 32 , wherein the terminating agent is selected from the group consisting of an aldehyde, a nitrile, an organic acid, water, and combinations thereof.
34. The process of claim 16 , further comprising:
arresting the formation of the copper nanoparticles by performing an action selected from the group consisting of adding a terminating agent to the reaction mixture, cooling the reaction mixture to about −10° C. or below, centrifuging the reaction mixture, and combinations thereof.
35. The process of claim 16 , further comprising:
isolating the copper nanoparticles.
36. The process of claim 16 , wherein the reducing agent comprises NaBH 4 .
37. The process of claim 16 , wherein the copper nanoparticles range from about 3 nm to about 6 nm in size.
38. The process of claim 16 , wherein the first solution comprises about 1 part of the first surfactant, about 2 parts of the second surfactant, and about 1 part of the third surfactant.
39. The process of claim 16 , wherein the insoluble complex is uniformly distributed in the reaction mixture.
40. The process of claim 16 , wherein the reaction mixture has a water content of about 200 ppm or lower.