Method of producing gold nanoprisms

• US 20060207388A1
• Filed: 03/10/2006
• Published: 09/21/2006
• Est. Priority Date: 03/10/2005
• Status: Active Grant

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Mirkin, Chad A., Park, Sungho, Metraux, Gabriella, Millstone, Jill E.
• Granted Patent: US 7,588,624 B2
• Time in Patent Office: Days
• US Class Current: 75/371
• CPC Class Codes: B22F 1/054 Nanosized particles
• CPC Class Codes: B22F 1/0553 Complex form nanoparticles, e.g. prism, pyramid, octahedron
• CPC Class Codes: B22F 9/24 starting from liquid metal compounds, e.g. solutions
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C30B 29/02 Elements
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: C30B 7/00 Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions from molten solvents C30B9/00; by normal or gradient freezing C30B11/00; under a protective fluid C30B27/00

Abstract

The present invention relates to a method of producing gold nanoprisms. In particular, gold nanoprisms having uniform shapes and edge lengths and thickness are produced utilizing a three step growth process.

Claims

1. A method of producing gold nanoparticles comprising the steps of

a) admixing a suspension of gold seed nanoparticles and a first growth solution to form a first mixture,

wherein the volume ratio of first growth solution to suspension is at least 2:

1,

wherein the gold seed nanoparticles have a diameter of about 3 to about 10 nm, and

wherein the first growth solution comprises a gold salt, a base, a reducing agent, and a surfactant, wherein the surfactant has a concentration in the first growth solution of at least 50% saturation at about 25°

C.;

b) admixing the first mixture and a second growth solution to form a second mixture,

wherein the volume ratio of second growth solution to first mixture is at least 2;

1,

wherein the second growth solution comprises a gold salt, a base, a reducing agent, and a surfactant, wherein the surfactant has a concentration in the second growth solution of at least 80% saturation at about 25°

C.; and

c) admixing the second mixture and a third growth solution to form a third mixture,

wherein the volume ratio of third growth solution to second mixture is at least 2;

1, and

wherein the third growth solution comprises a gold salt, a base, a reducing agent, and a surfactant, and wherein the surfactant has a concentration in the third growth solution of at least 80% saturation at about 25°

C.;

wherein the gold nanoparticles are triangular, spherical, or a combination thereof.

2. The method of claim 1 wherein the gold nanoparticles are triangular.

3. The method of claim 1 wherein the gold nanoparticles are spherical.

4. The method of claim 1 wherein the gold salt of one or more of the first growth solution, second growth solution, or third growth solution comprises HAuCl₄ or a potassium, calcium, sodium, or lithium salt thereof.

5. The method of claim 1 wherein the reducing agent of the first growth solution, second growth solution, and third growth solution, independently, is selected from the group consisting of ascorbic acid, sodium borohydride, 2-mercaptoethanol, dithiothreitol, hydrazine, lithium aluminum hydride, diisobutylaluminum hydride, oxalic acid, and Lindlar catalyst.

6. The method of claim 1 wherein the reducing agent of the first growth solution, second growth solution, and third growth solution comprises ascorbic acid.

7. The method of claim 1 wherein the surfactant of the first growth solution, second growth solution, and third growth solution, independently, is selected from the group consisting of tetrabutylammonium bromide, dodecyldimethylamonium bromide, cetyltrimethylammonium bromide, and mixtures thereof.

8. The method of claim 1 wherein the surfactant of the first growth solution, second growth solution, and third growth solution comprises cetyltrimethylammonium bromide.

9. The method of claim 1 wherein the first growth solution and the second growth solution comprise an identical gold salt, an identical reducing agent, and an identical surfactant.

10. The method of claim 1 wherein the first growth solution, the second growth solution, and the third growth solution comprise an identical gold salt, an identical reducing agent, and an identical surfactant.

11. The method of claim 10 wherein the gold salt comprises HAuCl₄ or a potassium, calcium, sodium, or lithium salt thereof.

12. The method of claim 10 wherein the reducing agent comprises ascorbic acid.

13. The method of claim 10 wherein the surfactant comprises cetyltrimethylammonium bromide.

14. The method of claim 1 further comprising filtering the third mixture.

15. The method of claim 1 wherein the gold nanoprisms are single crystalline.

16. The method of claim 1 wherein the gold nanoprisms are essentially free of rods, cubes, and branched structures.

17. The method of claim 1 wherein the concentration of the surfactant in one or more of the first growth solution, second growth solution, or third growth solution is at least 90% saturated at about 25°

C.

18. A method of maintaining a shape and increasing an edge length of gold nanoprisms prepared according to claim 1 comprising

a) adding a solution consisting essentially of a gold salt and a reducing agent to the gold nanoprisms, wherein a molar ratio of reducing agent to gold salt is at least 1.01:

1.

19. The method of claim 18 wherein step a) is repeated a plurality of times.

20. A method producing gold nanoparticles comprising

a) admixing a suspension of gold seed nanoparticles and a first growth solution to form a first mixture, wherein the gold seed nanoparticles have a diameter of about 3 to about 10 nm, wherein the volume ratio of first growth to suspension solution is at least 2:

1, and the first growth solution comprises;

HAuCl₄ or a potassium, calcium, sodium, or lithium salt thereof;

sodium hydroxide;

ascorbic acid; and

cetyltrimethylammonium bromide, wherein the cetyltrimethylammonium bromide has a concentration in the first growth solution of at least 80% saturation at about 25°

C.;

b) admixing the first mixture and a second growth solution to form a second mixture, wherein the volume ratio of second growth solution to first mixture is at least 2;

1 and wherein the second growth solution comprises;

HAuCl₄ or a potassium, calcium, sodium, or lithium salt thereof;

sodium hydroxide;

ascorbic acid; and

cetyltrimethylammonium bromide, wherein the cetyltrimethylammonium bromide has a concentration in the second growth solution of at least 80% saturation at about 25°

C.; and

c) admixing the second mixture and a third growth solution to form a third mixture, wherein the volume ratio of third growth solution to second mixture is at least 2;

1 and wherein the third growth solution comprises;

HAuCl₄ or a potassium, calcium, sodium, or lithium salt thereof;

sodium hydroxide;

ascorbic acid; and

cetyltrimethylammonium bromide, wherein the cetyltrimethylammonium bromide has a concentration in the third growth solution of at least 80% saturation at about 25°

C., and

wherein the gold nanoparticles are triangular, spherical, or a combination thereof.

21. A method of measuring or monitoring the growth of gold nanoprism edge lengths comprising determining a λ

_max of a quadrupole resonance and correlating the λ

_max to the edge length.