Synthesis of uniform anisotropic nanoparticles
Methods of synthesizing various metal nanoparticle structures having high uniformity, using iterative reduction and oxidation conditions, is provided herein.
1. A method of preparing gold circular disk nanoparticle comprising
(a) admixing gold triangular prisms, a stabilizing agent, and an oxidizing agent in an aqueous solution to form a first intermediate;
(b) admixing the first intermediate, a gold salt, and a reducing agent, and optionally a base and halide salt, in an aqueous solution to form a second intermediate;
(c) admixing the second intermediate, a stabilizing agent, and oxidizing agent in an aqueous solution to form the gold circular disk nanoparticle; and
(d) optionally repeating steps (b) and (c) at least once to increase the uniformity of the resulting circular disk nanoparticles;
wherein the gold circular disk nanoparticles are formed in a yield of at least 70%.
2. The method of claim 1 , wherein the gold circular disk nanoparticles are formed in a yield of at least 90%.
3. The method of claim 1 , wherein the circular disk nanoparticles having uniformity as measured by a coefficient of variation (CV) of less than 30%.
4. The method of claim 3 , wherein the circular disk nanoparticles have a CV of 10% or less.
5. The method of claim 1 , wherein the oxidizing agent of steps (a) and (c) comprises HAuCl 4 .
6. The method of claim 5 , wherein the HAuCl 4 concentration correlates to the gold triangular prism edge length: at 8 μM for an edge length of 60 nm or less; at 10 μM for an edge length of 80 nm to 120 nm; at 12 μM for an edge length of 140nm; and at 13 μM for an edge length of 180 nm.
7. The method of claim 1 , wherein the stabilizing agent is selected from the group consisting of cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), cetylpyridinium chloride (CPC), and a mixture thereof.
8. The method of claim 1 , wherein the gold salt comprises HAuCl 4 .
9. The method of claim 1 , wherein the reducing agent comprises ascorbic acid.
10. The method of claim 1 , wherein steps (b) and (c) are repeated at least twice.
11. The method of claim 1 , wherein the gold triangular prisms are prepared by
(1) admixing a stabilizing agent, an iodide salt, a gold salt, a base, a reducing agent, and nanoparticle seeds to form gold triangular prisms; and
(2) isolating the gold triangular prisms.
12. The method of claim 11 , wherein the concentration of nanoparticle seeds is 20 to 300 pM for a selected edge length of the gold triangular prism of 30 nm to 250 nm.
13. The method of claim 1 , wherein the isolating comprises adding a halide salt to the mixture resulting from step (1) and the concentration of the halide salt is selected in view of the edge length of the gold triangular prisms: 0.4M halide salt for triangular prisms with an edge length of 30 nm to 80 nm; 0.2M halide salt for triangular prisms with an edge length of 90 nm to 120 nm; 0.1M halide salt for triangular prisms with an edge length of 130 nm to 170 nm; and 0.05M halide salt for triangular prisms with an edge length of 180 nm to 250 nm.
14. A method of preparing uniform gold spherical nanoparticles comprising
(a) admixing gold nanorods, a stabilizing agent, and an oxidizing agent in an aqueous solution to form a first intermediate;
(b) admixing the first intermediate, a gold salt, and a reducing agent, and optionally a base and halide salt, in an aqueous solution to form a second intermediate;
(c) admixing the second intermediate, a stabilizing agent, and an oxidizing agent in an aqueous solution to form the gold spherical nanoparticles; and
(d) optionally repeating steps (b) and (c) at least once to increase the uniformity of the resulting gold spherical nanoparticles, as measured by a coefficient of variation (CV); wherein
(1) the method is performed in the absence of ethylene glycol, dimethylformamide, diethylene glycol, dimethylsulfoxide, toluene, tetrahydrofuran, hexane, octane, and oleic acid;
(2) the gold spherical nanoparticles are formed in a yield of at least 90%; and
(3) the gold spherical nanoparticles have a diameter of 1 nm to 99 nm.
15. The method of claim 14 , wherein the spherical nanoparticles have a CV of 3% or less.
16. The method of claim 14 , wherein the oxidizing agent of steps (a) and (c) comprises HAuCl 4 .
17. The method of claim 14 , wherein the gold salt comprises HAuCl 4 .
18. The method of claim 14 , wherein the reducing agent comprises ascorbic acid.
19. The method of claim 14 , wherein any one of step (a), (b), and (c) is performed for 0.5 hr to 2 hr.
20. The method of claim 19 , wherein each of step (a), (b), and (c) is performed for 0.5 hr to 6 hr.