Single-crystalline metal nanorings and methods for synthesis thereof
In various embodiments, methods for synthesizing single-crystalline zero-valent metal nanorings, such as single-crystalline copper nanorings, are described herein. The methods include providing a solution containing a metal cation, a complexing agent bound to the metal cation, thereby forming a metal complex that is at least partially soluble in the solution, and a reducing agent operable for reducing the metal complex to a zero-valent metal and then heating the solution for a sufficient time and at a sufficient temperature until zero-valent metal nanorings form. The solution may be an aqueous solution in an embodiment. Single-crystalline metal nanorings produced by the methods described herein may have a diameter less than about 100 μm and a wall thickness between about 10 nm and about 500 nm.
1. A method for synthesizing zero-valent metal nanorings, said method comprising:
providing a solution comprising:
a) a metal cation;
b) a complexing agent bound to the metal cation;
wherein the complexing agent makes the metal cation at least partially soluble in the solution; and
c) a reducing agent operable for reducing the metal cation to a zero-valent metal; and heating the solution for a sufficient time and at a sufficient temperature until zero-valent metal nanorings form,
wherein the sufficient temperature is between about 180° C. and about 210° C.
2. The method of claim 1 , wherein the zero-valent metal nanorings are single-crystalline.
3. The method of claim 1 , wherein the solution further comprises water.
4. The method of claim 1 , wherein the zero-valent metal nanorings are copper nanorings.
5. The method of claim 4 , wherein the metal cation comprises a Cu (I) salt.
6. The method of claim 5 , wherein the Cu (I) salt comprises CuC 1 .
7. The method of claim 4 , wherein the metal cation is a Cu (I) salt, the complexing agent is N-methyl pyrrolidone (NMP) and the reducing agent is poly(vinyl alcohol) (PVA).
8. The method of claim 1 , wherein the complexing agent is NMP.
9. The method of claim 1 , wherein the reducing agent is PVA.
10. The method of claim 1 , wherein the reducing agent is operable for reducing the metal cation to a zero-valent metal upon heating the solution.
11. The method of claim 1 , wherein the sufficient time is less than about 7 days.
12. A solvothermal method for synthesizing single-crystalline zero-valent metal nanorings, said method comprising:
providing an aqueous solution comprising:
a) water;
b) a metal cation;
c) a complexing agent bound to the metal cation, comprising a metal complex that is at least partially soluble in the solution; and
d) a reducing agent operable for reducing the metal complex to a zero-valent metal upon being heated; and
heating the aqueous solution for a sufficient time and at a sufficient temperature until single-crystalline zero-valent metal nanorings form;
wherein reduction of the metal complex takes place during at least a portion of the time that heating occurs, and
wherein the sufficient temperature is between about 180° C. and about 210° C.
13. The method of claim 12 , wherein the metal cation is a monovalent transition metal cation.
14. The method of claim 12 , wherein the single-crystalline zero-valent metal nanorings are copper nanorings.
15. The method of claim 14 , wherein the metal cation comprises a Cu (I) salt.
16. The method of claim 15 , wherein the Cu (I) salt is CuCl.
17. The method of claim 16 , wherein the reducing agent is PVA.
18. The method of claim 16 , wherein the complexing agent is NMP.
19. The method of claim 14 , wherein the metal cation is a Cu (I) salt, the complexing agent is NMP and the reducing agent is PVA.
20. The method of claim 12 , wherein the sufficient time is less than about 7 days.
21. A solvothermal method for synthesizing single-crystalline copper nanorings, said method comprising:
providing an aqueous solution comprising:
a) water;
b) a Cu (I) salt comprising a Cu (I) cation;
c) NMP complexed to the Cu (I) cation to form a Cu (I)-NMP complex that is at least partially soluble in the aqueous solution; and
d) a reducing agent operable for reducing the Cu (I)-NMP complex to copper metal upon being heated; and
heating the aqueous solution for a sufficient time and at a sufficient temperature until single-crystalline copper nanorings form;
wherein reduction of the Cu (I)-NMP complex takes place during at least a portion of the time that heating occurs, and
wherein the sufficient temperature is between about 180° C. and about 210° C.
22. The method of claim 21 , wherein the single-crystalline copper nanorings have a diameter of less than about 100 μm.
23. The method of claim 21 , wherein the sufficient time is less than about 7 days.
24. The method of claim 21 , wherein the reducing agent is PVA.