Multipod nanostructures and methods

1. A method of forming metal multipod nanostructures, the method comprising:

providing a mixture disposed in a microwave reaction vessel, the mixture comprising

a metal acetylacetonate,

a reducing agent comprising a C 1 -C 30 hydrocarbyl-amine, and

a carboxylic acid of formula (A)

wherein R is a monovalent C 1 -C 30 hydrocarbyl; and

contacting the mixture with microwaves to form the metal multipod nanostructures,

wherein the contacting of the mixture with microwaves comprises (i) contacting the mixture with a first plurality of microwaves effective to heat the mixture to a first temperature, (ii) reducing the first temperature of the mixture to a second temperature, and (iii) contacting the mixture with a second plurality of microwaves for a time effective to heat the mixture to the first temperature.

2. The method of claim 1 , further comprising repeating steps (ii) and (iii) from 1 to 8 times.

3. The method of claim 1 , wherein the first temperature is about 260° C. to about 300° C.

4. The method of claim 1 , wherein the second temperature is about 220° C. to about 250° C.

5. The method of claim 1 , wherein the time effective to heat the mixture to the first temperature with the second plurality of microwaves is about 1 minute to about 20 minutes.

6. The method of claim 1 ,

wherein the second plurality of microwaves comprises microwaves of different wattages.

7. The method of claim 1 ,

wherein the second plurality of microwaves consists of microwaves of the same wattage.

8. The method of claim 1 , wherein the metal acetylacetonate and the reducing agent are present in the mixture at a mole ratio of about 0.3:25 to about 3:25.

9. The method of claim 1 , wherein the reducing agent and the carboxylic acid of formula (A) are present in the mixture at a mole ratio of about 25:2 to about 25:8.

10. The method of claim 1 , wherein the metal acetylacetonate comprises a Ni acetylacetonate.

11. The method of claim 1 , wherein the metal acetylacetonate is selected from the group consisting of a Pt acetylacetonate, a Pd acetylacetonate, a Cu acetylacetonate, a Co acetylacetonate, a Au acetylacetonate, an Fe acetylacetonate, and a Rh acetylacetonate.

12. The method of claim 1 , wherein the C 1 -C 30 hydrocarbyl-amine is an unsaturated C 1 -C 30 hydrocarbyl-amine.

13. The method of claim 1 , wherein the C 1 -C 30 hydrocarbyl-amine is oleylamine.

14. The method of claim 1 , wherein the carboxylic acid of formula (A) is oleic acid.

15. A method of forming metal multipod nanostructures, the method comprising:

(i) providing a mixture disposed in a microwave reaction vessel, the mixture comprising (a) nickel acetylacetonate, (b) oleylamine, and (c) oleic acid,

(ii) contacting the mixture with a first plurality of microwaves effective to heat the mixture to a first temperature, wherein the first temperature is about 260° C. to about 300° C.,

(iii) reducing the first temperature of the mixture to a second temperature, wherein the second temperature is about 220° C. to about 250° C.,

(iv) contacting the mixture with a second plurality of microwaves for a time effective to heat the mixture to the first temperature,

(v) reducing the first temperature of the mixture to the second temperature, and

(vi) contacting the mixture with the second plurality of microwaves for the time effective to heat the mixture to the first temperature to form the metal multipod nanostructures;

wherein the time effective to heat the mixture to the first temperature with the second plurality of microwaves is about 1 minute to about 20 minutes.

16. The method of claim 15 , further comprising repeating steps (v) and (vi) from 1 to 20 times.

17. The method of claim 15 , wherein the metal multipod nanostructures include arms having an average aspect ratio of about 3 to about 5.