Synthetic control of metal oxide nanocrystal sizes and shapes
View Patent ↗A general, reproducible, and simple synthetic method that employs readily available chemicals permits control of the size, shape, and size distribution of metal oxide nanocrystals. The synthesis entails reacting a metal fatty acid salt, the corresponding fatty acid, and a hydrocarbon solvent, with the reaction product being pyrolyzed to the metal oxide. Nearly monodisperse oxide nanocrystals of Fe 3 O 4 , Cr 2 O 3 , MnO, Co 3 O 4 , NiO, ZnO, SnO 2 , and In 2 O 3 , in a large size range (3-50 nm), are described. Size and shape control of the nanocrystals is achieved by varying the reactivity and concentration of the precursors.
1. A method of making nanometer-scale metal oxide particles, comprising:
a. combining a metal fatty acid salt, a fatty acid, and a hydrocarbon solvent to form an admixture thereof; and
b. heating the admixture to a temperature of at least 300° C. until the metal oxide particles are formed.
2. The method of claim 1 , wherein the metal oxide is an oxide of Fe, Mn, Cr, Ni, Co, Zn, In or Sn, or combination thereof.
3. The method of claim 1 , wherein the metal oxide particles are crystalline, semi-crystalline or polycrystalline.
4. The method of claim 1 , wherein a monodisperse distribution of the metal oxide particles is formed.
5. The method of claim 1 , wherein the metal oxide particles have a particle size in the range of about 5 nm to about 100 nm.
6. The method of claim 1 , wherein the metal fatty acid salt comprises a metal selected from the group consisting of Fe, Mn, Cr, Ni, Co, Zn, In and Sn.
7. The method of claim 1 , wherein the metal fatty acid salt is a stearate, oleate or myristate salt.
8. The method of claim 1 , wherein the fatty acid is selected from stearic acid, oleic acid, and myristic acid.
9. The method of claim 1 , wherein the hydrocarbon solvent comprises octadecene, n-eicosane, n-tetracosane, and combinations thereof.
10. The method of claim 1 , wherein the molar ratio of fatty acid to metal fatty acid salt is in the range of 10 or lower.
11. The method of claim 1 , further comprising combining an amine or alcohol activation reagent with the metal fatty acid salt.
12. The method of claim 1 , further comprising annealing the metal oxide particles at elevated temperature.