Structured catalytic nanoparticles and method of preparation
A method of making a structured, doped, cerium oxide nanoparticle includes (a) forming a first reaction mixture including cerium(III), an optional metal ion other than cerium, a base, a stabilizer, and a solvent, (b) contacting the first reaction mixture with an oxidant, (c) forming a cerium oxide nanoparticle core by heating the product of step (b), (d) forming a second reaction mixture by combining with the first reaction mixture one or more metal ions other than cerium, and an optional additional quantity of cerium(III), and (e) forming a shell surrounding the core of cerium oxide by heating the second reaction mixture to produce a product dispersion of structured cerium oxide nanoparticles.
1. A method of making a structured, doped, cerium oxide nanoparticle, comprising:
a. forming a first reaction mixture comprising cerium(III), an optional metal ion other than cerium, a base, a stabilizer, and a solvent;
b. contacting said first reaction mixture with an oxidant;
c. forming a cerium oxide nanoparticle core by heating the product of step b);
d. forming a second reaction mixture by combining with the first reaction mixture one or more metal ions other than cerium, and an optional additional quantity of cerium(III); and
e. forming a shell partially or continuously surrounding said core of cerium oxide by heating said second reaction mixture to produce a product dispersion of structured cerium oxide nanoparticles.
2. The method of claim 1 , wherein the first reaction mixture further comprises one or more metal ions other than cerium; and wherein the identity and/or relative quantity of metal ions differs from that of the second reaction mixture.
3. The method of claim 1 , wherein step d) further comprises addition of cerium (III) ions and oxidant.
4. The method of claim 1 , wherein the heating of step c) or step e) raises the reaction mixture to about 50° C. to 100° C.
5. The method of claim 1 , wherein the addition of metal ions in step d) is performed concurrently with the addition of the oxidant in step b).
6. The method of claim 5 , wherein the introduction of the metal ions commences at about the midpoint of the introduction of the oxidant.
7. The method claim 1 , further comprising a step of diluting or concentrating the product dispersion of step e).
8. The method claim 1 , further comprising a step of diafiltration of the product dispersion to less than 10 mSiemens.
9. The method claim 7 , further comprising a step of diafiltration of the product dispersion to less than 10 mSiemens.
10. The method claim 1 , wherein the stabilizer is an alkoxylated carboxylic acid.
11. The method of claim 10 , wherein the alkoxylated carboxylic acid is methoxyacetic acid.
12. The method of claim 1 , wherein the base is ammonium hydroxide.
13. The method of claim 1 , wherein the oxidant is air, molecular oxygen or hydrogen peroxide.
14. The method of claim 1 , wherein the metal ion other than cerium are selected from the group consisting of ions of: Li, Mg, Sc, Ti, V, Cr, Zr, Mn, Fe, Co, Ni, Cu, Ag, Au, Bi, Pd, Pt, Pr, Gd, Sm, Y, La, and combinations thereof.
15. The method of claim 1 , wherein the metal ion other than cerium is an ion of a transition metal.
16. The method of claim 1 , wherein the amount of metal ion other than cerium in steps a) and d) are equal.
17. The method of claim 15 , wherein the metal ion other than cerium is an ion of iron, zirconium, or a combination thereof.
18. The method of claim 17 , wherein the metal ion other than cerium is iron; and the quantity of iron ion added in step d) is greater than that added in step a).
19. The method of claim 17 , wherein the metal ion other than cerium added in step d) consists essentially of iron ion.
20. The method of claim 17 , wherein zirconium ion is the metal ion other than cerium, and the amount added in step d) is greater than that in step a).
21. The method of claim 17 , wherein zirconium ion is the metal ion other than cerium, and the amount added in step d) is less than that in step a).