Synthesis of metal oxide, titania nanoparticle product, and mixed metal oxide solutions

1. A method for preparing a titania nanoparticle product, the method comprising:

(a) combining titanium (IV) tetraalkoxide with tetraalkylammonium hydroxide in a molar ratio of between 4.46:1 and 35.72:1 to form a solution in the absence of added alcohol; and

(b) exposing the solution to elevated temperature and elevated pressure to provide a titania nanoparticle product.

2. The method of claim 1 , wherein the combining in (a) is carried out in the presence of water.

3. The method of claim 1 , wherein the combining in (a) comprises combining titanium (IV) tetraalkoxide with tetraalkylammonium hydroxide in a molar ratio of between 4.46:1 and 35.72:1 to form a solution in the absence of an organic solvent.

4. The method of claim 1 , wherein the solution is prepared by adding titanium tetraalkoxide to an aqueous solution of tetraalkylammonium hydroxide.

5. The method of claim 1 , wherein the combining in (a) is carried out in the presence of water, and wherein the solution is prepared by adding titanium tetraalkoxide to an aqueous solution of tetraalkylammonium hydroxide.

6. The method of claim 1 , comprising adding a second metal oxide precursor to the solution of tetraalkylammonium hydroxide and titanium (IV).

7. The method of claim 1 , comprising adding a second metal oxide precursor to the solution of tetraalkylammonium hydroxide and titanium (IV), wherein the titania nanoparticle product comprises an additional metal oxide.

8. The method of claim 1 , wherein the solution is prepared by adding titanium tetraalkoxide to an aqueous solution of tetraalkylammonium hydroxide, and wherein the method further comprises adding a second metal oxide precursor to the solution of tetraalkylammonium hydroxide and titanium (IV).

9. The method of claim 1 , wherein the exposing comprises:

exposing the solution to elevated temperature and elevated pressure for a first period of time t1;

reducing the temperature and pressure; and

increasing the temperature and pressure for a second period of time t2.

10. The method of claim 1 , comprising contacting the titanium (IV) tetraalkoxide with water in an absence of unbound alkoxide prior to the combining of (a).

11. The method of claim 1 , wherein the combining in (a) forms an alcohol hydrolysis product, and wherein no more than 4 equivalents of alcohol are present after formation of the hydrolyzed product.

12. The method of claim 1 , wherein the combining in (a) forms an alcohol hydrolysis product, and wherein no more than 4 equivalents of alcohol are present after formation of the hydrolyzed product, wherein the method further comprises removing substantially all of the alcohol hydrolysis product formed in (a) prior to (b).

13. The method of claim 1 , wherein the resulting titania nanoparticle product possesses a positive charge in solution.

14. The method of claim 1 , wherein the titania nanoparticle product comprises titania nanoparticles with an average hydrodynamic diameter of less than 100 nm.

15. The method of claim 1 , wherein the titania nanoparticle product comprises titania nanoparticles having anatase phase crystal domains.

16. The method of claim 1 ,

wherein the titania nanoparticle product comprises a titanate of the form H v M x Ti y O z ,

wherein M is a tetraalkylammonium ion, v is an integer, and x, y, and z are non-zero integers.

17. A method for forming a coating, the method comprising forming said coating by depositing, in a layer by layer fashion, a first deposition solution comprising a polyelectrolyte and a second deposition solution comprising the titania nanoparticle product prepared according to claim 1 , wherein the refractive index of the coating is greater than 1.95.

18. The method of claim 17 , wherein the method further comprises exposing the coating to heat sufficient for calcination, wherein the calcination results in an increased refractive index and improved mechanical durability of the coating.