Porous titanium dioxide coatings and methods of forming porous titanium dioxide coatings having improved photocatalytic activity

1. A method of forming a porous, pure anatase titanium dioxide coating on a substrate, comprising:

preparing a titanium dioxide sol-gel composition comprising at least one porosity agent;

coating the substrate with the sol-gel composition; and

removing the porosity agent.

2. The method of claim 1 , wherein said porosity agent is polyethylene glycol.

3. The method of claim 2 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 5 wt % of the total weight of the sol-gel composition.

4. The method of claim 3 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 10 wt % of the total weight of the sol-gel composition.

5. The method of claim 4 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 20 wt % of the total weight of the sol-gel composition.

6. The method of claim 1 , wherein the substrate comprises a glass substrate.

7. The method of claim 6 , wherein the glass substrate is chosen from clear or low-iron glass.

8. The method of claim 1 , wherein the porosity agent is removed by heating the coated substrate at a temperature greater than about 600° C.

9. A method of improving at least one of antimicrobial properties, self-cleaning properties, hydrophilicity, and temperability of a pure anatase titanium dioxide coating, comprising:

preparing a titanium dioxide sol-gel composition comprising at least one porosity agent;

coating a substrate with the sol-gel composition; and

heating the coated substrate to remove the porosity agent without forming rutile phase titanium dioxide.

10. The method of claim 9 , wherein the porosity agent is polyethylene glycol.

11. The method of claim 10 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 5 wt % of the total weight of the sol-gel composition.

12. The method of claim 11 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 10 wt % of the total weight of the sol-gel composition.

13. The method of claim 12 , wherein the polyethylene glycol is present in the sol-gel composition in an amount comprising at least about 20 wt % of the total weight of the sol-gel composition.

14. The method of claim 9 , wherein said substrate is chosen from clear or low-iron glass.

15. A substrate comprising a porous anatase titanium dioxide coating, wherein the porous anatase titanium dioxide coating comprises a water contact angle less than about 12°.

16. The substrate comprising a porous anatase titanium dioxide coating according to claim 15 , wherein the porous anatase titanium dioxide coating comprises a water contact angle less than about 10°.

17. The substrate comprising a porous anatase titanium dioxide coating according to claim 15 , wherein the substrate is a glass substrate.

18. The substrate comprising a porous anatase titanium dioxide coating according to claim 17 , wherein the porous anatase titanium dioxide coating comprises a visible light transmission greater than about 75%.

19. The substrate comprising a porous anatase titanium dioxide coating according to claim 17 , wherein the porous anatase titanium dioxide coating comprises a reflection of incident light at the porous anatase titanium dioxide coating of less than about 26.5%.

20. A porous, pure anatase titanium dioxide coating having at least one of improved antimicrobial properties, improved self-cleaning properties, improved hydrophilicity, and improved temperability, wherein said porous, pure anatase titanium dioxide coating is made by:

preparing a titanium dioxide sol-gel composition comprising at least one porosity agent;

coating a substrate with the sol-gel composition; and removing the porosity agent.