Methods for producing metal oxide films
Described herein is a technology for the creation of “smooth” metal oxide films or coatings using organic cross-linking agents to enable low-temperature sintering. These metal oxide films can be used in conjunction with low-melting temperature substrates, such as plastics, metal, metal oxide, and glass, providing exquisite control over surface roughness.
1. A method for producing a patterned structure of microchannels on a substrate, comprising the steps of: (a) coating the substrate with a layer comprising a metal oxide film precursor and a linking agent precursor; (b) exposing the coated surface to patterned actinic radiation that activates the linking agent precursor in a patterned fashion to form a linking agent, the linking agent reacting with the metal oxide film precursor to produce a patterned structure of microchannels comprising a metal oxide film.
2. The method of claim 1 , wherein the metal oxide film precursor comprises metal oxide particles.
3. The method of claim 1 , wherein the metal oxide film precursor is a metal oxide sol gel.
4. The method of claim 1 , wherein the metal oxide is selected from the group consisting of Aluminum Oxide (Al 2 O 3 ), Zinc(II) Oxide (ZnO), Titanium(II) Oxide (TiO), Titanium(III) Oxide (Ti 2 O 3 ), Titanium(IV) Oxide (TiO 2 ), Cerium(III) Oxide (Ce 2 O 3 ), and Cerium(IV) Oxide (CeO2).
5. The method of claim 2 , wherein the particles are nanoparticles.
6. The method of claim 2 , wherein the particles are microparticles.
7. The method of claim 3 , wherein the sol gel is formed by hydrolyzing a metal alkoxide solution by acid catalysis in situ.
8. The method of claim 7 , wherein the metal alkoxide is a titanium alkoxide.
9. The method of claim 8 , wherein the titanium alkoxide is titanium isopropoxide.
10. The method of claim 1 , wherein the linking agent precursor is a protected oligocarboxylic acid.
11. The method of claim 10 , wherein the oligocarboxylic acid is a di- or tri-carboxylic acid.
12. The method of claim 11 , wherein the oligocarboxylic acid is terephthalic acid or trimeric acid.
13. The method of claim 10 , wherein the oligocarboxylic acid comprises n carboxylic acid groups, and n−1 of those groups are protected.
14. The method of claim 13 , wherein the linking agent precursor is activated by deprotecting at least a second carboxylic acid group.
15. The method of claim 10 wherein the oligocarboxylic acid is a fully protected oligocarboxylic acid.
16. The method of claim 15 wherein the linking agent precursor is activated by deprotecting at least two protected carboxylic acid groups.
17. The method of claim 1 , wherein the linking agent precursor is directly activated.
18. The method of claim 17 , wherein the linking agent precursor comprises an o-nitrobenzoyl ester group that is directly cleaved by light to release o-nitrobenzaldehyde.
19. The method of claim 1 , wherein the linking agent precursor is indirectly activated.
20. The method of claim 19 , further comprising applying a layer comprising a photoacid generator prior to step (b).
21. The method of claim 20 , wherein the photoacid generator is activated in step (b) by exposure to actinic radiation, thereby generating a superacid that cleaves a protecting group on the linking agent precursor to form a linking agent.
22. The method of claim 21 , wherein the photoacid generator is diphenyliodinium hexafluoroantimonate and the actinic radiation is visible light, and wherein exposure of the photoacid generator to visible light results in the creation of hexafluoroantimonic acid.
23. The method of claim 1 , wherein the metal oxide film precursor and linking agent precursor are provided as a mixture.
24. The method of claim 1 , wherein the linking agent precursor is added to the metal oxide film precursor.