The present disclosure is generally related to methods of forming metal oxide nanostructures and nanostructures thereof, in particular, titania nanostructures.
Titania is a well-know material with a broad range of applications including photonic crystals, photocatalysts, and photovoltaic cells. While several methods are known for nanostructuring titania, including thermal imprinting, many challenges remain mainly due to the properties of commonly-used sol-gel type titania precursors. The sol-gel type titania precursors are formed at low pH (approximately 1), are generally highly reactive and moisture sensitive, and form gels. They are often diluted in organic solvents during the sol-gel reaction to mitigate gelation, which causes large volume shrinkages during the nanostructuring process. Further, they are usually highly viscous and require high pressure for the nanostructuring process. Prior work directed toward thermal imprinting titania nanostructures used sol-gel type precursors [C. Goh, K. M. Coakley, M. D. McGehee, Nano Lett. 5, 1545 (2005), P. Yang, T. Deng, D. Zhao, P. Feng, D. Pine, B. F. Chmelka, G. M. Whitesides, G. D. Stucky, Science, 282, 2244, (1998)] or a mixture of titania colloidal particles and polymers [M. Wang, H.-G. Braun, and E. Meyer, Chem. Mater. 14, 4812 (2002)].