Ordered Macroporous Rutile Titanium Dioxide By Emulsion Templating

Vinothan N. Manoharan, Arnout Imhof, James D. Thorne, and David J. Pine

(Department of Chemical Engineering, University of
California, Santa Barbara 93106; AI, Van der Waals-Zeeman Institute,
University of Amsterdam, The Netherlands)

We present a technique for producing macroporous rutile titanium dioxide containing ordered spherica pores with diameters from 100 to 1000 nanometers. We make these materials by a sol-gel process with self-assembled colloidal emulsion droplets as templates. The emulsion droplets have sufficient monodispersity and stability to arrange themselves in small face-centered-cubic crystallites when concentrated in a sol. Our method differs from others involving colloidal crystals as templtes in that our sol-gel route allows us to make monolithic (centimeter scale) materials with high index of refraction contrast (2.8:1, compared to 2.4:1 for other macroporous titania materials). The resulting structures show broad, deep minima in the transmission spectra for visible light.