Chem. Mater. 2005, 17, 6805-6813

Synthesis and Characterization of Three-Dimensionally Ordered Macroporous Carbon/Titania Nanoparticle Composites

Zhiyong Wang, Nicholas S. Ergang, Mohammed A. Al-Daous, and Andreas Stein*

Department of Chemistry, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455

Abstract

Three-dimensionally ordered macroporous (3DOM) carbon/titania nanoparticle composites were prepared in a program aimed at developing methods for assembling integrated multifunctional porous materials. The host material, 3DOM carbon, was synthesized by colloidal crystal templating with poly(methyl methacrylate) spheres, using a resorcinol-formaldehyde (RF) sol as a carbon source. This 3DOM support was pre-treated with nitric acid to enhance the surface charge, and surface functional groups were characterized by Fourier-transform infrared spectroscopy and acid-base titration. The modified support was then pre-coated with multiple layers of polyelectrolytes, and finally coated with TiO₂ nanoparticles by hydrothermal reaction of an aqueous solution of titanium(IV) bis(ammonium lactato) dihydroxide (TAL) at varying concentrations, temperatures and reaction times. Higher hydrothermal reaction temperatures favored the formation of larger TiO₂ crystallites. The coating thickness increased at higher Ti precursor concentrations. Powder X-ray diffraction patterns indicated that the phase composition of the TiO₂ layer varied with different synthesis conditions. Scanning electron microscopy images revealed that the most uniform coating of TiO₂ was obtained at a reaction temperature of 200 ˚C with a TAL concentration of 0.2 M. This sample was characterized in more detail by transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and nitrogen-sorption techniques.