Tunable Surface Oxidation States in Si/SiO_2 Nanostructures Prepared from Si/SiO_2 Mixtures and Phenol Hydroxylation Activity

摘要

Heterogeneous catalysts, adsorbents, and solid-state electronic sensors are derived from either single or multiple metal oxides sometimes combined with high surface area oxides such as silica or alumina. The surface oxidation state of these solids, at least in part, determines their performance. Current materials preparation techniques require postsynthesis treatment(s) to achieve the desired surface oxidation state(s). We have recently reported the preparation of nonporous nanoparticles, which appear spherical and nearly monodisperse from the reaction/interaction of Si and SiO_2. Herein , employing these nanospheres, we show arresting data on preparing a solid with the desired average surface oxidation state without a postsynthesis treatment. The average surface oxidation state without a postsynthesis treatment. The average surface oxidation states of the solid were adjusted by varying the amounts of the metalloid ions/ atoms in the starting materials. The inherent simplicity of the technique is general to many mixed metal oxides without the need for liquid solvents, and thus the preparation is environmentally friendly. Finally, supported metal oxides can be prepared in two steps, which therefore makes the new technique economically attractive as a replacement fro the current preparation methods that often require up to five steps for a given synthesis. Furthermore, within this study, we also suggest a surprising explanation for the activity of fumed silica.