CREATION OF TEMPLATED COMPLEX TOPOLOGICAL MORPHOLOGIES IN COLLOIDAL SILICA

We have developed a new method to create complex monodisperse silicon dioxide particles which contain voids with unique morphologies. These particles are prepared from monodisperse silica spheres (ca. 100 nm) which contain CdS inclusions organized as large patches on the silica sphere surfaces, as small quantum dots within the spheres, as interior spherical shells, or as the central cores of the silica spheres. We create voids with the identical morphology as the CdS inclusions by etching out the CdS inclusions with strong acid. The silica sphere-CdS composite particles are prepared within a microemulsion reaction medium as described in the accompanying paper (Chang, S.-Y.; et al. J. Am. Chem. Soc., preceding paper in this issue). The etched silica particles have craters on their surface, 2.4-nm diameter spherical voids dispersed within the silica spheres, hollow cores, or hollow shells separating silica shells from silica cores. In addition, we have formed unique ellipsoidal cavities within doublets of silica spheres. These doublets were formed through the attachment of silica spheres by CdS patches on the silica surfaces. A silica shell was subsequently grown around the sphere doublets. Etching away the CdS results in ellipsoidal caverns connecting the two spheres of each doublet. These high surface area materials have geometrically tailorable voids and may prove useful as novel catalyst support media.