Swellable Microsphere of a Layered Silicate Produced by Using Monodispersed Silica Particles

Abstract

Monodispersed spherical particles are potentially available for various applications as building blocks for photonic crystals, chromatography stationary phase, and drug support for controlled release. Immobilization of a molecular recognizable unit to the surface of the spherical particles is important in such applications. Here we report that silica spheres of submicrometer size were covered by a swellable layered silicate, which plays a role in accommodating cationic species. The coverage was conduced by using colloidal monodispersed silica spheres as a sacrificial template in the presence of urea and layered silicate sources (LiF and MgCl2) at 373 K. X-ray diffraction peaks ascribed to hectorite (smectite group of layered clay) were observed in the resulting solid. The zeta potential distribution of the resulting solid had a single peak and shifted from that of the original silica. Transmission electron microscopy (TEM) observations revealed that stacks of the silicate layers lay on the surface of the silica core. Quantitative ion exchange reactions of the interlayer cations with a cationic surfactant were shown. The layered silicate was firmly glued onto the silica particles because the silicate with a cationic dye did not flake off from the product.