Oriented Nanocrystal Mosaic in Monodispersed CaCO3 Microspheres with Functional Organic Molecules

Monodispersed microspheres of vaterite CaCO3 with a diameter adjusted to the range of 1-10 mu m were produced through an amorphous intermediate with polystyrene sulfate. Whereas the microspheres were composed of nanocrystals with a diameter of ca. 20 nm covered with the organic polymer, the crystallographic direction of the entire sphere was evaluated to be macroscopically uniform from its single-crystalline features on polarization anisotropy and morphological evolution into a hexagonal shape with an additional growth process. A particular mosaic with a radially grown backbone structure consisting of oriented nanocrystals was suggested to exist in the microspheres from the electron diffraction patterns. The rigid mosaic framework was covered with a flexible organic component. Thus, various functional organic molecules including hydrophilic and hydrophobic dyes were successfully introduced into the microspheres due to the amphiphilic nature of the organic phase.