Production of hollow microspheres from nanostructured composite particles

Uniform inorganic and hybrid inorganic-organic hollow microspheres have been produced by coating colloidal core templates with alternating layers of oppositely charged nanoparticles and polymer, and thereafter removing the core either by heating or chemical treatment. The multilayers were constructed by consecutively depositing the nanoparticles and polymer onto the colloidal templates, utilizing the electrostatic attraction between the particles and polymer for layer build-up. Hollow silica spheres were obtained by calcining polymer latex spheres coated with multilayers of silica nanoparticles (SiO2) bridged by polymer [poly-(diallyldimethylammonium chloride) (PDADMAC)]. Exposure of SiO2/PDADMAC multilayer-coated polymer latex colloids to acidic solutions, dimethyl sulfoxide, or tetrahydrofuran yielded hollow composite silica-polymer spheres. The fabricated hollow spheres have been characterized using scanning and transmission electron microscopy. The approach employed is well suited to generating hollow spheres of controlled diameter, wall thickness, and composition.