Multilayered Titania, Silica, and Laponite Nanoparticle Coatings on Polystyrene Colloidal Templates and Resulting Inorganic Hollow Spheres

The applicability of the layer-by-layer (LbL) technique for the formation of a range of polymer-core inorganic-shell particles and inorganic hollow spheres is demonstrated. Titanium dioxide, silica, and Laponite nanoparticles were used as the inorganic building blocks for multilayer formation on polystyrene (PS) sphere templates. Composite organic−inorganic particles were formed by the controlled assembly of the preformed nanoparticles in alternation with oppositely charged polyelectrolytes onto PS microspheres. The influence of nanoparticle type, shape (spherical to sheetlike), and size (3−100 nm), and the diameter of the PS sphere templates (210−640 nm) on the formation of multilayer shells was examined by transmission and scanning electron microscopy. In addition, the LbL technique for coating polymer spheres has been shown to be adaptable with small variations in the coating steps used to optimize the nanoparticle coatings of the different materials. For example, the number of polyelectrolyte multilayers separating the nanoparticle layers, and the number of nanoparticle/polyelectrolyte deposition cycles were varied to generate uniformly coated nanocomposite spheres. These hybrid core−shell particles were subsequently calcined to create well-defined hollow spheres with predetermined diameters. Such hollow spheres may find application in diverse areas, ranging from photonics to fillers and pigments to microencapsulation.