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

TLDR

Hollow spheres can be applied in photonics, as fillers and pigments, and for microencapsulation. Layer‑by‑layer assembly of TiO₂, silica, or Laponite nanoparticles with oppositely charged polyelectrolytes on polystyrene spheres, followed by controlled multilayer deposition and calcination, produces uniform inorganic shells and hollow spheres of tunable size. The study shows that LbL assembly yields polymer‑core inorganic‑shell particles and hollow spheres, and that small adjustments to coating steps optimize nanoparticle coatings for different materials.

Abstract

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.