Cross-linked, luminescent spherical colloidal and hollow-shell particles

Luminescent core-shell particles were prepared by the layer-by-layer deposition of polystyrenesulfonate (PSS) and water-soluble ionene precursor polymers containing fluorene units (PI) onto spherical colloidal particles. Subsequent cross-linking of the PI in the multilayer shell formed the luminescent conjugated oligo-fluorenes. In a further step, removal of the PI/PSS multilayer coated core yielded luminescent hollow capsules. The formation, characterization, and properties of the PI/PSS-coated colloids and PI/PSS hollow capsules have been investigated by electrophoresis (EPM), single particle light scattering (SPLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and cyclic voltammetry (CV). EPM and SPLS measurements confirmed the regular deposition of PI/PSS multilayers on the particles, while TEM and AFM demonstrated the formation of hollow capsules composed of PI/PSS multilayers. CV experiments verified cross-linking of the multilayers, which showed an irreversible oxidation process. The procedure employed permits the incorporation of luminescent polymer materials into cross-linked multilayer shells on high surface area colloidal particles and the preparation of luminescent free-standing, three-dimensional hollow capsules after core removal.