Hollow Titania Spheres from Layered Precursor Deposition on Sacrificial Colloidal Core Particles

Abstract

The preparation of monodisperse hollow titania spheres with defined diameter, wall thickness and crystal phase is reported. The hollow spheres have been produced by the layered deposition of a water-soluble titania precursor, e.g. titanium(IV) bis (ammonium lactato) dihydroxide (TALH), in alternation with poly(diallydimethylammonium chloride) (PDADMAC) onto submicrometer-sized template particles e.g. polystyrene (PS) particles, followed by calcination at elevated temperatures. the layer-by-layer growth of the coating on the colloid particles was observed by microelectrophoresis and transmission electron microscopy (TEM). Calcination of the TALH/PDADMAC-coated particles resulted in intact, hollow titania spheres, as confirmed by scanning electron microscopy (SEM) and TEM. Calcining the coated particles at 450 or 950° C resulted in hollow sphere consisting of titania in anatase or rutile form, respectively. Nanometer-level control over the sphere wall thickness was achieved by varying the number of layers deposited on the PS particles. The hollow titania spheres produced can be used in photonic applications, where hollow spheres of high refractive index materials are desired, and in catalysis.