A General Method to Coat Colloidal Particles with Titania

We describe a general one-pot method for coating colloidal particles with amorphous Mania. Various colloidal particles such as silica particles, large silver colloids, gibbsite platelets, and polystyrene spheres were successfully coated with a Mania shell. Although there are several ways of coating different particles with Mania in the literature, each of these methods is applicable to only one type of material. The present method is especially useful for giving the opportunity to cover many types of colloidal particles with Mania and forgoes the use of a coupling agent or a precoating step. We can produce particles with a smooth Mania layer of tunable thickness. The monodispersity, which improves during particle growth, and the high refractive index of Mania make these particles potential candidates for photonic crystal applications. We also describe various ways of fabricating hollow Mania shells, which have been intensively studied in the literature for their applications in electronics, catalysis, separations, and diagnostics. Note that our method initially produces amorphous shells on the particles, but these can be easily turned into crystalline Mania by a calcination step. We also find that the growth of Mania is a surface-reaction-limited process.