Nanoparticulate Titanium Dioxide Particles with a Crystalline Core, a Metal-Oxide Shell and an Outer Skin Containing Organic Groups, and Method for the Manufacture Thereof

摘要

This invention refers to particles with a crystalline core of titanium dioxide that has an average diameter of ≦̸30 nm measured with the XRD/Scherrer method, a shell made of a metal oxide that has no photocatalytic properties and an outer skin that carries organic radicals. A suspension of these particles is conveniently prepared with a process that encompasses the following steps: The supply of a dispersion that has crystalline titanium dioxide particles having an average diameter of ≦̸30 nm whose surface has been modified with organic groups in solution that contains a dissolved, hydrolytically condensable compound of a metal M whose oxide should form the shell mentioned above, in which case an organic solvent or a mixture of an organic solvent and water is used as solvent, and adjusting the pH of the solution in such a way that a full deagglomeration of the nanoparticles occurs, the stirring of the dispersion in the presence of a sufficient quantity of water for the hydrolytic condensation of the dissolved, hydrolytically condensable compound of the metal M until the organic constituents with which the modified TiO2 particles were coated are displaced, and an oxidic shell of the metal M has formed, and after preferably at least some of the solvent/water from the product obtained has been removed and a surface-modifying component of the oxidic shell and the causing of the formation of an outer skin that has organic groups with the help of this component on the particles has been added.