| Abstract
| - A procedure has been developed to coat colloidal polystyrene spheres with a smooth and well-definedlayer of amorphous titanium dioxide. The thickness of the coating can be easily varied from a few nanometersupward and can be increased further by seeded growth. The resulting composite particles are verymonodisperse. The core−shell particles can be turned into spherical hollow titania shells by dissolutionof the polystyrene cores in suspension or by calcination of the dried particles in a furnace. Calcination alsocrystallizes the titania into its anatase form. The coated particles were characterized with electrophoresis,thermogravimetric analysis, X-ray diffraction, electron microscopy, and light scattering. We find that thecoating strongly densifies when the particles are dried but that it is not dense and about twice as thickwhen the particles are still in suspension. Calcination results in spherical shells composed of a densearrangement of TiO2 (anatase) nanocrystals. This way, we obtained colloidal crystals consisting of hollowshells.
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