Hollow spheres with tailored shell structures and large internal voids are attractive materials as high-performance catalyst supports, biomaterials, photonic-band-gap materials, thermal and acoustical insulation materials, and electrode materials. Various types of hollow spheres with different compositions, such as polymer, silica, carbon, metal, or metal oxide, can be synthesized by a number of methods, using vesicles, emulsions, spray-drying, hydrothermal reduction, layer-by-layer assembly, and hard templating methods.'11 Among such systems, hollow carbon spheres (HCS), especially those with graphitic shells, are very attractive owing to their special properties, that is, good electrical conductivity, outstanding thermal stability, and satisfactory oxidation resistance at moderate temperature.
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