The fabrication of Pt nanoparticles encapsulated in hollow carbon nanospheres using TiO2 nanoparticles as both the photocatalyst and the inorganic mold is demonstrated (see figure). These spheres are found to have high surface area and ultrathin shells with well-developed microporosity, and thus can be used as catalysts. This new imprinting method can be used to synthesize any desired nanostructures using predesigned TiO2 photocatalysts.