Uniform Mesoporous Anatase-Brookite Biphase TiO2 Hollow Spheres with High Crystallinity via Ostwald Ripening

With biocompatible oxalic acid as chelating agent, uniform titania hollow spheres were solvothermally obtained. The hollow spheres are composed of 23% brookite phase and 77% anatase phase with good crystallinity. These biphase hollow spheres, possessing large surface area and mesoporousity, form via a typical asymmetric Ostwald ripening mechanism. During this facile process, the oxalic acid plays essential roles in producing the hollow sphere structure, both maintaining the uniformity of the spherical structure and transferring titanium ions during the Ostwald ripening process.