Hydrothermal synthesis of hierarchical TiO₂ microspheres using a novel titanium complex coordinated by picolinic acid

Phase- and morphology-control of TiO₂ was performed by a facile hydrothermal method using a novel water-soluble titaniumpicolinato complex as a precursor. Single-phase rutile or brookite type titania can be obtained by tailoring the pH of the complex solution. Rutile with a hierarchical microstructure was synthesized using an excess amount of ligand as an additive and the final product consisted of microspheres with mesopores formed by a self-assembly of nanorods. The anisotropic growth of nanorods with a high aspect ratio was explained by a capping mechanism.