Synthesis of hierarchically nanostructured TiO2 spheres with tunable morphologies based on a novel amphiphilic polymer precursor and their use for heavy metal ion sequestration

TiO2 has several important applications but its structures and morphologies are usually difficult to tune because of the uncontrollable and fast sol–gel reactions of current TiO2 precursors. This paper presents a facile and general method for the fabrication of hierarchically nanostructured TiO2 spheres with controllable morphologies based on a novel amphiphilic polymeric TiO2 precursor. By adjusting the conditions of hydrolysis and condensation reactions of this precursor, TiO2 spheres with various morphologies, including hierarchical porous, hollow, and raspberry-like structures, can be easily produced. The as-obtained spheres have hierarchical structures with specific surface areas larger than 200 m2 g−1 and mean pore sizes of several nanometers. The mechanism study indicates that the amphiphilic polymer assists the aggregation, abruption, migration, and crystallization of certain TiO2 units during hydrolysis and condensation and contributes to the formation of TiO2 spheres with various morphologies. The as-obtained specific hierarchically nanostructured TiO2 spheres exhibit a considerably higher adsorption capability for Cr(VI) anions in aqueous solution compared with the previously reported TiO2 nanomaterials, showing a high potential for heavy metal ion sequestration applications.