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

Abstract

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.