We demonstrate a facile strategy to access OD nanoparticles to 3D hierarchical structures through a hydrothermal process. The morphology of the products is alkali concentration-dependent, which was systematically investigated. As the NaOH concentration rising, morphology transformations from yolk-shell, hollow hierarchical 3D nanospheres to 1D nanowires are achieved. The crystal phase, the transformation relationship, and the formation mechanisms were studied as well. Furthermore, TiO2 with diversified morphologies was evaluated as styrene oxidation catalyst and showed excellent catalytic activities and chemical stability. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.