WO 3 · n H 2 O Crystals with Controllable Morphology/Phase and Their Optical Absorption Properties.

In this work, a one-step hydrothermal route is developed to prepare WO 3 · n H 2 O crystals with various morphology/phases, for which any surfactants, templates, or structure-directing agents are not used. Five types of WO 3 · n H 2 O crystals, including o-WO 3 ·H 2 O nanoplates, rectangular m-WO 3 nanosheets, o-WO 3 ·0.33H 2 O microspheres, h-WO 3 nanorods, and bundle-like h-WO 3 hierarchical structures, are successfully obtained by adjusting the amount of H 2 SO 4 and reaction temperature. According to the experimental results, the formation mechanism for various WO 3 · n H 2 O species is proposed. In addition, the optical absorption properties of these WO 3 · n H 2 O crystals are also investigated by UV-vis absorption spectra.