WO₃·nH₂O Crystals with Controllable Morphology/Phase and Their Optical Absorption Properties

In this work, a one-step hydrothermal route is developed to prepare WO₃·nH₂O crystals with various morphology/phases, for which any surfactants, templates, or structure-directing agents are not used. Five types of WO₃·nH₂O crystals, including o-WO₃·H₂O nanoplates, rectangular m-WO₃ nanosheets, o-WO₃·0.33H₂O microspheres, h-WO₃ nanorods, and bundle-like h-WO₃ hierarchical structures, are successfully obtained by adjusting the amount of H₂SO₄ and reaction temperature. According to the experimental results, the formation mechanism for various WO₃·nH₂O species is proposed. In addition, the optical absorption properties of these WO₃·nH₂O crystals are also investigated by UV-vis absorption spectra.