Hydrothermal Synthesis of Bi₂WO₆ Uniform Hierarchical Microspheres

Bi 2 WO 6 uniform hierarchical microspheres were grown on a large scale at 180 °C by a simple hydrothermal method with the help of the surfactant poly(vinyl pyrrolidone) (PVP). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the product. The result indicated that three-dimensional (3D) Bi 2 WO 6 microspheres were constructed layer-by-layer from a large number of two-dimensional (2D) sheets, which were composed of numerous interconnected square nanoplates with a mean side length of 65 nm. Pore-size distribution analysis showed that both mesopores and macropores existed in the 3D microstructures. The formation mechanism was discussed on the basis of the results of time-dependent experiments. It was demonstrated that PVP played a key role in the formation of such hierarchical microspheres. By adjusting the amount of PVP, Bi 2 WO 6 with different morphologies can be attained accordingly. UV−vis spectroscopy was further employed to estimate the band gap energy of the hierarchical structures. Our work may shed some light on the design of other well-defined complex nanostructures, and the as-grown architectures may have potential applications.