Synthesis of urchin-like CdWO₄ microspheres via a facile template free hydrothermal method

Urchin-like CdWO₄ microspheres with hollow interiors have been successfully synthesized by a facile template free hydrothermal treatment method. The urchin-like CdWO₄ hollow spheres are composed of radiatively assembled single-crystalline CdWO₄ nanorods with lengths of several hundred nm and widths of 25-80 nm. The samples exhibit a blue-green emission in the range of 450-500 nm with the emission peak centered around 470 nm when excited at 293 nm. The effects of the preparation conditions such as the hydrothermal synthesis temperature, hydrothermal synthesis time, and the dosage of urea on the crystalline phase as well as morphology of final products have been systematically investigated. The successful synthesis of CdWO₄ with a uniform urchin-like morphology relies on not only the choice of peroxo-polytungstic acid precursor, but also a controlled pH adjustment with the help of urea, both of which contribute to a homogenous nucleation and crystal growth process. It is also found that increasing the synthesis temperature, time and dosage of urea will enhance the photoluminescence (PL) emission of resultant materials. Our contribution provides a simple approach to synthesize CdWO₄ materials with hierarchical architectures and potential applications as detectors in X-ray devices.