Room Temperature Synthesis, Growth Mechanism, Photocatalytic and Photoluminescence Properties of Cadmium Molybdate Core-Shell Microspheres

In this paper, we report the first synthesis of homogeneous core-shell CdMoO4 microspheres on a large scale by a facile aqueous solution route with the assistance of sodium dodecyl sulfate (SDS) at room temperature. The as-synthesized product is characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, UV-vis absorption spectroscopy, and photoluminescence spectroscopy. The core-shell microspheres have an average diameter of about 4 mu m and the shell has a uniform thickness of about 200 run. The shell is composed of single-crystalline nanoparticles 50 nm in size. The effect of various reaction conditions on the morphology and size of CdMoO4 products is investigated. The results show that different kinds of surfactants, the concentration of SDS, and reaction times are crucial factors for the formation of core-shell CdMoO4 microspheres. A possible three-step growth mechanism is presented for the formation of homogeneous core-shell CdMoO4 microspheres. The calcined core-shell CdMoO4 microspheres at 500 degrees C for 2 h exhibit an excellent photocatalytic activity in the degradation of rhodamine B (RhB) under UV light irradiation. The photodegradation of RhB fits the first-order kinetics with K of 0.048 and 0.013 min(-1) for the calcined and uncalcined core-shell microspheres, respectively. Photoluminescence measurement shows a strong and broad blue emission peak of 354 nm for the core-shell CdMoO4 microspheres. The successful synthesis of core-shell CdMoO4 microspheres may provide some insight into the design of homogeneous core-shell structures of molybdates for potential applications in photocatalysts and optical devices.