Visible-light-induced photodegradation of methylene blue using ZnO/CdS heteronanostructures synthesized through a novel thermal decomposition approach

ZnO/CdS heteronanostructures with different shell thicknesses (20–45 nm) have been successfully synthesized by a novel thermal decomposition approach, and the synthesis involves three steps. In the first step, ZnO nanorods were synthesized by homogeneous precipitation method. Then, the surface of ZnO nanorods was functionalized using citric acid as the surface-modifying agent. Finally, the cadmium sulfide (CdS) shell was deposited on the surface-modified ZnO nanorods by the thermal decomposition of cadmium acetate and thiourea in ethylene glycol at 180 °C. The ZnO/CdS heteronanostructures were characterized using X-ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy. SEM and TEM results indicate the deposition of CdS shell on the ZnO nanorods, and DRS results show blue shift of CdS band gap absorption with respect to bulk CdS. PL results show evidence for synergistic interaction between ZnO and CdS. The ZnO/CdS heteronanostructures were explored as catalyst for visible-light-induced photocatalytic degradation of methylene blue in an aqueous solution. The ZnO/CdS samples show higher photocatalytic activity for the degradation of methylene blue compared with pure ZnO nanorods and CdS nanoparticles. The possible mechanism for the formation of CdS shell on the ZnO nanorods and the mechanism for photodegradation of methylene blue are explained in detail.