Synthesis of SiOx@CdS core-shell nanoparticles by simple thermal decomposition approach and studies on their optical properties

SiOx@CdS core-shell nanoparticles have been synthesized by a simple thermal decomposition approach. The synthesis involves two steps. In the first step, SiOx spheres were synthesized using StÖber's process. Then, cadmium sulfide nanoparticles were deposited on the SiOx spheres by the thermal decomposition of cadmium acetate and thiourea in ethylene glycol at 180 °C. Electron microscopy results show uniform deposition of cadmium sulfide nanoparticles on the surface of SiOx spheres. Electron diffraction patterns confirm crystalline nature of the cadmium sulfide nanoparticles on silica and high resolution transmission electron microscopy images clearly show the lattice fringes due to cubic cadmium sulfide. Diffuse reflectance spectroscopy results show blue shift of band gap absorption of SiOx@CdS core-shell nanoparticles with respect to bulk cadmium sulfide and this is attributed to quantum size effect. Photoluminescence results show enhancement in intensity of band edge emission and weaker emission due to surface defects in SiOx@CdS core-shell nanoparticles compared to pure cadmium sulfide nanoparticles.