Preparation and optical properties of alloyed ZnxCd1‐xS/alginate core/shell nanoparticles

ZnxCd1-xS/alginate core/shell nanoparticles were synthesized via a colloidal route by reacting zinc and cadmium ions with sulfide ions, followed by coating with alginate. The crystal structure, morphology, size and optical properties of the core/shell nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, UV/vis and photoluminescent spectra, respectively. The ZnxCd1-xS nanoparticles are spherical and have a cubic structure with a mean crystalline size of 2–4 nm. The band gap of ZnxCd1-xS/alginate core/shell nanoparticles increases with increasing Zn/Cd molar ratio, and the UV/vis absorption blue-shifts correspondingly. Two emissions related to zinc and sulfide ion vacancies were observed for the ZnxCd1-xS/alginate core/shell nanoparticles due to the surface changes from the alginate coating. A cadmium-related emission was observed for both the uncovered ZnxCd1-xS and ZnxCd1-xS/alginate core/shell nanoparticles, which has a significant blue-shift with increasing Zn/Cd molar ratio. Copyright © 2014 John Wiley & Sons, Ltd.