Water-soluble ZnS:Mn/ZnS core/shell nanoparticles prepared by a novel two-step method

ZnS:Mn/ZnS core/shell nanoparticles were synthesized by a novel two-step method in aqueous solution. First, oleic acid-coated ZnS:Mn nanoparticles with narrow size distribution were prepared by solvothermal method. Then the as-synthesized ZnS:Mn nanoparticles were changed into water-soluble ones through ligand exchange. ZnS shell was finally deposited upon the surfaces of the ZnS:Mn cores in the aqueous solution using mercaptopropionic acid (MPA) as capping/stabilizing agent. Optical property and structure of the ZnS:Mn/ZnS core/shell nanoparticles were characterized by UV–visible absorption spectra, photoluminescence spectroscopy, transmission electron microscopy and X-ray diffraction. Results show that the ZnS:Mn/ZnS core/shell nanoparticles are highly crystalline and nearly monodisperse. Furthermore, the core/shell nanoparticles are water-soluble and have improved fluorescence property, indicating their potential application in biological labeling.