Zn0@ZnS Core-Shell Nanoparticles via Oxidation of Intermediate Zn0 Nanoparticles

Zn-0@ZnS core-shell nanoparticles were prepared via reduction of ZnCl2 to Zn-0 nanoparticles and subsequent partial oxidation with elemental sulfur. The intermediate, highly reactive Zn-0 nanoparticles were obtained by sodium naphthalenide ([NaNaph]) reduction of ZnCl2 in tetrahydrofuran (THF). After centrifugation, the Zn-0 nanoparticles were redispersed in a solution of sulfur in toluene and oxidized by subsequent heating to reflux. According to electron microscopy (HRTEM, HAADF-STEM), the Zn-0@ZnS core-shell nanoparticles exhibit a mean outer diameter of 12 +/- 4 nm, consisting of an inner Zn-0 core (8 nm in diameter) and a ZnS shell (2 nm in diameter). HRTEM and XRD confirm the crystallinity of both core and shell. The Zn-0@ZnS nanostructure shows synergistic properties of core and shell: the ZnS layer efficiently passivates the reactive Zn-0 metal core against oxidation, whereas the optical properties point to dominating metallic behavior of the Zn-0 metal core despite of the ZnS shell.