Synthesis of Zn2SiO4@ZnO Core-Shell Nanoparticles and the Effect of Shell Thickness on Band-gap Transition

A combined sol-gel and annealing method was used for the synthesis of Zinc Silicate-Zinc Oxide (Zn2SiO4@ZnO) core-shell nanoparticles with high bandgap value. First, different thicknesses of ZnSiO3 shell were successfully coated on to ZnO nanoparticle surfaces by varying the Na2SiO3/ZnCl2 precursor concentrations. Then, by applying a relatively low annealing temperature (780 °C), the amorphous ZnSiO3 reacted with ZnO to form crystalline Zn2SiO4 shell. The structure and elements of the core-shell nanoparticles were characterized by TEM, XRD, EDS, and the band gap values were measured by UV–Vis spectroscopy. The Zn2SiO4@ZnO nanoparticles showed mostly spherical core-shell morphology and high band gap value (Eg = 5.5 eV) at high Zn2SiO4 loading, which are promising for semiconductor and luminescent applications.