Precisely Designed Synthesis of Hollow Zn2SiO4 Particles from ZnO/SiO2 Core/Shell Particles with Varied Silica Thicknesses

Abstract

ZnO/SiO₂ core/shell particles were prepared by the hydrolysis and condensation of tetraethyl orthosilicate on ZnO nanoparticles (particle size of ca. 50–200 nm) and ZnO nanorods (diameter of 124 nm and length of 400–950 nm). The silica shell thickness was varied (28 to 40 nm) to adjust the composition (Si/Zn ratio) by reiterating the coating procedure. Heat treatment of ZnO nanoparticle/SiO₂ core/shell particles with suitable stoichiometry (Si/Zn ratio of 0.5) at 1000 °C resulted in the formation of single-phase Zn₂SiO₄ as hollow particles. The use of ZnO with different morphologies (ZnO nanorods) (leading to ZnO nanorods/SiO₂ core/shell particles) with a Si/Zn ratio of 0.616 confirmed the generality of the synthetic method by the formation of hollow Zn₂SiO₄ nanorods as the main product despite the presence of minor amounts of ZnO. This study demonstrates a systematic structural design to obtain ZnO/SiO₂ core/shell particles with precisely tuned composition and its application to the formation of hollow Zn₂SiO₄ particles of different morphologies.