Hybrid Core–Shell Microparticles Based on Vaterite Polymorphs Assembled via Freezing-Induced Loading

Abstract

The hybrid core–shell system was fabricated based on pre-synthesized vaterite microparticles and iron oxide nanoparticles applying two technical approaches: physical adsorption of the nanoparticles from a suspension at room temperature and a newly developed method of freezing-induced loading. A combination of transmission electron microscopy and X-ray diffraction paired with precision nanomanipulation allows us to analyze the inner structure of the hybrid system, indicating that both vaterite and calcite phases were covered by Fe3O4 shells. The freezing-induced loading was found to be more preferable due to the formation of the core–shell nanoparticles in a more stable polymorphic composition of calcium carbonate when compared to physical adsorption.