Revealing the Formation of Well-Dispersed Polystyrene@ZIF-8 Core–Shell Nanoparticles by Analytical Ultracentrifugation

Significant progress has been made in the synthesis and application of core–shell nanoparticles in the past decade. But particle agglomerations are hard to avoid as the formation mechanisms of core–shell nanoparticles are still vague and not clear even for the simplest and most straightforward hard-templating method. Here, analytical ultracentrifugation (AUC) is applied to investigate the formation of polystyrene@ZIF-8 core–shell nanoparticles, as a model to understand the hard-templating method. It has been found that the concentration of the ZIF-8 precursor influences both the ZIF-8 shell formation and the agglomeration of the polystyrene (PS) template. An overdiluted ZIF-8 precursor is not suitable for ZIF-8 shell formation, while a highly concentrated ZIF-8 precursor causes strong aggregation of the PS core. By applying the optimal precursor concentration identified by AUC, well-dispersed polystyrene@ZIF-8 core–shell nanoparticles can be obtained.