Molecular Enrichment in the Cavity of Hollow Mesoporous Silica Particles: the Effect of the Cavity Size

ABSTRACT Hollow particles have attracted attention in various applications such as adsorbents and catalytic supports owing to their unique functions derived from their morphology. Molecules are reported to be concentrated within hollow cavities (i.e., molecular enrichment), which improves the performance of functional materials such as adsorbents and catalysts. However, the concentration of molecules localized within hollow cavities has not been experimentally quantified so far. In the present work, the enrichment of rhodamine B (RhB) in the cavities of hollow mesoporous silica particles (Hollow m SiO 2 ) is quantitatively demonstrated. Three different types of particles (spherical, core‐shell, and hollow particles) with comparable sizes are prepared to estimate the molecular concentration in the hollow cavity. Through adsorption experiments of RhB with each particle, it is revealed that the RhB concentration in the hollow cavity is much higher than in the bulk solutions. The enrichment is also found to be enhanced with a decrease in cavity size. The quantitative methodology of molecular concentration in hollow cavities is applicable to other molecules such as reactants for catalytic reactions. This reveals the impact of the enrichment effect on the performance of various applications, achieving appropriate design of hollow‐structured materials.