Evaluating the internal structure of monodispersed mesoporous silica spheres by small-angle X-ray scattering

Abstract Although the spherical morphology and mesoporous structure of monodispersed mesoporous silica spheres (MMSS) have been extensively investigated by scanning electron microscopy and transmission electron microscopy, the statistical distribution of mesopores from the surface to the center of a particle, average density of the spheres, and volume fraction of silica have not been investigated. Herein, small-angle X-ray scattering (SAXS) was performed on aqueous dispersions of MMSS with diverse sphere diameter, mesopore radius, and nanoparticle inclusion. The SAXS spectra fitted by a spherical model showed that the mesopores were homogeneously distributed in each particle. The mass density of the MMSS was obtained from the zero scattering intensity, and the volume fraction of silica was calculated considering the absorbed water in the pores. While the sphere diameter and mesopore radius had little influence, nanoparticle inclusion induced an increase in the volume fraction of silica.