Tetraalkoxysilane Assisted Self-Emulsification Templating for Mesoporous Silica Nanoparticles with Controlled Mesostructures

Although mesoporous silica nanoparticles (MSNs) have been intensively investigated, their mesostructure and formation mechanism are still a topic of debate. Here, we demonstrate that the formation of MSNs is a result of dynamic two-level template collaborative self-assembly of microemulsion droplets and spherical micelles, whose surfaces are both partly covered by silicate species. The stability of microemulsion droplets spontaneously formed by water-surfactant-tetraalkoxysilanes (TAOS) ternary system determines the final morphology and particle size of MSNs, and we definitively confirms that the dendritic MSNs (DMSNs) with unique hierarchical pore structures is a metastable intermediate product, which could be kinetically transferred to regular MSNs undergoing a fast structural collapse of microemulsion droplets with the continuous consumption of TAOS. Our research further highlights the prominent role of self-emulsification of organic silane reagents in sol-gel chemistry to tune the morphology and structure of final products.