Synthesis of monodisperse silica spheres with solid core and mesoporous shell: Morphological control of mesopores

Monodisperse spherical silica particles with solid core and mesoporous shell were synthesized by adopting silica particles as core host components and surfactant molecules as structure-directing agents for the mesoporous shell. Here, two different types of surfactant molecules, octadecyltrimethoxysilane (C₁₈-TMS) and cetyltrimethylammonium bromide (C₁₆-TMABr) were utilized as porogens for the formation of mesoporous shell over the spherical silica particles. While the C₁₈-TMS generated solid core/disordered mesoporous shell (SCDMS) silica spheres, the C₁₆-TMABr produced solid core/ordered mesoporous shell (SCOMS) silica spheres. Interestingly, the mesoporous channels generated in the SCOMS silica spheres were in the direction perpendicular to the silica surface. Also, the mesopores of the SCOMS silica spheres were expanded by addition of 1,3,5-trimethylbenzene (TMB) and decane mixture. The core sizes, shell thickness, and nanoporosity of the silica particles were controlled by monitoring the size of the silica sphere core, the amount and ratio of TEOS and C₁₈-TMS or C₁₆-TMABr added, additives and the thermal treatment.