Formation of Double Shells with Different Porosity on Silica Nanocores#

We report on the preparation of hierarchically doubled shells of different porosity on monodispersive silica nanocores by the direct formation of the outer shell with larger mesopores (D > similar to 2.5 nm) on the surface of the initial single shell of smaller mesopores (D < similar to 2.5 nm). An organic template solution containing cetyltrimethylammonium bromide, 1,3,5-trimethylbenzene, and decane was used for the formation of the larger mesoporous shells, while the initial shell was prepared with the use of only one type of structure-directing agent, namely cetyltrimethylammonium bromide. The resulting core-shell silica nanoparticles are spherical, monodispersive, and show a distinct bimodal porosity. Pore sizes of those shells were easily controlled by varying the molar ratio of the pore expansion agents.