Size-tuning of hollow periodic mesoporous organosilica nanoparticles (HPMO-NPs) using a dual templating strategy

Monodispersed hollow periodic mesoporous organosilica nanoparticles (HPMO-NPs) with a controlled core cavity and a periodic mesoporous organosilica (PMO) shell are successfully synthesized using a dual templating approach. The PMO shell synthesized by the sol–gel route exhibits a hybrid organic-inorganic framework based on phenylene bridges. The HPMO spherical nanoparticles with a diameter above 500 nm were characterized using a multiscale approach through TEM, BET, SAXS, and FT-IR. They are shown to offer an open periodic mesoporosity, a hollow cavity with a size tailored by the diameter of the core template, and finally, a high surface area (833 m 2 · g −1 ). In addition, we demonstrate that, through the same approach, the size of these hollow spherical nanoparticles can be tuned. Indeed, sub-50-nm hollow nanoparticles with mesoporous shells have also been obtained. The differences observed in the textural properties of these two sizes of hollow mesoporous nano-objects are discussed. Graphical Abstract In this work, we focused on the synthesis of hollow periodic mesoporous organosilica nanoparticles (HPMO-NPs) with the precise tuning of the core cavity and the PMO shell. The aim is to obtain two widely different sizes (above 500 nm and below 50 nm) while following the same synthesis strategy. For that, we subsequently used two templating routes: (1) spherical dense silica as a hard template to form the core cavity and (2) a cationic surfactant (CTAB) as soft template co-assembling with a bridged organosilane 1,4-Bis-triethoxysilylbenzene (BTEB) to form the mesoporous organosilica shell. Na 2 CO 3 and HCl solutions are used to successively deliver the two kinds of porosity. Here, the silica cores with fixed diameters, easily obtained using the Stöber method, allow the control of the core cavity size of the HPMO-NPs.