Tuning pore size of mesoporous silica nanoparticles simply by varying reaction parameters

Mesoporous silica nanoparticles (MSN) with tunable pore size have been proved to be excellent potential in molecular-related applications. Herein, in this study, we designed to synthesize MSN with tunable pore size by varying the n-octadecyltrimethoxysilane (C18TMS)/tetraethylorthosilicate (TEOS) molar ratio or the ethanol (EtOH)/H2O volume ratio in a water-ethanol-ammonia system, where C18TMS acted as structure-directing agent, TEOS as silica source, ammonia as catalyst, EtOH and H2O as solvents. The as-obtained MSN were characterized by the scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption analysis. The results showed that the as-synthesized MSN possessed spherical morphology with diameter ranging from 100 to 200 nm, and the pore size of MSN could be easily tailored from 2.4 to 6.5 nm simply by varying the C18TMS/TEOS molar ratio from 0.32 to 0.74 and the EtOH/H2O volume ratio from 3.6 to 7.5. Meanwhile, the pore volume also could be adjusted from 0.6 to 1.0 cm3/g by this strategy. These results suggested that our strategy could effectively enlarge and adjust the mesopores of the MSN. We supposed our approach may provide a platform of nanotechnology for preparation of porous silica materials with adjustable mesopores which would be great potential in practical applications where different sizes of molecules were involved.