Functionalization of mesoporous silica nanoparticles through one-pot co-condensation in w/o emulsion

In this work, three different functionalized mesoporous silica nanoparticles (MSNs) were synthesized through the co-condensation synthesis in oil/water emulsion. Hexadecyltrimethoxysilane, triethoxy-3-(2-imidazolin-1-yl)propylsilane and (3-mercaptopropyl)triethoxysilane were used as organo-substituted silica precursors with variable molar ratio with respect to tetraethylorthosilicate (TEOS, 1:4, 1:9, 1:19). The occurred functionalization was investigated by Infrared Spectroscopy and FT-Raman and 29Si {1H} CP-MAS-NMR spectroscopy. Results show that the three materials were successfully functionalized. The influence of the different pendant groups and their concentration on the mesostructured pore organization of the obtained nanoparticles respect to the non-functionalized mesoporous silica was evaluated by means of Transmission Electron Microscopy and N2 sorption measurements. Bulky aliphatic C16 chains, especially in higher concentration, causes severe changes in mesoporous structure, leading to a more heterogeneous material. The imidazoline groups, instead, change the mesostructured morphology of the pores to an irregular but more interconnected one, while the presence of mercaptopropyl groups does not bring significant modifications. The different structural modifications in pore morphology observed between the samples is due to the different interactions between derivatized silica precursors and the components of the emulsion.