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.

Highlights

• Long aliphatic alkyl chains (C16) tend to disrupt micellar systems preventing homogeneous condensation.

• Mercaptopropyl groups do not influence pore structure, allowing high functionalization of the material.

• Imidazoline groups rearrange mesostructured porosity, maintaining high surface area e pore volume.

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.

Alessandro Gottuso, Francesco Armetta, Alessio Cataldo, Viviana Mollica Nardo, Francesco Parrino, Maria Luisa Saladino,
Functionalization of mesoporous silica nanoparticles through one-pot co-condensation in w/o emulsion,
Microporous and Mesoporous Materials, Volume 335, 2022, 111833, ISSN 1387-1811,
https://doi.org/10.1016/j.micromeso.2022.111833.