In-depth study of factors affecting the formation of MCM-41-type mesoporous silica nanoparticles

Abstract

Mesoporous silica nanoparticles (MSN), especially MCM-41 type, have been broadly studied and used in different applications such as catalysis, nanomedicine and environmental science. One of the most advantageous properties of these materials is their easy and tunable synthesis. Nevertheless, in spite of the efforts made by researchers in the last decades, there is still no complete understanding of the mechanism and factors affecting the formation of MCM-41 type MSN, and some parameters are disregarded in the reported synthesis protocols. Considering that the fine-tuning of the parameters affecting nanoparticle synthesis is the basis for obtaining well-defined nanodevices with advanced complex functionalities, an in-depth study of the factors affecting the formation of MCM-41 type MSN is carried out in this work. We analyzed the first stages of MSN formation, namely the silica-surfactant templating and nanoparticle nucleation and growth, and found that hydrolysis and condensation rates play a central role in nanoparticle formation. Furthermore, we found that some disregarded parameters in the MCM-41 type synthesis, such as the stirring strength or the surfactant addition rate, modulate nucleation and growth, influencing the hydrolysis and condensation rates. Finally, we studied the aging and the evolution of the MSN by analyzing the consolidation of the silica framework over time. Therefore, we further elucidate some points about the mechanism and factors affecting the formation of mesoporous silica, which brings us closer to obtaining reproducible, homogeneous and tailored-made MCM-41 type MSN.