Effective Use of Alkoxysilanes with Different Hydrolysis Rates for Particle Size Control of Aqueous Colloidal Mesostructured and Mesoporous Silica Nanoparticles by the Seed-Growth Method

The particle sizes of mesoporous silica nanoparticles most greatly affect their properties, including cellular uptake, cytotoxicity, and dispersity. The growth of colloidal mesostructured silica nanoparticles (CMSS) with particle sizes less than 100 nm was controlled by a modified seed-growth method by using alkoxysilanes (Si(OR)₄, R: Me, Et, Pr, and Bu) with different hydrolysis rates as additives. It was confirmed that the approximate matching of the hydrolysis rates of the added silanes with the consumption rates, determined by the total outer surface area of the seeds, is most important. CMSS with narrow particle-size distributions (e.g., 60 or 80 nm in size) were successfully prepared. Si(OPr)₄ was the most suitable additive, though Si(OEt)₄ was also useful for controlled growth. Si(OBu)₄ was usable but needed varied conditions for controlled growth. The mesostructures and the high dispersity of nanoparticles were retained, even after removal of the surfactants of the CMSS by dialysis. These findings should contribute to the more precise control of particle sizes of mesoporous silica nanoparticles and to the deeper understanding of their properties.