The dynamics of nanophase formation during Stober silica synthesis

Stober synthesis produces monodisperse, spherical silica nanoparticles that range in size from 5 to 2000 nm. The ability to produce such geometrically “well-defined” particles has prompted investigations to elucidate the fundamental mechanisms by which Stober spheres are formed. However, the mechanisms for particle formation and growth have yet to be thoroughly studied at the earliest stages.; In this dissertation, the early nucleation and aggregation dynamics of Stober silica particles are investigated. Silica nuclear magnetic resonance (29Si-NMR), small-angle x-ray scattering (SAXS), dynamic light scattering (DLS), Doppler electophoretic light scattering (DELS), and transmission electron microscopy (TEM) are used to examine the mechanisms that control the growth of silica nanoparticles.; It is shown that the formation of nuclei is controlled by a supersaturation of the hydrolyzed monomers, which leads to the continuous production of the primary particles. Furthermore, these particles densify through monomer addition.; Once the silica nanoparticles were formed, controlled salt addition progressively increased the electrolyte concentration, which electrostatically destabilized the primary particles, causing them to aggregate. These particles were much more stable in methanol than in ethanol.