Effect of Oscillation Mode on the Dispersion of Silica Nanoparticles Synthesized by the Stöber Method

Particle size and size distribution are critical parameters that strongly influence the performance, reproducibility, and applicability of nanoparticles. In this work, we systematically investigated the effect of oscillation mode on the particle size and dispersion of SiO2 nanoparticles synthesized via the Stöber method. Multiple commonly used laboratory mixing and oscillation modes—including stirring, horizontal shaking, vertical shaking, rotating, vertical shaking combined with rotating, water bath sonication, probe sonication, and static conditions—were comparatively evaluated. Particle size and size distribution were characterized by transmission electron microscopy and dynamic light scattering, and the polydispersity index (PDI) was quantitatively analyzed. The results demonstrate that stirring, horizontal shaking, vertical shaking, and rotating produce silica nanoparticles with comparable average sizes and consistently low PDI values within the investigated parameter range, indicating similar performance among these moderate and continuous oscillation modes under the studied conditions. In contrast, vertical shaking combined with rotating, water bath sonication, and probe sonication lead to larger particle sizes and broader size distributions, accompanied by elevated PDI values. Although static conditions yield smaller average particle sizes, the resulting particles exhibit the highest PDI, reflecting poor size uniformity. These findings provide practical process-level guidance for selecting appropriate oscillation modes to achieve reproducible and uniform silica nanoparticle synthesis in general laboratory settings.