Coulombic interaction: The origin of hollow silica nanoparticles from charged polystyrene template

The research on the preparation and application of monodispersed hollow silica nanoparticles (HSNs) has never been stopped during the past few decades, but its formation mechanism has always been a topic worthy of debate. Herein, the typical template strategy was adopted to reveal the driving force of forming HSNs including three vital stages: preparation of well-defined sacrificial polystyrene (PS) nanosphere templates, deposition of silicon dioxide on PS template to form PS/SiO2 core/shell composites by a modified Sto & BULL;ber method, calcination of PS templates to generate HSNs. Therein, the deposition step determined if hollow structure can be obtained. PS templates with different sizes and surface properties were used to evaluate the deposition process, which was carefully monitored and characterized by microscopies (SEM, Cryo-FIB/SEM, and TEM), dynamic light scattering (DLS), and Zeta Potential. We found that only positively charged PS templates can induce the deposition of hydrolyzed silicon source, in the form of negatively charged solid SiO2 nanoparticles with the diameter of ~20 nm under the catalysis of alkali, by the Coulombic interactions. Then the deposited SiO2 shell could grow up due to the rapid condensation of silanol groups on both SiO2 shells and free solid SiO2 nanoparticles under alkaline condition. This article for the first time proved the formation process and mechanism of HSNs in detail, demonstrating great potential for regulating and preparing various functional hollow nanoparticles by diverse supramolecular interactions.

Automated summary

This study investigated the preparation mechanism of monodispersed hollow silica nanoparticles (HSNs) using a template strategy. It was found that only positively charged polystyrene (PS) templates could induce the deposition of hydrolyzed silicon source and promote the growth of SiO2 shells through the condensation of silanol groups. This research provides detailed insights into the formation process and mechanism of HSNs.