Effect of SiCl4 on the preparation of functionalized mixed-structure silica from monodisperse sol–gel silica nanoparticles

Mesoporous functionalized nanoparticles (nanosilica) and functionalized mixed-structure silica with surface Si–Cl groups were prepared via a SiCl4 hydrolysis base-catalyzed sol–gel process. This study presents hierarchically structured systems formed via growth and self-assembly of functionalized silica nanospheres on the surface of Sylopol-948, generating functionalized mixed-structure silica. The fabricated materials were characterized by nitrogen adsorption, small angle X-ray (SAXS), dynamic light scattering (DLS), zeta potential (ZP), infrared spectroscopy (FT-IR), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX). The incorporation of Si–Cl groups (0.02–0.43 Cl/Si) on the surface—to functionalize the nanoparticles and modify their properties—was confirmed by SEM–EDX and cyclic voltammetry. In functionalized mixed-structure silica, the SBET value (567 m2/g) increases, particle size (13.6–17.2 nm) decreases and surface charge (−9.0 mV) diminishes as SiCl4 concentration increases. In functionalized nanosilica, a lower SiCl4 concentration results in a higher SBET value (730.6 m2/g), smaller nanoparticle size (6.0–12.4 nm) and higher surface charge (−22.9 mV). These materials were experimentally compared and found to demonstrate improved characteristics compared to Stöber nanosilica, non-functionalized mixed-structure silica, and Sylopol-948.