In-Situ Preparation of Surface-Functionalized SiO₂ Nanoparticles with Controllable Sizes

Controllable preparation of small-sized SiO₂ nanoparticles via sol–gel method remains a big challenge due to high reactivity of these nanoparticles. In this study, we demonstrated that when introducing coupling reagents, typically 3-(methacryloxy)propyltrimethoxysilane during reaction, the growth of silica nanoparticles can be inhibited to a large degree and the diameters can be kept nearly constant. Further, the minimum diameter can be greatly reduced to around 10 nm. DLS and SEM measurements indicated that the dispersion of the size of as-prepared silica nanoparticles was narrow. No obvious aggregation was found in the absence of any stabilizing reagents. FT-IR results showed that the surface of the silica was functionalized with considerably large number of vinyl groups. Further grafting experiment demonstrated that the amount of vinyl groups was adequately large for the grafting of polymers to form core–shell structures. Overall, the coupling reagents served not only as surface modifier, but also as terminator of sol–gel reaction.