Unexpected "Hammerlike Liquid" to Pulverize Silica Powders to Stable Sols and Its Application in the Preparation of Sub-10 nm SiO Hybrid Nanoparticles with Chirality.

Silane coupling agents are well-known as surface modifiers for various kinds of silica (SiO). However, in the present research, it has been found that they can also work as "hammerlike liquid" to pulverize different kinds of bulk amorphous SiO in aqueous systems. This new function was typically clarified by using 3-aminopropyltrimethoxysilane (APS) and bundles of chiral SiO nanofibers (with average diameter of ∼10 nm) as raw materials. By a simple reflux of the mixture of SiO nanofibers and excessive APS in pure HO, the solid-containing mixture turned into a completely clear solution that contained sub-10 nm, amine-modified, and water-soluble hybrid SiO sols (HS-sols). Moreover, this solution showed blue luminescence under ultraviolet irradiation. Furthermore, the circular dichroism and vibrational circular dichroism spectra revealed that the HS-sols are optically active even though the pristine chiral SiO nanofibers were completely destroyed. It was considered that the chirality of SiO nanofibers was due to the asymmetric arrangement of Si and O atoms in chiral domains (<10 nm) on the Si-O-Si network of SiO, and these domains are still preserved in chiral HS-sols. This green method has high potential for the recycling of rich SiO sources to obtain functional SiO nanomaterials with applications such as optical display, imaging, and chiral recognition. Also, it offers a tool for the analysis of the structural properties of SiO on the molecular scale.