Silica nanotubes and their assembly assisted by boric acid to hierachical mesostructures

Fine control of the self-assembly of silicon species to hierachical materials has attracted research attention for many years. The mesostructures produced by such processes under weak acidic-basic conditions mimic bioenvironments are the focus of current research. In this study, mesoporous silicas with various novel morphologies such as mesoporous spheres, nanotubes, and oligomeric nanotubes have been systematically synthesized by using boric acid in the system, which is the key reagent for the fine control of the assembly of the silica precursors. The as-prepared materials are characterized using transmission electron microscopy (TEM), small-angle X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and nitrogen sorption measurements. The results support the assembly process of the nanomicelle of silica and surfactant under the conditions of boric acid, from which the synergistic weak interactions cause the morphology evolution of silicas. The current research provides effective information for understanding the formation of mesoporous silica under conditions mimicking biosilification processes.