Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

Taguchi, Tomitsugu; Yamaguchi, Kenji

SiO nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO was -cristobalite. We also demonstrate that single-crystal SiO nanotubes can be transformed into amorphous SiO nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO composite nanotube, in which crystalline and amorphous SiO coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO nanotubes is crucial. We can also obturate, capsulate, and cut a SiO nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.