A Chirality Indicator for the Surfaces of the Silica Nanotubes

The chirality of the silicas attracted much attention, due to their potential applications in asymmetric catalysis and enantioseparation. However, their chirality has not been well understood. Herein, a chirality indicator for the surfaces of the silica nanotubes was developed. The helical silica nanotubes were prepared through a sol–gel transcription approach. The handedness was controlled by that of the self-assemblies of the low-molecular-weight amphiphiles. 4-Triethoxysilyl-1,1′-biphenyl (TSB) was modified on the surfaces of silica nanotubes through covalent bonds. The circular dichroism (CD) spectra of the TSB-modified silica nanotubes indicated that the chirality of silica surfaces could be transferred to the twist of the biphenyl rings. The origin of these CD signals was characterized using time-dependent density functional theory.