Origin of the Strain Energy Minimum in Imogolite Nanotubes

Abstract

We have systematically analyzed the structure of imogolite and their energetics, to understand the physics governing control over imogolite nanotube diameter and strain energy. In this work, we have presented evidence that the arrangements of inner and outer hydroxyl (OH) groups, that is hydrogen bond (HB) networks, play an important role in the formation of imogolite nanotubes and their structural stability. The outer HB significantly affects the Al-O distances and generates two different structures. Even though the relaxation of inner and outer Al-O and Si-O bond distances is the driving force for tubular imogolite formation, we show that the origin of the strain energy minimum, that is high monodispersity of diameter in imogolite nanotubes, is the inner HB networks. The preference for zigzag chirality and the formation mechanism of tubular imogolite also can be understood based on HB networks. Therefore, we present that a comprehensive understanding of the origin of high monodispersity of diameter and the preference for zigzag chirality in imogolite nanotubes provide useful insight into the researches of technical applications of imogolite nanotubes.