Unzipping of carbon nanotubes is geometry-dependent.

Carbon nanotube (CNT) unzipping is a facile and efficient technique to produce narrow graphene nanoribbons. The diameter and chirality of CNTs control the geometry of the unzipped nanoribbons. In this work, we analyze the energetics of oxidation- and hydrogenation-induced unzipping processes. Empirical reactive potential-based energy calculations show that there is a geometry-dependent energy barrier for oxidation-induced unzipping, which is absent in the exothermal hydrogenation process. These results are discussed by considering the unzipping process as crack nucleation and propagation processes in a pre-stressed cylindrical shell. Fitting our simulation data through the theoretical model provides a quantitative way to estimate the key parameters in CNT unzipping that can be used to optimize the experimental procedure.