The electronic properties and nonlinear optical responses of the intermediate structures in rolling graphene to carbon nanotubes

Abstract

From the same piece of finite size graphene (F-graphene) sheet through different directions (zigzag edge or armchair edge), (4, 4) and (8, 0) carbon nanotube clips form. The electronic properties of the intermediate structures in the two rolling processes 44 (zigzag) and 80 (armchair) have been investigated using quantum chemistry method. The magnetism of the F-graphene sheet disappears with the rolling operation in 44, while it is maintained throughout the whole rolling operation in 80. Furthermore, the highest occupied molecular orbital (HOMO) α and HOMO β gradually extend to the whole framework from the zigzag edges with the rolling operation in 44, and they gradually localize to the lower and upper half of the framework in 80. Oxygen passivation along the opening of the intermediate structures effectively improves the nonlinear optical (NLO) response of the intermediate structures in both the zigzag and the armchair processes. Oxygen passivation along the armchair opening in 80 enhances the βtot value, yet does not bring essential changes to the electron transitions contributed to the NLO response. Oxygen passivation along the zigzag opening in 44 is able not only to enhance the βtot value but also to change the transition nature of electron excitations with a major contribution to the NLO response.