▎ 摘　　要

Using a LCAO method, which is based on spinless sp(3) scheme, we have studied the electronic properties of graphene nanoribbons with zigzag edges (ZGNRs) terminated partially by methylene groups. Metal-semiconductor transition is proved when the H atoms at both sides of ZGNRs are partially substituted by methylene groups. Furthermore, when one-third of H atoms are substituted and the distribution of methylenes is symmetric, the band gap comes to about 0.59 eV, which is the widest energy gap in this work. Otherwise, when the addends at both sides are of asymmetric distribution, a band gap of only 0.21 eV is obtained. These results suggest that the addends at the edge of ZGNRs play an important role in modifying the electronic properties. (C) 2011 Elsevier B.V. All rights reserved.