Synthesizing graphene nanoribbons(GNRs)with smooth edges and controllable widths is a prerequisite for many graphene applications.[l] We proposed t,^r0 efficient methods of making narrow GNRs: using a single transition metal atom to unzip single-walled carbon nanotubes(SWNTs)in H2 gas;[2] and applying a uniaxial external strain to cut graphene sheet into GNRs on oxidation.