“…The nanostructures such as nanoribbons, 2,11 quantum dots, 2,5,[8][9][10][11][12][13][14] and quantum rings (QRs) 2,5-7,11 based on graphene have attracted much attention. It has been illustrated that the confinement of Dirac fermions at a nanometer scale is not trivial due to Klein's paradox, 15,16 which seriously limits graphene's potential application for building electronic devices, because confining carriers are crucial for applications.…”