Periodic graphene nanobuds.

Periodic graphene nanobuds (PGNBs) can be engineered by attaching C(60) buckyballs onto a graphene monolayer, where C(60) molecules form a periodic lattice structure. Structural and electronic properties of two prototype PGNBs are investigated for the first time by using the first-principles methods. In type I PGNB, C(60) buckyballs are covalently bonded to a graphene monolayer, while in type II the fragmented buckyballs are fused onto the graphene monolayer. It is found that type I PGNBs can be either semiconducting or semimetallic, depending on the pattern of chemical bonding between C(60) and graphene. Type II PGNBs are generally semimetallic. In particular, one hallmark electronic structure of the graphene monolayer, i.e., conic Dirac points, is still preserved in type II PGNBs except for the "ripped" graphene monolayer. The diversity in electronic structures renders PGNB a promising carbon material for applications in nanoelectronics and cold electron field emission. Furthermore, multilayer PGNBs form a porous network structure with surface areas greater than 2000 m(2)/g, which can be exploited for gas storage.