▎ 摘　　要

Based on the non-equilibrium Green's function method combined with the density functional theory, we investigate the transport properties of a zigzag trigonal graphene flake (zTGF) adsorbed by a single atom (F or H) or a single group (OH or CH3) at the central site and connected to two symmetric Au electrodes by Au-S bonds. The results show that the OH adsorption can enhance the conductance, followed by the negative differential resistance effects, while the conductance for the zTGF adsorbed by H and CH3 is lowered obviously, and rectifying characteristics can be observed for the H-adsorbed system. The adsorbing action alters the molecular level position and the spatial distribution of the molecular orbital, leading to different transport properties.