Long-range ordered and atomic-scale control of graphene hybridization by photocycloaddition
Miao Yu, Chong Chen, Qi Liu, Cristina Mattioli, Hongqian Sang, Guoqiang Shi, Wujun Huang, Kongchao Shen, Zhuo Li, Pengcheng Ding, Pengfei Guan, Shaoshan Wang, Ye Sun, Jinping Hu, André Gourdon, Lev Kantorovich, Flemming Besenbacher, Mingshu Chen, Fei Song, Federico Rosei
Abstract
Chemical reactions that convert sp2 to sp3 hybridization have been demonstrated to be a fascinating yet challenging route to functionalize graphene. So far it has not been possible to precisely control the reaction sites nor their lateral order at the atomic/molecular scale. The application prospects have been limited for reactions that require long soaking, heating, electric pulses or probe-tip press. Here we demonstrate a spatially selective photocycloaddition reaction of a two-dimensional molecular network with defect-free basal plane of single-layer graphene. Directly visualized at the submolecular level, the cycloaddition is triggered by ultraviolet irradiation in ultrahigh vacuum, requiring no aid of the graphene Moiré pattern. The reaction involves both [2+2] and [2+4] cycloadditions, with the reaction sites aligned into a two-dimensional extended and well-ordered array, inducing a bandgap for the reacted graphene layer. This work provides a solid base for designing and engineering graphene-based optoelectronic and microelectronic devices. The controllable functionalization of graphene at the molecular level may prove useful for graphene-based electronics, but is difficult to do in a precise fashion. Now it has been shown that a photocycloaddition reaction between a hydrogen-bonded network of maleimide-derived molecules and single-layer graphene can produce a functionalized array with long-range order.