Tuning the properties of graphene using a reversible gas-phase reaction

Graphene, because of its remarkable electronic and structural properties, has attracted considerable attention in both the scientific and technological communities. However, a major roadblock to the realization of graphene-based field-effect transistors is that large-area graphene behaves as a semimetal with zero bandgap, making it unsuitable for real applications in sensing, detecting and switching systems. Surface functionalization could result in the construction of periodic micro/nanostructures by breaking sp 2 bonds and forming sp 3 bonds. Therefore, direct chemical grafting might provide a useful way to covalently modify graphene to tailor its properties. Owing to the inert reactivity of its surface, however, only a few chemical reactions have been used to modify its atomic structure. Here, we demonstrate a controllable and efficient means of mild plasma methylation to manipulate the reversible interconversion of two distinct species of graphene (one crystalline and the other methylated). The strategy of incorporating diverse functional substituents (that is, methyl groups and hydrogen atoms) into graphene, instead of a single type of chemical group, could provide a useful route for the development of different applications, such as chemical/biosensors and multifunctional electrical circuits. Moreover, this finely tunable, methylated graphene is stable at room temperature, which suggests that it has intrinsic potential for novel applications in graphene-based optoelectronic devices, inviting further studies. Graphene: Taking the mild route The discovery of graphene — a sheet of graphite that is only one atom thick — has sparked much enthusiasm in the science and technology communities. Dubbed ‘wonder material’ owing to its intriguing and promising properties, graphene is poised to play a crucial role in applications that range from electronic to biomedical devices; however, tuning its properties remains challenging. Grafting methyl (–CH 3 ) groups on its surface, for example, can open a band gap in its electronic structure, but too many functional groups will damage the original sheet. Xuefeng Guo and co-workers from Peking University have now described a route that circumvents previous issues. Through a mild gas-phase reaction between graphene and methane plasma, the researchers incorporated both methyl groups and hydrogen atoms to the sheet in a controlled, and reversible, manner. This process, which introduces two functional groups, may enable in