Free-Standing Janus Graphene Oxide with Anisotropic Properties for 2D Materials as Surfactant.

We present a simple and facile approach to creating asymmetrically modified graphene oxide sheets by grafting polymers with different polarities. Single-layered Janus graphene derivatives were prepared by grafting polymers with different polarities at the liquid-gas interface through one step functionalization. This approach allows obtaining free-standing monolayers of Janus graphene oxide sheets for large area, and also controlling the morphology (i.e., wrinkled Janus graphene oxide sheets) by a compression monolayer. A neutron reflectivity technique is used to check the functionalization on each side of the monolayer, and the results are compared with contact angles to determine its amphiphilic nature. The free-standing Janus monolayers become robust after UV-irradiation, and are able to withstand various solvents. Because these robust Janus graphene films can maintain their anisotropic functionalities over time, this technique provides a new strategy for fabricating functional materials that require amphiphilic properties (i.e., oil-water separation membranes and chemical compatibilizers functioning as a 2D surfactant) and different electrical functionalities (i.e., flexible lightweight p-n junction semiconductors and stimuli-driven actuators).