Edge-selectively functionalized graphene nanoplatelets.

Graphene, as a single layer of graphite, is currently the focal point of research into condensed matter owing to its promising properties, such as exceptional mechanical strength, high thermal conductivity, large specific surface area, and ultrahigh electron-transport properties. Therefore, various physical and chemical synthetic procedures to prepare graphene and/or graphene nanoplatelets have been rapidly developed. Specifically, the synthesis of edge-selectively functionalized graphene (EFG) has been recently reported by using simple and scalable approaches, such as "direct" Friedel-Crafts acylation reactions in a mild acidic medium and a mechanochemical ball-milling process. In these approaches, chemical functionalization predominantly take place at the edges of the graphitic layers via the covalent attachment of targeted organic "molecular wedges". In addition, the distortion of the crystalline structures in the basal plane, which is beneficial for preserving the unique properties of the graphitic framework, can be minimized. In addition, the efficient exfoliation of graphene can be achieved, owing to the strong repulsive forces from the covalently linked wedges and strong shear forces during the reaction. Furthermore, EFG shows promising potential in many useful applications, such as highly conductive large-area films, metal-free electrocatalysts for the oxygen-reduction reaction (ORR), and as additives in composite materials with enhanced properties. Herein, we summarize the recent progress and general aspects of EFG, including synthesis, reaction mechanism, properties, and applications.