Manipulating the electronic and chemical properties of graphene via molecular functionalization

Graphene, a single atomic layer of sp²-hybridized carbon atoms arranged in a hexagonal structure and the Nobel winning material in 2010, has attracted extensive research attention in the last few years due to its outstanding physical, chemical, electrical, optical and mechanical properties. To further extend its potential applications, intensive research efforts have been devoted to the functionalization of graphene. Examples include improving graphene solubility by attaching different chemical functional groups to its basal plane, modulating the charge carrier type and concentration via surface transfer doping by coating it with various metals films or organic molecules, improving the bio-selectivity by decorating it with different π-conjugated organic molecules, and so on. Different methods have been developed to functionalize graphene. Among them, non-covalent molecular functionalization represents one of the most effective and promising methods. The extended π-conjugation is largely preserved without creating extensive structural defects on the graphene sheet, thereby retaining the high charge carrier mobility. In this review, a brief summary about different functionalization methods of graphene and its derivatives by covalent and non-covalent interactions will be presented, with particular focus on the non-covalent molecular functionalization. A broad review of the applications of non-covalently functionalized graphene and its derivatives will be presented in detail, including field-effect-transistors, organic optoelectronics, and molecular sensing.