Controlled grafting of colloidal nanoparticles on graphene through tailored electrostatic interaction.

Nanoparticle/graphene hybrid composites have been of great interest in various disciplines due to their unique synergistic physicochemical properties. In this study, we report a facile and generalized synthesis method for preparing nanoparticle/exfoliated graphene (EG) composites by tailored electrostatic interactions. EG was synthesized by an electrochemical method, which produced selectively oxidized graphene sheets at the edges and grain boundaries. These EG sheets were further conjugated with polyethyleneimine to provide positive charges at the edges. The primary organic ligands of the colloidal nanoparticles were exchanged with Cl- or MoS42- anions, generating negatively charged colloidal nanoparticles in polar solvents. By simple electrostatic interactions between the EG and nanoparticles in a solution, nanoparticles were controllably assembled at the edges of the EG. Furthermore, the generality of this process was verified for a wide range of nanoparticles, such as metals, semiconductors, and magnets, on the EG. As a model application, designed composites with size-controlled FeCo nanoparticles/EG were utilized as electromagnetic interference countermeasure materials that showed a size-dependent shift of the frequency ranges in the electromagnetic absorption properties. The current generalized process will provide the possibility for large-scale production of well-designed graphene nanocomposites for electronic and energy applications.