Controlling Self-Assembly of Reduced Graphene Oxide at the Air-Water Interface: Quantitative Evidence for Long-Range Attractive and Many-Body Interactions

Industrial-scale applications of two-dimensional materials are currently limited due to lack of a cost-effective and controlled synthesis method for large-area monolayer films. Self-assembly at fluid interfaces is one promising method. Here, we present a quantitative analysis of the forces governing reduced graphene oxide (rGO) assembly at the airwater interface using two unique approaches: area-based radial distribution functions and a theoretical DerjaguinLandauVerweyOverbeek (DLVO) interaction potential for disks interacting edge-to-edge. rGO aggregates at the airwater interface when the subphase ionic strength results in a Debye screening length equal to the rGO thickness (similar to 1 mM NaCl), which is consistent with the DLVO interaction potential. At lower ionic strengths, area-based radial distribution functions indicate that rGOrGO interactions at the airwater interface are dominated by long-range (tens of microns) attractive and many-body repulsive forces. The attractive forces are electrostatic in nature; that is, the force is weakened by minor increases in ionic strength. A quantitative understanding of rGOrGO interactions at the airwater interface may allow for rational synthesis of large-area atomically thin films that have potential for planar electronics and membranes.