Impact of Copper Ions on the Structuration of the Polydopamine Layer for the Functionalization of Graphene Nanoplatelets

Graphene and its derivatives, such as graphene nanoplatelets (GNPs), are considered promising materials to be combined with copper for composite foil fabrication. However, the use of GNPs in liquid-phase processes remains challenging due to their hydrophobicity; thus, tailoring their wettability is a subject of rising interest. Among the possible approaches, functionalization with polydopamine (PDA) demonstrated a high degree of versatility. This process, especially the impact of the various process parameters on the final PDA coatings, is still a poorly explored topic. Our contribution investigates the nanostructure of the PDA layer on functionalized GNPs and the impact of the presence of copper ions in the functionalization process. Of all parameters tested, the presence or absence of copper ions in the dopamine polymerization process is revealed to be a key parameter controlling the morphology and thickness of the final PDA coating. Indeed, introducing Cu²⁺ during the functionalization process results in a thicker coating onto GNPs and promotes the formation of free-standing PDA particles alongside GNP functionalization. Such straightforward polymeric addition on GNPs allows for their facilitated dispersion and stability in aqueous media, a step toward enhancing the processability easiness of a promising material.