Ultrastrong Carbon Nanotubes/Graphene Papers via Multiple π–π Cross-Linking

Considering the extraordinary properties of graphene nanosheets, graphene-based materials from a molecular level to a macroscopic level as paper-like graphene films have recently grown for promising applications in many fields. However, there is still a major challenge in the design of the interface between adjacent graphene nanosheets so as to achieve high strength, high toughness, and high conductivity. Herein, we construct the high-performance graphene-based papers by using graphene as the matrix, carbon nanotubes (CNTs) as the reinforcement, and a long-chain molecule (1-pyrenylbutyric acid–linear diamine–1-pyrenylbutyric acid, PBA-diamine-PBA) as the bridging agent. The multiple π–π interactions between the fused rings, graphene nanosheets, and CNTs are generated among the aromatic rings of PBA, rGO, and CNTs, which significantly improve the mechanical properties and electrical properties of the cross-linked composite papers (abbreviated to CLP-X, where X is the carbon chain length). Furthermore, the linear diamines with different lengths of carbon chain affect the properties of papers after cross-linking. Especially, the as-obtained graphene-based paper (CLP-6) shows a high tensile strength (625.2 MPa), high toughness (28.5 MJ/m³), and high electrical conductivity (233.4 S/cm) as well as high solvent stability, which maintains the premium stability in different solvents. The improvement of strengthening and toughening mainly comes from the effective stress transfer and the reduction of slipping distance between rGO and CNTs during the stretching, with the help of multiple π–π cross-linking by in situ Raman analysis and simulation calculations. In addition, the high electrical conductivity leads to an excellent electromagnetic interference shielding capability (44,502 dB·cm²/g). The distinguished electric heating performance with rapid response to temperature changes is also recognized. Therefore, the proposed interface design is demonstrated as an effective way for developing a graphene-based paper with superior properties.