Graphene Thin Films by Noncovalent-Interaction-Driven Assembly of Graphene Monolayers for Flexible Supercapacitors

Macroscopic assembly can create advanced materials with hierarchical structure and translate the properties of individual building blocks into ensembles for specific applications. Here, we demonstrate the fabrication of freestanding graphene oxide (GO) films composed of only two Langmuir-Blodgett-induced monolayers under the synergy of wrinkled GO nanosheets and strong noncovalent interaction between GO and melamine. We found that the strongest noncovalent interaction ever measured (similar to 1 nN) was a synergistic effect of a charge-transfer interaction and hydrogen bonding. The as-obtained film delivered a large optical transmittance of 84.6% at 550 nm and a high mechanical strength of 45 MPa at a notable elongation of 3.5%. The reduced GO film, with a resistance of 420 Omega sq(-1), exhibited excellent electromechanical stability for 10,000 cycles at a bend radius of 1.5 mm. With the merits of a unique structure and outstanding properties, such an ultrathin film demonstrates its potential in the application of all-solid-state flexible supercapacitors.