Three‐Dimensional Self‐Assembly of Graphene Oxide Platelets into Mechanically Flexible Macroporous Carbon Films

Abstract

Graphene is an atom-thick, two-dimensional material comprised of a monolayer hexagonal sp-hybridized carbons. It is flexible, has a large specific surface area, and exhibits excellent electrical and thermal conductivities and also good mechanical properties. Moreover, given the low cost of natural graphite, the potential for obtaining large quantities of graphene by a low-cost production process is high. As such, graphene and its chemically modified forms are promising building blocks for accessing highly ordered assemblies that are suitable for nanoelectronics, energy storage/conversion, catalysis, composites, and other applications. Although previous efforts have demonstrated that graphene-based platelets may be assembled into papers, thin films, or other two-dimensional constructs, the ability to control the assembly such platelets into three-dimensional (3D) structures could result in the carbon materials that exhibit very large surface areas, unusual or novel physical and electronic properties, unsurpassed chemical functionality, and other attractive features that are necessary for the aforementioned applications. Herein we demonstrate the self-assembly of graphene oxide (GO) platelets into mechanically flexible, macroporous 3D carbon films with tunable porous morphologies. Selfassembly is the spontaneous bottom-up organization of preexisting components into patterned structures. The intrinsic parallelism and scalability inherent to self-assembly can, in principle, enable low-cost, large-scale syntheses of highly ordered nanostructures. Indeed, as will be described below, the self-assembly of chemically modified graphene platelets into a complex 3D morphology was achieved by the “breath-figure” method, which is a straightforward procedure for synthesizing large-area porous polymer films. The breath-figure method as employed herein is illustrated in Figure 1A. Briefly, polymer-grafted GO platelets were synthesized and dispersed in an organic solvent. The dispersion was then cast onto a suitable substrate and exposed to a stream of humid air. Endothermic evaporation of the volatile organic solvent resulted in the spontaneous conden-