Tunable assembly of graphene oxide surfactant sheets: wrinkles, overlaps and impacts on thin film properties

Graphene oxide (GO) sheets are a unique type of soft building block for creating functional graphene based materials and devices. Rapid progress has been made in the chemistry and applications of GO. However, there is a pressing need for rational assembly strategies of these two-dimensional (2D) sheets, which is crucial for determining the microstructures and thus final properties of bulk GO or graphene materials. For example, wrinkles and overlaps are the two fundamental morphologies between flexible, interacting sheets that are usually convoluted in solution-processed thin films. Based on the recent discovery of the surfactant-like property of GO sheets and their pH dependent amphiphilicity, now we are able to control the tiling of such 2D sheets to obtain thin films with either a wrinkled or overlapped type of microstructure, thus allowing us to deconvolute how these two basic microstructures affect the electrical and optical properties of the final thin films. The work here provides a well-defined example of the materials science paradigm, the microstructure-properties relationship, for this new soft material.