Langmuir - Blodgett Assembly of Graphene Oxide Sheets

Introduction Graphene oxide is the liquid oxidation of graphite powder, and consists of a single atomic carbon network derivitized by phenol hydroxyl and epoxide groups on the basal plane and carboxylic acid groups at the edges[1, 2]. The chemical functionalization breaks the extended π−π conjugation of graphene, resulting in an insulating material. However the conductivity may be partially restored through reduction methods such as chemical or thermal treatments [3, 4]. The oxygen functionalizations make the sheet more hydrophilic and the ionizable carboxylic acid groups induce an electrostatic repulsion between the sheets, allowing GO to readily form a stable single layer colloidal dispersion in water [5], making possible large scale solution processing of the material. GO is therefore thought of as a promising precursor to graphene based materials. It will then be important to understand how to assemble the sheets into the desired the structures. Furthermore, since GO is a unique soft layered material which could be considered of both a molecule and colloid, it is of fundamental scientific curiosity to understand the interactions between the sheets. In order to gain insight into the inter-sheet interactions of these highly anisotropic sheets, they were assembled at the air-water interface using the Langmuir-Blodgett technique and pH was used to tune the packing behavior of compressed films.