Structure control of ultra-large graphene oxide sheets by the Langmuir-Blodgett method

As a unique type of soft building block, graphene oxide (GO) dispersions are easy to process to produce electronic devices. Developing methods to produce large sized GO with controllable structure is the key for these applications. Here, ultra-large graphene oxide (UL-GO) sheets (up to similar to 100 mu m in lateral size) were produced in aqueous media and deposited onto substrates with controllable structure, including flat, rippled, standing collapsed, folded, over folded, highly curved, and scrolled morphologies, via the Langmuir-Blodgett (L-B) technique. The MD simulations show that the GO becomes much softer than pristine graphene sheets due to the sp(3)-hybridization caused by oxygen containing functional groups and this is the reason why a series of distinct structures were observed. To demonstrate the fabrication of a transparent conductor, the close-packed flat UL-GO films on poly(ethylene terephthalate) (PET) were reduced with a low-temperature chemical reduction process in a hydriodic (HI) acid aqueous solution, achieving a sheet resistance as low as 8.1 k Omega/sq with 90% transparency.