Conductive nanofilms with oppositely charged reduced graphene oxides as a base for electroactive coatings and sensors

Abstract

We demonstrate a method for the formation of multilayers composed of reduced graphene oxide (rGO), which can be used for transparent, conducting thin films. Using the layer-by-layer (LbL) assembly of positively and negatively charged GO sheets, we could obtain thin films with highly controllable sheet resistance. The natural negative charge of graphene oxide was turned to positive by the amidation reaction. After forming the multilayer films, the graphene oxide underwent thermal reduction at temperatures above 150 °C. The (rGO+/rGO-) films were characterized by UV-Vis and scanning electron microscopy (SEM), and their conductivity was measured by the four-point method. We found that after deposition of five (rGO+/rGO-), the coating structure reached the percolation limit, and the film resistance decreased more gradually to around 20 kW/sq for the films obtained by eleven deposition cycles with graphene oxide reduced at 250 °C. The formation of thin films on polyimide allows the forming of new flexible conductive materials, which can find applications, e.g., in biomedicine as new electroactive, low-cost, disposable sensors.