Flexible and ultrathin polyelectrolyte conductive coatings formed with reduced graphene oxide as a base for advanced new materials

摘要

Graphene is a hydrophobic material and cannot be used for the formation of multilayer coatings with the conventional layer-by-layer (LbL) technique. In our work, we proposed to use for that purpose the suspension of graphene oxide (GO) and to reduce it to the reduced graphene oxide (rGO). GO is negatively charged, and as easily suspended in water, it can be used as an anionic layer together with some cationic polyelectrolytes for the multilayer film formation. The several reduction methods were compared to transform GO towards reduced graphene oxide (rGO), e.g., UV illumination, thermal reduction and chemical reduction using hydrazine. It can be observed that thermal reduction of GO above the temperature 180 degrees C was the most effective process leading to the formation of sp(2)-hybridized carbon atoms and can be directly applied for GO containing films. The XPS spectra showed that after the reduction process the ratio of the sp(2) carbon increased to c.a. 80 at.%. The structure and properties of the coatings before and after reduction were studied using UV-Vis, spectroscopic ellipsometry and scanning electron microscopy (SEM). We demonstrated that it was possible to get thin rGO conductive films on quartz and polyimide (PI) plates measuring surface conductivity with the use of the four-point method. The building of films on PI allows creating flexible new materials, which may be applied in biomedicine as, e.g., electroactive sensors.