Multilayer films of cationic graphene-polyelectrolytes and anionic graphene-polyelectrolytes fabricated using layer-by-layer self-assembly

Extremely thin sheets of carbon atoms called graphene have been predicted to possess excellent thermal properties, electrical conductivity, and mechanical stiffness. To harness such properties in composite materials for multifunctional applications, one would require the incorporation of graphene. In this study, new thin film composites were created using layer-by-layer (LBL) assembly of polymer-coated graphitic nanoplatelets. The positive and negative polyelectrolytes used to cover graphene sheets were poly allylamine hydrochloride (PAH) and poly sodium 4-styrenesulfonate (PSS). The synthesized poly allylamine hydrochloride-graphene (PAH-G) and poly sodium 4-styrenesulfonate-gaphene (PSS-G) were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and thermo gravimetric analysis (TGA). The multilayer films created by spontaneous sequential adsorption of PAH-G and PSS-G were characterized by ultra violet spectroscopy (UV-vis), scanning electron microscopy (SEM), and AFM. The electrical conductivity of the graphene/polyelectrolyte multilayer film composites measured by the four-point probe method was 0.2 S cm−1, which was sufficient for the construction of advanced electro-optical devices and sensors.

Graphical abstractDownload full-size imageResearch highlights▶ Successful multilayer thin films are created using layer-by-layer (LBL) assembly of PAH-G and PSS-G. ▶ The average thickness of the graphene oxide, PAH-G and PSS-G film is ∼1 nm, ∼7 nm and ∼4 nm respectively. ▶ The electrical conductivity of multilayer film PDDA-(PSS-G/PAH-G)6 composites measured by the four-point probe method is 0.2 S cm−1. ▶ The thickness of the multilayer film is found to be ∼65 nm with 82% transmittance at 550 nm.