Properties of graphene inks stabilized by different functional groups

Abstract

Different graphene inks have been synthesized by chemical methods. These uniform dispersionswere stabilized by various functional groups such as room temperature ionic liquid,polyaniline, polyelectrolyte (poly[2,5-bis(3-sulfonatopropoxy)-1,4-ethynylphenylene-alt-1,4-ethynylphenylene] sodium salt) and poly(styrenesulfonate) (PSS). The dispersions can beeasily cast into high-quality, free-standing films but with very different physiochemicalproperties such as surface tension and adhesion. SEM and AFM methods havebeen applied to have a detailed study of the properties of the inks. It is foundthat graphenes modified by p-type polyaniline show the highest surface tension.Diverse surface adhesive properties to the substrate are also found with variousfunctional groups. The different viscoelasticities of graphene inks were related tothe microscopic structure of their coating layer and subsequently related to theconfiguration, chemistry and molecular dimensions of the modifying molecules toestablish the property–structure relationship. Modifications of graphene inks madefrom chemical reduction cannot only enable cost-effective processing for printableelectronics but also extend the applications into, for example, self-assembly ofgraphene via bottom-up nano-architecture and surface energy engineering of thegraphenes. To fabricate useful devices, understanding the surface properties ofgraphene inks is very important. It is the first paper of this kind to study thesurface tension and adhesion of graphene influenced by different functional groups.