Conjugated-polyelectrolyte-functionalized reduced graphene oxide with excellent solubility and stability in polar solvents

Abstract

Conjugated-polyelectrolyte (CPE)-functionalized reduced graphene oxide (rGO) sheets are synthesized for the first time by taking advantage of a specially designed CPE, PFVSO3, with a planar backbone and charged sulfonate and oligo(ethylene glycol) side chains to assist the hydrazine-mediated reduction of graphene oxide (GO) in aqueous solution. The resulting CPE-functionalized rGO (PFVSO3-rGO) shows excellent solubility and stability in a variety of polar solvents, including water, ethanol, methanol, dimethyl sulfoxide, and dimethyl formamide. The morphology of PFVSO3-rGO is studied by atomic force microscopy, X-ray diffraction, and transmission electron microscopy, which reveal a sandwich-like nanostructure. Within this nanostructure, the backbones of PFVSO3 stack onto the basal plane of rGO sheets via strong π–π interactions, while the charged hydrophilic side chains of PFVSO3 prevent the rGO sheets from aggregating via electrostatic and steric repulsions, thus leading to the solubility and stability of PFVSO3-rGO in polar solvents. Optoelectronic studies show that the presence of PFVSO3 within rGO induces photoinduced charge transfer and p-doping of rGO. As a result, the electrical conductivity of PFVSO3-rGO is not only much better than that of GO, but also than that of the unmodified rGO.