A structural study on ethylenediamine- and poly(amidoamine)-functionalized graphene oxide: simultaneous reduction, functionalization, and formation of 3D structure

Graphene oxide (GO) nanosheets were simultaneously modified and reduced with ethylenediamine (EDA). Then, EDA-treated GO (RGO-NH2) was exposed to iterative alkylation and amidation reactions to synthesize poly(amidoamine) (PAMAM)-grafted GO nanosheets. Reactions were continued until 4th generation PAMAM was grafted onto GO layers (RGO-4.0GD). FT-IR results confirmed the synthesis of the different structures, while TGA curves showed that the reactions that occurred were non-ideal and PAMAM was not grafted as expected. Also, XRD patterns showed that there is a resistance against the intercalation of nanolayers named stitching. According to the Raman spectra, the modification progression resulted in a more disordered structure of the graphene layers due to grafting PAMAM generations whereas reduction occurred continuously. Morphological studies were performed by recording SEM and TEM images. The results showed that the treated-GO nanosheets re-stack together, while distinguishable edges of nanolayers were observed.