Graphene oxide (GO) nanosheets were simultaneously modified and reduced with ethylenediamine (EDA). Then, EDAtreated GO (RGO-NH2) was exposed to iterative alkylation and amidation reactions to synthesize poly(amidoamine) (PAMAM)-grafted GO nanosheets. Reactions were continued until 4 th generation of PAMAM were grafted onto GO layers (RGO-4.0GD). FT-IR results approved the synthesis of different structures, while TGA curves showed that reactions occurred 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 Raman spectra, modification progression resulted in more disorder structure of graphene layers due to grafting PAMAM generations whereas reduction occurred continuously. Morphological studies were performed according to SEM and TEM images. Results showed that treated-GO nanosheets restacks together, while distinguishable edge of nanolayers was observed.

No abstract

Radical coupling was used to modify graphite with maleic anhydride (MAH). Azobisisobutyronitrile (AIBN) as radical generator activated MAH radically and it was reacted with defects at the surface of nanolayers. A set of batches with different reaction times (24, 48 and 72 h) were performed to obtain fully-modified nanolayers (GMA1, GMA2 and GMA3, respectively). Fourier transform infrared results approved the synthesis of MAHgrafted graphite. Thermogravimetric analysis showed that 5.9, 11.1 and 13.2 wt% of MAH was grafted onto the surface of GMA1, GMA2 and GMA3, respectively, and that was approved by X-ray photoelectron spectroscopy results. Also, X-ray diffraction patterns showed that d-spacing increased from 0.34 nm for graphite to 1.00 nm for all modified samples. However, GMA1 showed a weak peak related to graphite structure that disappeared when reaction time was increased. After modification with MAH, lamella flake structure of graphite was retained whereas the edges of sheets became distinguishable as depicted by scanning electron microscopy images. According to Raman spectra, modification progression resulted in more disorder structure of nanolayers due to grafting of MAH. Also, transmission electron microscopy images showed graphite as transparent layers while after modification, surface of nanolayers became folded due to the opposite effects of π-conjugated domains and electrostatic repulsion of oxygen-containing groups.