Synthesis of alkylamine functionalized graphene oxide by gamma irradiation

This research aims to alter hydrophilic GO to becomes hydrophobic. Gamma-ray (γ-ray) irradiation technique was used to functionalize GO with various alkyl chain length of an alkylamine. Functionalization of alkylchain onto the GO was confirmed by X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (1H NMR), and X-ray Photoelectron Spectroscopy (XPS). XRD analysis showed the diffraction peak of graphite was shifted from 2θ=26.40o to lower angle at 2θ=10.20o corresponding to an increasing the interlayer spacing from 0.34 nm of graphite to 0.87 nm of GO upon oxidation. Further increasing of interlayer up to 2.68 nm for GO-A18 was observed after functionalization suggested the long alkylchain was successful intercalated between graphene sheets. FTIR result verified the existence of oxygen functionalities on GO after been oxidized by modified Hummers method. Functionalization by γ-ray irradiation method was able to attach alkylchain on the surfaces of GO by the appearance of significant peaks around 2928-2863 cm-1corresponding to the C-H stretching vibration of the alkyl chain (CH2). 1H NMR analysis also supported these findings by the emergence of small intensity at ~0.88 ppm (-CH3) and the very intense signal at ~1.25 ppm (-CH2). Simultaneously, this method showed reduction effect by removing some of the oxygen functionalities that have been confirmed by decreasing of O/C ratio in XPS analysis. The effects of various alkyl lengths functionalized-GO on morphological and thermal properties were investigated. The addition of alkylchain on GO surfaces significantly improves the thermal stability of GO, suggesting their great potential for hydrophobic material in for various applications. Scanning Electron Microscopy (SEM) analysis showed an increase in surface roughness after functionalization which gives huge influences on the wetting properties of the substance as the water contact angle of GO-A18 gives higher value up to 114.11o. Therefore, this gamma irradiation technique has been successfully functionalized GO and simultaneously reduce them to becomes hydrophobic materials.

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