Efficient Preparation of Large-size Graphene Oxide Sheet and its Mosaic-like Monolayer

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Efficient Preparation of Large-size Graphene Oxide Sheet and its Mosaic-like Monolayer
Kim, Jung-Woo
Shin, Hyoen Suk
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Graduate School of UNIST
The thesis focuses on the high-yield preparation of graphene oxide (GO) by the intercalation of tetrabutylammonium hydroxide (TBAOH) into graphite oxide and its mosaic-like monolayer. GO has a layered structure with many oxygen-containing groups. Thus, GO has been a graphene-like material but also used as based material for a variety of chemical modification. The large size GO sheets could be separated from graphite oxide by centrifugation, but the yield was very low. By intercalation of TBA into graphite oxide, large size GO sheets could be obtained in high yield. Furthermore, TBA-treated GO formed mosaic-like monolayer by a simple spin-coating on substrate. The XRD pattern of TBA-intercalated graphite oxide was identical to pattern for the GO in water as a form of single sheets, indicating that graphite oxide could be efficiently exfoliated by intercalation of TBA. The single sheet yield of TBA-treated graphite oxide approximately 48%, while that of graphite oxide without TBA intercalant was only 18%, the layer thickness of TGO and GO were 1.29 and 0.93nm, respectively, which indicates TBA residues on GO sheets, the existence of TBA was identified by using EA and XPS. It confirms the existence of TBA on GO sheet. The existence of TBA on GO sheets was also identified from element analysis and XPS. Interestingly, the morphology of spin-coated TGO film on hydrophilic substrates such as SiO2 wafer and quartz formed a mosaic-like monolayer. This mosaic-like TGO monolayer also formed on hydrophobic substrates such as CVD grown graphene and Cu foil It assembled out the adsorption of TBA on GO creates low electrostatic repulsion between neighboring sheets, which helps the formation of mosaic-like monolayer by preventing overlapping of sheets. The external reflection FTIR spectroscopy study showed that the mosaic-like TGO monolayer fabricated by the simple spin-coating have same molecular orientation of functional groups as Langmuir-Blodgett film which is a typical method to make a monolayer with specific orientation of functional groups.
Energy Conversion & Storage
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