Sweet graphene I: toward hydrophilic graphene nanosheets via click grafting alkyne-saccharides onto azide-functionalized graphene oxide

• Grafting mono and disaccharides onto graphene oxide (GO).
• Using click reaction to obtain hydrophilic graphene nanosheets via two approaches.
• Stability of sugar-grafted GO in basic media for two weeks.
• Reduction of sugar-grafted GO by sodium ascorbate during click.

Water-soluble graphene nanosheets (GNS) were fabricated via functionalization of graphene oxide (GO) with mono and disaccharides on the basal plane and edges using Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of azides and terminal alkynes (Click chemistry). To graft saccharides onto the plane of GO, it was reacted with sodium azide to introduce azide groups on the plane. Then, it was treated with alkyne-modified glucose, mannose, galactose, and maltose. In the next approach, we attached 1,3-diazideoprop-2-ol onto the edges of GO and it was subsequently clicked with alkyne-glucose. The products were analyzed by Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy, thermogravimetric analysis (TGA), and X-ray diffraction spectrometry. FTIR and TGA results showed both sugar-grafted GO sheets were reduced by sodium ascorbate during click-coupling reaction which is an advantage for this reaction. Besides, glycoside-grafted GNS were easily dispersed in water and stable for two weeks.

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