Surface functionalization of graphene oxide with tannic acid: Covalent vs non-covalent approaches

However, van der Waals forces among GO layers result in aggregation, yet its dispersion, large-scale production, and reinforcing efficiency remain challenging. In this project, simple and environmentally friendly methods via covalent and non-covalent routes have been developed to exfoliate and prepare surface-functionalized GO nanosheets with tannic acid (TA), a biological macromolecule with antioxidant activity.

Four esterification strategies were tested: direct, carbodiimide activated, oxalyl chloride acylation and via an acid-functionalized GO intermediate. The resulting samples have been extensively characterized to get knowledge on the GO-TA interactions and the degree of grafting, as well as their surface topography, level of hydrophilicity, solubility/dispersibility, thermal and antibacterial properties. The covalent grafting of TA renders the GO surface more hydrophobic, resulting in improved dispersion in organic solvents.