Polyphenol-Reduced Graphene Oxide: Mechanism and Derivatization

In this work, tea polyphenols (TPs) were employed as an environmentally friendly and highly efficient reducer and stabilizer for graphene oxide (GO). The results from XPS, Raman, and conductivity studies of reduced graphene indicated the efficient deoxidization of GO. The adsorption of oxidized TPs onto graphene supplies steric hindrance among graphene sheets to keep them individually dispersed in water and some solvents. To investigate the reduction mechanism, epigallocatechin gallate (EGCG), the primary component of TPs, was used as a model. Characterization by 1H NMR and FTIR spectroscopies indicated that the gallic units in EGCG were converted to galloyl-derived orthoquinone and the flavonoid structure survived during the reduction. To further enhance the organosolubility of the resultant graphene, derivatization of the graphene was conducted by galloyl-derived orthoquinone–thiol chemistry. The successful derivatization was found to greatly improve the organosolubility of graphene in solvents with low boiling points.