Thus, concentrated sulfuric acid (H2SO4, 95-98%) is initially added to a reactor and cooled down to summarizes the ratios of reactants to obtain the three different C/O ratios as described in Table (Geh(6), Geh (10) and Geh( )). Since the temperature is kept low during the radical formation period, the decreased intercalation associated with the overall decreased radical reactivity (but with increased reactivity at the graphene's edges in relation to the basal plane) will greatly favor the functionalization at the graphene's edges. After the reaction, the resulting suspension is cooled to 5 °C, diluted (2 mL of H2O per 1 mL of H2SO4) (Figure , step 4), quenched with a 35% H2O2 solution (0.06 ml H2O2 per 1 mL 5% KMnO4) (Fig. , step 5), and left stirring for 2 h at RT. Then, the resulting suspension is transferred to a separation funnel and left overnight to precipitate. The precipitated slurry is then separated and cleaned with 1 cycle of washing using 10% HCl (7 mL of HCl per 1mL H2SO4). For applications demanding higher purity, the washed slurry is dialyzed (10 kDa molecular weight membrane) until stable pH. Very high carbon contents (up to 89% C), mainly represented by C sp 2 are observed for all samples, even with increasing oxidation (Figure ). When the most oxidized sample (Geh( )) is annealed at 150°C, the number of functional groups decreases to less than half, with a mild increase in C sp (Figure ) associated to the condensation reactions among sheets (see Section S2.5). The graphitic basal plane preservation also gives rise to high thermal stability (Figure ), with temperatures of maximum degradation (Tmax) above 600°C (under oxidative atmosphere) for all oxidation levels, which are higher than those expected for GO . The lack of functional groups in the basal plane also leads to the absence (for Geh (10) and Geh( )) or presence of a broad XRD (001) diffraction peak (for Geh( )), which is also shifted to a higher 2θ (i.e. smaller interlayer distance). The (002) diffraction peak is also slightly shifted to lower 2θ, with decreased intensity and broader profile as oxidation increases. This indicates that the re-stacked layers increasingly curve with enlarging the oxidized edge area (Figure ) , which is also more prone to defect-dependent corrugation . All systems form stable dispersions in water, but present dominant π-π* transitions of C sp 2 , observed by the UV/Vis absorbance band at λmax = 269 nm (Figure ).