Further analysis of the C1s spectra was performed following the deconvolution of the highresolution C1s spectra to 1 asymmetric Lorentzian function and 4 Gaussian-Lorentzian components, with peaks centred at 284.6, 286.5, 287.8, 288.6, and 290.2 eV (Figure ). These binding energy values were attributed to the formation of: (i) sp 2 and sp 3 hybridisations of carbon (C-C & C=C) in the graphitic backbone; (ii) single bonds between carbon and oxygen (C-O) in hydroxyls and ethers, including phenols and epoxides, respectively; (iii) double bonds between carbon and oxygen (C=O), indicating the presence of carbonyl groups in the form of aldehydes, ketones and quinones; (iv) multiple bonds between carbon and oxygen, resulting in the occurrence of carboxyls, anhydrides and esters, such as lactones (O-C=O) . The fifth component corresponds to the satellite peak π-π* due to the presence of delocalised π electrons in the graphene lattice . The high-resolution O1s spectra were also deconvoluted to 3 components fitted by Gaussian-Lorentzian functions, peaking at 530.7, 532.2, and 533.9 eV (Figure ). These energies could be attributed to: (i) O=C bonds from the aforementioned carbonyl and carboxyl groups; (ii) O-C bonds from hydroxyls and ethers; (iii) O-C in carboxyls and esters (O=C-O), respectively . The combination of both C1s and O1s spectra validated our fitting assignments, and revealed a high degree of oxidation of all 3 GO materials, with C-O bonds dominating the surface chemistry (Tables S4-S5, Supporting Information). Although we could observe a slightly lower abundance of C-O bonds in the C1s spectra of us-GO (Figure ), which led to a higher abundance of C-C bonds compared to the other two GO materials, these differences were not statistically significant (p = 0.1325). The analysis of the O1s spectra (Figure ), however, indicated a decreased amount of oxygen atoms involved in C-O bonds in us-GO compared to the other GO materials (p = 0.0417).