SUPPLEMENTARY INFORMATION D0:10.1038/NMAT2858 Supplementary Fig.S4 summarizes the TOTAL intensity of all oxide modes of GO(three layers) as a function of thermal annealing.The initial integrated intensity decreases from~1.0 cm to -0.08 cm after a 750C anneal,when only ~8-10%of oxygen remains in three layers of GO. Upon annealing to 850C,the integrated area of the edge ether (mode centered at 800 cm) increases to a value of~3.0 cm,namely by a factor of~40. (C=O,COOH) 4x102I V(C-OH) +H20 ('n 'e)eouequosqy (a)GO(multi layers) C-o. C-N,N-N) (-O-)6p3 (b) (C=C) 5x103I 700 750 800 850 900 V(C-N,N-N) (b)After 36 hours (c)After 2 days 800 12001600 2800 3200 3600 Wavenumber(cm) Supplementary Figure S5 Time-dependent study of wet chemical reduction of GO(multi layers)in aqueous media.Tranmission infrared absorbance spectra of (a)GO(multi layers) 8 NATURE MATERIALS www.nature.com/naturematerials8 nature MATERIALS | www.nature.com/naturematerials supplementary information doi: 10.1038/nmat2858 8 Supplementary Fig. S4 summarizes the TOTAL intensity of all oxide modes of GO (three layers) as a function of thermal annealing. The initial integrated intensity decreases from ~1.0 cm-1 to ~0.08 cm-1 after a 750o C anneal, when only ~8-10% of oxygen remains in three layers of GO. Upon annealing to 850o C, the integrated area of the edge ether (mode centered at 800 cm-1) increases to a value of ~3.0 cm-1, namely by a factor of ~40. Supplementary Figure S5 Time-dependent study of wet chemical reduction of GO (multi layers) in aqueous media. Tranmission infrared absorbance spectra of (a) GO (multi layers)