SUPPLEMENTARY INFORMATION D0:10.1038/NMAT2858 C-O-C loss COOH loss 10 C=O formation (a)175C:60c C-OH loss (b)350C:175C C=O loss (g)500C:350C baseline M(d750C:500C C-O formation G0-1L 人 900 12001500 1800 800300032003400 3600 Wavenumber(cm-1) Supplementary Figure S1 Transmission infrared differential spectra of reduced GO(single layer).Variations upon thermal annealing at (a)175C:60C (b)350C:175C (c)500C:350C (d)750C:500C are represented in the following oxygen species:hydroxyl desorption (namely phenol,C-OH)(3050-3800 cmand~1070 cm)including all C-OH vibrations from COOH and H2O,formation of ketonic groups(1600-1650 cm,1750-1850 cm)in (a)and their loss in (b), loss of carboxyl(COOH)(1650-1750 cm including C-OH vibrations at 3530 cm and 1080 cm )loss of epoxide(C-O-C)(1230-1320 cmof asymmetric stretching and-850 cmof bending motion),formation of etheric groups (900-1100 cm),all other C-O and C=O contribution in B- region(1100-1280 cm)and sp2-hybridized C=C(1500-1600 cm,in-plane vibrations). 2 NATURE MATERIALS www.nature.com/naturematerials2 nature MATERIALS | www.nature.com/naturematerials supplementary information doi: 10.1038/nmat2858 2             ν()      °° °° °°   ()   °°  ν () Supplementary Figure S1 Transmission infrared differential spectra of reduced GO (single layer). Variations upon thermal annealing at (a) 175°C:60°C (b) 350°C:175°C (c) 500°C:350°C (d) 750°C:500°C are represented in the following oxygen species: hydroxyl desorption (namely phenol, C-OH) (3050-3800 cm-1 and ~1070 cm-1) including all C-OH vibrations from COOH and H2O, formation of ketonic groups (1600-1650 cm-1, 1750-1850 cm-1) in (a) and their loss in (b), loss of carboxyl (COOH) (1650-1750 cm-1 including C-OH vibrations at 3530 cm-1 and 1080 cm- 1 ), loss of epoxide (C-O-C) (1230-1320 cm-1 of asymmetric stretching and ~850 cm-1 of bending motion), formation of etheric groups (900-1100 cm-1), all other C-O and C=O contribution in β- region (1100-1280 cm-1) and sp2 -hybridized C=C (1500-1600 cm-1, in-plane vibrations)