nature materials SUPPLEMENTARY INFORMATION DOl10.1038/NMAT2858 Unusual infrared-absorption mechanism in thermally reduced graphene oxide M.Acik',G.Lee',C.Mattevi2,M.Chhowalla2',K.Cho'and Y.J.Chabal* Department of Materials Science and Engineering,University of Texas at Dallas,Richardson, TX75080 2Rutgers University,Materials Science and Engineering,Piscataway,NJ,USA 08854 'Present address:Department of Materials,Imperial College,London,UK SW7 2AZ *Authors to whom correspondence should be addressed to: chabal@utdallas.edu NATURE MATERIALS www.nature.com/naturematerials 1
SUPPLEMENTARY INFORMATION doi: 10.1038/nmat2858 nature materials | www.nature.com/naturematerials 1 1 SUPPLEMENTARY INFORMATION Novel infrared absorption mechanism in thermally reduced graphene oxide M. Acik1 , G. Lee1 , C. Mattevi2† , M. Chhowalla2 †, K. Cho1 and Y. J. Chabal1* 1 Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX 75080 2 Rutgers University, Materials Science and Engineering, Piscataway, NJ, USA 08854 Ɨ Present address: Department of Materials, Imperial College, London, UK SW7 2AZ *Authors to whom correspondence should be addressed to: chabal@utdallas.edu Unusual infrared-absorption mechanism in thermally reduced graphene oxide
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/naturematerials
2 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)
DOE:10.1038/NMAT2858 SUPPLEMENTARY INFORMATION Section 1. Brief description of the structural evolution of single layer GO after annealing at 175- 750°C(Fig.S1). Between 60 and 175C,epoxide species decompose completely,most of the hydroxyl and carboxyl species are removed while some C=O containing ketonic species are formed (Supplementary Fig.Sla).Hydroxyl,carboxyl and ketonic species continuously disappear between 175 and 350C while some C-O containing etheric groups are formed(Supplementary Fig.S1b).No hydroxyl groups can be observed after 350C (Supplementary Figs S1c-d) probably because they can easily decompose due to strong interaction with neighboring hydroxyl and carboxyl groups,leading to formation of intermediate ketones [S1].Interestingly,the in- plane vibration(1580 cm)of the C=C bonds is observable only below 350C(Supplementary Figs Sla-b)for two reasons:1)the amount of sp2hybridization increases when out-of-plane oxygen species,such as hydroxyl(C-OH),carboxyl(COOH)and epoxide (C-O-C)groups are removed and 2)usually weak C=C phonon absorption is enhanced when the symmetry is perturbed by neighboring oxygen. [S1]Bagri,A.et al.Structural evolution during the reduction of chemically derived graphene oxide.Nat.Chem.2,581-587(2010). NATURE MATERIALS www.nature.com/naturematerials
nature materials | www.nature.com/naturematerials 3 doi: 10.1038/nmat2858 supplementary information 3 Section 1. Brief description of the structural evolution of single layer GO after annealing at 175- 750°C (Fig. S1). Between 60 and 175°C, epoxide species decompose completely, most of the hydroxyl and carboxyl species are removed while some C=O containing ketonic species are formed (Supplementary Fig. S1a). Hydroxyl, carboxyl and ketonic species continuously disappear between 175 and 350°C while some C-O containing etheric groups are formed (Supplementary Fig. S1b). No hydroxyl groups can be observed after 350o C (Supplementary Figs S1c-d) probably because they can easily decompose due to strong interaction with neighboring hydroxyl and carboxyl groups, leading to formation of intermediate ketones [S1]. Interestingly, the inplane vibration (1580 cm-1) of the C=C bonds is observable only below 350o C (Supplementary Figs S1a-b) for two reasons: 1) the amount of sp2 hybridization increases when out-of-plane oxygen species, such as hydroxyl (C-OH), carboxyl (COOH) and epoxide (C-O-C) groups are removed and 2) usually weak C=C phonon absorption is enhanced when the symmetry is perturbed by neighboring oxygen. [S1] Bagri, A. et al. Structural evolution during the reduction of chemically derived graphene oxide. Nat. Chem. 2, 581-587 (2010)
SUPPLEMENTARY INFORMATION D0:10.1038/NMAT2858 Edge (-O-) 1v(0- 10 (800cm1) FWHM 0850℃(G0-3L) ('n 'e)aouequosqv (100cm-1) (m)750℃(G0-3L) (im850℃(Sio /Si) (Si-OH) 800 1000 1200 1400 (a)850C:750C(G0-3L) 5x103 (b)850℃：750℃(Si0,/Si) 6009001200150018002100240027003000330036003900 Wavenumber(cm-1) Supplementary Figure S2 Transmission infrared differential (a)and absorbance (i-ii) spectra of GO (three layers:3L)at high temperatures(850-750C).A new peak appears at 800 cm with fwhm of-100 cm.A loss corresponding to Si-OH was observed at~980 cm. The inset shows the absorbance spectra at 750C (i)and 850C (ii)anneals for single layer GO and (iii)bare clean SiO2/Si surface at 850C referenced to the room temperature clean SiOz/Si surface.Absorbance unit is abbreviated as 'a.u.'. 4 NATURE MATERIALS www.nature.com/naturematerials
4 nature MATERIALS | www.nature.com/naturematerials supplementary information doi: 10.1038/nmat2858 4 Supplementary Figure S2 Transmission infrared differential (a) and absorbance (i-ii) spectra of GO (three layers: 3L) at high temperatures (850-750°C). A new peak appears at 800 cm-1 with fwhm of ~100 cm-1. A loss corresponding to Si-OH was observed at ~980 cm-1. The inset shows the absorbance spectra at 750°C (i) and 850°C (ii) anneals for single layer GO and (iii) bare clean SiO2/Si surface at 850°C referenced to the room temperature clean SiO2/Si surface. Absorbance unit is abbreviated as ‘a. u.’
DO:10.1038/NMAT2858 SUPPLEMENTARY INFORMATION 0.8 0.4 0.4 20 0.0 0.0 0.4 30 0.4 0.0 04 40 匹 0.0 0.8 0.4 50 88 0.4 0.4 70 0.0 0.0L L, 0.60.8 1.01.21.41.6 0.60.81.01.21.41.6 v(x1000cm') v(x1000cm') 0.2 d e 1296cm-1 1400 01 。“。 1300 0.0 ◆ 1200 1160cm-1 ◆ 0.1 1100 ◆ 1000 ■ 0.0 。*。。*。。,1026Cm 900 0 800 0.0 -8 6 4 -2 0 2 2 3456789“ 00 E(eV) number of O atoms Supplementary Figure S3 Cluster simulation results for finite number of edge ether.(a) Cluster models for agglomerated edge ethers increasing from two to seven,(b)their simulated IR intensities where the asymmetric C-O-C stretch mode is indicated by the red line.(c) Examination of the asymmetric C-O-C stretch mode frequency as indicated by the red line with increasing carbon rings along (middle:v=1428 cm)or away (bottom:v=1400 cm)from the NATURE MATERIALS|www.nature.com/naturematerials
nature materials | www.nature.com/naturematerials 5 doi: 10.1038/nmat2858 supplementary information 5 1296 cm-1 1160 cm-1 1026 cm-1 ∞ Supplementary Figure S3 Cluster simulation results for finite number of edge ether. (a) Cluster models for agglomerated edge ethers increasing from two to seven, (b) their simulated IR intensities where the asymmetric C-O-C stretch mode is indicated by the red line. (c) Examination of the asymmetric C-O-C stretch mode frequency as indicated by the red line with increasing carbon rings along (middle: ν=1428 cm-1) or away (bottom: ν=1400 cm-1) from the