1 Supporting information for On-Demand Doping of Graphene by ...
Supporting information for On-Demand Doping of Graphene by Stamping with a Chemically Functionalized Rubber Lens Yongsuk Choi,1† Qijun Sun,1† Euyheon Hwang,1,2 Youngbin Lee,1 Seungwoo Lee,1 Jeong Ho Cho1,3* 1
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea. 2 Department of Physics, Sungkyunkwan University, Suwon 440–746, Republic of Korea 3 School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea. † Y. Choi and Q. Sun contributed equally to this work. Corresponding author: [email protected]
Figure S1. Fabrication procedure of PDMS lens.
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Chemical analysis of the doped graphene films by X-ray photoemission spectroscopy (XPS)
The chemical states of the doped graphene samples were analyzed using X–ray photoemission spectroscopy (XPS, K-alpha, Thermo Fisher). For contact–doping, the graphene films was contacted with dopants (PEI or TFSA)–modified PDMS lens for 10 min. For comparison, the graphene films doped by typical dip–coating method were prepared by dipping the graphene films in 40 mM PEI ethanol solution (or 40 mM TFSA nitromethane solution) for 10 min. Figure S2 shows the high-resolution XPS spectra of the pristine graphene film and PEI-doped graphene films fabricated by dip-coating and stamping methods. In Figure S2a, the deconvoluted C1s spectra of the pristine graphene film exhibited four distinct components, including sp2–hybridized carbons (284.6 eV), C–O (286.0 eV), C=O (287.4 eV), and O–C=O (289.1 eV).1, 2 The oxygen–bearing functional groups were originated from the residual PMMA on the graphene surface.2, 3 After doping with PEI, the peak at 285.9 eV increased dramatically, which was assigned to C–N groups in PEI dopant molecules (almost same position with the peak of C–O groups).4, 5 In accord with the C1s spectra, N1s spectra yielded more detailed information about the change in the chemical states of graphene films after PEI doping (Figure S2b). For PEI–doped graphene film, the N1s peak has three components, centered at 399.5, 401.0, and 401.9 eV, corresponding to secondary amines, tertiary amines, and protonated amines in PEI dopant molecules, respectively.6
Figure S2. High-resolution XPS (a) C1s and (b) N1s spectra of the pristine graphene film and PEI–doped graphene films fabricated by dip-coating and stamping. Figure S3 shows the high–resolution XPS spectra of the pristine graphene film and TFSA-doped graphene films fabricated by dip–coating and stamping methods. After TFSA doping, new carbon peak was 2
observed at 292.9 eV for both doped samples, which can be assigned to C–F groups in TFSA dopant molecules (Figure S3a).7 The adsorption of TFSA molecules onto the graphene surface was also confirmed by F1s spectra in Figure S3b. Overall, the two doping methods yielded a slight difference in the doping efficiency. Under the same treatment time, the contact doping method provided graphene film with more number of n– or p–type dopants.
Figure S3. High-resolution XPS (a) C1s and (b) F1s spectra of the pristine graphene film and TFSA–doped graphene films fabricated by dip-coating and stamping.
Figure S4. Doping stability of the TFSA-doped graphene with time evolution at room temperature under vacuum and ambient conditions. 3
References 1. Sheng, Z. H.; Shao, L.; Chen, J. J.; Bao, W. J.; Wang, F. B.; Xia, X. H. Catalyst-Free Synthesis of Nitrogen-Doped Graphene via Thermal Annealing Graphite Oxide with Melamine and Its Excellent Electrocatalysis. ACS Nano 2011, 5, 4350-4358. 2. Lee, W. H.; Park, J.; Sim, S. H.; Lim, S.; Kim, K. S.; Hong, B. H.; Cho, K. Surface-Directed Molecular Assembly of Pentacene on Monolayer Graphene for High-Performance Organic Transistors. J. Am. Chem. Soc. 2011, 133, 4447-54. 3. Ben Amor, S.; Baud, G.; Jacquet, M.; Nanse, G.; Fioux, P.; Nardin, M. XPS Characterisation of Plasma-Treated and Alumina-Coated PMMA. Appl. Surf. Sci. 2000, 153, 172-183. 4. Dillon, E. P.; Crouse, C. A.; Barron, A. R. Synthesis, Characterization, and Carbon Dioxide Adsorption of Covalently Attached Polyethyleneimine-Functionalized Single-Wall Carbon Nanotubes. ACS Nano 2008, 2, 156-164. 5. Liu, H. Y.; Kuila, T.; Kim, N. H.; Ku, B. C.; Lee, J. H. In situ Synthesis of the Reduced Graphene Oxide-Polyethyleneimine Composite and Its Gas BarrierPproperties. J. Mater. Chem. A 2013, 1, 3739-3746. 6. Hwang, H.; Joo, P.; Kang, M. S.; Ahn, G.; Han, J. T.; Kim, B. S.; Cho, J. H. Highly Tunable Charge Transport in Layer-by-Layer Assembled Graphene Transistors. ACS Nano 2012, 6, 2432-2440. 7. Kim, S. M.; Jo, Y. W.; Kim, K. K.; Duong, D. L.; Shin, H. J.; Han, J. H.; Choi, J. Y.; Kong, J.; Lee, Y. H. Transparent Organic P-Dopant in Carbon Nanotubes: Bis(trifluoromethanesulfonyl)imide. ACS Nano 2010, 4, 6998-7004.
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SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea. 2 Department of Physics, Sungkyunkwan University, Suwon 440–746, Republic of Korea 3 School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea. † Y. Choi and Q. Sun contributed equally to this work. Corresponding author: [email protected]
Figure S1. Fabrication procedure of PDMS lens.
1
Chemical analysis of the doped graphene films by X-ray photoemission spectroscopy (XPS)
The chemical states of the doped graphene samples were analyzed using X–ray photoemission spectroscopy (XPS, K-alpha, Thermo Fisher). For contact–doping, the graphene films was contacted with dopants (PEI or TFSA)–modified PDMS lens for 10 min. For comparison, the graphene films doped by typical dip–coating method were prepared by dipping the graphene films in 40 mM PEI ethanol solution (or 40 mM TFSA nitromethane solution) for 10 min. Figure S2 shows the high-resolution XPS spectra of the pristine graphene film and PEI-doped graphene films fabricated by dip-coating and stamping methods. In Figure S2a, the deconvoluted C1s spectra of the pristine graphene film exhibited four distinct components, including sp2–hybridized carbons (284.6 eV), C–O (286.0 eV), C=O (287.4 eV), and O–C=O (289.1 eV).1, 2 The oxygen–bearing functional groups were originated from the residual PMMA on the graphene surface.2, 3 After doping with PEI, the peak at 285.9 eV increased dramatically, which was assigned to C–N groups in PEI dopant molecules (almost same position with the peak of C–O groups).4, 5 In accord with the C1s spectra, N1s spectra yielded more detailed information about the change in the chemical states of graphene films after PEI doping (Figure S2b). For PEI–doped graphene film, the N1s peak has three components, centered at 399.5, 401.0, and 401.9 eV, corresponding to secondary amines, tertiary amines, and protonated amines in PEI dopant molecules, respectively.6
Figure S2. High-resolution XPS (a) C1s and (b) N1s spectra of the pristine graphene film and PEI–doped graphene films fabricated by dip-coating and stamping. Figure S3 shows the high–resolution XPS spectra of the pristine graphene film and TFSA-doped graphene films fabricated by dip–coating and stamping methods. After TFSA doping, new carbon peak was 2
observed at 292.9 eV for both doped samples, which can be assigned to C–F groups in TFSA dopant molecules (Figure S3a).7 The adsorption of TFSA molecules onto the graphene surface was also confirmed by F1s spectra in Figure S3b. Overall, the two doping methods yielded a slight difference in the doping efficiency. Under the same treatment time, the contact doping method provided graphene film with more number of n– or p–type dopants.
Figure S3. High-resolution XPS (a) C1s and (b) F1s spectra of the pristine graphene film and TFSA–doped graphene films fabricated by dip-coating and stamping.
Figure S4. Doping stability of the TFSA-doped graphene with time evolution at room temperature under vacuum and ambient conditions. 3
References 1. Sheng, Z. H.; Shao, L.; Chen, J. J.; Bao, W. J.; Wang, F. B.; Xia, X. H. Catalyst-Free Synthesis of Nitrogen-Doped Graphene via Thermal Annealing Graphite Oxide with Melamine and Its Excellent Electrocatalysis. ACS Nano 2011, 5, 4350-4358. 2. Lee, W. H.; Park, J.; Sim, S. H.; Lim, S.; Kim, K. S.; Hong, B. H.; Cho, K. Surface-Directed Molecular Assembly of Pentacene on Monolayer Graphene for High-Performance Organic Transistors. J. Am. Chem. Soc. 2011, 133, 4447-54. 3. Ben Amor, S.; Baud, G.; Jacquet, M.; Nanse, G.; Fioux, P.; Nardin, M. XPS Characterisation of Plasma-Treated and Alumina-Coated PMMA. Appl. Surf. Sci. 2000, 153, 172-183. 4. Dillon, E. P.; Crouse, C. A.; Barron, A. R. Synthesis, Characterization, and Carbon Dioxide Adsorption of Covalently Attached Polyethyleneimine-Functionalized Single-Wall Carbon Nanotubes. ACS Nano 2008, 2, 156-164. 5. Liu, H. Y.; Kuila, T.; Kim, N. H.; Ku, B. C.; Lee, J. H. In situ Synthesis of the Reduced Graphene Oxide-Polyethyleneimine Composite and Its Gas BarrierPproperties. J. Mater. Chem. A 2013, 1, 3739-3746. 6. Hwang, H.; Joo, P.; Kang, M. S.; Ahn, G.; Han, J. T.; Kim, B. S.; Cho, J. H. Highly Tunable Charge Transport in Layer-by-Layer Assembled Graphene Transistors. ACS Nano 2012, 6, 2432-2440. 7. Kim, S. M.; Jo, Y. W.; Kim, K. K.; Duong, D. L.; Shin, H. J.; Han, J. H.; Choi, J. Y.; Kong, J.; Lee, Y. H. Transparent Organic P-Dopant in Carbon Nanotubes: Bis(trifluoromethanesulfonyl)imide. ACS Nano 2010, 4, 6998-7004.
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