Supplementary data

Conversion of Langmuir-Blodgett Monolayers and Bilayers of Poly(amic acid) through Polyimide to Graphene

Hye Jin Jo1,5, Ji Hong Lyu2,3,5, Rodney S. Ruoff2,3, Hyunseob Lim2,3, Seong In Yoon1, Hu Young Jeong4, Tae Joo Shin4, Christopher W. Bielawski1,2,3,* and Hyeon Suk Shin1,2,3,*

1Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea

2Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea

3Center for Multidimensional Carbon Materials (CMCM), Institute of Basic Science (IBS), UNIST-gil 50, Ulsan 689-798, Republic of Korea

4UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea

5These authors contribute this work equally

*E-mail: shin@unist.ac.kr (HSS), bielawski@unist.ac.kr (CWB)

Figure S1. 1H NMR spectra of (a) BTDA-PDA, (b) BTDA-ODA, (c) PMDA-PDA and (d) PMDA-ODA (DMSO-d6.)

Figure S2. (a) SEM image of monolayer PAA (BTDA-PDA) on Cu obtained using a LB method. A darker side is PAA and the brighter side is bare Cu substrate. Scale bar is 500 µm. (b) AFM image of monolayer PAA (BTDA-PDA) on a SiO2/Si substrate obtained using a LB method. The thickness of PAA (BTDA-PDA) film is approximately 0.7 nm. Scale bar is 1 µm. Figure S3. Langmuir-Blodgett isotherms of (a) BTDA-PDA salt, (b) BTDA-ODA salt, (c) PMDA-ODA salt, and (d) PMMA.

Table S1. Summary of polymer thicknesses on SiO2 (300 nm)/Si substrates as a function of the number of layers, as measured by AFM by calculating the difference in height between the bare substrate and the coated polymer film.

BTDA-PDA

BTDA-ODA

PMDA-PDA

PMDA-ODA

PMMA

1 layer

0.7

0.6

0.8

0.7

0.8

2 layer

2.0

2.1

2.3

2.2

1.9

3 layer

3.7

3.0

3.2

3.4

3.3

5 layer

5.7

5.8

5.4

6.1

4.6

Figure S4. Dark-field transmission electron microscopy (DF-TEM) images of single graphene domains of (a) PI-GR (BTDA-PDA) and (b) graphene grown from conventional CH4 gas on a holey carbon grid. All scale bars are 2 μm. Graphene from CH4 gas was grown by the conventional method which used 15 sccm of CH4 and 10 sccm of H2 at 1050 oC for 30 min. (c and d) Tables represent calibrated area of single domains from (a) and (b), respectively.

Figure S5. Optical images of (a) PI-GR (BTDA-PDA) and (b) graphene grown from CH4 (g). The graphene shown in panel (b) reveals the presence of adlayers on surface. Scale bars are 10 μm.

Figure S6. Conversion of PAA (BTDA-PDA) films on SiO2/Si substrates. The experimental conditions used for the material on the SiO2/Si substrate was the same as that used for the Cu foil (see main text). (a) Raman spectra obtained after annealing LB 1, 2, and 3 layers of PAA (BTDA-PDA) on a SiO2/Si substrate. (b and c) Photographs of BTDA-PDA on a SiO2/Si substrate before (b) and after (c) annealing at 1050 oC. Left and right sides of the dotted line are uncoated and coated regions with BTDA-PDA, respectively. There was no change of the boundary line after annealing. (d) Optical image for LB monolayer of BTDA-PDA on SiO2/Si substrate after annealed at 1050 oC. Similar to (c), the left side of the dotted line is uncoated region. (e) Raman spectra of marked points in (d) show an absence of signal on the left side and peaks consistent with that of amorphous carbon in the right side for the annealed BTDA-PDA. Scale bar of (d) is 10 µm. (f and g) SEM images of (f) 2 layer and (g) 3 layer LB film of PAA (BTDA-PDA) after annealing at 1050 oC on SiO2/Si, which show boundary lines of uncoated and coated regions. The insets show Raman spectra for amorphous carbon in the coated regions. Scale bars represent 200 µm. (h) Conversion result of half-coated PAA (BTDA-PDA) LB monolayer on Cu foil. After annealing at 1050 oC, graphene is observed even in the uncoated Cu region (the left side of Cu foil before annealing) although it contains defects or vacancies.

Figure S7. Raman spectra after annealing PAA (BTDA-PDA) at 1000 oC without an intermittent annealing process at 240 °C. The intense D band signal around at 1350 cm-1 is indicative of defective graphene.

Figure S8. Optical image of graphene as synthesized from monolayer BTDA-PDA; the material contains approximately 7.2 % vacancies. The average area of vacancies is about 8 %, indicating the coverage of 92 %. No vacancies were observed when graphene was grown from bilayer PAA. The scale bar represents 100 µm.

Figure S9. Raman spectra of PMMA-GR recorded from spin-coated solutions of 0.02, 0.033, and 0.1% PMMA.

Figure S10. Raman spectra of BTDA-PDA annealed at different temperature (240, 350, 650, 850, and 1050 oC) for 20 min and graphitic domain size calculated by the equation shown. The integrated intensity ratio, ID/IG, was used to determine the in-plane crystallite size La (nm) using the Tuinstra-Koenig relationship [1]. λ is the wavelength of Raman excitation (488 nm). At 1,050 oC, a significant D peak could not be detected which prevent calculation of the corresponding crystallite size. We independently confirmed that there were no D and G peaks on bare Cu without PAA.

Figure S11. Raman spectra recorded for graphene grown from (a) PMDA-ODA and (b) PMDA-PDA at 450 oC for various periods of time: 0 min (black), 5 min (red), 20 min (blue) and 60 min (green).

Reference

[1] Cancado LG, Takai and Enoki T 2006 General equation for the determination of the crystallite size La of nanographite by Raman spectroscopy Appl. Phys. Lett. 88 163106

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