www.sciencemag.org/content/344/6181/289/suppl/DC1 Supplementary Material for Ultimate Permeation Across Atomically Thin Porous Graphene Kemal Celebi, Jakob Buchheim, Roman M. Wyss, Amirhossein Droudian, Patrick Gasser, Ivan Shorubalko, Jeong-Il Kye, Changho Lee, Hyung Gyu Park* *To whom correspondence should be addressed: [email protected]Published 18 April 2014, Science 344, 289 (2014) DOI: 10.1126/science.1249097 This PDF file includes: Materials and Methods Figs. S1 to S11 Full Reference List
22
Embed
Supplementary Material for - · PDF fileSupplementary Material for ... Changho Lee 3 & Hyung Gyu Park 1* 1 Nanoscience for Energy Technology and Sustainability, ETH Zurich,...
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
www.sciencemag.org/content/344/6181/289/suppl/DC1
Supplementary Material for
Ultimate Permeation Across Atomically Thin Porous Graphene
Kemal Celebi, Jakob Buchheim, Roman M. Wyss, Amirhossein Droudian, Patrick Gasser, Ivan Shorubalko, Jeong-Il Kye, Changho Lee, Hyung Gyu Park*
Ultimate Permeation across Atomically Thin Porous Graphene
Kemal Celebi1†, Jakob Buchheim1†, Roman M. Wyss1, Amirhossein Droudian1, Patrick Gasser1, Ivan Shorubalko2, Jeong-Il Kye3, Changho Lee3 & Hyung Gyu Park1*
1 Nanoscience for Energy Technology and Sustainability, ETH Zurich, Sonneggstrasse 3, CH-8092 Zürich, Switzerland. 2 Laboratory for Electronics/Metrology/Reliability, EMPA (Swiss Federal Laboratories for Materials Science and Technology), Überlandstrasse 129, CH-8600 Dübendorf, Switzerland 3 Materials & Components R&D Laboratory, LG Electronics Advanced Research Institute, 38 Baumoe-ro, Seocho-gu, Seoul 137-724, Korea. * To whom correspondence should be addressed: [email protected] † These authors contributed equally to this work.
Materials and Methods
Graphene synthesis
Graphene was grown on copper foils (Alfa Aesar #13382) in a cold-wall chemical vapor
deposition system (Aixtron AG). The samples were annealed for 30 min at 950°C under Ar
(1500 sccm) and H2 flow (100 sccm), followed by a two-step growth with flowing ethylene at
25 sccm for 2 min and 50 sccm for 1 min. All growths were carried out at 4 mbar chamber
pressure.
Graphene Transfer
Graphene was transferred using a spin-coat-and-back-etch method in order to obtain double
layer graphene on the target substrate (36). Our modified method begins with the spinning of
1
poly (methyl methacrylate) PMMA (950k, 2% Anisol) on as-grown graphene at 4000 rpm,
yielding sub-100-nm polymer layers. The PMMA/graphene/copper is then placed on the
surface of (NH4)2S2O8 solution (0.5 M in water) to etch the copper. After 10 min, the sample
is removed from the solution and the backside of the foil is cleaned to remove graphene
remainder. The successive, 90-min-long etch removes the copper entirely, leaving the
PMMA/graphene layer. The floating PMMA/graphene layer is transferred to a DI-water bath
for rinsing. Another as-grown graphene on a copper foil is used to fish out the rinsed sample
and left for air-drying, yielding double layer graphene between copper and PMMA. The
procedure for the copper foil removal is then repeated as described above. The second fish-out
is performed by the holey SiNx frame, followed by air-dry and a subsequent hotplate anneal
for 30 min at 180°C, which relaxes PMMA and promotes the adhesion of graphene on the
target substrate. The PMMA is finally removed in a quartz tube furnace at 400°C for 2 hours,
under 500 sccm H2 : 500 sccm Ar flow.
FIB patterning and membrane characterization
The freestanding double layer graphene was patterned using Focused Ion Beam (FIB) milling.
Two FIB methods were employed. First, for pores diameters between 16 nm and 1000 nm,
Ga+ ion beam (FEI Helios 450) exposure (30 kV, 33 pA) was used. A dose of ~0.5-5×10-5
pA/nm2 yielded well-defined pore size distributions. In the second method, sub-10-nm pores
were drilled by a He+ ion FIB (Zeiss Orion Plus) using a 30 kV, 16 pA beam and an exposure
dose of ~6×10-3 pA/nm2. Sub-100-nm pores are drilled using single pixel exposures at high
dwell times. Too high dosage or increased pore density were avoided, due to the possibility of
tearing of the graphene, connecting nearby pores (Fig. S7). The geometry and edge structures
of graphene pores were investigated by high-resolution transmission electron microscopy (Cs-
corrected HRTEM, JEM ARM 200F, JEOL, Japan) at an accelerating voltage of 200 kV (Fig.
S8). After patterning, the membranes were thoroughly investigated for larger holes, cracks 2
and patterning-induced defects by acquiring high resolution SEM (FEI Helios 450) images of
each patterned window. The pore sizes were subsequently characterized using these SEM
images (5 kV, 25 pA). Pore diameter distributions were determined using an image analysis
software (ImageJ 1.45s).
Characterization of pore-edge chemistry (XPS and TOFSIMS)
Samples of freestanding double-layer graphene in the patterned (2500-5000 10-nm-diameter
pores) and unpatterned (pristine graphene) states were investigated for possible differences in
the oxygen content. Since patterning leaves dangling carbon bonds at the pores formed in
graphene, it is expected that at these positions water and possibly oxygen would react to
saturate these dangling bonds. To assess the oxygen content, patterned and unpatterned
samples were mounted on Au coated Si wafers inside the FIB chamber and later analyzed by
X-ray photoelectron spectroscopy (XPS). The utilized probe was a monochromatized Al Kα
X-ray beam with a diameter of about 8 µm in a Quantum 2000 imaging XPS spectrometer
(Physical Electronics Instruments, Inc.). Imaging analysis was not possible, although the SiNx
support frame of 50×50 µm in size could well be localized. This enabled the area-selective
analysis of oxygen, carbon, silicon and nitrogen through their most intense core level lines
(O1s, C1s, N1s, Si2p).
The data show that the relative amount of oxygen with respect to carbon (i.e., the sensitivity-
corrected intensity ratio O/C) is enhanced in the patterned sample by about 10±5% as
compared to the unpatterned sample. This result corroborates the presence of dangling bonds
in graphene as a consequence of the FIB patterning and environmental exposure. Additional
time-of-flight secondary ion mass spectrometry (TOFSIMS) data comparing the fragments
O+, O-, OH- and CO- from both samples show clearly higher oxygen-containing signals from
the patterned sample. In an analogous way, this finding can be an additional support for the
3
presence of oxidation-passivated pores in the porous graphene membrane. From the acquired
data, we could mention about pore edge shape and edge chemistry as follows.
Edge shape - To fabricate our membranes, we use double-layer graphene formed by double
transferring of CVD-grown, polycrystalline graphene sheets, with crystalline sizes ranging
from sub-µm to a few µm. Thus the physically torn edges are likely to take a random
crystalline direction. Actually, the edges produced by FIB are shown random by transmission
electron microscopy (Fig. S8).
Edge chemistry - From the fact that the FIB-perforated graphene samples are taken out of the
FIB chamber and exposed to a slightly humid laboratory environment, we anticipate that
oxidation might proceed and passivate the pore edges. Passivation by oxygen-containing
chemical moieties via strong oxidation has been observed by other researchers, suggesting
that the pore edges can be terminated by carbonyl, hydroxyl, or carboxyl groups. It is,
therefore, possible that the edges of the graphene pores are also terminated by these oxygen-
containing moieties, although their number density may not be as high as observed by the
above studies. Another possibility is that trace carbon and hydrogen in the FIB chamber can
bind to the edges right after the ion bombardment, providing partial hydrogen termination.
The XPS and TOFSIMS data suggest that there exist oxygen-containing moieties at the pore
edge, but we cannot rule out unambiguously the existence of hydrogen termination. It is likely
that the graphene pore edges are terminated by a variety of chemical moieties from oxygen to
hydrogen containing species.
Effect of edge chemistry to transport - Edges are particularly important for small pores, as the
edge chemistry can alter the flow rates and selectivity. There have been theoretical studies
showing significant edge effects, such as water permeation enhancement by hydrophilic edge
termination (OH) (37), H2/CH4 selectivity reduction by N-functionalization (38), anion
4
blockage by F and N functionalization and cation blocking by H-termination (39), as well as
ion blockage by carboxyl groups (40, 41). These studies use sub-nm pores, where the electron
clouds of the functional group take up a significant portion of the pore area. For our
membranes, on the other hand, the pore sizes are 1-3 orders of magnitude larger than such
functional groups, e.g., the size of a C-O group is ~0.40 nm (considering van der Waals radii
of C (~0.11 nm) and O (~0.15 nm) and the C-O covalent bond length of ~0.14 nm) and the
size of a C-N group is ~0.42 nm (considering van der Waals radii of C and N (~0.16 nm) and
the C-N bond length of ~0.15 nm), and therefore we can safely neglect the effect of the edge
chemistry on the direct permeation .
Raman measurement of graphene membrane
We conducted two-dimensional Raman scans on both patterned (four 1 μm pores in one 4-
100 nm spacing). (A) SEM image of membrane scanned. (B) G peak (1600 cm-1) of
unpatterned (left) and patterned (right) double layer graphene membrane. (C) D peak (1350
cm-1) of unpatterned (left) and patterned (right) double layer graphene membrane.
2μm
D peak (1350 cm-1) 1.0
0
G peak (1600 cm-1)1.0
0
A
B
C
15
Fig. S10. (A) SEM image before and after baking a 50-nm-pore graphene membrane in
oxidizing environment for 2 hours at 250°C. (B) SEM image before and after immersing a 50-
nm-pore graphene membrane into 1 M H2SO4 for >2 hours. (C) SEM image before and after
immersing a 50-nm-pore graphene membrane in acetone for >2 hours.
1μm
Before acetone exposure
1μm
After acetone exposure
After H2SO4 exposure
1μm
Before H2SO4 exposure
After baking in air
1μm
Before baking in air
1μm
A
B
C
16
Fig. S11. (A) Peeled graphene covering a large portion of the membrane area. (B) A close-up
SEM image of 50-nm-wide graphene pores clogged after the water permeation experiment.
200nm500nm
A B
17
References and Notes 1. X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, A. Velamakanni, I. Jung, E. Tutuc, S.
K. Banerjee, L. Colombo, R. S. Ruoff, Large-area synthesis of high-quality and uniform graphene films on copper foils. Science 324, 1312–1314 (2009). doi:10.1126/science.1171245
2. K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J. H. Ahn, P. Kim, J. Y. Choi, B. H. Hong, Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457, 706–710 (2009). doi:10.1038/nature07719 Medline
3. K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, A. A. Firsov, Electric field effect in atomically thin carbon films. Science 306, 666–669 (2004). doi:10.1126/science.1102896
4. J. S. Bunch, S. S. Verbridge, J. S. Alden, A. M. van der Zande, J. M. Parpia, H. G. Craighead, P. L. McEuen, Impermeable atomic membranes from graphene sheets. Nano Lett. 8, 2458–2462 (2008). doi:10.1021/nl801457b Medline
5. V. Berry, Impermeability of graphene and its applications. Carbon 62, 1–10 (2013). doi:10.1016/j.carbon.2013.05.052
6. S. Garaj, W. Hubbard, A. Reina, J. Kong, D. Branton, J. A. Golovchenko, Graphene as a subnanometre trans-electrode membrane. Nature 467, 190–193 (2010). doi:10.1038/nature09379 Medline
7. S. P. Koenig, L. Wang, J. Pellegrino, J. S. Bunch, Selective molecular sieving through porous graphene. Nat. Nanotechnol. 7, 728–732 (2012). doi:10.1038/nnano.2012.162 Medline
8. S. C. O’Hern, C. A. Stewart, M. S. Boutilier, J. C. Idrobo, S. Bhaviripudi, S. K. Das, J. Kong, T. Laoui, M. Atieh, R. Karnik, Selective molecular transport through intrinsic defects in a single layer of CVD graphene. ACS Nano 6, 10130–10138 (2012). doi:10.1021/nn303869m Medline
9. K. Celebi, M. T. Cole, J. W. Choi, F. Wyczisk, P. Legagneux, N. Rupesinghe, J. Robertson, K. B. Teo, H. G. Park, Evolutionary kinetics of graphene formation on copper. Nano Lett. 13, 967–974 (2013). doi:10.1021/nl303934v Medline
10. H. W. Kim, H. W. Yoon, S. M. Yoon, B. M. Yoo, B. K. Ahn, Y. H. Cho, H. J. Shin, H. Yang, U. Paik, S. Kwon, J. Y. Choi, H. B. Park, Selective gas transport through few-layered graphene and graphene oxide membranes. Science 342, 91–95 (2013). doi:10.1126/science.1236098
11. H. Li, Z. Song, X. Zhang, Y. Huang, S. Li, Y. Mao, H. J. Ploehn, Y. Bao, M. Yu, Ultrathin, molecular-sieving graphene oxide membranes for selective hydrogen separation. Science 342, 95–98 (2013). doi:10.1126/science.1236686
12. R. A. Sampson, On Stokes’s current function. Philos. Trans. R. Soc. London A 182, 449–518 (1891). doi:10.1098/rsta.1891.0012
13. K.-K. Tio, S. S. Sadhal, Boundary conditions for stokes flows near a porous membrane. Appl. Sci. Res. 52, 1–20 (1994). doi:10.1007/BF00849164
14. M. Knudsen, Die Gesetze der Molekularströmung und der inneren Reibungsströmung der Gase durch Röhren. Ann. Phys. 333, 75–130 (1909). doi:10.1002/andp.19093330106
15. N. Dongari, A. Sharma, F. Durst, Pressure-driven diffusive gas flows in micro-channels: from the Knudsen to the continuum regimes. Microfluid. Nanofluid. 6, 679 (2009).
16. L. Lund, A. Berman, Flow and self‐diffusion of gases in capillaries. Part I. J. Appl. Phys. 37, 2489 (1966). doi:10.1063/1.1708841
17. R. D. Present, A. J. Debethune, Separation of a gas mixture flowing through a long tube at low pressure. Phys. Rev. 75, 1050–1057 (1949). doi:10.1103/PhysRev.75.1050
18. A. Gugliuzza, E. Drioli, A review on membrane engineering for innovation in wearable fabrics and protective textiles. J. Membr. Sci. 446, 350–375 (2013). doi:10.1016/j.memsci.2013.07.014
19. S. A. Brewer, Recent advances in breathable barrier membranes for individual protective equipment. Rec. Pat. Mat. Sci. 4, 1 (2011). doi:10.2174/1874465611104010001
20. T. Yoon, J. H. Mun, B. J. Cho, T.-S. Kim, Penetration and lateral diffusion characteristics of polycrystalline graphene barriers. Nanoscale 6, 151–156 (2013).
21. L. M. Robeson, The upper bound revisited. J. Membr. Sci. 320, 390–400 (2008). doi:10.1016/j.memsci.2008.04.030
22. Y. Li, F. Liang, H. Bux, W. Yang, J. Caro, Zeolitic imidazolate framework ZIF-7 based molecular sieve membrane for hydrogen separation. J. Membr. Sci. 354, 48–54 (2010). doi:10.1016/j.memsci.2010.02.074
23. Z. Tang, J. Dong, T. M. Nenoff, Internal surface modification of MFI-type zeolite membranes for high selectivity and high flux for hydrogen. Langmuir 25, 4848–4852 (2009). doi:10.1021/la900474y Medline
24. R. M. de Vos, H. Verweij, High-selectivity, high-flux silica membranes for gas separation. Science 279, 1710–1711 (1998). doi:10.1126/science.279.5357.1710
25. K. Nagai, A. Higuchi, T. Nakagawa, Gas permeability and stability of poly (1‐trimethylsilyl‐1‐propyne‐co‐1‐phenyl‐1‐propyne) membranes. J. Polym. Sci. B 33, 289–298 (1995). doi:10.1002/polb.1995.090330214
26. M. E. Rezac, B. Schöberl, Transport and thermal properties of poly (ether imide)/acetylene-terminated monomer blends. J. Membr. Sci. 156, 211–222 (1999). doi:10.1016/S0376-7388(98)00346-9
27. D. Shekhawat, D. R. Luebke, H. W. Pennline, “A review of carbon dioxide selective membranes: A topical report,” Report DOE/NETL 2003/1200 (U.S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA, 2003).
28. W. J. Koros, R. Mahajan, Pushing the limits on possibilities for large scale gas separation: Which strategies? J. Membr. Sci. 175, 181–196 (2000). doi:10.1016/S0376-7388(00)00418-X
29. P. Bernardo, E. Drioli, G. Golemme, Membrane gas separation: A review/state of the art. Ind. Eng. Chem. Res. 48, 4638–4663 (2009). doi:10.1021/ie8019032
30. B. Freeman, Y. Yampolskii, I. Pinnau, Materials Science of Membranes for Gas and Vapor Separation (Wiley, New York, 2006).
31. A. Mehta, A. L. Zydney, Permeability and selectivity analysis for ultrafiltration membranes. J. Membr. Sci. 249, 245–249 (2005). doi:10.1016/j.memsci.2004.09.040
32. R. Shukla, M. Balakrishnan, G. P. Agarwal, Bovine serum albumin-hemoglobin fractionation: Significance of ultrafiltration system and feed solution characteristics. Bioseparation 9, 7–19 (2000). doi:10.1023/A:1008194300403 Medline
33. S. Nakatsuka, A. S. Michaels, Transport and separation of proteins by ultrafiltration through sorptive and non-sorptive membranes. J. Membr. Sci. 69, 189–211 (1992). doi:10.1016/0376-7388(92)80039-M
34. H. Guo, G. Zhu, I. J. Hewitt, S. Qiu, “Twin copper source” growth of metal-organic framework membrane: Cu3(BTC)2 with high permeability and selectivity for recycling H2. J. Am. Chem. Soc. 131, 1646–1647 (2009). doi:10.1021/ja8074874 Medline
35. B. Elyassi, M. Sahimi, T. T. Tsotsis, Silicon carbide membranes for gas separation applications. J. Membr. Sci. 288, 290–297 (2007). doi:10.1016/j.memsci.2006.11.027
36. J. W. Suk, A. Kitt, C. W. Magnuson, Y. Hao, S. Ahmed, J. An, A. K. Swan, B. B. Goldberg, R. S. Ruoff, Transfer of CVD-grown monolayer graphene onto arbitrary substrates. ACS Nano 5, 6916–6924 (2011). doi:10.1021/nn201207c Medline
37. D. Cohen-Tanugi, J. C. Grossman, Water desalination across nanoporous graphene. Nano Lett. 12, 3602–3608 (2012). doi:10.1021/nl3012853 Medline
38. D. E. Jiang, V. R. Cooper, S. Dai, Porous graphene as the ultimate membrane for gas separation. Nano Lett. 9, 4019–4024 (2009). doi:10.1021/nl9021946 Medline
39. K. Sint, B. Wang, P. Král, Selective ion passage through functionalized graphene nanopores. J. Am. Chem. Soc. 130, 16448–16449 (2008). doi:10.1021/ja804409f Medline
40. D. Konatham, J. Yu, T. A. Ho, A. Striolo, Simulation insights for graphene-based water desalination membranes. Langmuir 29, 11884–11897 (2013). doi:10.1021/la4018695 Medline
41. A. K. Mishra, S. Ramaprabhu, Functionalized graphene sheets for arsenic removal and desalination of sea water. Desalination 282, 39–45 (2011). doi:10.1016/j.desal.2011.01.038
42. H. Lin, E. Van Wagner, B. D. Freeman, L. G. Toy, R. P. Gupta, Plasticization-enhanced hydrogen purification using polymeric membranes. Science 311, 639–642 (2006). doi:10.1126/science.1118079
43. M. K. Small, W. Nix, Analysis of the accuracy of the bulge test in determining the mechanical properties of thin films. J. Mater. Res. 7, 1553–1563 (1992). doi:10.1557/JMR.1992.1553
44. C. S. Ruiz-Vargas, H. L. Zhuang, P. Y. Huang, A. M. van der Zande, S. Garg, P. L. McEuen, D. A. Muller, R. G. Hennig, J. Park, Softened elastic response and unzipping in chemical vapor deposition graphene membranes. Nano Lett. 11, 2259–2263 (2011). doi:10.1021/nl200429f Medline
45. S. P. Koenig, N. G. Boddeti, M. L. Dunn, J. S. Bunch, Ultrastrong adhesion of graphene membranes. Nat. Nanotechnol. 6, 543–546 (2011). doi:10.1038/nnano.2011.123 Medline