Supporting Information for
Quaternary Ammonium and Phosphonium Based Deep
Eutectic Solvents for the Solution-based Exfoliation of
Graphene
M. H. Chakrabarti, S. Eslava, I. M. AlNashef, N. S. A. Manan, F. S.
Mjalli, N. P. Brandon, P. V. Aravind , M. A. Hashim
All electrochemical exfoliation experiments were performed using 50/50 (by weight)
mixtures of DES and water. That is because when the exfoliation experiments were carried
out in pure ionic liquid and DES (which had been extensively bubbled with argon to
remove dissolved oxygen), higher activation voltages of 6−10 V were needed to initiate the
exfoliation. The corresponding yield was poor and is not shown in the main body of
results. Similar to the literature report [1], we found that a 50/50 water/DES mixture
provided the best results.
b)
a)
10 µm
Fig. S1 Representative SEM images of (a) some few-layered graphene produced
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electrochemically; (b) produced via ultrasound using any DES listed in Table 1 (except
DES 7). Other images are essentially identical and are not shown
Table S1 Eutectic molar compositions (denoted by the molar ratio) and freezing
temperatures of twelve DES employed in this investigation [2]. The freezing temperatures
for a several of the DES were not available in the literature.
HBD
Abbreviation
Eutectic
composition
(Salt : HBD)
Freezing
point
(°C)
N,N-diethylenethanol ammonium
chloride
EG a
DES 1
1:3
–22
Methyltriphenylphosphonium
bromide
EG a
DES 2
1:3
–46
Choline chloride
OA a
DES 3
1:1
34
Methyltriphenylphosphonium
bromide
TEG a
DES 4
1:3
–8
Choline chloride
TEG a
DES 5
1:2
-
N,N-diethylenethanol ammonium
chloride
TEG a
DES 6
1:2
-
Methyltriphenylphosphonium
bromide
Ga
DES 7
1:3
–5.5
Choline chloride
Ga
DES 8
1:2
–40
N,N-diethylenethanol ammonium
chloride
Ga
DES 9
1:2
–1
Choline chloride
TFA a
DES 10
1:2
–45
Choline chloride
Urea
DES 11
1:2
12
Choline chloride
EG a
DES 12
1:2
–66
Salt
a
EG = ethylene glycol, G = glycerol, OA = oxalic acid, TEG = tri-ethylene glycol and TFA = 2,2,2-tri-
fluoroacetamide
2
a)
b)
Fig. S2 Representative TEM images of exfoliated graphene samples in DES (a) produced
electrochemically, and (b) produced through ultrasound
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a)
1 µm
b)
Fig. S3 Representative AFM amplitude image shows overlapping FLG flakes for (a)
electrochemical exfoliation, and (b) ultrasound-assisted exfoliation in DES
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Average Intensity (arb.)
Sample 9 side 2
Average spectrum
100
50
0
1000
1500
2000
2500
3000
3500
Raman shift (cm-1)
Fig. S4 Representative average Raman spectra of graphene exfoliated ultrasonically in any
arbitrary DES listed in Table 1 (except from DES 7)
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150
Average Intensity (arb.)
Sample 9 side 1
Average spectrum
100
50
0
1000
1500
2000
2500
3000
3500
Raman shift (cm-1)
Fig. S5 Representative average Raman spectra of electrochemically exfoliated graphene
flakes in any arbitrary DES (numbered as per Table 1 except from DES 7). Note that the
spectrum for DES 1 is slightly different and is shown in the main text. The quality of
graphene flakes obtained using DES 1 was much better than those obtained from other DES
(as is evident from the average Raman spectra shown above)
References
1. Lu, J., Yang, J.X., Wang, J., Lim, A., Wang, S., Loh, K.P.: One-pot synthesis of
fluorescent carbon nanoribbons, nanoparticles, and graphene by the exfoliation of graphite
in ionic liquids. ACS Nano 3, 2367–2375 (2009)
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2. Zhang, Q., Vigier, K.D.O., Royer, S., Jérôme, F.: Deep eutectic solvents: syntheses,
properties and applications. Chem. Soc. Rev. 41, 7108–7146 (2012)
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