Electronic Supplementary Information
Ionic Liquids as Recycling Solvents for The Synthesis of Magnetic Nanoparticles
Flavia C. C. Oliveira,a Fernando B. Effenberger,b Marcelo H. Sousa,c Renato F. Jardim,d Pedro K. Kiyohara,d Jairton Dupont,e Joel C. Rubim*a and Liane M. Rossi*b
1. Experimental details
Synthesis of ionic liquids
The synthesis of BMI.NTf2 and BMI.PF6 were done by modification of the process developed by Cassol et al.( C. C. Cassol,
G. Ebeling, B. Ferrera, J. Dupont, Adv. Synth. Catal. 348 (2006) 243) and involves the following steps:
Synthesis of Butyl Methanesulfonate: Methanesulfonyl chloride (1.60 mol) was added under vigorous stirring to a solution of
n-butanol (1.60 mol) and triethylamine (1.60 mol) in dichloromethane. The reaction temperature was kept between 10-20oC.
Then, the organic layer was washed with water. The combined organic extracts were dried over MgSO4 and the solvent was
removed under reduced pressure to give a colorless liquid.
Synthesis of 1-Butyl-3-methylimidazolium Methanesulfonate: equimolar amounts of butyl methanesulfonate and 1-
methylimidazole (1.59 mol) were mixed and the reaction mixture was kept at room temperature. One crystal of 1-butyl-3-
methyl imidazolium methanesulfonate was added and the resulting crystalline reaction mass was kept at room temperature for
24 h. Recrystallization was performed using acetone as solvent.
Synthesis of 1-n-butyl-3-methylimidazolium trifluoromethanosulfonimide (BMI.NTf2): A mixture of 1-butyl-3-
methylimidazolium methanesulfonate (165 mmol), LiNTf2 (174 mmol) and distilled water (65 mL) were vigorously stirred for
30 min and dichloromethane (200mL) was added. The organic phase was separated, washed with water and dried with MgSO4
and filtered through a basic alumina column. Solvent evaporation system was used to dichloromethane evaporation.The final
product was a viscous and colorless liquid, the BMI.Tf2N ionic liquid. The purity (> 97%) of the ionic liquid was determined
by 1HNMR using the intensity of the 13C satellites of the imidazolium N-methyl group as internal standard. The 1HNMR
spectrum was recorded on a Varian Mercury Plus spectrometer (300 MHz) at room temperature.
Synthesis of 1-n-butyl-3-methylimidazolium hexafluorophophate (BMI.PF6): A mixture of 1-butyl-3-methylimidazolium
methanesulfonate (470 mmol), KPF6 (493 mmol) and distilled water (250 mL) were vigorously stirred for 30 min. The upper
aqueous phase was separated and discarded. Then, KPF6 (23 mmol) and distilled water (40 mL) were added to the remaining
layer. The mixture was stirred for 15 min followed by the addition of 200 mL of dichloromethane. The organic phase was
separated, dried with MgSO4 and filtered through a basic alumina column. Solvent evaporation system was used to
dichloromethane evaporation. The purity (> 94%) of the product was verified as described above for the BMI.NTf2.
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2. Characterization techniques
NIR spectra of Fe3O4 NPs obtained at 150 oC (a) and 250 oC
Figure S-1. NIR spectra of Fe3O4 NPs obtained at 150 oC (a)
and 250 oC (b). The spectra were recorded from a thin film of
the sample dispersed in hexane in a NaCl window.
FTIR spectra of Fe3O4 NPs obtained at 250 oC
Figure S-2. Infrared spectra of: (a) BMI.NTf2 ionic liquid
before the reaction; (b) a thin film of the magnetite NPs covered
by oleylamine as obtained in the synthesis;
(c) BMI.NTf2 ionic liquid after the 20th reaction is completed at
250 oC in 1.5 h of reaction.
.
Figure S-3. Photographs of a magnetic fluid (Fe3O4 NPs dispersed in cyclohexane) exposed to a permanent magnet (Nd): far
from the sample (a), closer (b) and touching the glass wall (c)
0
.1
.2
.3
.4
.5
.6
3500 3000 2500 2000 1500 1000 500 wavenumber/cm-1
Abs
orba
nce
(a)
(b)
(c)
ν(N
H)
ν(CH)
ν(Fe
-O)
δ(N
H)
0
.1
.2
.3
.4
.5
.6
3500 3000 2500 2000 1500 1000 500 wavenumber/cm-1
Abs
orba
nce
(a)
(b)
(c)
ν(N
H)
ν(CH)
ν(Fe
-O)
δ(N
H)
.14
.16
.18
.2
.22
.24
.26
800 1000 1200 1400 1600 1800 2000 2200 2400 Wavelength/nm
Abs
orba
nce
(b)
(a)
.14
.16
.18
.2
.22
.24
.26
800 1000 1200 1400 1600 1800 2000 2200 2400 Wavelength/nm
Abs
orba
nce
.14
.16
.18
.2
.22
.24
.26
800 1000 1200 1400 1600 1800 2000 2200 2400
.14
.16
.18
.2
.22
.24
.26
800 1000 1200 1400 1600 1800 2000 2200 2400 Wavelength/nm
Abs
orba
nce
(b)
(a)
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CHN Analysis
Table S-1. Results of CHN analysis for samples prepared at 150 oC
TGA results
Figure S-4. TGA curves for the indicated samples
(magnetite/OA obtained at 150 oC in BMI.NTf2). Note
the weight loss of 13.5% begins near 250 oC and ends
near 400 oC (red curve). This is due to the release of OA
from the magnetite surface. This weight % corresponds
to nearly one monolayer of OA.
1H-NMR analysis
Figure S-5. 1H-NMR spectra of pure cyclohexene (upper curve) and of
the cyclohexene solution containing Pd(OAc)2 as catalyst after ten
minutes of purging with the gas liberated in the synthesis of Fe3O4
nanoparticles (lower curve). The Pd(OAc)2 catalyst promotes the
hydrogenation of cyclohexene leading to the formation of cyclohexane.
IL %C
(m/m)
%H
(m/m)
%N
(m/m)
%oleylamine
(m/m)
%oleylamine
(m/m) calc.1
BMI.NTf2 11.42 2.17 0.62 14.13 12.7 1 Mass percent of OA calculated for a monolayer of OA and considering that two molecules of OA
occupies 1 nm2.
ca
0246 PPM
cb
ab
d
d
a
b
c
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Results for the BMI.PF6
Figure S-6. FTIR spectra of (a) BMI.PF6 and (b)
Fe3O4 NPs obtained in BMI.PF6 at 250 oC after 1.5 h
of reaction.
TEM and HRTEM (BMI.PF6)
Figure S-7 (left) TEM image and histrogram (inset, mean diameter 6.2 ±0.9 nm) of Fe3O4 NPs obtained in BMI.PF6 at 150 oC
and 1.5 h of reaction in the presence of OA. (right) a HRTEM image of a Fe3O4 nanocrystal.
Table S-2 CHN Analysis for the Fe3O4 obtained in BMI.PF6 at 150 oC in 1.5 h of reaction
IL %C (m/m)
%H (m/m)
%N (m/m)
%oleylamine (m/m)
%oleylamine (m/m) calc.1
BMI.PF6 12.28 2.29 0.55 15.12 16.7 1 Mass percent of OA calculated for a monolayer of OA and considering that two molecules of OA
occupies 1 nm2
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Magnetization measurements
Figure S-8. Hysteresis loop at 300 K for the Fe3O4 NPs
obtained at 150 oC in BMI.PF6.
TEM Results for NiFe2O4 and MnFe2O4 obtained in BMI.NTf2
Figure S-9. TEM micrographs and histograms of NiFe2O4 (e,f) and MnFe2O4 (g,h) NPs. (e,g) were obtained after 1.5 h and
(f,h) after 3.0 h of reaction at 200 oC.
Figure S-10. HRTEM images of Fe3O4 NPs obtained after 1.5 h (a) and 3.0 h of reaction at 200 oC.
100 nm 100 nm
(h)
100 nm
(g)
Fre
que
ncy
/ %
5 6 7 8 9 10 11 12 13 140
10
20
30
40
50
Particle size / nm
5 6 7 8 9 10 11 12 13 140
5
10
15
20
25
30F
req
ue
ncy
/ %
Particle size / nm100 nm 100 nm100 nm
(h)
100 nm
(g)
Fre
que
ncy
/ %
5 6 7 8 9 10 11 12 13 140
10
20
30
40
50
Particle size / nm
5 6 7 8 9 10 11 12 13 140
5
10
15
20
25
30F
req
ue
ncy
/ %
Particle size / nm5 6 7 8 9 10 11 12 13 14
0
5
10
15
20
25
30F
req
ue
ncy
/ %
Particle size / nm
100 nm
(e)
100 nm
(f)
Fre
que
ncy
/ %
3 4 5 6 7 8 9 10 11 120
5
10
15
20
25
30
35
Particle size / nm
3 4 5 6 7 8 9 10 11 1205
10152025303540
Fre
que
ncy
/ %
Particle size / nm
100 nm
(e)
100 nm
(f)
Fre
que
ncy
/ %
3 4 5 6 7 8 9 10 11 120
5
10
15
20
25
30
35
Particle size / nm3 4 5 6 7 8 9 10 11 12
0
5
10
15
20
25
30
35
Particle size / nm
3 4 5 6 7 8 9 10 11 1205
10152025303540
Fre
que
ncy
/ %
Particle size / nm
3 4 5 6 7 8 9 10 11 1205
10152025303540
Fre
que
ncy
/ %
Particle size / nm
-80000 -40000 0 40000 80000-30
-20
-10
0
10
20
30
M (
em
u/g)
H (Oe)
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Magnetic measurements
Figure S-11. Hysteresis loops at 300 K for (c) Fe3O4 and (d) MnFe2O4 obtained at 200 oC for (○) 1.5 h and (●) 3 h reaction
times. The insets show the hysteresis loops at lower magnetic fields.
FTNIR and FTIR spectra
Figure S-12. NIR spectra of Fe3O4 (a) and CoFe2O4 (b) NPs
obtained at 200 oC in 1.5 h reaction. The spectra were recorded
from a thin film of the sample dispersed in hexane in a NaCl
window. The NIR spectrum of CoFe2O4 NPs shows two main
absorptions near 1640 and 1350 nm, as observed before for
CoFe2O4 NPs obtained by the co-precipitation method.
Figure S-13. FTIR spectra of Fe3O4 (a), CoFe2O4 (b), NiFe2O4
(c), and MnFe2O4 (d) NPs obtained in BMI.NTf2 after 1.5 h of
reaction at 200 oC.
Abs
orba
nce
Wavenumber/cm-1
0
.2
.4
.6
.8
1
3000 2500 2000 1500 1000 500
ν(CH)
572
581
589
571
(a)
(b)
(c)
(d)
δ(N
H)
Abs
orba
nce
Wavenumber/cm-1
0
.2
.4
.6
.8
1
3000 2500 2000 1500 1000 500
ν(CH)
572
581
589
571
(a)
(b)
(c)
(d)
δ(N
H)
Abs
orba
nce
0
.1
.2
.3
.4
800 1200 1600 2000 2400 Wavelength/nm
(a)
(b)Abs
orba
nce
0
.1
.2
.3
.4
800 1200 1600 2000 2400 Wavelength/nm
(a)
(b)
0
.1
.2
.3
.4
800 1200 1600 2000 2400 0
.1
.2
.3
.4
800 1200 1600 2000 2400 Wavelength/nm
(a)
(b)
-4.0 -2.0 0 2.0 4.0
-40
0
40
M/e
mu.
g-1
H/kOe
-400 -200 0 200 400
0
H/Oe
20
-20
-60
60
(c)
-4.0 -2.0 0 2.0 4.0
-40
0
40
M/e
mu.
g-1
H/kOe
-400 -200 0 200 400
0
H/Oe
20
-20
-60
60
(c)
-40
0
40
M/e
mu.
g-1
20
-20
-4.0 -2.0 0 2.0 4.0H/kOe
-400 -200 0 200 400H/Oe
0
(d)
-40
0
40
M/e
mu.
g-1
20
-20
-4.0 -2.0 0 2.0 4.0H/kOe
-400 -200 0 200 400H/Oe
0
(d)
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Table S-3 CHN Analysis for the ferrite NPs obtained in BMI.NTf2 at 150 oC after 1.5 h of reaction
Sample %C
(m/m) %H (m/m)
%N (m/m)
%oleylamine (m/m) exp.
%oleylamine (m/m) calc.1
Wheightloss%2
Fe3O
4 14.13 2.71 0.77 13.30 14.6 12.3
CoFe2O
4 13.53 2.25 0.30 16.08 19.7 13.8
NiFe2O
4 11.83 1.98 0.72 14.51 14.6 12.2
MnFe2O
4 11.77 1.53 0.42 13.72 13.8 12.8
1 Mass percent of OA calculated for a monolayer of OA and considering that two molecules of OA occupies 1 nm2 2 Mass percent of OA as obtained by TGA (see Fig.S-14)
TGA results
Figure S-14. TGA measurements for Fe3O4 (a), CoFe2O4 (b), NiFe2O4 (c), and MnFe2O4 (d) samples obtained after 1.5 h of
reaction in BMI.NTf2 at 200 oC. (See Table S-3 for the weightlosses corresponding to the OA decomposition).
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
Fe3O4
(a)
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
Fe3O4
(a)
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
Wei
ghtlo
ss%
CoFe2O4
(b)
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
Wei
ghtlo
ss%
CoFe2O4
(b)
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
(c)
NiFe2O4
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
(c)
NiFe2O4
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
MnFe2O4
(d)
100.0 200.0 300.0 400.0 500.0 600.0
Temperature/oC
80.0
90.0
100.0
110.0
Wei
ghtlo
ss%
MnFe2O4
(d)
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Results for the synthesis in DPE
TEM Results for Fe3O4 obtained in DPE and OA
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 190
5
10
15
20
Fre
quen
cy (
%)
Particle size / nm
Figure S-15. TEM micrograph and size distribution histogram (lognormal function) of Fe3O4 NPs prepared by decomposition
of Fe(Acac)3 in DFE and oleylamine.
CHN Analysis
Table S-4. Results of CHN analysis for samples prepared in DPE
TGA results
Figure S-16. TGA measurements for Fe3O4 obtained in DPE.
(See Table S-4 for the weightloss corresponding to the OA
decomposition).
%C
(m/m)
%H
(m/m)
%N
(m/m)
%
oleylamine
(m/m)
%
oleylamine
(m/m) calc.1
Wheightloss%2
16.07 1.60 0.68 19.9 18.5 9.1
1 Mass percent of OA calculated for a monolayer of OA and considering that two molecules of OA
occupies 1 nm2 2 Mass percent of OA as obtained by TGA (see Fig.S-16)
0 100 200 300 400 500 600 700 800
90
92
94
96
98
100
Wei
gh
tloss
/ %
Temperature /oC
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