Electronic Supplementary Material (ESI) for RSC Advances.
This journal is © The Royal Society of Chemistry 2016
Supplementary information Section
A step ahead towards the green synthesis of monodisperse gold
nanoparticles: the use of crude glycerol as a greener and low-cost
reducing agent
Rashida Parveena and Germano Tremiliosi Filhoa*
a Institute
of Chemistry of São Carlos, University of São Paulo, P.O. Box 780, CEP 13560-970,
São Carlos, SP, Brazil
*Corresponding Author: [email protected] (G.T Filho); Phone: +55-163373-9951
1.0
0.9
Absorbance (a.u)
0.8
0.7
Commercial glycerol (99.5%)
CG-73
CG-65
0.6
0.5
0.4
0.3
0.2
0.1
0.0
200
300
400
500
600
700
800
wavelength, nm
Fig. S1: UV-Visible spectrum of pure glycerol (black curve), CG-73 (red curve) CG-65 (blue curve).
62.4
72
commercial glycerol
CG-73
90
85
80
75
70
65
60
55
50
ppm
Fig. S2: 13C-NMR spectrum of commercial glycerol (above) and CG-73 after simple filtration through
a 0.2 µm syringe-fitted filter (below).
The
13C-NMR
spectrum (Fig. S2) of commercial glycerol (Panreac) demonstrates two
signals at 62.4 ppm and 72.0 ppm which are assigned to the primary and secondary
aliphatic carbon atoms, respectively. The spectrum of CG-73 shows the same peaks at the
same position as the pure commercial glycerol and no additional peaks are observed. This
shows the absence of any significant quantity of organic impurities, in agreement with the
FTIR analysis (Fig. S3)
Fig. S3: (a) FTIR spectrum of CG-73 as compared to commercial glycerol (99.5 %) and (b) the same
spectra in absorption mode zoomed in the region 1500–1800 cm-1 to show the details of the bands
in this region (inset). Various vibrational modes have been marked in the Fig.
The FTIR spectra of both CG-73 and commercial glycerol are almost similar and shows
peaks at 3345 cm-1 (O–H stretching), 2933–2881 cm-1 (–H stretching), 1652 cm-1 (H2O
bending), 1420–1460 cm-1 (C–O–H bending), 1110 cm-1 (C–O stretching of secondary
alcohols) and 926 cm-1 (O–H bending). The FTIR spectra of CG-73, however, shows a
prominent and broader feature centered at 1651 cm-1. This broad band between 1500–
1800 cm-1 can be resolved into two components, the components at 1583 cm-1 being
assigned to the ‒COO- functionality (Fig. S3b). Thus traces of fatty acids or soap may be
present in CG-73 sample.
Fig. S4: Gas chromatogram of CG-65 sample. The compounds responsible for these peaks, as
identified from mass spectrograms (Fig. S5) have been denoted on the RHS of the figure.
Fig. S5: Mass spectra of separated components in CG-65 sample. The chemical structures of
corresponding compounds, as identified by MS, have also been shown.
(a)
AuNPs prepared with CG-65
0.8
(b)
80
Mean size = 8 ± 1.5 nm
60
519
0.6
Frequency
Absorbance (a.u)
70
0.4
50
40
30
20
0.2
10
0.0
400
500
600
wavelength (nm)
700
800
0
0
4
8
12
size (nm)
16
20
Fig. S6: (a) UV-Visible spectrum and (b) particle size distribution as measured by TEM of AuNPs prepared
using CG-65. Conditions of synthesis 3.75 x 10-3 mmoles HAuCl4, 1% PVP and 13.2 pH.
Fig. S7: (a) SEM image of AuNPs prepared using 0.1 mol L-1 CG-73 and TEM images of AuNPs
prepared using (b) 0.2 mol L-1 and (c) 0.4 mol L-1 CG-73 . The average particle size of AuNPs along
with standard deviation has been indicated above each image.
Fig. S8: Representative high resolution TEM image of AuNPs prepared using CG-73
PVP = 1.3%
35
25
20
15
25
20
15
10
10
5
5
0
0
4
8
12
size, nm
16
Mean size = 9
SD = 1.8
30
% chances
% chances
30
PVP = 1.0%
35
Mean size = 6 nm
SD = 1.4
20
0
0
4
8
12
size, nm
16
20
Fig. S9: DLS measurements of AuNPs prepared using different PVP concentration at fixed pH
(~13.2), fixed glycerol (0.2 mol L-1) and fixed HAuCl4 (3.75 x 10-3) concentration. SD stands for
standard deviation, which represents the breadth of size distribution of AuNPs
[OH-] = 0.1 mol L-1
15
12
9
6
[OH-] = 0.2 mol L-1
25
%chances
%chances
18
20
mean size = 7 nm
SD =1.8
15
10
5
3
5
%chances
0
30
Mean size = 9 nm
SD = 2
10
size, nm
35
30
25
20
15
10
5
0
15
0
5
10
size, nm
15
[OH-] = 0.4 mol L-1
mean size = 7.00nm
SD =1.6
5
10
size, nm
15
Fig. S10: Hydrodynamic diameter of AuNPs prepared using different OH- concentrations at fixed
PVP concentration (1 %), fixed glycerol (0.2 mol L-1) and fixed HAuCl4 (3.75 x 10-3 mmoles)
concentration. SD stands for standard deviation, which represents the width of size distribution of
AuNPs
Fig. S11: TEM images of PDAC-stabilized AuNPs prepared using different pH while keeping other
parameters constant. The letter M denotes concentration in mol L-1.
30
PDAC=1.30 %
20
15
10
20
15
10
5
5
10
35
30
25
20
15
10
5
20 30
size (nm)
40
50
0
10 20 30 40 50 60
size (nm)
30
PDAC=0.05 %
% chances
%chances
0
PDAC=1.00 %
25
25
% chances
%chances
30
25
PDAC=0.03%
20
15
10
5
0 5 101520253035404550
size, nm
0 5 10 15 20 25 30 35 40 45 50
size (nm)
Fig. S12: DLS particles size distribution of PDAC-stabilized AuNPS obtained using different
concentration of PDAC; all other experimental conditions are the same for each sample.
PDAC=1 %
glycerol = 0.2 mol L-1
0.8
0.8
(v)
(iv)
(iii)
PDAC=1 %
glycerol = 0.2 mol L-1
NaOH = 0.1 mol L-1
517
0.6
0.5
0.4
0.3
-1
(i) 0.01 mol L NaOH
(ii) 0.05 mol L-1 NaOH
(iii) 0.1 mol L-1 NaOH
(iv) 0.2 mol L-1 NaOH
(v) 0.3 mol L-1 NaOH
0.2
0.1
(i)
0.0
0
10
20
30
40
time (min)
50
60
Absorbance (a.u)
0.6
(ii)
515
0.7
0.7
Absorbance at 520 nm
(b)
0.5
0.4
523
528
0.3
0.2
535
0
5
10
15
20
25
30
35
40
45
50
55
60
time (min)
(a)
0.9
0.1
0.0
400
500
600
700
Wavelength (nm)
800
Fig. S13: (a) Time evolution of the absorbance band at 520 nm as function of pH in presence of both
1% PDAC and 0.2 mol L-1 glycerol and (b) complete electronic absorption spectra taken at 0 min
through 60 min at 05 minutes interval of PDAC-stabilized AuNPs (sample (iii) in Fig S13a) prepared
using 0.1 mol L-1 NaOH, 1% PDAC, 0.2 mol L-1 glycerol and 3.75 x 10-3 mmole HAuCl4.
Fig. S13a shows the temporal changes in the absorbance of the SPR band at 520 nm. It can
be observed that growth of AuNPs is very slow at NaOH of 0.01 mol L-1 or lower. The curves
show a sharp increase in absorbance at higher NaOH concentration (NaOH > 0.01 mol L-1).
The slope of the absorbance curves shows a decrease at some point (at 18 min in curve (iii)
and 6 min in curve (v), for example). Considering the fact that absorbance at only 520 nm is
measured, this change in slope is related to the change in particle size and corresponding
change in absorption wavelength as the reaction proceeds. Fig. S13b clearly shows the shift
in optical spectra or absorption maximum for the sample prepared using 0.1 mol L-1 NaOH.
Preparation of AgNPs using crude glycerol (CG)
Fig. S14: UV-Visible spectrum and TEM images (inset) of AgNPs prepared using crude glycerol as reducing
agent. Synthesis conditions: 20 µL AgNO3 (0.005 mol L-1), 1 mL crude glycerol (0.2 mol L-1 prepared in 0.8 mol
L-1 NaOH solution) and 1 mL PVP (1%).
0.40
0.35
0.1mol L-1 NaOH
0.5 mol L-1 NaOH
0.8 mol L-1 NaOH
1 mol L-1 NaOH
Absorbance (a.u)
0.30
0.25
0.20
PVP 1%
0.15
0.10
0.05
0.00
300
400
500
600
700
800
wavelength (nm)
Fig. S15: UV-Visible spectra of AgNPs prepared using crude glycerol in the presence of different
concentrations of NaOH under otherwise identical conditions. Synthesis conditions: 20 µL AgNO3
(0.005 mol L-1), 1 mL crude glycerol (0.2 mol L-1 prepared in NaOH solution of varying
concentration) and 1 mL PVP (1%).