Surface Vibrational Structure of Colloidal Silica and Its Direct ...
Supporting Information for:
Surface Vibrational Structure of Colloidal Silica and Its Direct Correlation with Surface Charge Density Tove Lagström,1 Tobias A. Gmür,2 Luca Quaroni,3,‡ Alok Goel,2 and Matthew A. Brown2,* 1.
Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zurich, Switzerland
2.
Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, CH-8093 Zurich, Switzerland
3.
Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
‡Current address: Functional Genomics Center Zurich, CH-8057 Zurich, Switzerland.
Corresponding Author Email: [email protected], Phone: +41 44 632 3048
S1
10 wt.%, 9 nm SiO2, 40 mM NaCl b
0.10
a
pH 10.0
c
pH 9.0
d
pH 8.0
e
pH 7.3
f
pH 6.4
3500 3000 2500 2000 1500 1000 Wavenumber [1/cm]
pH 2.0
3500 3000 2500 2000 1500 1000 Wavenumber [1/cm]
Figure S1. ATR-FTIR spectra of 10 wt.% colloidal 9 nm silica in 40 mM NaCl at pH 10.0 (a), 9.0 (b), 8.0 (c), 7.3 (d), 6.4 (e) and 2.0 (f).
S2
10 wt.%, 9 nm SiO2, 40 mM NaCl b
0.10
a
pH 10.0
c
pH 9.0
d
pH 8.0
e
pH 7.3
f
pH 6.4
1400
1200
1000
Wavenumber [1/cm]
800
pH 2.0
1400
1200
1000
800
Wavenumber [1/cm]
Figure S2. ATR-FTIR spectra of 10 wt.% colloidal 9 nm Ludox SM colloidal silica in 40 mM NaCl at pH 10.0 (a), 9.0 (b), 8.0 (c), 7.3 (d), 6.4 (e) and 2.0 (f). Only the silica regions of the spectra are shown. See Figure S1 for the complete spectra.
S3
2
Surface Charge Density [µC/cm ]
0 -5 -10 -15 0
2
4 6 8 Suspension pH
10
Figure S3. Surface charge density of 9 nm Ludox SM colloidal silica in 40 mM NaCl as determined from potentiometric titration.
Table S1: Surface charge density of 9 nm Ludox SM colloidal silica in 40 mM NaCl (values in red are determined from the Sigmoid fit with confidence interval 95).
pH 10.08 10.06 10.03 10.01 10.00 9.98 9.97 9.95 9.87 9.86 9.75 9.75 9.70 9.59 9.58 9.45 9.37 9.35 9.17 9.02
SCD μC/cm2 −17.81 −16.97 −16.85 −16.70 −16.84 ± 0.2 −16.56 −17.23 −16.39 −15.94 −16.63 −15.29 −15.28 −15.71 −14.46 −14.45 −14.41 −13.42 −13.25 −13.05 −11.79 S4
9.00 9.00 8.29 8.07 8.00 7.91 7.07 7.00 6.77 6.77 6.00 5.08 5.00 4.89 4.47 4.21 4.00 3.70 3.35 3.31 3.08 3.00 2.94 2.93 2.92
−11.61 −11.86 ± 0.2 −9.31 −8.00 −7.78 ± 0.2 −7.36 −5.25 −4.77 ± 0.2 −4.15 −4.15 −2.72 ± 0.2 −1.36 −1.38 ± 0.2 −1.13 −0.85 −0.62 −0.55 ± 0.2 −0.41 −0.27 −0.28 −0.18 −0.04 ± 0.2 0.00 0.00 0.00
S5
Ludox SM Ludox HS Ludox TM
1400
1300
1200
1100
1000
900
800
Wavenumber [1/cm] Figure S4. ATR-FTIR spectra of 10 wt.% colloidal 9 (red, Ludox SM), 14 (blue, Ludox HS) and 25 nm (black, Ludox TM) silica in 40 mM NaCl at pH 9.0.
Transmission electron microscopy (TEM). The size and distribution of the silica nanoparticles (Ludox HS and TM) were determined using ex situ TEM. Small drops from each suspension (0.3 wt.%) were placed onto copper grids. In all cases the electrolyte concentration was 50 mM, and the pH adjusted by the addition of concentrated HCl. The grids were dried in ambient air before being transferred to vacuum. The micrographs were measured with a FEI Tecnai G2 Spirit microscope (120 kV). The sizes and distributions of all samples measured are shown in Figure S5.
S6
Ludox HS-40 pH 1 Ludox HS-40 pH 10
80 60
mean = 14.1 ± 2.4 nm mean = 14.4 ± 2.9 nm
Counts
40 20 60 40
Ludox TM-50 pH 1 Ludox TM-50 pH 10 mean = 25.2 ± 4.3 nm mean = 25.2 ± 3.9 nm
20
0
10
20
30
40
50
Particle diameter [nm] Figure S5. Ludox HS and TM colloidal silica particle size distributions measured by TEM. The mean value and standard deviation for each suspension is shown.
S7
Surface Vibrational Structure of Colloidal Silica and Its Direct Correlation with Surface Charge Density Tove Lagström,1 Tobias A. Gmür,2 Luca Quaroni,3,‡ Alok Goel,2 and Matthew A. Brown2,* 1.
Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zurich, Switzerland
2.
Laboratory for Surface Science and Technology, Department of Materials, ETH Zürich, CH-8093 Zurich, Switzerland
3.
Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
‡Current address: Functional Genomics Center Zurich, CH-8057 Zurich, Switzerland.
Corresponding Author Email: [email protected], Phone: +41 44 632 3048
S1
10 wt.%, 9 nm SiO2, 40 mM NaCl b
0.10
a
pH 10.0
c
pH 9.0
d
pH 8.0
e
pH 7.3
f
pH 6.4
3500 3000 2500 2000 1500 1000 Wavenumber [1/cm]
pH 2.0
3500 3000 2500 2000 1500 1000 Wavenumber [1/cm]
Figure S1. ATR-FTIR spectra of 10 wt.% colloidal 9 nm silica in 40 mM NaCl at pH 10.0 (a), 9.0 (b), 8.0 (c), 7.3 (d), 6.4 (e) and 2.0 (f).
S2
10 wt.%, 9 nm SiO2, 40 mM NaCl b
0.10
a
pH 10.0
c
pH 9.0
d
pH 8.0
e
pH 7.3
f
pH 6.4
1400
1200
1000
Wavenumber [1/cm]
800
pH 2.0
1400
1200
1000
800
Wavenumber [1/cm]
Figure S2. ATR-FTIR spectra of 10 wt.% colloidal 9 nm Ludox SM colloidal silica in 40 mM NaCl at pH 10.0 (a), 9.0 (b), 8.0 (c), 7.3 (d), 6.4 (e) and 2.0 (f). Only the silica regions of the spectra are shown. See Figure S1 for the complete spectra.
S3
2
Surface Charge Density [µC/cm ]
0 -5 -10 -15 0
2
4 6 8 Suspension pH
10
Figure S3. Surface charge density of 9 nm Ludox SM colloidal silica in 40 mM NaCl as determined from potentiometric titration.
Table S1: Surface charge density of 9 nm Ludox SM colloidal silica in 40 mM NaCl (values in red are determined from the Sigmoid fit with confidence interval 95).
pH 10.08 10.06 10.03 10.01 10.00 9.98 9.97 9.95 9.87 9.86 9.75 9.75 9.70 9.59 9.58 9.45 9.37 9.35 9.17 9.02
SCD μC/cm2 −17.81 −16.97 −16.85 −16.70 −16.84 ± 0.2 −16.56 −17.23 −16.39 −15.94 −16.63 −15.29 −15.28 −15.71 −14.46 −14.45 −14.41 −13.42 −13.25 −13.05 −11.79 S4
9.00 9.00 8.29 8.07 8.00 7.91 7.07 7.00 6.77 6.77 6.00 5.08 5.00 4.89 4.47 4.21 4.00 3.70 3.35 3.31 3.08 3.00 2.94 2.93 2.92
−11.61 −11.86 ± 0.2 −9.31 −8.00 −7.78 ± 0.2 −7.36 −5.25 −4.77 ± 0.2 −4.15 −4.15 −2.72 ± 0.2 −1.36 −1.38 ± 0.2 −1.13 −0.85 −0.62 −0.55 ± 0.2 −0.41 −0.27 −0.28 −0.18 −0.04 ± 0.2 0.00 0.00 0.00
S5
Ludox SM Ludox HS Ludox TM
1400
1300
1200
1100
1000
900
800
Wavenumber [1/cm] Figure S4. ATR-FTIR spectra of 10 wt.% colloidal 9 (red, Ludox SM), 14 (blue, Ludox HS) and 25 nm (black, Ludox TM) silica in 40 mM NaCl at pH 9.0.
Transmission electron microscopy (TEM). The size and distribution of the silica nanoparticles (Ludox HS and TM) were determined using ex situ TEM. Small drops from each suspension (0.3 wt.%) were placed onto copper grids. In all cases the electrolyte concentration was 50 mM, and the pH adjusted by the addition of concentrated HCl. The grids were dried in ambient air before being transferred to vacuum. The micrographs were measured with a FEI Tecnai G2 Spirit microscope (120 kV). The sizes and distributions of all samples measured are shown in Figure S5.
S6
Ludox HS-40 pH 1 Ludox HS-40 pH 10
80 60
mean = 14.1 ± 2.4 nm mean = 14.4 ± 2.9 nm
Counts
40 20 60 40
Ludox TM-50 pH 1 Ludox TM-50 pH 10 mean = 25.2 ± 4.3 nm mean = 25.2 ± 3.9 nm
20
0
10
20
30
40
50
Particle diameter [nm] Figure S5. Ludox HS and TM colloidal silica particle size distributions measured by TEM. The mean value and standard deviation for each suspension is shown.
S7
