Interactions of Humic Acid with Nanosized Inorganic Oxides
Page S1
Supporting Information Cover Sheet
Interactions of Humic Acid with Nanosized Inorganic Oxides Kun Yang1,2, Daohui Lin1,2 and Baoshan Xing2,* 1
Department of Environmental Science, Zhejiang University, Hangzhou 310028, China; Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA *Corresponding author phone: (413) 545-5212; fax: (413)545-3958; e-mail: [email protected]. 2
Number of pages: 7 Number of tables: 1 Number of figures: 6 Journal: Langmuir Date prepared: Nov 7, 2008
Page S2
Extraction of Humic Acids Humic acid (HA) extraction involved mixing peat (air-dried and passed through a 2-mm sieve) with 0.1 mol/L NaOH at a solid to solution ratio of 10:1 (v:w) in a 1000-mL bottle. The air in the bottle was replaced with N2 gas, and the mixture was shaken for 24 h at room temperature. After being mixed, the suspension was centrifuged at 3500g for 30 min, and the supernatant was collected for acidification (pH 1.5 with 1.0 mol/L HCl) to obtain HA. Precipitated HA in acidified supernatant was separated and collected by centrifugation at 3500g for 30 min. After that, HA was de-ashed three times using 0.1 M HCl and 0.3 M HF mixtures at a ratio (g/mL) of 1:20, rinsed with deionized water, freeze-dried, gently ground to pass through a 100-µm sieve, and stored for subsequent use. Description of the forms of Nano-oxides The TiO2 group is composed of rutile, anatase, and brookite. Rutile and brookite as well as anatase all have the same elemental chemistry, TiO2, but they have different structures. Anatase is a polymorph with the two other minerals. At higher temperatures, about 915 degrees Celsius, anatase will automatically revert to the rutile structure. Rutile is more common and more well known mineral of the three, while anatase is the rarest. Anatase shares many of the same or nearly same properties as rutile such as luster, hardness and density. However, due to the structural difference, anatase and rutile differ slightly in crystal behavior and more distinctly in cleavage. More information regarding the different mineral structures and properties of TiO2 group can be obtained from http://ruby.colorado.edu/~smyth/min/tio2.html and http://mineral.galleries.com/minerals/oxides/anatase/anatase.htm.
Al2O3 exists in several forms, the principal being gamma- and alpha-alumina (or corundum). Alpha-Al2O3 is the pure form obtained by calcination at high temperature. Beta-Al2O3, which contains a small amount of alkali metal oxide, is the compound Na2O.Al2O3. Gamma-Al2O3 is stable to about 1000oC and contains traces of water or hydroxyl ions. According to the description of the supplier (http://www.mrnm.com.cn/product_2.htm), porous SiO2 nanoparticle is called as P-form SiO2, while spherical SiO2 nanoparticle is called as S-form SiO2. FTIR Spectroscopy of Nano-oxides The FTIR spectra of six nano-oxides are presented in Figure S1. The broad absorption bands at 2500-3700 and 1628 cm-1 in Figure S1 can be assigned to hydroxyl group stretching on the surface of nano-oxides and water (1). Three types of bound hydroxyl groups at least (at around 3620, 3480 and 3300 cm-1, respectively) can be recognized (Figure 1). Among these nano-oxides, nanosize P-SiO2, S-SiO2, γ-Al2O3 and TiO2 have abundant hydroxyl groups on their surfaces due to the relative absorption intensities at 2500-3700 and 1628 cm-1, while nanosize a-Al2O3 and ZnO have few hydroxyl groups. Other absorption bands showed the impurity and their bulk counterparts. For nano-SiO2, absorption bands at around 1080, 938, 792 and 456 cm-1 can be assigned to the Si-O-Si stretching, Si-OH stretching, Si-O-Si bending and Si-O-Si vibration, respectively (2,3). For nano-TiO2, the broad absorption bands in the region of 400-800 cm-1can be assigned to the stretching of Ti-O-Ti, the peak at 1390 cm-1 to a titanium-acetate complex, and the peak at 1122 and 1040 cm-1corresponding respectively to the end and bridging butoxyl groups (4). For nano-Al2O3, the broad absorption bands in the region of 400-848 cm-1 for γ-Al2O3 can be assigned to the stretching of Al-O-Al, while the stretching of Al-O-Al for α-Al2O3 showing two peaks: a broad absorption bands in the region of 500-800 cm-1 and another bands at around 456
Page S3
cm-1. The band at 1510 and 1390 cm−1 can be assigned to the asymmetric and symmetric O-C-O stretching vibration of adsorbed carbonate anion at the nano-Al2O3 surface (5). For nano-ZnO, The peaks at 1390 and 1510 cm-1 were also the symmetric and asymmetric O–C–O stretching vibration of adsorbed carbonate anion, respectively (5,6). The lattice vibration of carbonate generated absorption peaks at 1122, and 848 cm-1 (7). The peak at 456 cm-1 is attributed to a Zn–O stretching vibration. FTIR Spectroscopy of HA and bound HA The spectra of HA and nano-oxide bound HA are typical of those generally shown for humic acids (8-10), showing major absorption bands in the regions: 3700-2500 cm-1 (a strong broad absorption of H-bonded–OH stretching and water), 2926/2856 cm-1 (asymmetric/symmetric C-H stretching of aliphatic -CH2), 1722 cm-1 (C-O vibration of carboxyl), 1680 cm-l (conjugated C=C or H-bonded C=O stretching of carbonyl), 1580-1620 cm-1 (stretching of aromatic C=C), 1514 cm-1 (the ring vibrating modes of ortho-substituted aromatic compounds), 1460/1374 cm-1 (the coupled C-O stretching and the OH in plane bending vibration, respectively), strong shoulders around 1280/1070 cm-1 (C-O stretching of Phenolic /aliphatic OH). References: [1] Hofman, R.; Westheim, J.G.F.; Pouwel, I.; Fransen, T.; Gellings, P.J. FTIR and XPS studies on corrosion-resistant SiO2 coatings as a function of the humidity during deposition. Surf. Inter. Anal. 1996, 24, 1-6. [2] Demsar, A.; Colaric, B.; Rus, S.; Lindav, J.; Svegelj, F.; Orel, B.; Pracek, B.; Zalar, A. FTIR spectroscopy and AES study of water containment in SiO2 thin films. Thin. solid films 1996, 281-282, 409-411. [3] Pagacova, J.; Plsko, A.; Stanovae, I.; Jona, E.; Muellerova, J.; Exnar, P.; Lukac, A.; Mar-Cekova, L. The influence of preparation conditions on porous SiO2 structure studied by FTIR Spectroscopy. Chem. Listy 2007,101,673-679. [4] Sui, R.H.; Rizkalla, A.S.; Charpentier, P.A. FTIR study on the formation of TiO2 nanostructures in supercritical CO2. J. Phys. Chem. B, 2006, 110, 16212 -16218. [5] Wijnja, H.; Schulthess, C.P. ATR–FTIR and DRIFT spectroscopy of carbonate species at the aged γ-Al2O3/water interface. Spectrochimica Acta Part A. 1999, 55, 861-872. [6] Liu, J.; Ding, D.; Wang, L.; Han, Y. Preparation and characterization of uniform circinate aggregates of sheet ZnO nanoparticles. RARE METALS, 2008, 27, 36-40. [7] Wahab, R.; Ansari, S.G.; Kim, Y.S.; Dar, M.A.; Shin, H.S. Synthesis and characterization of hydrozincite and its conversion into zinc oxide nanoparticles. J. Alloys Compounds 2008,461, 66-71. [8] Kang, S.; Xing, B. Humic acid fractionation upon sequential adsorption onto goethite. Langmuir 2008,24,2525-2531. [9] Gu, B.; Schmitt, J.; Chen, Z.; Liang, L.; McCarthy, J.F. Adsorption and desorption of natural organic matter on iron oxide: mechanisms and models. Environ.Sci.Technol. 1994,28,38-46. [10] Stevenson, F.J. Humus chemistry: Genesis, composition, reactions. 2nd ed. John Wiley & Sons:New York, 1994.
Page S4
Table S1.
Purity, Diameter and Surface Hydroxyl Content of Nano-oxides
Nano-oxides nano-P-SiO2 nano-S-SiO2 nano-TiO2 nano-α-Al2O3 nano-γ-Al2O3 nano-ZnO
Purity, %
Diameter, nm
>99.5% >99.5% >99% >99.5% >99.5% >99.5%
20±5 nm 30±5 nm 50±5 nm 150±5 nm 60±5 nm 20±5 nm
Notation P form, Surface Hydroxyl Content >45% S form, Surface Hydroxyl Content >19% anatase form α form γ form
1122 1080 1040 938 848
1390
3620
1510
3480
792
1628
3300
SP1 P-SiO 2
Absorbance
S-SiO 2 SS1
ZnO ZnO 3900
3400
2900
2400
1900
1400
900
400
1400
900
400
TiO2 TiO 2
γ-Al MC2R 2O3 MC2A
α-Al2O3
3900
3400
2900
2400
1900
Wave numbers, cm-1
Figure S1. FTIR spectra of six nano-oxides.
456
Adsorption maxima, mg TOC/g
Page S5 100 80 γ-Al2O3
TiO2
60 y = 0.2802x + 9.2991
ZnO
40
2
R = 0.9527
20 α-Al2O3
0 0
100
200
300
400
SBET, m2/g
Surface area normalized adsorption maxima, mg TOC/m2
Figure S2. Positive linear relationship of HA adsorption maxima with total surface area (SBET) for nanosized TiO2, γ-Al2O3, ZnO and α-Al2O3.
1
α-Al2O3 y = -0.3768x + 0.8148
0.8
2
R = 0.9594 0.6
ZnO
γ-Al2O3
0.4
TiO2 P-SiO2
0.2
S-SiO2 0 0
0.5
1
1.5
2
2.5
3
H content, %
Figure S3. Positive linear relationship of surface area (SBET) normalized HA adsorption maxima with H content of nanosized TiO2, γ-Al2O3, ZnO and α-Al2O3.
Page S6
1040 1390 1122 1510 1600 1628
Absorbance
2926
(a) (b) (c) (d)
3900
3400
2900
2400
1900
1400
900
400
-1
Wave numbers, cm
Figure S4. FTIR Spectra of nano-TiO2 (a), HA coated nano-TiO2 (b), nano-ZnO (c) and HA coated nano-ZnO (d). The adsorbed butoxyl groups with peaks at 1122 and 1040 cm-1 for nano-TiO2 and carbonates with peak at 1122 cm-1 for nano-ZnO were replaced and released by HA, showing these peaks disappeared after HA coating. 0.6
γ-Al2O3
0.5
TiO2
0.18
0.6
0.15
0.5
0.4
C
0.7
ZnO
0.12
0.4 0.3 y = 2.03x - 0.1077 0.2
2
R = 0.9995
2
R = 0.9781
2
R = 0.9607
0.06
0.2
0.1
0.03
0.1 0
0 0
0.1
0.2
0.3
0.4
-0.3
-0.2
-0.1
y = 0.8721x + 0.0452
0.09
y = 1.2476x + 0.3746
0.3
0
0
0.1
0.2
0.3
0
0.05
0.1
0.15
H
Figure S5. Atomic carbon (C) versus atomic hydrogen (H) for bound HA with nanosized γ-Al2O3, TiO2 and ZnO. Atomic carbon (C) and atomic hydrogen (H) of nano-oxide bound HA were calculated from the C and H elemental compositions (Table 1) with the following equations: (Ci-C0)/12.011 and (Hi-H0)/1.008, respectively, where Ci and Hi is the percent mass content of elemental carbon and hydrogen in HA coated nano-oxides, C0 and H0 is the percent mass content of elemental carbon and hydrogen in nano-oxides before HA coating, 12.011 and 1.008 (g/mol) are the molar mass of atomic carbon and hydrogen. Dotted lines represent the regression results of linear model, where the slopes of linear lines show the atomic ratio of carbon to hydrogen (C/H) of nano-oxide bound HA.
Page S7 0 80
MC2A α-Al 2O3 MC2A-HAA1% HA50 MC2A-HAA2% HA100 HAA HA
60 40
2
4
6
8
10
12
0 -10
ZnO ZnO HA250 ZnO-HAA5% HA1000 ZnO-HAA20% HA HAA
-20
20
-30
0 0
2
4
6
8
10
12
-20
-40
-40
-50
-60 -80
-60
50
0
0 MC2R γ-Al 2O3 MC2R-HAA5% HA250 MC2R-HAA10% HA500 MC2R-HAA30% HA1500 HA HAA
40
Zeta potential, mV
30 20 10
2
4
6
8
10
12
4
6
8
10
12
-10 -20
0 -10 0
2
4
6
8
10
12
-20
-30 -40
P-SiO SP1 2 SP1-HAA1% HA50 HAA HA
-30 -40
-50
-50 -60
-60
50
0
0 TiO22 TiO TiO2-HAA2% HA100 TiO2-HAA5% HA250 TiO2-HAA10% HA500 TiO2-HAA20% HA1000 HAA HA
40 30 20 10
-10
-20
0 -10 1
3
5
7
9
2
S-SiO SS1 2 SS1-HAA1% HA50 HAA HA
-30
11
-20
-40
-30 -40
-50
-50
-60
-60
pH
Figure S6. Comparison of the zeta potential of HA coated nano-oxides with HA and nano-oxides at various pH. The number after HA represents the initial HA concentration used for coating of nano-oxides.
Supporting Information Cover Sheet
Interactions of Humic Acid with Nanosized Inorganic Oxides Kun Yang1,2, Daohui Lin1,2 and Baoshan Xing2,* 1
Department of Environmental Science, Zhejiang University, Hangzhou 310028, China; Department of Plant, Soil and Insect Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA *Corresponding author phone: (413) 545-5212; fax: (413)545-3958; e-mail: [email protected]. 2
Number of pages: 7 Number of tables: 1 Number of figures: 6 Journal: Langmuir Date prepared: Nov 7, 2008
Page S2
Extraction of Humic Acids Humic acid (HA) extraction involved mixing peat (air-dried and passed through a 2-mm sieve) with 0.1 mol/L NaOH at a solid to solution ratio of 10:1 (v:w) in a 1000-mL bottle. The air in the bottle was replaced with N2 gas, and the mixture was shaken for 24 h at room temperature. After being mixed, the suspension was centrifuged at 3500g for 30 min, and the supernatant was collected for acidification (pH 1.5 with 1.0 mol/L HCl) to obtain HA. Precipitated HA in acidified supernatant was separated and collected by centrifugation at 3500g for 30 min. After that, HA was de-ashed three times using 0.1 M HCl and 0.3 M HF mixtures at a ratio (g/mL) of 1:20, rinsed with deionized water, freeze-dried, gently ground to pass through a 100-µm sieve, and stored for subsequent use. Description of the forms of Nano-oxides The TiO2 group is composed of rutile, anatase, and brookite. Rutile and brookite as well as anatase all have the same elemental chemistry, TiO2, but they have different structures. Anatase is a polymorph with the two other minerals. At higher temperatures, about 915 degrees Celsius, anatase will automatically revert to the rutile structure. Rutile is more common and more well known mineral of the three, while anatase is the rarest. Anatase shares many of the same or nearly same properties as rutile such as luster, hardness and density. However, due to the structural difference, anatase and rutile differ slightly in crystal behavior and more distinctly in cleavage. More information regarding the different mineral structures and properties of TiO2 group can be obtained from http://ruby.colorado.edu/~smyth/min/tio2.html and http://mineral.galleries.com/minerals/oxides/anatase/anatase.htm.
Al2O3 exists in several forms, the principal being gamma- and alpha-alumina (or corundum). Alpha-Al2O3 is the pure form obtained by calcination at high temperature. Beta-Al2O3, which contains a small amount of alkali metal oxide, is the compound Na2O.Al2O3. Gamma-Al2O3 is stable to about 1000oC and contains traces of water or hydroxyl ions. According to the description of the supplier (http://www.mrnm.com.cn/product_2.htm), porous SiO2 nanoparticle is called as P-form SiO2, while spherical SiO2 nanoparticle is called as S-form SiO2. FTIR Spectroscopy of Nano-oxides The FTIR spectra of six nano-oxides are presented in Figure S1. The broad absorption bands at 2500-3700 and 1628 cm-1 in Figure S1 can be assigned to hydroxyl group stretching on the surface of nano-oxides and water (1). Three types of bound hydroxyl groups at least (at around 3620, 3480 and 3300 cm-1, respectively) can be recognized (Figure 1). Among these nano-oxides, nanosize P-SiO2, S-SiO2, γ-Al2O3 and TiO2 have abundant hydroxyl groups on their surfaces due to the relative absorption intensities at 2500-3700 and 1628 cm-1, while nanosize a-Al2O3 and ZnO have few hydroxyl groups. Other absorption bands showed the impurity and their bulk counterparts. For nano-SiO2, absorption bands at around 1080, 938, 792 and 456 cm-1 can be assigned to the Si-O-Si stretching, Si-OH stretching, Si-O-Si bending and Si-O-Si vibration, respectively (2,3). For nano-TiO2, the broad absorption bands in the region of 400-800 cm-1can be assigned to the stretching of Ti-O-Ti, the peak at 1390 cm-1 to a titanium-acetate complex, and the peak at 1122 and 1040 cm-1corresponding respectively to the end and bridging butoxyl groups (4). For nano-Al2O3, the broad absorption bands in the region of 400-848 cm-1 for γ-Al2O3 can be assigned to the stretching of Al-O-Al, while the stretching of Al-O-Al for α-Al2O3 showing two peaks: a broad absorption bands in the region of 500-800 cm-1 and another bands at around 456
Page S3
cm-1. The band at 1510 and 1390 cm−1 can be assigned to the asymmetric and symmetric O-C-O stretching vibration of adsorbed carbonate anion at the nano-Al2O3 surface (5). For nano-ZnO, The peaks at 1390 and 1510 cm-1 were also the symmetric and asymmetric O–C–O stretching vibration of adsorbed carbonate anion, respectively (5,6). The lattice vibration of carbonate generated absorption peaks at 1122, and 848 cm-1 (7). The peak at 456 cm-1 is attributed to a Zn–O stretching vibration. FTIR Spectroscopy of HA and bound HA The spectra of HA and nano-oxide bound HA are typical of those generally shown for humic acids (8-10), showing major absorption bands in the regions: 3700-2500 cm-1 (a strong broad absorption of H-bonded–OH stretching and water), 2926/2856 cm-1 (asymmetric/symmetric C-H stretching of aliphatic -CH2), 1722 cm-1 (C-O vibration of carboxyl), 1680 cm-l (conjugated C=C or H-bonded C=O stretching of carbonyl), 1580-1620 cm-1 (stretching of aromatic C=C), 1514 cm-1 (the ring vibrating modes of ortho-substituted aromatic compounds), 1460/1374 cm-1 (the coupled C-O stretching and the OH in plane bending vibration, respectively), strong shoulders around 1280/1070 cm-1 (C-O stretching of Phenolic /aliphatic OH). References: [1] Hofman, R.; Westheim, J.G.F.; Pouwel, I.; Fransen, T.; Gellings, P.J. FTIR and XPS studies on corrosion-resistant SiO2 coatings as a function of the humidity during deposition. Surf. Inter. Anal. 1996, 24, 1-6. [2] Demsar, A.; Colaric, B.; Rus, S.; Lindav, J.; Svegelj, F.; Orel, B.; Pracek, B.; Zalar, A. FTIR spectroscopy and AES study of water containment in SiO2 thin films. Thin. solid films 1996, 281-282, 409-411. [3] Pagacova, J.; Plsko, A.; Stanovae, I.; Jona, E.; Muellerova, J.; Exnar, P.; Lukac, A.; Mar-Cekova, L. The influence of preparation conditions on porous SiO2 structure studied by FTIR Spectroscopy. Chem. Listy 2007,101,673-679. [4] Sui, R.H.; Rizkalla, A.S.; Charpentier, P.A. FTIR study on the formation of TiO2 nanostructures in supercritical CO2. J. Phys. Chem. B, 2006, 110, 16212 -16218. [5] Wijnja, H.; Schulthess, C.P. ATR–FTIR and DRIFT spectroscopy of carbonate species at the aged γ-Al2O3/water interface. Spectrochimica Acta Part A. 1999, 55, 861-872. [6] Liu, J.; Ding, D.; Wang, L.; Han, Y. Preparation and characterization of uniform circinate aggregates of sheet ZnO nanoparticles. RARE METALS, 2008, 27, 36-40. [7] Wahab, R.; Ansari, S.G.; Kim, Y.S.; Dar, M.A.; Shin, H.S. Synthesis and characterization of hydrozincite and its conversion into zinc oxide nanoparticles. J. Alloys Compounds 2008,461, 66-71. [8] Kang, S.; Xing, B. Humic acid fractionation upon sequential adsorption onto goethite. Langmuir 2008,24,2525-2531. [9] Gu, B.; Schmitt, J.; Chen, Z.; Liang, L.; McCarthy, J.F. Adsorption and desorption of natural organic matter on iron oxide: mechanisms and models. Environ.Sci.Technol. 1994,28,38-46. [10] Stevenson, F.J. Humus chemistry: Genesis, composition, reactions. 2nd ed. John Wiley & Sons:New York, 1994.
Page S4
Table S1.
Purity, Diameter and Surface Hydroxyl Content of Nano-oxides
Nano-oxides nano-P-SiO2 nano-S-SiO2 nano-TiO2 nano-α-Al2O3 nano-γ-Al2O3 nano-ZnO
Purity, %
Diameter, nm
>99.5% >99.5% >99% >99.5% >99.5% >99.5%
20±5 nm 30±5 nm 50±5 nm 150±5 nm 60±5 nm 20±5 nm
Notation P form, Surface Hydroxyl Content >45% S form, Surface Hydroxyl Content >19% anatase form α form γ form
1122 1080 1040 938 848
1390
3620
1510
3480
792
1628
3300
SP1 P-SiO 2
Absorbance
S-SiO 2 SS1
ZnO ZnO 3900
3400
2900
2400
1900
1400
900
400
1400
900
400
TiO2 TiO 2
γ-Al MC2R 2O3 MC2A
α-Al2O3
3900
3400
2900
2400
1900
Wave numbers, cm-1
Figure S1. FTIR spectra of six nano-oxides.
456
Adsorption maxima, mg TOC/g
Page S5 100 80 γ-Al2O3
TiO2
60 y = 0.2802x + 9.2991
ZnO
40
2
R = 0.9527
20 α-Al2O3
0 0
100
200
300
400
SBET, m2/g
Surface area normalized adsorption maxima, mg TOC/m2
Figure S2. Positive linear relationship of HA adsorption maxima with total surface area (SBET) for nanosized TiO2, γ-Al2O3, ZnO and α-Al2O3.
1
α-Al2O3 y = -0.3768x + 0.8148
0.8
2
R = 0.9594 0.6
ZnO
γ-Al2O3
0.4
TiO2 P-SiO2
0.2
S-SiO2 0 0
0.5
1
1.5
2
2.5
3
H content, %
Figure S3. Positive linear relationship of surface area (SBET) normalized HA adsorption maxima with H content of nanosized TiO2, γ-Al2O3, ZnO and α-Al2O3.
Page S6
1040 1390 1122 1510 1600 1628
Absorbance
2926
(a) (b) (c) (d)
3900
3400
2900
2400
1900
1400
900
400
-1
Wave numbers, cm
Figure S4. FTIR Spectra of nano-TiO2 (a), HA coated nano-TiO2 (b), nano-ZnO (c) and HA coated nano-ZnO (d). The adsorbed butoxyl groups with peaks at 1122 and 1040 cm-1 for nano-TiO2 and carbonates with peak at 1122 cm-1 for nano-ZnO were replaced and released by HA, showing these peaks disappeared after HA coating. 0.6
γ-Al2O3
0.5
TiO2
0.18
0.6
0.15
0.5
0.4
C
0.7
ZnO
0.12
0.4 0.3 y = 2.03x - 0.1077 0.2
2
R = 0.9995
2
R = 0.9781
2
R = 0.9607
0.06
0.2
0.1
0.03
0.1 0
0 0
0.1
0.2
0.3
0.4
-0.3
-0.2
-0.1
y = 0.8721x + 0.0452
0.09
y = 1.2476x + 0.3746
0.3
0
0
0.1
0.2
0.3
0
0.05
0.1
0.15
H
Figure S5. Atomic carbon (C) versus atomic hydrogen (H) for bound HA with nanosized γ-Al2O3, TiO2 and ZnO. Atomic carbon (C) and atomic hydrogen (H) of nano-oxide bound HA were calculated from the C and H elemental compositions (Table 1) with the following equations: (Ci-C0)/12.011 and (Hi-H0)/1.008, respectively, where Ci and Hi is the percent mass content of elemental carbon and hydrogen in HA coated nano-oxides, C0 and H0 is the percent mass content of elemental carbon and hydrogen in nano-oxides before HA coating, 12.011 and 1.008 (g/mol) are the molar mass of atomic carbon and hydrogen. Dotted lines represent the regression results of linear model, where the slopes of linear lines show the atomic ratio of carbon to hydrogen (C/H) of nano-oxide bound HA.
Page S7 0 80
MC2A α-Al 2O3 MC2A-HAA1% HA50 MC2A-HAA2% HA100 HAA HA
60 40
2
4
6
8
10
12
0 -10
ZnO ZnO HA250 ZnO-HAA5% HA1000 ZnO-HAA20% HA HAA
-20
20
-30
0 0
2
4
6
8
10
12
-20
-40
-40
-50
-60 -80
-60
50
0
0 MC2R γ-Al 2O3 MC2R-HAA5% HA250 MC2R-HAA10% HA500 MC2R-HAA30% HA1500 HA HAA
40
Zeta potential, mV
30 20 10
2
4
6
8
10
12
4
6
8
10
12
-10 -20
0 -10 0
2
4
6
8
10
12
-20
-30 -40
P-SiO SP1 2 SP1-HAA1% HA50 HAA HA
-30 -40
-50
-50 -60
-60
50
0
0 TiO22 TiO TiO2-HAA2% HA100 TiO2-HAA5% HA250 TiO2-HAA10% HA500 TiO2-HAA20% HA1000 HAA HA
40 30 20 10
-10
-20
0 -10 1
3
5
7
9
2
S-SiO SS1 2 SS1-HAA1% HA50 HAA HA
-30
11
-20
-40
-30 -40
-50
-50
-60
-60
pH
Figure S6. Comparison of the zeta potential of HA coated nano-oxides with HA and nano-oxides at various pH. The number after HA represents the initial HA concentration used for coating of nano-oxides.
