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Supporting Information
Colorimetric Determination of Hydrogen Peroxide by Morphological
Decomposition of Ag Nanoprisms Coupled With Chromaticity Analysis
Kritchapon Nitinaivinij,a Tewarak Parnklang,a Chuchaat Thammacharoen,a
Sanong Ekgasit a and Kanet Wongravee †a
aSensor Research Unit (SRU), Department of Chemistry, Faculty of Science, Chulalongkorn University,
Bangkok, Thailand 10330, Fax :+66 2218 7585; Tel : +66 2218 7589
†Corresponding author ( Email : [email protected] )
Electronic Supplementary Material (ESI) for Analytical Methods.This journal is © The Royal Society of Chemistry 2014
Contents
Figure S1. Normalized UV-visible spectra of red-AgNPrs for three repetitions.
Figure S2. The influences of (A) pH and (B) temperature on the AgNPrs with the insets of AgNPr
solution color at various pH and temperatures.
Figure S3. (A) Time-resolved LSPR spectra of AgNPrs after addition of 100 µM H2O2 from 0 to 15 min
of incubation time. (B) Variations of absorbance and peak position of the in-plane dipole
LSPR with incubation time. (C) Variations of absorbance and peak position of the out-of-plane
quadrupole LSPR with incubation time.
Figure S4. Extinction spectra of the original red-AgNPrs, red-AgNPrs interacting with hydrogen
peroxide, and the solution after the conversion of silver ions to silver nanospheres by the
addition of a reducing agent (NaBH4).
Figure S5. Extinction spectra of blue-AgNPrs when exposed to H2O2 at various concentrations ranging
from 1 to 1,000 M, with the corresponding inset photographs showing the color of the
colloidal AgNPr solution after incubation with H2O2 for 60 min.
Figure S6. Normalized ATR FT-IR spectra of virgin starch, starch on AgNPrs, and starch on AgNPrs
after incubation with H2O2 at various concentrations ranging from 1 to 1000 μM for 60 min.
The infrared band assignment table is also included.
Figure S7. Red chromaticity level of the AgNPrs with glucose oxidase enzyme after incubating with
glucose and various potential sugar species. Inset photo shows the corresponding digital
images of the AgNPrs solutions.
300 400 500 600 700 8000.00
0.25
0.50
0.75
1.00N
orm
aliz
ed A
bsor
banc
e
wavelength (nm)
Red AgNPrs stock 2013/08/24Red AgNPrs stock 2013/10/30Red AgNPrs stock 2014/03/04
Figure S1. Normalized UV-visible spectra of red-AgNPrs for three repetitions.
2 3 4 5 6 7 8 9 10 11
0
1
2
3
4
5
6
(n
m)
pH
pH 3 pH 10
20 30 40 50 60 70 80 90
0
4
8
12
16
(n
m)
Temp. (oC)
28oC 90oC
A B
Figure S2. The influences of (A) pH and (B) temperature on the AgNPrs with the insets of AgNPr
solution color at various pH and temperatures.
The effect of pH and temperature on the synthesized of AgNPrs was monitored by using UV-visible
spectroscopy. A pH of AgNPr solution was adjusted to pH 3-10 using either 20% acetic acid or 10%
NH4OH. A temperature of AgNPr solution was adjusted in the range of 28oC – 90oC using water bath.
The of AgNPrs and corresponding solution color at various pH and temperature are depicted in Figure
1A and 1B, respectively. The results reveal that no significant changes in LSPR of AgNPrs ( = 0) in
the range of pH 3-8. In addition, no considerable changes in LSPR of AgNPrs is observed in the
temperature range of 28-40oC. The increase and the color of the AgNPr solution became pale orange
only when pH > 9 or temperature > 45 ºC.
To gain an insight into understanding the decomposition profile and the evaluation of the optical
characteristics of the AgNPr solution as a LSPR-based hydrogen peroxide sensor, 100 µM of H2O2 was
introduced to 10 ppm of AgNPr solution in a quartz cuvette. The time-resolved LSPR band of AgNPrs
incubated with the imposed H2O2 from 0 to 15 min was monitored by UV-visible spectroscopy
(Figure S1). The in-plane dipole LSPR of AgNPrs (λmax = 502 nm) gradually blue-shifted after the
addition of H2O2, while the out-of-plane quadrupole LSPR (λmax = 340 nm) remained unchanged. These
results indicate that the lateral size of AgNPr decreased, while the aspect ratio of the morphology
remained the same, i.e. the thickness of AgNPr constantly decreased along with the lateral size.
0 200 400 600 800 1000300
350
400
450
500
max (nm) Absorbance
time (sec)
max
(nm
)
0.0
0.1
0.2
0.3
0.4
0.5out-of-plane quadrupole LSPR
Absorbance
0 200 400 600 800 1000400
450
500
550
600
max (nm) Absorbacne
time (sec)
max
(nm
)
in-plane dipole LSPR
0.0
0.4
0.8
1.2
1.6
Absorbance
300 400 500 600 700 8000.0
0.5
1.0
1.5
Abso
rban
ce
wavelength (nm)
0 min
5 min
A B
C
Figure S3. (A) Time-resolved LSPR spectra of AgNPrs after addition of 100 µM H2O2 from 0 to 15 min
of incubation time. (B) Variations of absorbance and peak position of the in-plane dipole
LSPR with incubation time. (C) Variations of absorbance and peak position of the out-of-plane
quadrupole LSPR with incubation time.
300 400 500 600 700 8000.0
0.5
1.0
Abso
rban
ce
wavelength (nm)
504
400
340
Red-AgNPrsRed-AgNPrs + H2O2 (1000 µM)Red-AgNPrs + H2O2 (1000 µM) + NaBH4
Red AgNPls10 ppm
+ H2O21000 µM
+ NaBH4
2 hours
1 hour
Figure S4. Extinction spectra of the original red-AgNPrs, red-AgNPrs interacting with hydrogen
peroxide, and the solution after the conversion of silver ions to silver nanospheres by the
addition of a reducing agent (NaBH4).
The original AgNPr solution employed in the study exhibited the red-wine color with an in-plane
dipole LSPR peak centered at 504 nm. The complete degradation of AgNPrs was observed when a high
concentration of H2O2 (1000 M) was introduced. From inset of Figure S3, it can be seen that the solution
color changed from red to colorless. This observation confirms the etching phenomenon on AgNPrs after
interacting with H2O2 as expressed by the following chemical equations [1-5]:
Ag+ + e- Ag E0 = 0.7996 V
H2O2 + 2e- 2HO- E0 = 0.8670 V
2Ag + H2O2 2Ag+ + 2HO- E0 = 0.0680 V
The formation of silver ions as the reaction products from the decomposition of AgNPrs by H2O2
was verified by the addition of a strong reducing agent (NaBH4) into the degraded AgNPr solution. The
result in Figure S3 shows that a new plasmon absorption peak at 400 nm emerges in the extinction
spectrum, in correspondence with the change of the solution color from colorless to yellow after the
addition of sodium borohydride. The plasmon absorption peak at 400 nm is a characteristic plasmon band
of silver nanospheres. The silver nanospheres are formed by the following chemical reaction:
Ag+ + BH4- → Ag0 + ½H2 + ½B2H6
Therefore, it can be confirmed that the etching reaction of H2O2 on AgNPrs induces the degradation of
silver atoms on AgNPrs to silver ions, and leads to the morphological transformation of AgNPrs.
References for Figure S4
1. C. M. Ho, S. King-Woon Yau, C. N. Lok, M. H. So and C. M. Che, Chem-Asian J., 2010, 5, 285–293.
2. J. Weiss, Trans. Faraday Soc., 1935, 31, 1547–1557.
3. F. T. Maggs and D. Sutton, Trans. Faraday Soc., 1958, 54, 1861–1870.
4. F. T. Maggs and D. Sutton, Trans. Faraday Soc., 1959, 55, 974–980.
5. Q. Zhang, C. M. Cobley, J. Zeng, L. P. Wen, J. Chen and Y. Xia, J. Phys. Chem. C, 2010, 114, 6396–6400.
300 400 500 600 700 8000.0
0.5
1.0
1.5
1000 M
Abso
rban
ce
Wavelength (nm)
AgNPrs
H2O2
1 M
AgNPrs
AgNPrs + 1 µM H2O2
AgNPrs + 5 µM H2O2
AgNPrs + 50 µM H2O2
AgNPrs + 100 µM H2O2
AgNPrs + 500 µM H2O2
AgNPrs+ 1000 µM H2O2
AgNPrs + 10 µM H2O2
Figure S5. Extinction spectra of blue-AgNPrs when exposed to H2O2 at various concentrations ranging
from 1 to 1,000 M, with the corresponding inset photographs showing the color of the
colloidal AgNPr solution after incubation with H2O2 for 60 min.
2000 1800 1600 1400 1200 1000 800
Abso
rban
ce (a
.u.)
Wavenumbers (cm-1)
AgNPrs starch stabilizer
Starch-AgNPrs + H2O2 1 µM
Starch
Starch at pH 13 930
1014
1643
1587 1355
Starch-AgNPrs + H2O2 5 µM
Starch-AgNPrs + H2O2 10 µM
Starch-AgNPrs + H2O2 50 µM
Starch-AgNPrs + H2O2 100 µM
Starch-AgNPrs + H2O2 500 µM
Starch-AgNPrs + H2O2 1000 µM
Abs
orba
nce
(a.u
.)
Wavenumbers (cm-1)
Infrared band (cm-1) Infrared band assignment 860 CH2 deformation
930 Skeleton mode vibration of α-1,4 glycosidic linkage (C-O-C)
1200-900 Bridge β C1-O-C4
1500-1300 Vibration band related to the carbon and hydrogen atoms
1610-1500/1420-1300 COO- stretching vibration (carboxylic acid salt)
1642 Water adsorbed in the amorphous region of starch
1765 C=O stretching vibration of carboxylic acid
Figure S6. Normalized ATR FT-IR spectra of virgin starch, starch on AgNPrs, and starch on AgNPrs
after incubation with H2O2 at various concentrations ranging from 1 to 1000 μM for 60 min.
The infrared band assignment table is also included.
AgNPls
AgNPls +
GOx
AgNPls +
GOx +
Gluc
ose
AgNPls +
GOx +
Fruc
tose
AgNPls +
GOx +
Lacto
se
AgNPls +
GOx +
Malto
se
AgNPls +
GOx +
Sucros
e0.40
0.45
0.50No
rmal
ized
R• AgNPrs 10 ppm 1 mL• GOx(10 mg/mL) 20 μL• Sugar (40 μM) 1 mL• Incubate 60 min• Camera mode: Auto
Red
chro
mat
icity
leve
l (r)
Figure S7. Red chromaticity level of the AgNPrs with glucose oxidase enzyme (GOx) after incubating
with glucose and various potential sugar species. Inset photo shows the corresponding digital
images of the AgNPrs solutions.
