Copyright © 2011 American Scientific Publishers
All rights reserved
Printed in the United States of America
Science of
Advanced Materials
Vol. 3, 962–967, 2011
Well-Crystalline -Fe2O3 Nanoparticles for
Hydrazine Chemical Sensor Application
S. K. Mehta1 ∗ , Kulvinder Singh1 , Ahmad Umar2 ∗ , G. R. Chaudhary1 , and Sukhjinder Singh1
2
1
Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India
Promising Centre for Sensors and Electronic Devices (PCSED), Centre for Advanced Materials and Nano-Research (CAMNR),
Najran University, P.O. Box 1988, Najran, 11001, Kingdom of Saudi Arabia
This paper reports a facile synthesis, characterization and hydrazine chemical sensor applications
of -Fe2 O3 nanoparticles (NPs). These NPs were synthesized by simple hydrothermal process at
low-temperature of 130 C and characterized in detail in terms of their morphological, structural and
Delivered
by Ingentarevealed
to: that the as-synthesized nanoparcompositional properties. The detailed
characterization
Panjab
University-Fe2 O3 structure. The as-synthesized ticles were well crystalline and possess
rhombohedral
Fe2 O3 NPs were used as efficientIPelectron
mediators for the fabrication of hydrazine chemical
: 115.111.184.44
sensor which exhibits high sensitivity
andNov
low-detection
limit. The obtained sensitivity and detection
Thu, 01
2012 04:56:55
limit of the fabricated chemical sensor was found to be ∼1.59 A/cm2 M and 3.84 M, respectively. Importantly, to the best of our knowledge, this is the first report in which -Fe2 O3 was used
as an electron mediator for the fabrication of amperometric chemical sensor. Therefore, this work
shows that -Fe2 O3 NPs synthesized by simply method can be used for the fabrication of robust
hydrazine chemical sensors.
RESEARCH ARTICLE
Keywords: -Fe2 O3 Nanoparticles, Structural and Compositional Properties, Hydrazine
Chemical Sensor, Amperometry.
1. INTRODUCTION
Hydrazine (N2 H4 , a colorless compound, presents itself
as one of the significant chemical which is important
for the industries (chemical and pharmaceutical), environment, human health, agriculture and so on. It is widely
used as fuel in fuel cells, explosive, corrosion inhibitor,
antioxidant, emulsifier, catalyst, reducing agent, blowing
agents, pharmaceutical intermediates, photographic chemical, water treatment for corrosion protection, textile dyes,
and so on.1–5 It is also used as a starting material for
various insecticides, pesticides, herbicides and in various pharmaceutical products.4 In addition to this, N2 H4
is known as a neurotoxin and a carcinogenic and mutagenic compound, hence effecting the nervous system.5–7
High-level exposure of N2 H4 to the human could cause
eye, nose, throat irritations, nausea, temporary blindness,
dizziness, headache, coma and so forth.6 7 Even though,
N2 H4 is widely used in many industries but it is also a carcinogenic and hepatotoxic agent and hence could directly
show adverse effects to the human health. Thus, there is
a serious need to develop a robust, reliable, economical
∗
Authors to whom correspondence should be addressed.
962
Sci. Adv. Mater. 2011, Vol. 3, No. 6
and high sensitive chemical sensor for the determination of trace amounts of N2 H4 . In this regard, various
methods have been employed for the N2 H4 detection and
reported in the literature.3–11 The N2 H4 detection techniques include chemi-luminescence spectroscopy, coulometric titration, chromatography, electrochemical, device
based sensors and so on.1–11 Among various techniques,
the electrochemical detection technique provides a better platform to fabricate a robust sensor with high sensitivity, low-detection limit, good reproducibility and high
durability.1 For the fabrication of electrochemical sensors,
generally, artificial electron mediators are used which help
to transfer the electron from the electrode to the analyte.
For this purpose, several materials were used as an efficient electron mediators for the fabrication of electrochemical sensors and reported in the literature.1 2 Recently, it
was found that nanostructured materials can be used as
efficient electron mediators, hence several works on the
utilization of nanostructured materials as efficient electron
mediators have been reported in the literature.1–11 Among
various nanostructured materials, the metal oxides based
nanostructures possess special place due to their excellent
properties and wide applications.12–21
1947-2935/2011/3/962/006
doi:10.1166/sam.2011.1244
Mehta et al.
Well-Crystalline -Fe2 O3 Nanoparticles for Hydrazine Chemical Sensor Application
Among various metal oxide nanostructures, the hematite
The morphologies of as-synthesized -Fe2 O3 NPs
were characterized by field emission scanning elec(-Fe2 O3 is one of the promising materials due to its
tron microscopy (FESEM) and transmission electron
own properties such as most stable under ambient condimicroscopy (TEM). The structural property was examtions, non-toxic, high resistant to corrosion, etc. The excelined by X-ray diffractometer (XRD; PANanalytical Xpert
lent properties of -Fe2 O3 make this a promising material
Pro.) with Cu-K radiation ( = 154178 Å) in the range
for various applications, to name a few, as sensors, phoof 20–70 with scan speed of 10 /min. The chemical
tocatalysis, pigments, magnetic recording media and so
composition was examined by using energy dispersive
forth.20–22 Due to excellent properties and wide applicaspectroscopy (EDS), attached with FESEM and Fourier
tions, several -Fe2 O3 nanostructures were synthesized by
transform infrared (FTIR; Perkin Elmer-FTIR Spectrumvarious techniques such as hydrothermal process, sol–gel
100) spectroscopy in the range of 450–4000 cm−1 .
process, microwave heating method, co-precipitation, thermal evaporation and so on as reported in the literature.23–30
2.2. Fabrication of Amperometric Hydrazine
Even though -Fe2 O3 possessing excellent properties
Chemical Sensor Based on -Fe2 O3 Nanoparticles
and widely used for various high-technological applications, but, to the best of our knowledge, the utilization
For the fabrication of hydrazine chemical sensor based on
of -Fe2 O3 nanoparticles as efficient electron mediators
-Fe2 O3 NPs, the as-prepared NPs were coated on gold
for the fabrication of hydrazine chemical sensor is not
(Au) electrode (Au; surface area = 314 mm2 . Before
reported yet in the literature.
coating, the Au electrode was polished with alumina slurry,
This article reports a facile synthesis, detailed Delivered
character- by Ingenta to:
sonicated in distilled water and dried at room-temperature.
Panjab University
izations and effective utilization of -Fe2 O3 nanoparticles
The slurry was made by adding -Fe2 O3 NPs and butyl
IP : 115.111.184.44
(NPs) as efficient electron mediators for the fabrication
of
carbitol
acetate (BCA) in a particular ratio. The prepared
Thu, 01 Nov 2012
04:56:55
hydrazine chemical sensors. The NPs were characterized
slurry was then coated on the Au electrode and dried at
in terms of their morphological, structural and composi60 ± 5 C for 4–6 hrs to get a uniform layer over entire
tional properties. The fabricated hydrazine chemical sensor
electrode surface.
was stable and reproducible and exhibits high sensitivity
All the electrochemical experiments were performed at
of ∼1.59 A/cm2 M and detection limit of ∼3.84 M.
room-temperature with a Autolab Type-III cyclic voltam-
2.1. Synthesis and Characterizations of
As-Synthesized -Fe2 O3 Nanoparticles
Well-crystalline -Fe2 O3 NPs were synthesized by simple and facile hydrothermal process using iron chloride (FeCl3 · 6H2 O), hexamethylenetetramine (HMTA) and
ammonia (NH3 · H2 O) at low-temperature. For the synthesis of -Fe2 O3 NPs, all the chemicals were obtained
from Sigma-Aldrich and used as received without further purification. In a typical reaction process, 0.73 g
FeCl3 · 6H2 O and 0.63 g HMTA were dissolved in 30 ml,
each, distilled water (DW) and the obtained solutions were
mixed well under vigorous stirring which for 45 min. To
maintain the pH = 90, few drops of ammonia solution
was added in the resultant solution under continuous stirring. After stirring, the resultant solution was transferred
to Teflon-lined autoclave and heated up to 130 C for
5 hrs. After completing the reaction, the autoclave was
allowed to cool at room-temperature and finally brown colored product were obtained which were thoroughly washed
with DW, methanol and acetone, sequentially. Finally, the
obtained compound was dried at room-temperature and the
synthesized nanomaterials were characterized in detail in
terms of their morphological, structural and compositional
properties.
Sci. Adv. Mater. 3, 962–967, 2011
3. RESULTS AND DISCUSSION
3.1. Morphological, Structural and Compositional
Properties of As Synthesized -Fe2 O3
Nanoparticles
The general morphologies of as-synthesized -Fe2 O3 NPs
were characterized by FESEM and results are shown in
Figures 1(a) and (b). From the observed micrographs, it is
clear that the synthesized structures are nanoparticles and
grown in high density. The NPs possess almost hexagonal morphologies. It was seen that due to high density, the
NPs are close to each other and many NPs are agglomerated in small spheres. The typical diameters of the NPs
are ∼70 ± 10 nm (Fig. 1(b)). To closely monitor the morphologies, the as-synthesized NPs were characterized by
TEM. Figure 1(c) exhibits the typical TEM image of assynthesized -Fe2 O3 NPs which exhibits the full consistency with the observed FESEM images. The NPs possess hexagonal shape and due to dense growth, several
NPs are agglomerated with each other (Fig. 1(c)). The
typical diameter of as-synthesized NPs is in the range of
963
RESEARCH ARTICLE
2. EXPERIMENTAL DETAILS
meter using three-electrode configuration in which the
modified -Fe2 O3 /Au electrode was used as working electrode, a Pt wire as a counter electrode and an Ag/AgCl
(sat. KCl) as a reference electrode. For all the measurements, 0.1 M phosphate buffer solution (PBS; pH = 70)
was used.
Well-Crystalline -Fe2 O3 Nanoparticles for Hydrazine Chemical Sensor Application
Mehta et al.
Delivered by Ingenta to:
Panjab University
IP : 115.111.184.44
Thu, 01 Nov 2012 04:56:55
RESEARCH ARTICLE
Fig. 1.
(a) and (b) FESEM images, (c) TEM image and (d) EDS spectrum of as-synthesized -Fe2 O3 nanoparticles.
60–80 nm. The compositions of as-synthesized -Fe2 O3
nanoparticles were examined by EDS analysis. Figure 1(d)
exhibits the typical EDS spectrum of as-synthesized NPs
which clearly confirms that the synthesized NPs are composed of Fe and oxygen. In addition to this, a small peak
related with Pt was also seen in the spectrum which is
originated due to Pt coating during EDS measurements.
No peak related with any other impurity has been detected
in the spectrum which confirms that the synthesized NPs
are pure iron oxide.
The crystallinity and crystal phases of as-synthesized Fe2 O3 NPs were examined by X-ray diffraction. As can
be seen in Figure 2, all the obtained diffraction reflections
are well matched with the rhombohedral -Fe2 O3 structure
as mentioned in the JCPDS card number 84–0311. The
obtained XRD results are well matched with the already
reported literature.22 In addition to this, due to high and
strong diffraction reflections, it can be concluded that the
as-synthesized -Fe2 O3 nanoparticles are well-crystalline.
No other diffraction reflection except rhombohedral Fe2 O3 was observed in the pattern which confirmed that
the synthesized product is well-crystalline -Fe2 O3 without any significant impurity.
To examine the chemical compositions, the assynthesized -Fe2 O3 NPs were characterized by FTIR
spectrum. Figure 3 shows the typical FTIR spectrum of assynthesized -Fe2 O3 nanoparticles. Several well-defined
absorption bands at 465, 555, 1630 and 3405 cm−1 were
observed in the spectrum. The origination of two absorption band at 465 and 555 cm−1 were due to the formation
964
of Fe–O bond and hence confirms the formation of iron
oxide. A short and strong absorption peaks appeared at
1632 cm−1 and 3405 cm−1 , respectively can be attributed
to the bending vibration of absorbed water and surface
hydroxyl, and O–H stretching mode, respectively.2231
For the synthesis of -Fe2 O3 NPs, FeCl3 · 6H2 O, HMTA
and NH3 · H2 O were used. During the reaction process,
firstly, FeCl3 · 6H2 O was reacted with NH3 · H2 O and forms
Fe(OH)3 according to the following chemical reaction:
FeCl3 ·6H2 O+6NH3 ·H2 O → FeOH3s +3NH4 Claq (1)
In addition to this, during synthesis, at particular
temperature HMTA decomposed into formaldehyde and
Fig. 2. Typical XRD pattern of as-synthesized -Fe2 O3 nanoparticles.
Sci. Adv. Mater. 3, 962–967, 2011
Well-Crystalline -Fe2 O3 Nanoparticles for Hydrazine Chemical Sensor Application
Mehta et al.
Fig. 3.
Typical FTIR spectrum of as-synthesized -Fe2 O3 nanoparticles.
Fig. 4. Cyclic voltammogram of -Fe2 O3 NPs/Au modified electrode
using with 1 mM hydrazine (black line) and without hydrazine (red line)
in 0.1 M PBS (pH 7) at the scan rate of 50 mV/s.
ammonia. Ammonia reacts with water to give OH− ions
which drives the crystallinity and growth of -Fe2 O3 .
50 mV/s. It is clear from the obtained CV graph that the Delivered
According to the literature, NPs growth does not
involve by Ingenta to:
Fe
Panjab University
2 O3 /Au electrode behaves different in the presence and
the absorption of HMTA.32 Instead, the role of HMTA
the
absence of N2 H4 . A clear peak at 0.4 V (Ipa 5.91 A)
IP NPs
: 115.111.184.44
in NPs growth is to keep the crystallization of
in
the
CV has been noticed in the presence of hydrazine
01 Nov
04:56:55
under thermodynamic control by the slowThu,
release
of 2012
which
is due to the oxidation of hydrazine while no peak
OH− ions. The chemical reaction involved for the forwas
observed
in the CV graph in absence of hydrazine.
mation of OH− ions during HMTA decomposition are as
The electrochemical response is irreversible as no cathodic
follows:
current is observed during the reverse sweep. Hence, this
(2)
NH3 + H2 O → NH4+ + OH−
(3)
Therefore, secondly, the generated OH− ions from the
HMTA also react with iron chloride hexahydrate and form
Fe(OH)3 . Finally, the obtained Fe(OH)3 decomposed into
iron oxide and water according to the chemical reaction
mentioned below:
2FeOH3 → Fe2 O3 + 3H2 O
(4)
Therefore, the continuous formation of Fe(OH)3 intermediate leads to the formation of stable -Fe2 O3
nanostructures.
3.2. Electrochemical Hydrazine Chemical Sensor
Performance of -Fe2 O3 Nanoparticles Modified
Gold Electrode
For the application point of view, the as-synthesized
-Fe2 O3 NPs were used as efficient electrode mediators
for the fabrication of hydrazine chemical sensor. For the
fabrication of electrochemical hydrazine sensor, slurry of
as-synthesized -Fe2 O3 NPs was coated on Au electrode
and used the modified electrode as working electrode.
Figure 4 represents the cyclic voltammogram (CV)
for -Fe2 O3 modified (-Fe2 O3 /Au) electrode without
hydrazine (red line) and with 1 mM hydrazine (black line)
in 0.1 M phosphate buffer (pH 7) at the scan rate of
Sci. Adv. Mater. 3, 962–967, 2011
reveals that -Fe2 O3 is an effective mediator for the oxidation of hydrazine.
To calculate the number of electrons involved in
the electrochemical oxidation of hydrazine, the CV of
-Fe2 O3 /Au electrode was done at different scan rates.
Figure 5(a) shows the typical cyclic votammetric response
at different scan rates from 50 mV/s to 800 mV/s (50, 60,
70, 80, 90, 100, 200, 300, 400, 500, 600, 700 and
800 mV/s). It is clear from the obtained CV graph that with
increasing the scan rates the peak currents also increases
which shows that the oxidation process is diffusion controlled. In other words the electrons transfer is very fast
and the current is limited by the diffusion of the hydrazine
to the surface of the electrode.
Figure 5(b) exhibits the anodic peak current (Ia versus
square root of scan rate ( 1/2 . The anodic peak current
exhibits linear relationship with 1/2 . The number of electrons involved in the oxidation of hydrazine can be calculated using Randless-Sevick equation as mentioned below:
Ip = 269 × 105 n3/2 AD1/2 1/2 C
(5)
Where n is number of electrons actively participate in the
oxidation of hydrazine, A (cm2 is the area of electrode,
D is the diffusion coefficient of the hydrazine, is scan
rate and C is the concentration of the hydrazine. The total
number of electrons comes out to be 2 which satisfy the
given electrochemical oxidation reaction of hydrazine.33–37
N2 H4 + 5/2OH− → 1/2N3− + 1/2NH3 + 5/2H2 O + 2e−
(6)
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RESEARCH ARTICLE
CH2 6 N4 + 6H2 O → 6HCHO + 4NH3
Well-Crystalline -Fe2 O3 Nanoparticles for Hydrazine Chemical Sensor Application
(a)
Mehta et al.
(a)
(b)
(b)
RESEARCH ARTICLE
Delivered by Ingenta to:
Panjab University
IP : 115.111.184.44
Thu, 01 Nov 2012 04:56:55
Fig. 5. (a) Cyclic votammogarms obtained for -Fe2 O3 NPs/Au modified electrode at various scan rates from 50 mV/s to 800 mV/s (50, 60,
70, 80, 90, 100, 200, 300, 400, 500, 600, 700 and 800 mV/s) and (b) the
anodic peak current (Ia versus square root of scan rate ( 1/2 .
To further investigate the sensing efficiency of the modified -Fe2 O3 /Au electrode in the presence of hydrazine,
the amperometric studies were carried out under stirred
condition. Figure 6 demonstrates the pictorial representation of amperometric detection of hydrazine by using
-Fe2 O3 /Au electrode. It can be seen from the pictorial
representation that the gold electrode was modified with
iron oxide nanoparticles and oxidation of hydrazine by
the modified electrode was done according to the chemical reaction mentioned in Eq. (6) and finally amperometry
responses were observed.
Fig. 6.
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Fig. 7. (a) Amperometric response of the -Fe2 O3 NPs/Au modified
electrode with successive addition of hydrazine into 0. 1 M PBS buffer
solution (pH = 70). Inset (a) plot for the relationship between current
versus hydrazine concentrations; (b) The plot of 1/Current vs 1/Concentration exhibiting a linear relationship with the steady state current and
hydrazine concentration.
Figure 7(a) represents the typical amperometric
response with successive addition of hydrazine from
500 nM to 5000 nM at a constant potential of 0.4 V.
With the consecutive addition of N2 H4 the current response
also increases. Inset of Figure 7(a) demonstrates the relation between the response current and N2 H4 concentration
Systematic representation of the fabricated amperometric hydrazine chemical sensor based on -Fe2 O3 NPs/Au modified electrode.
Sci. Adv. Mater. 3, 962–967, 2011
Mehta et al.
Well-Crystalline -Fe2 O3 Nanoparticles for Hydrazine Chemical Sensor Application
for the fabricated amperometric N2 H4 chemical sensor.
The response current increases as the concentration of
hydrazine increases, and shows linear relationship between
current versus hydrazine concentrations. Figure 7(b)
exhibits the plot of 1/current versus 1/concentration and
exhibiting linear relationship with steady state current and
hydrazine concentration. The correlation coefficient (R) is
estimated to be 0.9942. The sensitivity of the fabricated
hydrazine sensor, obtained from the slope of calibration
curve, was ∼1.59 A/cm2 M. The calculated detection
limit, estimated based on signal to noise ratio (S/N), was
found to be 3.84 M. Importantly, this is the first report
in which -Fe2 O3 NPs have been used as efficient electron mediators for the fabrication of high sensitive a lowdetection limit hydrazine amperometric chemical sensor.
References and Notes
Received: 6 September 2011. Accepted: 29 November 2011.
Sci. Adv. Mater. 3, 962–967, 2011
967
RESEARCH ARTICLE
1. A. Umar and Y. B. Hahn (eds.), Metal Oxide Nanostructures and
Their Applications, American Scientific Publishers, USA (2010),
Vol. 5.
2. H. W. Schessl, Encyclopedia of Chemical Technology, 4th edn.,
edited by K. Othmer, Wiley, New York (1995), Vol. 13.
3. A. Umar, M. M. Rahman, S. H. Kim, and Y. B. Hahn, Chem.
Commun. 2, 166 (2008).
4. S. Amlathe and V. K. Gupta, Analyst 113, 1481 (1988).
5. S. Garrod, M. E. Bollard, A. W. Nicholls, S. C. Connor, J. Connelly,
J. K. Nicholson, and E. Holmes, Chem. Res. Toxicol. 18, 115 (2005).
6. E. H. Vernot, J. D. MacEwen, R. H. Bruner, C. C. Haus, and E. R.
Kinkead, Fundam. Appl. Toxicol. 5, 1050 (1985).
7. J. W. Mo, B. Ogorevc, X. Zhang, and B. Pihlar, Electroanalysis
12, 48 (2000).
8. A. Safavi and A. A. Ensafi, Anal. Chim. Acta 300, 307 (1995).
9. S. M. Golabi and H. R. Zare, Electroanal. 11, 1293 (1999).
10. T. J. Pastor, V. J. Vajgard, and V. V. Antonijević, Mikrochim. Acta
70, 131 (1978).
11. R. Gilbert and R. Rioux, Anal. Chem. 56, 106 (1984).
12. Caruso, R. A. Caruso, and H. Möhwald, Science 282, 1111 (1998).
Delivered by13.Ingenta
P. Poizot,to:
S. Laruelle, S. Grugeon, L. Dupont, and J. M. Tarascon,
4. CONCLUSION
Panjab University
Nature 407, 496 (2000).
14. X. Hu, J. C. Yu, J. Gong, Q. Li, and G. Li, Adv. Mater. 19, 2324
IP : 115.111.184.44
In summary, well-crystalline -Fe2 O3 NPsThu,
were01
synNov 2012(2007).
04:56:55
15. I. W. Hamley, Nanotechnol. 14, 39 (2003).
thesized, characterized and utilized as efficient electron
16. Y. Ding, P. X. Gao, and Z. L. Wang, J. Am. Chem. Soc. 126, 2066
mediators for the fabrication of effective hydrazine chem(2004).
ical sensors. The detailed morphological, structural and
17. B. Wang, W. Feng, M. Zhu, Y. Wang, and M. Wang, J. Nanopart.
compositional properties revealed that the as-synthesized
Res. 11, 41 (2009).
18. W. Schartl, Adv. Mater. 12, 1899 (2000).
high-yield -Fe2 O3 NPs are hexagonal in shape and pos19. X. Wang, J. Zhang, Q. Peng, and Y. D. Li, Nature 437, 121 (2005).
sessing well-crystalline rhombohedral -Fe2 O3 structure.
20. D. B. Yu, and V. W. Yam, J. Am. Chem. Soc. 126, 13200 (2004).
By detailed electrochemical experiments, it was confirmed
21. C. Hofmann, I. Rusakova, T. Ould-Ely, D. Prieto-Centurion, K. B.
that the as-synthesized -Fe2 O3 NPs exhibit good sensHartman, A. T. Kelly, A. Luttge, and K. H. Whitmire, Adv. Funct.
Mater. 18, 1661 (2008).
ing property for the amperometric detection of hydrazine.
22.
A. Umar, M. Abaker, M. Faisal, S. W. Hwang, and S. Baskoutas,
The calculated sensitivity and detection limit for the
J. Nanosci. Nanotechnol. 11, 1 (2011).
fabricated hydrazine chemical sensor was found to be
23. Y. Y. Fu, R. M. Wang, J. Xu, J. Chen, Y. Yan, A. V. Narlikar, and
∼1.59 A/cm2 M and ∼3.84 M, respectively. ImporH. Zhang, Chem. Phys. Lett. 379, 373 (2003).
24. K. Woo, H. J. Lee, J. P. Ahn, and Y. S. Park, Adv. Mater. 15, 1761
tantly, to the best of our knowledge, this is the first report
(2003).
in which -Fe2 O3 NPs have efficiently been used for the
25. D. D. Archibald and S. Mann, Nature 364, 430 (1993).
fabrication of amperometric hydrazine chemical sensor.
26. S. B. Wang, Y. L. Min, and S. H. Yu, J. Phys. Chem. C 111, 3551
Therefore, by this research, one can conclude that sim(2007).
27. J. Ma, J. Lian, X Duan, X. Liu, and W. Zheng, J Phys. Chem. C
ply synthesized -Fe2 O3 nanostructures can efficiently be
114, 10671 (2010).
used as electron mediators for the fabrication of hydrazine
28. G. Qui, H. Huang, H. Genuino, N. Opembe, L. Stafford,
chemical sensors.
S. Dharmarathna, and S. L. Suib, J. Phys. Chem. C 115, 19626
(2011).
29. K. Sue, T. Sato, S-I Kawasaki, Y. Takebayashi, S. Yoda, T. Furuya,
Acknowledgments: SKM and KS are thankful to
and T. Hiaki, Ind. Eng. Chem. Res. 49, 8841 (2010).
30. P. Tsokov, V. Blaskov, D. Klissuriski, and I. Tsolovski, J. Mater. Sci.
Department of Science and Technology (DST) and Coun28, 184 (1993).
cil of Scientific and Industrial Research (CSIR), India
31. Y. H. Ni, X. W. Wei, J. M. Hong, and Y. Ye, Mater. Sci. Eng. B 121,
for the financial assistance and fellowships. Ahmad Umar
42 (2005).
would like to acknowledge the support of the Ministry of
32. K. M. McPeak, T. P. Le, N. G. Britton, Z. S. Nickolov, Y. A. Elabd,
and J. B Baxter, Langmuir 27, 3672 (2011).
Higher Education, Kingdom of Saudi Arabia for grant33. A. Salimi and K. Abdi, Talanta 63, 475 (2004).
ing a Promising Centre on Sensors and Electronic Devices
34. S. M. Golabi and H. R. Zare, Electroanal. 11, 1293 (1999).
(PCSED) dated 24/3/1432 H, 27/02/2011. Ahmad Umar
35. A. Salimi, L. Miranzadeh, and R. Hallaj, Talanta 75, 147 (2008).
also acknowledges Promising Centre on Sensor and Elec36. S. K. Mehta, Khushboo, and A. Umar, Talanta 85, 2411 (2011).
37. J. Liu, Y. Li, J. Jiang, and X. Huang, Dalton Trans. 39, 8693 (2010).
tronic Device project (PCSED-01-11) for support.