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Advanced Materials Research Vol. 678 (2013) pp 369-372
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.678.369
Synthesis of Cadmium Oxide and its Electrochemical Detection of
Pollutants
K.Giribabu1, R. Suresh1, L. Vijayalakshmi2, A. Stephen3 and V. Narayanan1*
1
Department of Inorganic Chemistry, University of Madras, Guindy Campus, Chennai 600025
Tamil Nadu, India
2
CSI Ewart Women’s Christian College, Melrosapuram, Kancheepuram 603204
Tamil Nadu, India
3
Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025
Tamil Nadu, India
a
[email protected], [email protected] [email protected],
d
[email protected], e*[email protected]
Keywords: CdO, Electrocatalyst, 4-Nitrophenol, 2-Nitrophenol
Abstract. Cadmium oxide was synthesized using cadmium acetate and oleic acid as the precursor
and capping agent, the main role of oleic acid to cap the formed cadmium oxide and to control the
particle size. The formed cadmium oxide nanoparticles were characterized by using FT-IR,
XRD,FE-SEM and cyclic voltammetry. The electrochemical detection of pollutants (4-Nitrophenol
and 2-Nitrophenol) was carried out by coating the cadmium oxide onto the glassy carbon electrode
(GCE) by drop coating method. The electrocatalytic performance of the modified GCE electrode
was best with 4-Nitrophenol. In case of 2-Nitrophenol the electrocatalytic performance was not
observed but increase in current response indicates the ability of modified electrode to be a useful
one for sensing the environmental pollutants.
1. Introduction
Cadmium oxide (CdO) is a n-type II–IV semiconductor with a direct band gap of 2.5 eV and
an indirect band gap of 1.98 eV [1]. The unique combination of high electrical conductivity, high
carrier concentration and high transparency in the visible range of electromagnetic spectrum has
prompted its optoelectronic applications. Recently, CdO nanostructures have been synthesized in
different interesting morphologies including nanowires, nanotubes, nanofibers, nanorods,
nanoclusters, nanocubes, and nanobelts by different methods like hydrothermal method, template
assisted method, solvothermal methods, chemical co-precipitation method vapor phase transport,
thermal evaporation and sonochemical method etc., [2-3]. 4-Nitrophenol (4-NP) and 2-nitrophenol
(2-NP) is included in the US Environmental Protection Agency List of Priority Pollutants . 4-NP is
a hazardous substance that can have a major environmental impact due to its toxicity and
persistence. Hence, the determination of 4-NP is of great importance, and various methods have
been developed. Chromatographic methods [4] are commonly used to detect 4-NP and 2-NP.
Recently, electrochemical techniques based on various chemically modified electrodes [5-6] have
been published to detect 4-NP.
Here we report the synthesis of CdO using oleic acid as the surfactant and cadmium acetate
as the cadmium source. The as-synthesized CdO have employed for the sensing towards the 4-NP
and 2-NP.
2. Experimental
2.1 Reagents
Cadmium acetate, Oleic acid, sodium hydrogen phosphate and sodium dihydrogen
phosphate were purchased from Qualigens and used as received. 4-Nitrophenol and 2- Nitrophenol
were purchased from CDH, India. Other chemicals used were of analytical reagent grade. All
chemicals were used without further purification.
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Advances in Nanoscience and Nanotechnology
2.2 Synthesis of CdO nanoparticle
1.33 g of cadmium acetate was dispersed in 12 mL hot oleic acid and stirred well. After the
formation of white precipitate the mixture was kept in an oil bath. The oil bath temperature was
maintained at 140 oC for 3 h. To remove oleic acid, the resulting suspension was washed with hot
ethanol three times. Further, the sample was pyrolysed at 450 oC for 3 h.
2.3 Characterization
FTIR spectroscopy of the CdO was studied using Schimadzu FTIR 8300 series instrument.
The phase and structure of CdO was analyzed by a Rich Siefert 3000 diffractometer with Cu-Kα1
radiation (λ = 1.5418 Å). The electrochemical experiments were performed on a CHI 600A
electrochemical instrument using the as-modified electrode and bare GCE as working electrode, a
platinum wire was the counter electrode, and saturated calomel electrode (SCE) was the reference
electrode.
2.4 Preparation of CdO Coated GCE
CdO coated GCE was prepared by following the literature method [7, 8] as follows.The
CdO suspension was prepared by dispersing a 5 mg CdO in 10 mL of distilled ethanol during 20
min of ultrasonic agitation. Prior to modification, the GCE was mechanically polished with alumina
paste of different grades to mirror finish, rinsed, and sonicated in redistilled water for 2 min.
Finally, the GCE was coated with 10 µL of the suspension and dried in air.
3. Result and discussion
3.1 XRD, FE-SEM and FTIR studies
The XRD pattern of CdO (Fig. 1) shows the diffraction peak that matches with standard file
card (JSPDCS.05-0640). It was observed that the diffraction peaks of CdO show narrow peaks
indicating the agglomerated particles of the sample. The FTIR spectrum of CdO is shown in Fig. 2.
The spectrum exhibits a common broad band near 3400 cm−1 due to the OH-stretching vibrations of
free and hydrogen-bonded hydroxyl groups. The band at 580, 968 and 1400 cm−1 [9, 10, 11] are
characteristic of CdO. The FE-SEM images clearly indicates the formation of nanoparticles in the
range of 200-250 nm of shown in Fig.3.
Fig. 1 XRD pattern of CdO nanoparticles
Fig. 2 FTIR spectrum of CdO nanoparticles
Fig. 3 FE-SEM images of CdO nanoparticles
Advanced Materials Research Vol. 678
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3.2 Electrocatalytic property
Fig. 4 shows the electrooxidation of 1- 5 mM 4-NP for CdO modified GCE at +0.69 V in
0.1 M PBS (Phosphate buffer solution) as the electrolyte. Bare GCE shows a broad oxidation peak
at+ 0.81 V. The modified GCE shows an oxidation peak with higher current response than the bare
GCE. Hence it is clear that the oxidation potential for 4-NP at the modified electrode was shifted to
less positive direction than the bare GCE, and the 4-NP oxidative current was largely increased
relative to the bare GCE, indicating the electro catalytic ability of the CdO modified electrode. Fig.5
shows effect of scan rate of the modified electrode in 1mM 4-NP. When increasing the scan rates
from 50-250 mVs-1 the anodic peak current increases, which is an indicative of the process is purely
diffusion-controlled process. The reason for the electrocatalytic property is the large surface area
when compared to that of the bare electrode, hence the electrocatalytic behavior of the modified
electrode was found to be more active for the sensing of 4-NP.
.
Fig. 4 Cyclic voltammogram of (a) bare and
CdO modified GCE for different
Concentrations of 4-NP (b-f: 1-5mM)
at 50 mV s-1
Fig. 5 Plot of square root of scan rate vs.
current response
Fig. 6 shows the electrooxidation of 1-5 mM 2-NP for CdO modified GCE at +0.79 V in 0.1
M PBS as the electrolyte. Bare GCE shows a broad oxidation peak at +0.78. With lower current
response when compared to that of modified electrode. Fig.7 shows effect of scan rate of the
modified electrode in 1mM 2-NP. When increasing the scan rates from 50-250 mVs-1 the anodic
peak current increases, which is an indicative of the process is purely diffusion controlled process.
The reason or the electrocatalytic property is the large surface area when compared to that of the
bare electrode, hence the electrocatalytic behavior of the modified electrode was found to be more
active for the sensing of 2-NP.
Fig. 6 Cyclic voltammogram of (a) bare and
CdO modified GCE for different
Concentrations of 2-NP (b-f: 1-5mM)
at 50 mV s-1
Fig. 7 Plot of square root of scan rate
current response
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4. Conclusion
Cadmium oxide nanoparticles were synthesized by two step procedure involving simple
steps. The synthesized nanoparticles have employed to modify the GCE to evaluate the
electrocatalytic performance towards environmental pollutants such as 4-NP and 2-NP. The
electrocatalytic performance was good with 4-NP with respect to the oxidation potential when
compared with bare GCE and for 2-NP the performance was found to be moderate, since increase in
current response alone observed not in shifting of the potentials.
Acknowledgment: The authors (KG) wish to acknowledge DST for their financial assistance in
the form of INSPIRE fellowship (Inspire fellow IF 10226) under ‘Assured Opportunity for research
career (AORC)’and NCNSNT, University of Madras for recording FE-SEM images.
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