Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
An electrochemical sensor for stripping voltammetric determination of cadmium (II) based on
multiwalled carbon nanotube functionalized with 1-(2-pyridylazo)-2-naphthol
Alireza Mohadesi, 1* Zahra Motallebi 1 and Ashraf Salmanipour 2
1
Department of Chemistry, Payame Noor University (PNU), P.O. Box 76175-559, Kerman, Iran
2
Department of Chemistry, Shahid Bahonar University of Kerman, P.O. Box 76175-133, Kerman, Iran
Abstract— The present work has focused on the modification of multiwalled carbon nanotube with a ligand, 1-(2-pyridylazo)-
2-naphthol (PAN), and its potential application for the development of a new, simple and selective modified glassy carbon
electrode for stripping voltammetric determination of Cd(II). this method demonstrates the powerful application of carbon
nanotubes in the field of mercury-free electrodes in voltammetric stripping analysis.
Traditional working electrodes for voltammetric
determination were generally based on a hanging drop
mercury electrode and a mercury film electrode. However, the
toxicity of the Hg and its precursors make these materials
undesirable for disposable in situ sensing applications.
Therefore, various chemically modified electrodes as mercuryfree
electrodes are applied for adsorptive stripping
voltammetry of heavy metal ions [1-3]. Adsorptive stripping
voltammetry generally applies an accumulation step prior to
the voltammetric scan in order to develop analysis methods
with higher levels of sensitivity. In this step, analyte (metal
ion) is adsorbed from sample solution to electrode surface
based on complexation between metal ion and ligand
immobilized on the electrode surface. In this sense, owing to
the strong sorption properties of carbon nanotubes and their
advantages in electrochemical measurements, this
nanostructured material has allowed some novel methods of
stripping analysis to be developed [1-6].
In this work, the multiwalled carbon nanotube (MWNT)
functionalized with a complex reagent (PAN) was prepared
and coated on a glassy carbon electrode (GCE). This modified
electrode was used successfully for anodic stripping
determination of Cd(II) in some real samples.
Before use, the MWNTs were purified and pretreated to
remove graphitic nanoparticles, amorphous carbon, and
catalyst impurities, and then functionalized with carboxylic
acid groups according to the literature [7]. After these
procedures, the carboxylic acid groups were introduced onto
the cross sections of the MWNTs. For preparation of PANfunctionalized
MWNT, the PAN dissolved in ethanol was
added to 1g of pretreated MWNT, step by step and the
solution was stirred for 12 hour till the solution became
colorless. Then the modified MWNTs were filtered and
washed with doubly distilled water and got dried at room
temperature. Then ultrasonication agitation for 30 min was
applied to disperse 2.0 mg PAN/MWNT into 1 ml of double
distilled water to give 2.0 mg/ml suspension. Before coating,
the GCE was polished with a nano-Al 2 O 3 powder (Fluka) on a
polishing pad (Metrohm) rinsed thoroughly with doubly
distilled water, then sonicated in aceton for 2 min. Finally, the
GCE was coated with 5 μL of 2.0 mg/ml PAN/MWNT
suspension and the water allowed evaporating at room
temperature in the air. The bare electrode was prepared by the
same procedure just with unfunctionalized MWNTs.
For differential pulse anodic (DPA) stripping voltammetric
experiments, the modified GCE was immersed in a 25 ml
solution of 0.1 M oxalate buffer pH 3.0 containing a known
amount of Cd(II) and a potential of -1.0 V was then applied
for 100 seconds (while stirrer was on, 600 rpm). Finally the
DPA stripping voltammogram was recorded (with 20 mV s−1
scan rate, 100 mV pulse amplitude, and 4 ms pulse period).
The scan was terminated at -0.4 V. All measurements were
carried out at room temperature (22 ± 1 °C).
Figure 1a shows typical DPA for the detection of Cd 2+
following closed-circuit accumulation onto PAN/MWNT film.
An anodic peak at -0.59 V can be observed, which is related to
the oxidation of accumulated and reduced Cadmium(II). To
prove further the importance of PAN as a chelator reagent in
the electrode surface, GCE modified with MWNT without
PAN were prepared, and used for the accumulation and
stripping of Cd 2+ . Figure 1c shows no significant peak, as
expected, in the case of unmodified MWNT. These results
show the importance of modification of MWNT with PAN for
the preconcentration of Cd 2+ .
Figure 1: DPA (20 mV/s) voltammograms in oxalate buffer pH 3.0 after
closed circuit accumulation (150 s at -0.9 V): (a) PAN/MWNT/GCE, with 50
μg L -1 Cd(II) in solution, (b) PAN/MWNT/GCE, no Cd(II) in solution, (c)
MWNT/GCE, with 50 μg L -1 Cd(II) in solution and (d) MWNT/GCE, no
Cd(II) in solution.
*Corresponding author: mohadesi_a@yahoo.com
[1] D. Sun et al, J Appl Electrochem 381223–1227 (2008)
[2] W. Yantasee et al., Environ. Health Perspect. 115 1683-1690 (2007)
[3] G.H. Hwang et al., Talanta 76 301–308 (2008)
[4] K. Wu et al., Anal. Chim. Acta 489 215–221 (2003)
[5] H. Xu et al., Electroanalysis 20 2655 – 2662 (2008)
[6] L. Zhu et al., Electroanalysis 20 527 – 533 (2008)
[7] X. Tan et al., Anal. Biochem. 337 111 (2005)
6th Nanoscience and Nanotechnology Conference, zmir, 2010 366