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. 2020 Nov 14;20(22):6502.
doi: 10.3390/s20226502.

Optimization and Analytical Behavior of Electrochemical Sensors Based on the Modification of Indium Tin Oxide (ITO) Using PANI/MWCNTs/AuNPs for Mercury Detection

Noor Aini Bohari  1 , Shafiquzzaman Siddiquee  1 , Suryani Saallah  1 , Mailin Misson  1 , Sazmal Effendi Arshad  2
Affiliations

Optimization and Analytical Behavior of Electrochemical Sensors Based on the Modification of Indium Tin Oxide (ITO) Using PANI/MWCNTs/AuNPs for Mercury Detection

Noor Aini Bohari et al. Sensors (Basel). .

Abstract

In the present study, indium tin oxide (ITO) was used as a transparent working electrode for the development of an electrochemical sensor for the detection of mercury (II) ions (Hg2+). The electrode was modified by direct electrodeposition of polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) followed by optimization of the analyte and operating conditions, aiming to improve the selectivity, sensitivity and reliability of the electrode for mercury detection. Successful immobilization of the PANI and nanomaterials (MWCNTs and AuNPs) on the ITO electrode was confirmed by Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The optimum conditions for mercury detection using the modified ITO electrode were pH 7.0 of Tris-HCl buffer (50 mM) in the presence of 1 mM methylene blue (MB) as a redox indicator, a scan rate of 0.10 V·s-1 and a 70 s interaction time. The electrochemical behavior of the modified electrode under the optimized conditions indicated a high reproducibility and high sensitivity of mercury detection. It is therefore suggested that the PANI/MWCNT/AuNP-modified ITO electrode could be a promising material for the development of on-site mercury detection tools for applications in fields such as diagnostics, the environment, safety and security controls or other industries.

Keywords: cosmetic; cyclic voltammetry (CV); differential pulse voltammetry (DPV); electrochemical sensor; mercury.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
A Computer-controlled potentiostat/galvanostat with a standard three-electrode system connected to an electrochemical cell where Tris-HCl and mercury are used as analytes.
Figure 2
Figure 2
Polyaniline/multiwalled carbon nanotube/gold nanoparticle (PANI/MWCNT/AuNP)-modified indium tin oxide (ITO) electrode: (a) Schematic representation, (b) SEM image, (c) energy-dispersive X-ray (EDX) spectra and (d) the corresponding elemental composition.
Figure 3
Figure 3
FTIR spectra of bare and modified ITO electrodes.
Figure 4
Figure 4
Comparison of electrochemical behavior for bare ITO, PANI/MWCNTs/ITO, PANI/AuNPs/ITO and PANI/MWCNTs/AuNPs/ITO in the presence of methylene blue (MB) as a redox indicator; (a) cyclic voltammogram and (b) the corresponding peak current.
Figure 5
Figure 5
The current response obtained from the measurement of three (3) types of redox indicator in (a) cyclic voltammetry (CV) and (b) the corresponding peak current in the presence of mercury in the electrolytic solution (50 mM Tris-HCl buffer, pH 7.0).
Figure 6
Figure 6
CV responses of different type of buffer (a) and pH (b) in the presence of 6 ppm mercury.
Figure 7
Figure 7
Peak current obtained from CV measurement showing the effect of different incubation times in the presence of 1 mM MB and 6 ppm of mercury (50 mM Tris-HCl buffer, pH 7.0).
Figure 8
Figure 8
Peak current from CV measurement showing the effect of different scan rates for the determination of 6 ppm mercury (pH 7.0, 50 mM Tris-HCl buffer).
Figure 9
Figure 9
Bar chart of the reproducibility of the developed sensor (n = 5).
Figure 10
Figure 10
The selectivity of the developed sensor.
Figure 11
Figure 11
Calibration curve between the current peak of differential pulse voltammetry (DPV) and the potential.
See this image and copyright information in PMC

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