Abstract
Heavy metals have a major contribution to biosphere pollution due to toxicity. The detection and monitoring of the environmental agents in soil, water and air is very important for the general health of humans and animals. It has been recently shown that electrochemical techniques such as differential pulse voltammetry (DPV) and square wave anodic stripping voltammetry (SWASV) using modified electrodes are very attractive methods for detecting heavy metals. The aim of this paper is to demonstrate the potential of hydrothermal process combined with electrochemical techniques to obtain modified electrodes based on functionalized carbon nanotubes (CNTs) and polyaniline (PANI) for metals detection. Commercial multi-walled carbon nanotubes (MWCNT) were functionalized by a mixture of HNO3/H2SO4 and further used for hydrothermal synthesis of CNT-PANI composites with different mass ratios. The resulted powders were analyzed by spectral (Fourier-Transform Infrared Spectroscopy) and thermal (Differential Scanning Calorimetry) methods, and then dispersed in a surfactant/electrolyte solution for preliminary electrochemical experiments (cyclic voltammetry, CV and DPV) to obtain modified electrodes. The influence of the CNT: PANI mass ratio and the synthesis time on the formation of composites with the desired structural and electrochemical properties were studied. It was found that CNT-PANI composite powder having mass ratio 1:4 and synthesis time 3h has the best structural and thermal characteristics and formed a weakly conductive film on the surface of the glassy carbon electrode. Preliminary electrochemical tests revealed the electroactive forms of polyaniline, through the presence of characteristic oxidation peaks but also reduction peaks, corresponding to reversible redox reactions, demonstrating that glassy carbon electrode has been electrochemically modified with CNT-PANI coatings. Further studies will be conducted to test the potential application of glassy carbon electrode modified with CNT-PANI coatings as electrochemical sensor for heavy metals detection.
Highlights
Heavy metals have a major contribution to biosphere pollution due to toxicity
Results obtained by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) analysis of carbon nanotubes (CNTs)-PANI composite powders shows that NTP-2 sample synthesized for 3h, with CNT:PANI mass ratio = 1:4 has the best structural and thermal characteristics among all the composite materials investigated in this study
3.3.Preliminary electrochemical tests The electrochemical methods used for the preliminary characterization of hybrid materials based on CNT functionalized with PANI are: cyclic voltammetry (CV) with scan rate 0.1 V/s and differential pulse voltammetry (DPV) with scan rate of 0.01 V/s
Summary
Heavy metals have a major contribution to biosphere pollution due to toxicity. Current methods for detecting metals that include spectral methods such as atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) are sensitive and selective. These techniques have disadvantages: sophisticated tools, high maintenance costs. It has recently been shown that electrochemical techniques such as differential pulse voltammetry (DPV) and square wave anodic stripping voltammetry (SWASV) using modified electrodes are alternative and very attractive methods for detecting heavy metals [2]
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