Preprint Article Version 1 This version is not peer-reviewed

Polypyrrole-Wrapped Carbon Nanotube Composite Films Coated on Diazonium-Modified Flexible ITO Sheets for the Electroanalysis of Heavy Metal Ions

Version 1 : Received: 16 November 2019 / Approved: 19 November 2019 / Online: 19 November 2019 (03:50:04 CET)

How to cite: Lo, M.; Seydou, M.; Bensghaïer, A.; Pires, R.; Gningue-Sall, D.; Aaron, J.; Mekhalif, Z.; Delhalle, J.; Chehimi, M.M. Polypyrrole-Wrapped Carbon Nanotube Composite Films Coated on Diazonium-Modified Flexible ITO Sheets for the Electroanalysis of Heavy Metal Ions. Preprints 2019, 2019110211 (doi: 10.20944/preprints201911.0211.v1). Lo, M.; Seydou, M.; Bensghaïer, A.; Pires, R.; Gningue-Sall, D.; Aaron, J.; Mekhalif, Z.; Delhalle, J.; Chehimi, M.M. Polypyrrole-Wrapped Carbon Nanotube Composite Films Coated on Diazonium-Modified Flexible ITO Sheets for the Electroanalysis of Heavy Metal Ions. Preprints 2019, 2019110211 (doi: 10.20944/preprints201911.0211.v1).

Abstract

Highly sensitive multicomponent materials designed for the recognition of hazardous compounds request a detailed knowledge of interfacial chemistry. It is a key parameter in the construction of the sensing (macro)molecular architectures. In this work, multi-walled carbon nanotubes (in short, CNTs) were deposited on diazonium-modified flexible ITO electrodes prior to electropolymerization of pyrrole. This three step process, including diazoniumelectroreduction, deposition of CNTs and electropolymerization, provided adhesively bonded polypyrrole-wrapped CNT composite coatings on aminophenyl-modified flexible ITO sheets. The aminophenyl (AP) groups were attached to ITO by electroreduction of the in situ generated aminobenzenediazonium compound in aqueous, acidic medium. For the first time, polypyrrole (PPy) was electrodeposited in the presence of both benzenesulfonic acid (dopant) and ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA) which acts as a chelator. The flexible electrodes were characterized by XPS, Raman and scanning electron microscopy (SEM) which provided strong supporting evidence for the wrapping of CNTs by the electrodeposited PPy. Indeed, the diameter of the nanotubes increased from 2-9 nm to ~24-35 nm for one voltammetric cycle and further to ~29-45 nm for 5 cycles. The PPy/CNT/NH2-ITO films generated by this strategy exhibit significantly improved stability and higher conductivity compared to a similar PPy coating without any embedded CNTs as assessed by from electrochemical impedance spectroscopy measurements. The potentiometric response was linear in the 10-8−3×10-7 mol.L-1Pb(II) concentration range and the detection limit was 2.9×10-9 mol.L-1 at S/N=3. The EGTA was found to drastically improve selectivity forPb(II) over Cu(II). To account for this improvement, density functional theory (DFT) was employed to calculate the EGTA-metal ion interaction energy which was found to be -374.6 and -116.4 kJ/mol for Pb(II) and Cu(II), respectively, considering solvation effects. This work demonstrates the power of a subtle combination of diazonium coupling agent, CNTs, chelators and conductive polymers to design high-performance electrochemical sensors for environmental applications.

Subject Areas

polypyrrole; diazonium; multiwalled carbon nanotubes; chelator; heavy metal ions; electrochemical sensors

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