Determination of peroxodisulfate ion using composite film containing naphthol green B and multi-walled carbon nanotubes

Abstract

An electrochemically active composite film which contains multi-walled carbon nanotubes (MWCNTs) incorporated with naphthol green B (NGB) was synthesized on glassy carbon, gold and indium tin oxide electrodes by potentiodynamic method. The presence of MWCNTs in the composite (MWCNTs-NGB) film modified electrodes mediates redox reaction of Fe^III/II present in NGB, whereas no redox reaction of NGB occurred at the bare electrode. The electrochemical impedance spectroscopy studies revealed that NGB and MWCNTs present in MWCNTs-NGB composite film enhances electron shuttling between the reactant and electrode surface. The surface morphology of the MWCNTs and MWCNTs-NGB were studied using atomic force microscopy, which revealed that NGB incorporated and covered the MWCNTs on the modified electrode. The MWCNTs-NGB composite film exhibits promising enhanced electrocatalysis towards S₂O₈²⁻. The response of S₂O₈²⁻ at MWCNTs and MWCNTs-NGB composite films was measured using both cyclic voltammetry and i–t curve techniques. The linear concentration range of S₂O₈²⁻ determination at MWCNTs-NGB composite film was from 15.9 μM to 7.1 mM. The sensitivity of MWCNTs-NGB composite film towards S₂O₈²⁻ was −301.9 μA mM⁻¹ cm⁻², and the limit of detection was 6.9 μM. These above values are better than the values obtained at MWCNTs film.