Elaboration of a chemical sensor based on polyaniline and sulfanilic acid diazonium salt for highly sensitive detection nitrite ions in acidified aqueous media

Abstract

In this study, polyaniline composite films were obtained by electrosynthesis of polyaniline (PANI) after electrodeposition of radicals generated from 4-aminobenzenesulfonic diazonium salt (ABS) on glassy carbon electrodes (GCE). The electrochemical reduction process of ABS and electropolymerization of aniline were investigated via cyclic voltammetry, electrochemical impedance spectroscopy and UV-visible absorption spectroscopy. The PANI/ABS/GCE showed higher reactivity with respect to the [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ redox couple as compared to the bare GCE and PANI/GCE. The surface morphology of the modified electrode, characterized by scanning electron microscopy, showed fibrous and porous nanotubes. The PANI/ABS/GCE was then applied for the detection of nitrite ions in an acidified aqueous solution. The electrode exhibited enhanced electrocatalytic activity towards the reduction of these ions. Furthermore, the modified electrode showed linear voltammetric responses towards NO₂⁻ at concentrations between 0.5 and 35 μM, with a detection limit of 0.48 μM. The sensitivity was found to be 23.04 μA μM⁻¹ cm⁻², and the relative standard deviation (RSD) was 1.67% and 4.99% for intra assay and inter assay, respectively, which indicated good reproducibility of the sensor. The stability of the PANI/ABS/GCE was investigated by periodically measuring the current response, which leveled off after 7 days and became equal to 80% of the initial value. Finally, no significant modifications in the electrode signal were noted after adding various ions (2.5 mM) to 0.1 M HCl.