Simultaneous square wave voltammetry detection of azo dyes using silver nanoparticles assembled on carbon nanofibers

Abstract

In this work, an electrochemical sensor for the simultaneous detection of sunset yellow (SY) and tartrazine (Tz) food dyes is developed. It is based on carbon nanofibers (CNF) superficially modified with silver nanoparticles (AgNP), supported on a carbon paste electrode (CPE). The CNF modification with AgNP was achieved by the layer-by-layer self-assembly method. The AgNP were characterized by Dynamic Light Scattering (DLS) and UV-visible spectrophotometry, whereas the electrode material, AgNP-CNF, was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The simultaneous detection of SY and Tz dyes was achieved by square wave voltammetry (SWV) and cyclic voltammetry (CV). The proposed sensor was able to detect the dyes at nanomolar concentrations within a wide linear range of 3.82 × 10−8–1.29 × 10−5 mol L−1. For the SY dye detection, a determination coefficient (r2) of 0.9911, a limit of detection (LOD) of 17.6 ± 8.6 nmol L−1, and a limit of quantification (LOQ) of 58.1 ± 28.5 nmol L−1 were found, and in the Tz case a r2 of 0.9726, a LOD of 30.9 ± 23.8 nmol L−1, and LOQ of 102.0 ± 78.5 nmol L−1 were obtained. Additionally, a DFT computational study was conducted to estimate the interaction energy between the AgNP and the azo dyes at the electrode-solution interface. The electrode herein proposed exhibited excellent selectivity in the presence of various interferents such as sodium benzoate, NaNO3, NaHCO3, glucose and citric acid, with good reproducibility, repeatability (% RSD: 97.3–111.1%) and stability. Finally, the sensor performance in detecting SY and Tz was validated by UV-visible spectrophotometry.