Synthesis of Fe₃O₄-aminopropylethoxysilane functionalized with cytochrome c and its application for electrochemical detection of phenolic compounds

In this study, a core–shell magnetic nanoparticle of Fe₃O₄-aminopropylethoxysilane (Fe₃O₄-APTES) functionalized with cytochrome c ((Fe₃O₄-APTES-cyt c)) was synthesized and employed for the construction of a modified carbon paste electrode. The modified electrode was utilized to investigate the electrochemical behavior and determine several phenolic compounds, including phenol, p-chlorophenol, and catechol, using cyclic voltammetry and chronoamperometry. The synthesized nanoparticle was characterized using scanning electron microscopy (SEM), dynamic light scattering (DLS), and Fourier transform infrared (FT-IR) spectroscopy. According to the cyclic voltammetric studies, the modified electrode displays a pair of anodic and cathodic peaks at 0.015 and − 0.015 V, respectively, corresponding to the redox pair of Fe (III)/Fe (II). However, in the electrolyte solution containing phenol, the electrode exhibited new peaks in the potential range of about 0.3–0.5 V, in addition to the phenol oxidation peak at 0.75 V, which can be attributed to the redox peaks of the phenol oxidation product. In the presence of phenol and H₂O₂, the observed current intensities of the phenol oxidation product increase, contributing to the peroxidase activity of cytochrome c (Cyt c). Chronoamperometry was also employed for the analytical determination of the phenolic compounds. The modified electrode exhibited a linear response of 1.0–16.0, 29.0–65.5, and 1.2–15.0 µM with sensitivities of 0.45, 0.37, and 0.35 µA/µM for phenol, p-chlorophenol, and catechol, respectively. The applicability of the modified electrode as an electrochemical sensor was also evaluated by monitoring the presence of the mentioned phenolic compounds in tap water.