Rumex nervosus-Derived Fe3O4 Nanoparticles as an Electrocatalyst for the Electrochemical Sensing of 2,4-D

The extensive use of 2,4-dichlorophenoxyacetic acid (2,4-D) in agriculture has led to water contamination and associated health risks, highlighting the need for eco-friendly detection strategies. Herein, Fe3O4 nanoparticles were green-synthesized for the first time using an aqueous extract of Rumex nervosus (R. nervosus) as a natural reducing and stabilizing agent and successfully employed for the electrochemical sensing of 2,4-D, representing the first reported application of R. nervosus-mediated Fe3O4 nanoparticles for this purpose. The phytochemical composition of the extract and synthesized R-Fe3O4 nanoparticles were systematically characterized. The R-Fe3O4-modified glassy carbon electrode (GCE) was evaluated for charge transfer properties using electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) showed no redox peak for 2,4-D at the bare GCE, whereas R-Fe3O4/GCE exhibited a distinct reduction peak at ~−1.5 V in 0.1 M phosphate buffer (pH 7), attributed to reductive dechlorination. Square-wave voltammetry (SWV) exhibited a linear response over the concentration range of 50–325 µM with a detection limit of 3.35 µM for 2,4-D. Although this performance is slightly above the guideline limits recommended by the World Health Organization (~0.14 µM) and the United States Environmental Protection Agency (~0.32 µM), it is suitable for the routine monitoring of elevated 2,4-D levels in environmental samples. The sensor demonstrated high selectivity with negligible interference and satisfactory recoveries of 96.6–98.3% in real water samples.