Plant-assisted synthesis of Fe3O4 nanoparticles for catalytic degradation of methyl orange dye and electrochemical sensing of nitrite

The present study details a more environmentally friendly method for synthesizing iron oxide nanoparticles (Fe₃O₄-NPs) utilizing Hibiscus sabdariffa (H. sabdariffa) leaf extract. The produced H. sabdariffa/Fe₃O₄-NPs underwent characterization through VSM, XRD, FESEM-EDX, TEM and FTIR analyses. The FESEM and TEM images revealed that the H. sabdariffa/Fe₃O₄-NPs had a narrow distribution and an average particle size of 5±2 nm. Catalytic degradation studies of the synthesized Fe₃O₄-NPs exhibited efficient reduction of methyl orange (MO) dye. The degradation of MO catalysed by H. sabdariffa/Fe₃O₄-NPs follow the pseudo-first order kinetics, with a rate constant of 0.0328 s⁻¹ (R2=0.9866). Moreover, in electrochemical sensing studies, the anodic peak current of nitrite (NO₂⁻) for H. sabdariffa/Fe₃O₄-NPs/GCE showed a linear relationship with its concentration within the range of 0.5–7.5 mM, achieving a detection limit of 0.29 μM. These findings demonstrate that the modified electrode with Fe₃O₄-NPs synthesized using H. sabdariffa leaf extract serve as a novel electrochemical sensor for determining NO₂⁻ with high sensitivity and reproducibility.