Acetaminophen Sensing Using NiFe2O4 Nanoparticle/Reduced Graphene Oxide Nanosheet Composites

Graphene oxide (GO), an oxygen-rich, chemically reactive carbon nanomaterial, offers a versatile platform for catalytic and sensing applications. In this work, we report a high-performance electrochemical sensor for acetaminophen detection based on nickel ferrite (NiFe₂O₄) nanoparticles anchored onto partially reduced graphene oxide (rGO). GO was synthesized via the Tour method and partially reduced with ethylene glycol during hydrothermal treatment. Two sensor configurations were fabricated: one with pristine NiFe₂O₄ nanoparticles and the other with a NiFe₂O₄/rGO nanocomposite. Scanning electron microscopy revealed that GO facilitates the formation of smaller, uniformly dispersed NiFe₂O₄ nanoparticles on its surface. The N₂ adsorption–desorption isotherm confirmed a mesoporous structure with narrow slit-like pores, enhancing the surface area. Electrochemical impedance spectroscopy and differential pulse voltammetry analyses revealed that the incorporation of rGO significantly reduces the charge-transfer resistance from 167.5 Ω for pristine NiFe₂O₄ to 121.7 Ω in the composite and increases the density of the electroactive sites. The NiFe₂O₄/rGO sensor exhibited an exchange current density of 365.9 μA/cm², a sensitivity of 673.25 μA/cm²·mM, and a detection limit of 0.14 μM, representing improvements of nearly 2 orders of magnitude over the pristine NiFe₂O₄ sensor. These enhancements have been attributed to the synergistic combination of the high redox activity of NiFe₂O₄, the nanoscale particle size, and the superior conductivity of rGO at the electrode–electrolyte interface.