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.