Electrochemical Sensing of Dopamine with a Nafion-Coated Reduced Graphene Oxide/Polypyrrole-Functionalized Magnetic Nanoparticles Composite

An electrochemical sensor based on a novel composite of electrochemically reduced graphene oxide, polypyrrole-coated magnetic nanoparticles (MNPs@PPy), and Nafion was developed for dopamine (DA) detection. The structural, thermal, and electrochemical properties of the composite were validated through a combination of advanced spectroscopic techniques, thermal profiling, electron microscopy, and impedance analyses. Under optimized conditions, differential pulse voltammetry (DPV) revealed a high sensitivity (1.573 A·M−1·cm−2, R2 = 0.9874) and a limit of detection (LOD) of 5.4 × 10−9 M for DA. The sensor displayed excellent selectivity, showing minimal interference from ascorbic acid, uric acid, and acetaminophen. Repeatability and reproducibility were confirmed (coefficient of variation ~8%). Real-sample analysis of urine and blood demonstrated recovery rates between 75 and 116%.