Sensitive electrochemical detection of dopamine using CuCo2O4/graphene quantum dots-modified carbon paste electrode

Abstract

This research investigates the fabrication and electrochemical characterization of a modified graphene paste electrode (MCPE) incorporating CuCo₂O₄ bimetallic oxide and its composite with graphene quantum dots (GQDs) for dopamine detection. The CuCo₂O₄ was synthesized via a hydrothermal method. The oxidation–reduction behavior of dopamine on the GQD/CuCo₂O₄/CPE indicates a quasi-reversible electrochemical reaction with an absorption-controlled electron transfer process and the kinetics of the catalytic reaction followed pseudo first-order. The average value of the electron transfer rate constant for GQD/CuCo₂O₄ was observed to be 0.047 s⁻¹. Characterization of the obtained materials was performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Subsequently, under optimized conditions, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were employed to evaluate the dopamine sensing performance of the MCPEs. The GQD/CuCo₂O₄ composite electrode exhibited a lower detection limit (0.004 μM) and quantification limit (0.013 μM) for DA compared to the CuCo₂O₄ electrode (0.0088 μM and 0.030 μM, respectively). The GQD/CuCo₂O₄ nanocomposite showed better sensitivity (33.0 mA/mM) than CuCo₂O₄ (17.9 mA/mM) due to the superior conducting nature of GQD. Finally, the applicability of the GQD/CuCo₂O₄-based MCPE was demonstrated by measuring DA in real samples.