Synergistic ternary MnO₂/(rGO@Ag) nanocomposites for sensitive electrochemical dopamine detection

The development of high-performance electrochemical sensors is vital for the accurate and sensitive detection of neurochemicals such as dopamine (DA), a critical biomarker for neurological disorders. In this study, we report the fabrication of a novel ternary nanocomposite (MRA-10), composed of MnO₂ nanosheets (NSs), silver nanoparticles (Ag NPs), and reduced graphene oxide (rGO). The nanocomposite was synthesized via a hydrothermal process followed by sonochemical integration and applied as a sensing layer on a glassy carbon electrode (GCE). Among the tested variants, MRA-10 (with 10 wt% rGO@Ag) exhibited the best electrochemical performance because of the synergistic interaction of the high surface area of MnO₂, the excellent electrical conductivity of rGO, and the catalytic activity of Ag. Structural analyses confirmed a uniform Ag distribution and a strong interfacial contact between the components. Electrochemical studies using EIS, CV, and DPV revealed a remarkably low charge transfer resistance (178.45 Ω), high electroactive surface area (0.0803 cm²), and superior sensitivity of 353.20 μA μM^-1 cm^-2. The sensor demonstrated a broad linear range (10-500 μM) and a low detection limit (0.2615 μM) for DA, with excellent reproducibility (RSD = 1.41%) and long-term operational stability. The DA oxidation mechanism followed a two-electron adsorption-controlled process. This study introduces a robust, scalable, and cost-effective electrode platform for neurotransmitter sensing with promising clinical and environmental diagnostic applications.