Palladium doped alpha-MnO2 nanorods on graphene as an electrochemical sensor for simultaneous determination of dopamine and paracetamol

Defect engineering at the atomic level has been one of the most prevalent research topics in the field of catalysis because defects act as superior active sites. However, defects are difficult to create, recognize, and fully comprehend. In this study, for the first time, we demonstrate that the defects creation by palladium atom on the surface of alpha-MnO2 nanorods supported graphene (Pd@alpha-MnO2/G). These defects significantly altered the electronic and crystalline structures of the as-prepared material, as well as improving the surface/interface properties for biomolecule determination. As a result, Pd@alpha-MnO2/G exhibited a higher electroactive surface area, conductivity, and synergistic effect in the simultaneous detection of dopamine (DA) and paracetamol (PA) owing to its defective nature. For instance, it showed wide detection ranges from 0.2 to 425 mu M and from 0.1 to 375 mu M with lower limits of detection of 0.086 and 0.059 mu M for DA and PA, respectively. It also showed high sensitivity (0.0591 and 0.0854 mu A mu M--(1) for DA and PA, respectively) and experienced no interference from the presence of a 100-fold excess of interferents. Importantly, we discussed the 2H(+)/2e(-) reaction mechanism of DA and PA oxidation on the Pd@alpha-MnO2/G surface, for an in-depth understanding of the process.