Mechanistic insights guiding the optimal design of Pd-NPs/PdOx electrocatalysts for dopamine-sensitive enzymatic biosensors

Herein, we propose the electrochemical synthesis of palladium-based nano-heterostructures from an electrolyte pre-heated at 40 ± 5 °C resulting in the formation of defect-rich palladium nanoparticles/palladium oxide (Pd-NPs/PdO x ) for the reliable detection of enzymatically generated quinone (Q), produced during the tyrosinase-catalyzed oxidation of dopamine (DA). Specifically, the presence of PdO x on the surface of electrodeposited Pd-NPs during the cathodic scan leads to the formation of Pd–OH species, which promote the reduction of adsorbed quinone (Q ads ), and enable continuous operation in the cathodic potential range without the need for surface regeneration. The signal from enzyme-generated quinone disappears when PdO x is removed. The insights gained were used to design a dopamine-sensitive, tyrosinase-based biosensor employing Pd-NPs/PdO x nano-heterostructures as a specific electrocatalyst for enzymatically generated quinones. Overall, these findings provide new perspectives on the role of defect-rich palladium oxides in neurotransmitter detection and electrocatalyst design.