Galvanically Deposited Fe₂O₃/α-FeO(OH) Thin Films Composite Towards Fast and Selective Enzyme-Free Electrochemical...

Precise and speedy determination of dopamine (DA) levels in bio-fluids is crucial since DA is a key neurotransmitter involved in regulating motor control, awareness, and emotional balance, and its abnormal concentration is directly linked to various neurological disorders. Accordingly, electrochemical nonenzymatic biosensors provide a promising platform for DA detection. In this study, a facile and low-cost galvanic deposition technique was employed to fabricate a nanostructured composite thin film of α-Fe₂O₃/α-FeO(OH), which enabled enhanced electrocatalytic activity and direct electron transfer at the electrode interface for DA detection. The sensor exhibited very low detection limit of 0.024 µM and excellent sensitivity of 20.6 µA cm^-2 µM^-1 toward DA oxidation to dopamine-o-quinone at an optimized operational potential of 0.75 V versus Ag/AgCl. With stable redox couple of Fe³⁺/Fe²⁺ in Fe₂O₃ and access to abundant electro-active sites provided by α-FeO(OH) charge transfer kinetics is smoothly facilitated. The OH radical assisted mechanistic confirmation of the oxidation pathway was validated using spectroscopic probes, ensuring reliability of the catalytic process. This technique demonstrated high selectivity against common interfering biomolecules such as ascorbic acid, uric acid etc., along with long-term stability, reproducibility, and repeatability, making it suitable for real-time DA monitoring in complex biological matrices such as serum or cerebrospinal fluid.