Boosting the Electrocatalytic Activity of Cobaltite Nanostructures by Zn Subtituation in Tetrahedral Positions for Ultrahigh-Sensitive Electrochemical Detection of Small Dopamine Molecule in Biofluid Samples: Insights from Both Experimental and Density Functional Theory Approaches

The adjustment of active metal ion centers and electronic structures for boosting the electrocatalytic activity of spinel oxide nanostructures is considered an efficient strategy for developing the advanced high-performance electrochemical sensors. Here, ZnCo2O4 (ZCO-NPs) and Co3O4 nanoparticles with a tendency to self-assembly into 1D nanostructure were prepared by a one-pot microwave-assisted hydrothermal method, and evaluated the electrochemical sensing performance towards small dopamine (DA) molecule in biofluid samples. The physicochemical properties were studied by combining experiments and density functional theory (DFT) calculation. The DFT calculation results indicate the ZnCo2O4 possesses the strongest affinity for dopamine amongst three tested biomolecules (ascorbic acid, dopamine, uric acid), while Co3O4 shows a higher affinity for ascorbic acid. Benefiting from the adjustment of surface catalyst centers and electronic structures induced by Zn substitution, the ZCO-NPs/SPE exhibited an approximate 36.6-fold increased electrochemical sensitivity towards DA than that of Co3O4-NPs. The ZCO-NPs-based electrochemical sensors also displayed outstanding performance in detection of DA with a detection limit as low as 56 nM, and reaching an electrochemical sensitivity of 5.2 µAµM-1cm-2. This work provides an innovative strategy based on reliable theoretical and experimental basis for the electronic structural regulation of spinel oxide nanostructures for ultrasensitive electrochemical sensing of small molecules