Dominant Factors Governing the Electron Transfer Kinetics and Electrochemical Biosensing Properties of Carbon Nanofiber Arrays

Carbon-based electrodes have been widely used in electroanalysis for more than half a century, but the factors governing the heterogeneous electron-transfer (HET) rate are still unclear. The effects of the exposed edge plane site density, inherent resistance of the carbon electrode, and adjustable resistors on the HET kinetics of several outer- and inner-sphere redox couples including [Fe(CN)₆]^3-/4-, Ru(NH₃)₆^3+/2+, Fe^3+/2+, dopamine, ascorbic acid, and uric acid are investigated using three kinds of carbon electrodes composed of core-shell quasi-aligned nanofiber arrays (QANFAs). The internal resistance is found to be a key factor affecting the HET kinetics and electrochemical biosensing properties. The electrodes exhibit high selectivity and sensitivity in dopamine detection in the presence of ascorbic acid and uric acid. In addition to the promising application to electrochemical biosensing, the core-shell TiC/C QANFAs encompassing a highly electroactive carbon shell and conductive TiC core provide insights into the design and construction of the ideal carbon electrode.