Determination of heterogeneous electron transfer rate constants at interdigitated nanoband electrodes fabricated by an optical mix-and-match process

• Gold interdigitated nanoband electrodes down to 400 nm have been fabricated using a mix-and-match optical lithographic process.
• A straightforward method to determine electron transfer rate constants combining generator-collector experiments and numerical simulations is presented.

Interdigitated microband electrodes are important electroanalytical tools, and have been used in the construction of advanced sensing and biosensing devices for a long time. Nanoband-based systems, on the other hand, are more difficult to come by, as their fabrication involves the use of costly and scarce e-beam lithography resources. In this work we present the fabrication of interdigitated nanobands down to 400 nm using optical techniques exclusively. The process combines a step-and-repeat process to define Cr–Au nano- and microbands, and a standard lithography to pattern the active areas and contacts through an SU-8 passivation layer. This work presents the physical and electrochemical characterization of these devices, and our results also show that generator–collector experiments at these nanometric devices can be used in conventional electroanalytical applications, but also to measure electrode kinetics. While electrode kinetics does not affect collection efficiency to a great extent, the fast mass transport rates achieved at these devices makes the voltammetric current critically dependent on electron transfer rates.

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