An Electrochemical Study with Three Redox Substances on a Carbon Based Nanogap Electrode Array

The interdigitated electrode arrays (IDAs) are widely applied for sensor applications. In the last decade, carbon has been increasingly used as an electrode material and competes with materials such as gold and platinum. A wide electrochemical window, nonspecific adsorption of biomolecules, chemical inertness, excellent biocompatibility, and low market price make carbon an attractive candidate for electrochemical biosensor applications. [1] We developed a carbon nanogap-IDA (nIDA) sensor based on reversible redox processes for electrochemical detection of biomolecules. [2] The advantages of an IDA configuration as such and a small gap size are signal amplification and a high signal to noise ratio. Bard et al. [3 and Aoki et al. [4] showed that signal amplification can be achieved using chronoamperometry due to a reversible redox process. The gap size between finger electrodes of the IDA is the crucial factor for the attainable gain. Our nIDA transducer is deployed for a lab-on-chip application based on enzyme-linked bioassay protocol where p-aminophenol is used as redox couple. Additionally, the fabricated nIDA transducer is used for the detection of the neurotransmitter dopamine. For a conclusive comparison of nIDAs with different electrode materials, ferrocene methanol was utilized. In this work, we report current results for the electrochemical characterization of the fabricated carbon nanogap IDAs. The three redox substances ferrocene methanol (FcMeOH), p-aminophenol (pAP) and dopamine (DA) were applied with 0.1 M KCl as supporting electrolyte. The information on the electron transfer during the reversible redox process was obtained by cyclic voltammetric measurements in generator/collector mode. In this mode, one working electrode (generator) is scanned while the second working electrode (collector) is fixed at a constant potential. Furthermore, chronoamperometric measurements were performed to determine the signal amplification and to obtain information on the sensitivity of the generated carbon nIDAs. A concentration range of 10 pM to 1 mM for all three redox pairs was investigated to analyse the sensitivity of the carbon nIDAs. The largest linear characteristic was achieved with ferrocene methanol in the concentration range of 5 nM to 1 mM during chronoamperometry. In this case the oxidation potential of +0.3 V and the reduction potential of -0.05 V relative to the Ag/AgCl reference electrode were applied to the working electrode 1 and the working