Using ferrocenes to assist in voltammetric characterization of carbon fiber microelectrodes after electrochemical and laser activation

In this report the voltammetry of water-soluble ferrocene derivatives is used to characterize the surface of carbon fiber microelectrodes before and after both electrochemical and laser activation procedures. Activation of carbon electrodes is necessary to produce a reproducible surface that will allow fast electron transfer. However, the activation method that is best suited for a given analysis can differ with analyte. In order to directly compare activation methods and characterize the resulting electrode performance, the voltammetry of a set of ferrocenes which have fast and well-known electrochemistry has been used. As expected, electrochemical activation (0.000 to 2.000 V (vs. SSCE) at 500 V/s for 15 seconds) resulted in a hydrophilic surface with increased surface area. Laser pretreatment (20 Hz pulsed nitrogen laser irradiation for 15 seconds) appeared to remove surface oxides thereby producing a more hydrophobic surface that facilitates the adsorption of neutral analytes. In general, anionic ferrocene derivatives exhibited more quasi-reversible voltammetry and were not as strongly adsorbed as the neutral analyte, particularly with electrochemically activated probes. In addition, neutral analytes show considerable adsorption, particularly at laser-activated electrodes, while the cationic analyte shows significant adsorption at only the electrochemically-pretreated electrodes, indicating surface-specific interactions.