Plasma-Treated Sputtered Nanocarbon Film Electrodes for Suppressing Electrochemical Fouling by Serotonin

The fouling of electrodes with large molecules and/or electrochemically oxidized biomolecules limits the potential applications of bioelectroanalysis. The present work examined the effects of various plasma treatments when applied to sputtered carbon film electrodes. This was done by assessing the electrode responses to serotonin, a neurotransmitter that can be adsorbed after electrochemical oxidation. Although the oxidation current of serotonin rapidly decreases after five potential cycles with 5-minute intervals at the untreated and H2O plasma-treated carbon films, the magnitudes of the currents were almost unchanged at the films after NH3 and NH3/H2O gas plasma treatments. Cyclic voltammetric measurements of Fe(CN)(6)(3-/4-) before and after serotonin oxidation revealed that there are no detectable fouling with oxidized serotonin by either the NH3 or NH3/H2O treatment, unlike the case with untreated and H2O plasma-treated carbon film electrodes. Similar to the serotonin response, both 5-hydroxyindoleacetic acid and 5-hydroxytryptophol show improved stable responses after the NH3/H2O plasma treatment. X-ray photoelectron spectroscopy data suggest that the suppression of fouling might be due to the electrostatic repulsion between the amino group of serotonin and surface charges after the NH3 and NH3/H2O treatments, in addition to the effects of hydrophilic surfaces generated by the plasma treatments. (C) The Author(s) 2020. Published by ECSJ.