Enhancement of Voltammetric Signals Using a Graphene Oxide Modified Carbon Electrode for Electrochemical Paper-Based Analytical Devices

This work presents an enhancement of the voltammetric signal on an electrochemical paper-based analytical device (ePAD) using a graphene oxide (GO) modified carbon electrode. The ePAD is fabricated using a screen printing technique for fabrication of the hydrophobic area and three electrode strips. The graphene film was directly prepared on ePAD by dropping 2 µL of GO dispersed in water onto the working electrode surface and leaving it to dry at room temperature. The electrochemical reduction process of GO was carried out by applying a constant voltage of -1.20 V (vs. Ag/AgCl electrode strip) in 0.1 M KCl for 800 s. The GO-modified carbon working electrode on ePAD was readily obtained and ready to use after removing KCl solution. We tested the enhancement of the voltammetric signal on ePAD with a 6 mM [Fe(CN)₆]^4–/3– redox couple in 0.1 M KCl supporting electrolyte solution. Our results obtained from cyclic voltammograms showed that the unmodified working electrode and the GO-modified working electrode on ePAD provided similar anodic and cathodic peaks. Due to accelerated electron transfer process, it was found that the GO-modified working electrode on ePAD provided approximately a 2-fold increase in voltammetric signals when compared to the unmodified working electrode on ePAD. The reproducibility (inter-day precision) of the voltammetric signal measurement using a GO-modified working electrode on ePAD was acceptable. The relative standard deviation (RSD) was 5-8%. Therefore, the GO-modified carbon working electrode on ePAD offers an effective approach to enhance the signal and sensitivity for chemical analysis.