Influence of the graphene oxide content in the ZnO/GO composite on the selectivity and sensitivity of the electrode for detecting diclofenac in water

Abstract

Diclofenac (DCF) is one of the most commonly used pharmaceuticals today. Due to its high consumption, DCF ends up in ecosystems and watercourses, where it becomes a pollutant, endangering the living world. Effective monitoring of contaminant concentrations in water is crucial for ensuring water quality, which can be achieved through electroanalytical methods. The performance of an electrochemical method is critically determined by the surface characteristics of the working electrode. Therefore, composites were designed to modify the surface of the working electrode to improve its properties. In this study, we propose zinc oxide/graphene oxide (ZnO/GO) composites with different weight percentages of GO relative to ZnO (0.005%, 0.01%, and 0.05%) to examine the influence of GO content on the characteristics of the electrode for the detection of DCF in water. The physicochemical characteristics of the materials were examined by X-ray diffraction analysis, Raman spectroscopy, and FESEM imaging. The materials were then combined with the carbon additive, distilled water, and ethanol into an ink to modify the glassy carbon electrode. After In Situ electrochemical reduction of GO, the obtained electrodes were tested for the oxidation of DCF in a neutral electrolyte (0.1 M phosphate buffer) by cyclic voltammetry (CV). CVs showed an irreversible anodic peak originating from the oxidation of DCF, as well as anodic and cathodic peaks originating from the oxidation/reduction of the decomposition product of the oxidized form of DCF. Parameters such as limit of detection (LOD), limit of quantification (LOQ), dynamic range, and sensitivity were evaluated. The measurements indicated that all electrodes are selective for DCF. The proposed materials are suitable for further investigation in the field of electrochemical detection of pharmaceuticals in aqueous electrolytes.