The Effect of Size and Content of Cerium Oxide on the Efficiency of a Composite Sensor for Hydroxyl Radicals Detection

Abstract

Hydroxyl radicals (•OH) are one of the biomarkers that are recognized during an initial stage of severe disease development. High concentrations of •OH in a human body may cause cancer, Alzheimer’s disease or Parkinson’s disease. Thus, to diagnose the onset of those diseases, a very sensitive analytical device is needed for •OH detection at low concentrations. The combination of a recognition system with an electrochemical technique is regarded as a promising method for •OH detection due to the rapid and direct measurement without the pretreatment of samples. In the current experiment, a glassy carbon electrode was modified with a graphene oxide/cerium oxide (GO/CeO2) composite to be used as a sensing device for hydroxyl free radicals. The GO/CeO2 composite was synthesized through a low-temperature solution process. Transmission electron microscopy (TEM) was used to determine the average size of CeO2 nanoparticles in the composite. X-ray powder diffraction (XRD) helped to confirm the composition of the GO/CeO2 composite. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interaction of the composite sensor with •OH in the Fenton reaction. The size and content of CeO2 nanoparticles in the composite were varied to study the effect of these two factors on the sensor performance. Regarding the effect of particle size on the sensor efficiency, 25 nm and 10 nm CeO2 nanoparticles were embedded in the composites separately. While the composite sensor with 25 nm CeO2 showed no oxidation current response with •OH, the composite with 10 nm CeO2 nanoparticles resulted in a significant increase in the oxidation current response. Different contents of CeO2 in the composite, 10, 25, 50, 75, and 90 % of CeO2 were also studied to determine the optimum ratio of CeO2 to GO. 75% of CeO2 in the composite showed the highest oxidation current response in •OH detection. Consequently, the composite sensor consisting of 25% GO and 75% of 10 nm CeO2 was found to be the most effective in the reaction with •OH. It is suggested that the size and content of CeO2 play an important role in the development of effective GO/CeO2 composite sensors for •OH detection.