Abstract
A composite sensor consisting of two separate inorganic layers of Prussian blue (PB) and a composite of cerium oxide nanoparticles (CeNPs) and graphene oxide (GO), is tested with •OH radicals. The signals from the interaction between the composite layers and •OH radicals are characterized using cyclic voltammetry (CV). The degradation of PB in the presence of H2O2 and •OH radicals is observed and its impact on the sensor efficiency is investigated. The results show that the composite sensor differentiates between the solutions with and without •OH radicals by the increase of electrochemical redox current in the presence of •OH radicals. The redox response shows a linear relation with the concentration of •OH radicals where the limit of detection, LOD, is found at 60 µM (100 µM without the PB layer). When additional composite layers are applied on the composite sensor to prevent the degradation of PB layer, the PB layer is still observed to be degraded. Furthermore, the sensor conductivity is found to decrease with the additional layers of composite. Although the CeNP/GO/PB composite sensor demonstrates high sensitivity with •OH radicals at low concentrations, it can only be used once due to the degradation of PB.
Highlights
Hydroxyl radicals (OH radicals) are one of the most reactive free radicals among reactive oxygen species (ROS)
The composition of the cerium oxide nanoparticles (CeNPs)/graphene oxide (GO) composite was confirmed by using a Rigaku Ultima III X-ray diffractometer with small angle X-ray scattering (SAXS)
Before any Prussian blue (PB) was immobilized on a working electrode, a glassy carbon electrode (GCE) was cleaned with 0.1 N sulfuric acid using cyclic voltammetry (CV) to eliminate impurities on the surface of electrode
Summary
Hydroxyl radicals (OH radicals) are one of the most reactive free radicals among reactive oxygen species (ROS). A sensor technology enabling real-time detection of OH radicals with high sensitivity and selectivity would be beneficial to medical diagnoses for such diseases at early stages [25,26,27]. A real-time composite sensor for detecting OH radicals has been developed by depositing two separate inorganic layers on a screen printed glassy carbon electrode (GCE). It is hypothesized that PB can increase the conductivity and sensitivity of the composite sensor at low concentrations of OH radicals. The sensitivity of sensor is an important factor in the detection of free radicals because it is necessary to be able to analyze even a small abnormal increase of OH radicals at an onset of oxidative stress-related diseases. To the best of our knowledge, this is a first real-time electrochemical sensor with the integration of PB and CeNPs for the detection of OH radicals in an aqueous system
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