Effect of Au nanoparticles on ZnO nanorods/α-Fe₂O₃ electrochemical sensor performance

In this study, the development of an efficient nano-electrode for fabricating electrochemical sensors to detect arsenic(v) in drinking water is presented. This nano-electrode is composed of a metal-semiconductor hybrid, namely ZnO NRs/α-Fe₂O₃/Au NPs, denoted as (ZFA), which was synthesized in three separate steps, including the low-temperature hydrothermal and dip-coating methods. The properties of the nanocomposite were characterized by UV-vis, FESEM, XRD and XPS. Moreover, its electrochemical characteristics were analyzed via several techniques, such as linear sweep voltammetry and square wave voltammetry in different water solutions with a wide range of arsenic concentrations from 0 to 50 μg L^-1. Results indicate that the ZFA nanocomposites that were prepared with different concentrations of Au NPs showed different characteristics. From optical measurements, the best Au NP sample having the highest surface plasmon resonance (SPR) effect was determined, and this sample was further utilized for sensing. Moreover, using the optimized sample and from electrochemical studies, the arsenic(v) sensor's limit of detection was found to be 2.25 ppb, which is lower than the maximum dose recommended by the World Health Organization. In general, the results indicate that the addition of Au NPs led to better optical absorption properties. The findings of this study indicate that the addition of Au improves the electrochemical catalytic activity of the ZFA nanocomposite, which can be utilized as an electrode to further develop efficient arsenic(v) sensing systems for detection in drinking water.