Au/ZnO nanocomposites decorated ITO electrodes for voltammetric sensing of selenium in water

Abstract Herein, we report an electrochemically synthesized Au/ZnO nanocomposite (NC) onto a disposable ITO electrode for selective detection of selenium (IV), the utmost toxic chemical species of selenium, in water using the square wave anodic stripping voltammetry as transduction technique. The NC is synthesized via one-step electrochemical reduction method. Raman, XPS, and EDAX analysis confirm the synthesis of the nanocomposite, while XRD and HR-TEM investigations reveal their crystalline nature, with a uniform distribution of spherical Au nanoparticles onto hexagonal ZnO. CV and EIS analysis of fabricated electrodes support their electro-analytical application. The analytical characteristics of the fabricated NC were optimized in terms of deposition potential, deposition time, electrolyte, pH and square wave characteristics (frequency, step-size, amplitude, etc.) to achieve a detection and quantification limit of 2.89 ppb and 8.75 ppb, respectively, with 2.55% (n = 3) RSD and 0.19 μA/ppb sensitivity. The NC is also tested against a variety of cations and anions, commonly found in water, such as Pb (II), Cu (II), Mg (II), Fe (III), Cd (II), iodide, phosphate, sulphate, bromide, etc. The observed electrode insulation towards these interfering ions is assigned to a high adsorption coefficient of ZnO towards selenium (IV) in the fabricated NC electrodes. The sensor performance is also validated against ion chromatography technique and spiked water sample collected from the field. The presented sensor electrodes could be a potential substitute for existing mercury and bulk electrodes for their easy integration into the field-deployable electrochemical analyzer for selenium screening in water.