Impedimetric sensing of uranyl ion based on phosphate functionalized cysteamine self-assembled monolayers

A phosphate functionalized cysteamine self-assembled monolayer based on gold electrode is designed for uranyl ion (UO₂²⁺) detection. The response of the modified electrode is studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The EIS data are approximated using constant phase element (CPE) model from which kinetic and analytical parameters are evaluated. Uranyl ion is recognized based on blocking effect against charge transfer between p-benzoquinone as a probe and the modified electrode. This effect is detected from linear variation of charge transfer resistance (R_ct) as a function of UO₂²⁺ concentration. From the analysis of the EIS data and approximated parameters, a method is developed for UO₂²⁺ determination based on impedimetric measurements.