Spontaneous immobilization of thiocyanate onto Au surface for the detection of uric acid in basic medium

Uric acid (UA), a biologically important chemical, exhibits detrimental environmental impacts on farmland as well as groundwater following irrational usage and maintenance. It is well known that determining the concentration of pollutants is the first step to control environmental pollution. Concerning this fact, a compact thiocyanate (SCN) adlayer based Au electrode was fabricated by a spontaneous immobilization of SCN^- ions on a polycrystalline Au surface pertaining to the selective detection of uric acid in a basic medium. The formed adlayer completely shielded the Au surface from routine passivation by uric acid species or its products, preventing electrode fouling. To verify the morphology of the electrode surface, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and linear polarization techniques were used. Voltammetric diagnosis revealed that the UA oxidation reaction on the SCN-adlayer based Au electrode basically follows first-order kinetics with a stepped mechanistic approach where one electron transfer is engaged in the rate-determining steps. On top of that, the limit of detection and the sensitivity were estimated to be 0.25 µM and 0.199 mA cm⁻² mM⁻¹, respectively. Interference studies also ascertain the fact that the proposed electrode is reasonably selective in the presence of cohabiting ionic species. Therefore, the developed sensor can be used in the analytical detection of UA in real samples.