Preparation of Ru–Pt bimetallic monolayer on nanoporous gold film electrode and its application as an ultrasensitive sensor for determination of methionine

Abstract

We report here the fabrication of ruthenium/platinum (RuPt) bimetallic monolayer coated on a nanoporous gold film electrode (RuPtNPGF) by underpotential deposition of copper (UPD) with the Cu layer then replaced spontaneously by Ru and Pt. The present method could provide a very low RuPt-loading electrode and the results demonstrated that ultra thin RuPt coating behaved efficiently as a bimetallic nanostructure RuPt for electrocatalytic oxidation of methionine. The structure and morphology of the catalyst were defined by using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), respectively. The RuPtNPGF electrode displayed good performance along with low working potential, high selectivity, and a low detection limit for the oxidation of methionine. Whereas at the surface of the bare electrode a redox peak for methionine cannot be observed, a sharp anodic peak at a potential of 0.73 V (vs. Ag/AgCl) in pH = 7.0 is obtained using the prepared RuPtNPGF electrode. Under optimized conditions differential pulse voltammetry (DPV) of methionine showed two linear ranges for the determination of methionine: 6–105 nmol L⁻¹ and 3–102 μmol L⁻¹ with a detection limit of 2 nmol L⁻¹. Finally, the proposed sensor was successfully applied for the determination of methionine in human urine, with satisfactory results.