Fabrication of Ru–Pd bimetallic monolayer on nanoporous gold film electrode with excellent electrocatalytic performance towards captopril oxidation

This paper describes a simple and novel method to construct ruthenium–palladium (RuPd) bimetallic thin films by coating thin layer of RuPd metals on the nanoporous gold film (NPGF) electrode. The codeposition of Ru and Pd was done through oxidation of copper underpotential deposition (UPD) layer by Ru and Pd ions. This low RuPd-loading electrode (RuPdNPGF) behaved as the nanostructured bimetallic RuPd for the detection of captopril (CAP). Whereas at the surface of the bare electrode an electrochemical activity for CAP cannot be observed, a very sharp anodic peak of the potential of −0.295 V (vs. Ag/AgCl) in pH = 7.0 is obtained using the prepared RuPdNPGF electrode. RuPdNPGF exhibited an excellent performance toward electrochemical oxidation of CAP without any additional mediator showing a significant decrease in the anodic over potential, a high sensitivity and a low detection limit (1.25 × 10−9 M) for CAP. Under the optimized conditions, the amperometric of CAP showed two linear ranges for determination of CAP: 2.50 × 10−9 to 4.75 × 10−7 M CAP and 2.5 × 10−6 to 3.25 × 10−5 M CAP. The results show that the RuPdNPGF electrode exhibited a selective, rapid response, good stability with excellent precision (RSD = 2.19%).