Electrochemistry at Bimetallic Pd/Au Thin Film Surfaces for Selec-tive Detection of Reactive Oxygen Species and Reactive Nitrogen Species.

In this work, we designed and fabricated Pd/Au bimetallic thin film electrodes with isolated Pd nanoparticles via underpotential deposi-tion of copper on a gold substrate followed by in situ redox replace reaction in a Pd salt solution. The Pd/Au electrode was characterized by AFM and XPS as well as multiple electrochemical techniques including CV and Electrochemical quartz crystal microbalance (EQCM) in sulphuric acid and phosphate buffer electrolytes. Results show that the reduction reactions of the analytes (i.e. H2O2 and 3-nitrotyrosine (3-NT)) at the Pd/Au thin film surfaces affect the nature and reactivity of Pd/Au surface electrochemistry including the ad-sorbed/absorbed hydrogen and/or the premonolayer palladium oxide redox processes at Pd. EQCM experiment supports the arrangement of small size Pd nanoparticle in Pd thin film in the presence of gold exhibits unusual properties, acting as a new physico-chemical dimen-sion between the electrode and target H2O2 and 3-NT molecules. The Pd/Au thin film was demonstrated as an extremely sensitive and selective probe for detection of common ROS and RNS (i.e. H2O2 and 3-NT). The integration of two different metallic species, Pd and Au, into a surface structure on nanoscale by exploiting their unique surface electrochemistry establishes an innovative analytical method for highly sensitive and selective detection of H2O2 and 3-NT simultaneously. This method has a general scope for detecting a broad range of redox active and non-redox active species simultaneously, which opening up new opportunities to develop new electrocatalytic materials and innovative sensing approaches.