Ultra-fast Redox Pulse for Stable Electrochemiluminescence on AuNP-Based Biosensors and Mechanism Investigation

A novel sandwich-type biosensor denoted as “MIP-analyte-Ab” was constructed on a glassy carbon electrode modified with gold nanoparticles (AuNPs@GCE), which is dedicated to explore a general solution for electrochemical tests in a relatively high potential range on Au electrodes. In particular, parasitic reactions of Au oxidation severely hindered the electrochemiluminescence (ECL) reactions of the Ru(bpy)₃²⁺/tripropylamine (TPrA) system. In this work, we designed an ultra-fast redox pulse to alleviate reversible oxidation of Au with a potential range of −0.5 to 0.9 V. Stable ECL signals were generated in the last 3 ms of each run (RSD = 5.86%), and interesting mechanisms were revealed. The ultra-high-frequency sampler indicated that free diffusion of TPrA^•+ was the rate-determining step at 0.9 V, and it followed a totally different route with ECL at 1.3 V. Furthermore, we proposed a particular ECL reaction route at 0.9 V with C5 desosamine of the analyte, azithromycin, involved for the first time, based on results of radical identification. We believe that our work paved the way for the application of Au-based sandwich-type biosensors in environmental monitoring.