Peroxydisulfate/oxygen system-based electrochemiluminescent immunosensing of Hg2+ using Pt/Pd nanodendrites-thiosemicarbazide/norfloxacin as a signal enhancer

Abstract

Herein, we describe a competitive-type electrochemiluminescence (ECL) strategy for Hg²⁺ determination based on the peroxydisulfate/oxygen (S₂O₈²⁻/O₂) system that uses Pt/Pd nanodendrites (Pt/Pd NDs)-thiosemicarbazide/norfloxacin (TN)-covered gold nanoparticles (Pt/Pd-TNG₅₀) as a signal enhancer. The Pt/Pd NDs, a dense array of Pt branches on a Pd core, possessed excellent catalytic properties to enhance ECL intensity by accelerating electron transfer. In addition, the binary intramolecular synergy of TN, which had cooperative interactions of powerful π–π stacking with a larger conjugated surface, could extremely enhance the ECL signal of the S₂O₈²⁻/O₂ system. Furthermore, we designed a competitive immunoassay method using a structured sensor where a monoclonal antibody (mAb) against Hg²⁺ exhibited high specificity and recognition of Hg²⁺, which greatly improved the specificity and sensitivity of the immunosensor. As a result, the proposed immunosensor gave Hg²⁺ detection with a low detection limit (16 pg mL⁻¹) and displayed high sensitivity and stability. Importantly, this work not only, for the first time to our knowledge, utilized Pt/Pd NDs as promising ECL emitters for bioprobe construction but also opened an efficient way for the detection of Hg²⁺ in environmental monitoring.