Enhanced electrochemiluminescence of luminol by an in situ silver nanoparticle-decorated graphene dot for glucose analysis

Abstract

Herein, a rapid, linker-free, single-step strategy for in situ synthesis of graphene quantum dot–luminol–Ag nanoparticle (GQD–luminol–AgNP) nanocomposites was designed by reducing AgNO₃ with an electrochemiluminescent reagent, luminol, in the presence of GQDs. The nanocomposites were characterized using transmission electron microscopy, UV-vis absorption spectroscopy, and EDS. The results indicated that many Ag nanoparticles (AgNPs) with an average diameter of about 5 nm were dispersed uniformly on the surface of GQD nanosheets. Luminol molecules were also decorated on the nanocomposite surface. Thus, the nanocomposites showed excellent electrochemiluminescence (ECL) activity in presence of H₂O₂. To build a glucose ECL-based biosensor, the prepared sensor was also modified with glucose oxidase (GOx). The GOx enzyme was covalently immobilized on the GQD–luminol–AgNP-modified glassy carbon electrode. The designed ECL biosensor showed great performance towards glucose detection in the concentration range between 25 and 250 μM with a satisfactory detection limit (8 μM).