A novel ratiometric molecularly imprinted electrochemiluminescence sensor for sensitive and selective detection of sialic acid based on PEI-CdS quantum dots as anodic coreactant and cathodic luminophore

In this study, a novel potential-resolved ratiometric electrochemiluminescence (ECL) sensor, using Ru(bpy) 3 2+ doped TiO 2 nanoparticles (TiO 2 -Ru(bpy) 3 2+ NPs) with polyethyleneimine (PEI) capped CdS quantum dots (PEI-CdS QDs) as new ECL emitter unit and molecularly imprinted polymer (MIP) as recognition element, was proposed for the first time. Owing to the large specific surface area and porosity of TiO 2 NPs plentiful Ru(bpy) 3 2+ was well immobilized on them. The obtained TiO 2 -Ru(bpy) 3 2+ NPs were able to catalyze the reduction of coreactant H 2 O 2 of PEI-CdS QDs, while the PEI-CdS QDs could serve as the coreactant of TiO 2 -Ru(bpy) 3 2+ NPs, thus their ECL was promoted by each other. Additionally, graphene oxide (GO) was used to facilitate the electron transfer and sialic acid (SA) imprinted poly(3-aminophenylboronic acid) was electrodeposited on the resulting GO/TiO 2 -Ru(bpy) 3 2+ @PEI-CdS/GCE. When SA concentration increased the anodic ECL signal from TiO 2 -Ru(bpy) 3 2+ NPs increased, while the cathodic ECL signal from PEI-CdS QDs declined. The sensor exhibited high sensitivity, selectivity and stability. Under the optimized conditions, the linear range was 1.0 nM - 0.1 mM and the detection limit was low to 0.017 nM (S/N = 3). Its good practical feasibility was confirmed by detecting SA in real samples with satisfactory results.