Electrochemiluminescent quantum dots as emerging next generation sensing platforms

Abstract

Electrochemiluminescent quantum dots (QDs) have attracted attention in sensing applications attributed to their ultra sensitivity along with the capability for real-time analysis and signal amplification. Quantum dots are candidates of choice in sensors due to advantages, including not only the outstanding nanostructures and multi-color of QDs tailored by the size, shape, and composition, but also the advanced surface modification and conjugation technologies. Further, electrochemiluminescence (ECL) integrates the distinct advantages of electrochemistry and spectroscopy resulting in fast response speed, simple operation processes, no background noise, and excellent sensitivity. Compared with conventional ECL luminophores (e.g. luminol and Ru(bpy)32+) and coreactants (H2O2, S2O82-, and triethylamine), QDs have high stability, functional flexibility, good catalytic activity, ideal opto-electronic properties, and low cost synthesis. The typical QD-based ECL sensors incorporate novel QDs, coating materials, and functional ligands to improve their detection signals and specific targeting. Further, QDs are employed as luminophores, coreactants, signal labels, ECL-RET donors, and acceptors in ECL sensors. Therefore, the present review recapitulates QDs-based electrochemiluminescent sensors reported to date starting with the structural properties responsible for electrochemiluminescence of QDs via annihilation and coractant pathways. This will be followed by a critical discussion on QDs modification methods used to incorporate the improved properties of QDs for achieving better stability, specificity, sensitivity, and reproducibility of ECL sensors. The special focus in the review is given on the sensing strategies and different roles of QDs in qualitative and quantitative determination of a variety of analytes along with extensive analysis of advantages and limitations of each method. The review also covers some technological advancements for e.g. use of smartphones and artificial intelligence in electrochemiluminescence sensing. Finally, the challenges and prospects in the future directions are featured based on the current development of QD-based ECL sensors.