Colloidal Quantum Dot Electrochemiluminescence: From Confined Excitons to Mechanism-Guided Bioanalysis.

Quantum dots (QDs) represent distinctive electrochemiluminescence (ECL) emitters whose excited-state properties can be engineered through quantum confinement, shell architecture, surface ligands, and interfacial chemistry. Thanks to their size-tunable emission, narrow spectral bandwidth, high brightness, and structurally engineerable excited-state landscape, QD ECL is attractive for ultrasensitive bioanalysis, multiplexed detection, and imaging-based analysis. Over the past two decades, QD ECL has evolved from defect-state-dominated demonstrations to a design-driven research field integrating nanocrystal engineering with mechanistic understanding. In this Letter, we discuss the evolution of QD ECL through the confined excitons and interfacial control over excited-state generation, emphasizing how size, shell structure, and interface design determine ECL efficiency, spectral behavior, and bioanalytical applications. We further highlight key challenges associated with mechanistic ambiguity, operational stability in complex media, batch-to-batch reproducibility, biocompatibility, and dynamic and spatially resolved bioanalysis. By connecting structural programmability with analytical performance, QD ECL is moving toward mechanism-guided next-generation bioanalysis.