Aggregation-induced electrochemiluminescence based on intramolecular charge transfer and twisted molecular conformation for label-free Immunoassay.

Organic emitters with exceptional properties exhibit significant potential in the field of aggregation-induced electrochemiluminescence (AIECL); however, their practicality is impeded by limited ECL efficiency (Φ). This paper investigates a novel type of AIECL emitter (BDPPA NPs), where an efficient intramolecular charge transfer (ICT) effect and highly twisted conformation contribute to a remarkable enhancement of ECL. The ICT effect reduces the electron transfer path, while the twisted conformation effectively restricts π-π stacking and intramolecular motions. Intriguingly, compared to the standard system of [Ru(bpy)]/TPrA, bright emissions with up to 54 % Φ were achieved, enabling direct visual observation of ECL through the co-reactant route. The label-free immunosensor exhibited distinguished performance in detecting SARS-CoV-2 N protein across an exceptionally wide linear range of 0.001-500 ng mL, with a remarkably low detection limit of 0.28 pg mL. Furthermore, this developed ECL platform exhibited excellent sensitivity, specificity, and stability characteristics, providing an efficient avenue for constructing platforms for bioanalysis and clinical diagnosis analysis.