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 (ΦECL). 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)32+]/TPrA, bright emissions with up to 54 % ΦECL 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−1, with a remarkably low detection limit of 0.28 pg mL−1. 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. [Display omitted] •A novel AIECL emitter with A-π-D-π-A configuration was successfully prepared.•The ECL efficiency is enhanced by twisted molecular conformation and ICT effect.•A label-free immunosensor was developed to detect SARS-CoV-2 N protein.•Low detection limit (0.28 pg mL−1) and a great linear range (0.001–500 ng mL−1).