Amplified aggregation-induced emission via donor-acceptor-donor molecular architecture: a high-sensitivity lateral flow immunoassay platform

Precise control over the structure of aggregation-induced emission luminogens (AIEgens) enables rapid development of tailored luminescent molecules. In this study, 4-(4-(1,2,2-triphenylvinyl)phenyl)benzo[c][1,2,5]thiadiazole (TPB) (donor-acceptor, D-A) and 4,7-bis(4-(1,2,2-triphenylvinyl)phenyl)benzo[c][1,2,5]thiadiazole (BTB) (donor-acceptor-donor, D-A-D) were designed and synthesized using tetraphenylene as a starting unit, guided by molecular engineering principles. Theoretical calculations and experimental results demonstrate that the D-A-D structure of BTB enhances intramolecular charge transfer, induces highly twisted molecular conformation, and imparts greater structural rigidity, thereby effectively suppressing non-radiative transitions. Subsequently, the spatial confinement effect of polystyrene microspheres restricts the rotational motion of BTB, enabling the construction of fluorescent nanoparticles (NPs) with higher quantum yields and excellent versatility. When applied to a lateral flow immunoassay (LFIA) platform, BTBNPs demonstrated significantly higher sensitivity than TPBNPs and AuNPs. Moreover, the sensitive detection of melatonin in biological samples was achieved. In conclusion, this study demonstrates that D-A-D-type AIEgens exhibit superior luminescence performance and greater potential than their D-A-type counterparts for constructing high-brightness fluorescent probes. It also establishes theoretical calculation methods for AIEgens and offers a valuable reference for their design, analysis, and application.