Surface‐Defect Engineered Benzothiazole Nanoparticles for Amplified Electrochemiluminescence: Monitoring Charge Transfer Kinetics and Ultrasensitive Biosensing

Abstract Benzothiazole derivatives hold promise for electrochemiluminescence (ECL) due to their unique physicochemical properties. However, their reliance on metal complexes in existing systems significantly restricts their biocompatibility and potential biomedical applications. This study pioneers a precisely engineered, metal‐free donor–acceptor (D–A) architecture, leveraging benzothiazole as the electron‐accepting moiety. Through the rational modulation of electron‐withdrawing ability and conjugation length via tailored functionalization, a novel series of aggregation‐induced electrochemiluminescent (AIECL) emitters are developed that are intrinsically compatible with aqueous biological media. Among these, engineered nanoparticles derived from carbazole‐benzothiadiazole derivatives (BTZ‐PCz NPs) with incorporated surface defects demonstrated superior ECL performance. Critically, scanning electrochemical microscopy (SECM) is employed to quantitatively analyze charge transfer dynamics in surface‐defect emitters, providing unambiguous evidence for the defect‐mediated charge transport processes that drive ECL enhancement. Moreover, capitalizing on the superior aqueous ECL properties of BTZ‐PCz NPs, a highly sensitive and label‐free detection platform for amyloid‐β42 (Aβ42), a pivotal biomarker of Alzheimer's disease, is developed. This work not only expands the library of efficient, water‐compatible AIECL materials by introducing benzothiazole‐based D–A systems, but more significantly, pioneers the application of SECM in quantifying surface defect‐enhanced ECL, thereby bridging the gap between material surface properties and ECL performance.