Adsorption-Based Aggregation-Induced Emission on Nanoparticles: A Promising Strategy for Generic Homogeneous Fluorescence Assay Platforms

Aggregation-induced emission (AIE), a "zero background" luminescent phenomenon, shows great potential for fluorescent analytical methods. Traditionally, AIE luminogen aggregation is achieved by modifying solvent polarity. However, analyte concentration variation in trace analysis cannot alter solvent polarity, making this approach incompatible with fluorescent analytical methods and limiting the exploitation of AIE's potential. Given the widespread use of adsorption in molecular recognition, we propose that adsorption-based aggregation-induced emission (adAIE) could unify molecular recognition and signal transduction, facilitating the development of simple, general fluorescent assays. This study seeks to elucidate the adAIE mechanism and significantly broaden its application in analytical chemistry. The adsorption capacities of various tetraphenylethylene compounds (TPEs) on two styryl-based nanopolymers and their corresponding induced fluorescence intensities were systematically investigated. The findings indicate that adAIE intensity increases with greater adsorption, with rapid changes observed during the initial adsorption phase, and displays behavior distinct from poor solvent driven AIE. Additionally, a quantitative relationship was established between adAIE sensitivity and its key influencing factors, specifically the adsorption capacity and optical parameters (ε and φ) of TPEs. Using this relationship, we developed a general, mix-and-measure, "turn-on" fluorescent assay to detect nanoplastics in water samples. Furthermore, a selective, homogeneous fluorescent assay for dopamine detection was achieved by combining adAIE with competitive adsorption based on boronate affinity. This work clarifies the adAIE mechanism, highlights its rapid response and high compatibility, opens new possibilities for AIE in analytical applications. Integrating universal molecular recognition (adsorption) with efficient signal transduction (AIE) provides separation-free and highly sensitive fluorescence sensing platforms.