Self-assembled nanomaterials based on aggregation-induced emission of AuNCs: Fluorescence and colorimetric dual-mode biosensing of organophosphorus pesticides

Organophosphorus pesticides (OPs) are widely used in agriculture. However, the residue and accumulation of OPs is a threat to food safety and human health. Thus, a sensitive and accurate OPs detection method is still pursued. Here, we utilized electrostatic adsorption to immobilize weak fluorescent AuNCs on the SiO2 surface, exciting its aggregation-induced emission (AIE) properties and achieving the amplification of the fluorescent signal. Furthermore, a fluorescence-colorimetric sensor based on self-assembled MnO2-AuNCs-SiO2 nanocomposites was constructed. Ascorbic acid (AA), the product of sodium l-ascorbyl-2-phosphate (AAP) in the presence of alkaline phosphatase (ALP), can decompose MnO2 and “turn on” the fluorescence sensor. Moreover, due to the inhibitory effect of OPs on ALP activity, a dual-mode detection method from fluorescence and colorimetry for OPs was developed. The linear range was from 1 μg/L to 50 mg/L with a detection limit of 0.4 μg/L in the fluorescence detection, while the linear range was from 0.1 μg/L to 50 mg/L with a detection limit of 0.09 μg/L in colorimetric analysis. Besides, the in-situ imaging of OPs in fresh vegetables was achieved and a visual semi-quantitative detection of OPs on a test paper was realized. Therefore, the fluorescent biosensor may show a potential value in field detection.