Amphiphilic polymer-mediated host-guest structure combined with layer-by-layer assembly: MOF-derived hollow...

An ultrasensitive method for rapid detection of norfloxacin (NOR) is crucial for ensuring the food safety and environmental protection. Ratiometric fluorescent sensors have attracted increasing attention as an effective detection strategy. However, there is still an urgent demand to design novel multi-color fluorescent beads with independent optical signals and hydrophilic functionalization. Herein, a novel strategy was proposed by combining poly (styrene-co-maleic anhydride) (PSMA) mediated with a layer-by-layer assembly approach to construct functionalized quantum dots (QDs) encoded molecularly imprinted microspheres with two strong fluorescence signals. Using PSMA molecules as mediator, the encapsulation of QDs and carboxylation of the microspheres were integrated in one-pot route, improving the preparation efficiency. Based on these dual-encoded microspheres, a ratiometric fluorescent sensor was fabricated for the fast quantitative detection of NOR by monitoring changes in fluorescence response with varying NOR concentrations. The hydrophilic modification endows the sensor with applicability in aqueous system. Under the optimum detection conditions, satisfactory spiked recoveries (92.08-103.55%) and precision (RSD < 4.84%) in chicken, pork, fish, and milk were obtained. The method limit of detection (LOD) value was measured to be 0.1 μg L^-1. Moreover, the unique hollow structure facilitated mass transfer, thereby reducing the detection time to 8 min. This work provides a pioneering and effective strategy for dual-encoded imprinted fluorescent microspheres and high-performance chemical sensing of food contaminants.