High-Performance Multiporous Imprinted Microspheres Based on N-Doped Carbon Dots Exfoliated from Covalent Organic Framework for Flonicamid Optosensing

High-performance, multiporous imprinted microspheres were prepared from nitrogen-doped carbon dots (N-CDs) using a one-pot reverse microemulsion surface-imprinting method. Here, the N-CDs were exfoliated from a common layer covalent organic framework in a top-down preparation, and an ionic liquid was added to improve the sensitivity and the fluorescence stability. The multiporous imprinted microspheres were successfully applied to flonicamid optosensing in fruits and vegetables with simultaneous analysis of 96 samples by multifunctional enzyme labeling. The fluorescence sensing procedure was performed on recyclable multiporous imprinted microspheres coupling with the interface of N-CDs by taking advantage of the fluorescence-resonance charge-transfer strategy between the N-doped carbon dots and flonicamid molecules, quenching the fluorescence intensity. The multiporous imprinted microspheres exhibited purple fluorescence, which decreased sharply in intensity as the concentration of flonicamid increased. The fluorescence quenching correlation with the concentration of flonicamid showed good linearity in the range of 0.02–0.2 μg g–1 with a detection limit of 0.0059 μg g–1. This research not only enriches the foundational study of flonicamid residues but also greatly expands the potential applications of multiporous imprinted microspheres for analysis of pesticide residues in agricultural, food, and environmental monitoring.