Fluorescent molecularly imprinted hydrogel sensing strip based on nitrogen-doped carbon dots and inverse opal photonic crystals applying for effective detection for imidacloprid in fruits and vegetables

This study integrated nitrogen-doped carbon dots (nitrogen-doped CDs) with remarkable fluorescence into a high-porosity inverse opal photonic crystal (IOPC) structure. A portable fluorescent hydrogel strip was developed by incorporating molecular imprinted biomimetic recognition, enabling the rapid identification and accurate detection of the insecticide imidacloprid (IMI). The ordered and hierarchical architecture of the IOPCs was advantageous to the uniform dispersion of nitrogen-doped CDs while providing efficient mass transfer channels for IMI. Additionally, the sensing strips achieved adsorption equilibrium within 20 min and demonstrated excellent selectivity, stability, and reusability. They showed a linear response to IMI across the range of 0.1–50 μg/mL (R² = 0.9905) with a detection limit of 0.065 μg/mL (S/N = 3). The spiked recoveries ranged from 88.2 % to 102.8 %, aligning well with HPLC results. This indicates that the developed fluorescent molecularly imprinted hydrogel sensing strip is an effective analytical tool for detecting IMI residues in food products.