Environmentally friendly ratiometric fluorescent microfluidic paper chip for rapid detection of difenoconazole

A novel ratiometric fluorescent imprinted microfluidic device was constructed to rapidly detect trace pesticide residues. NBD-APTES was used as control fluorescence, and the fluorescence of carbon quantum dots modified with cysteine (CDs-Cys) was constructed to achieve rapid visual detection of the bacteriostatic agent difenoconazole. The analytical performance of paper-based chips was studied in detail using scanning electron microscopy and laser confocal microscopy. Under optimized conditions, the linear range of the fluorescence sensor is 0.3–60 μmol/L, the LOD is 75 nmol/L, the recoveries are 102.1%–111.2%, and the accuracy is 3.1%–4.2%. Compared with the traditional liquid phase fluorescence sensing materials, the ratiometric fluorescence sensor under the solid phase matrix has better portability and storability, showing satisfactory fluorescence characteristics. In addition, the sensor was highly specific for separating and detecting difenoconazole and was successfully applied to actual sample. It opens up new ways for the combination of ratiometric fluorescence technology and paper-based microfluidic chip, and provides potential point-of-care applications.