Food-Safety-Facing Aflatoxin B1 Detector Verification by Combining N-CQDs Fluorescence Probes and Smartphone Image Analysis in Microfluidic Channel

Aflatoxin B1 (AFB1) poses a serious threat to food safety. Current routine detection of AFB1 mainly relies on laboratory-based methods, which, although highly accurate, suffer from long detection cycles and high costs. There is an urgent need to develop portable detection technologies suitable for rapid on-site screening. In this study, a portable AFB1 detection device based on the fluorescence quenching effect of nitrogen-doped carbon quantum dots (N-CQDs) was developed, integrating a microfluidic chip with smartphone-based image analysis technology to achieve full integration of the entire detection process. Meanwhile, the serpentine channel structure of the microfluidic chip was optimized through numerical simulation. The results showed that arc-shaped corners outperformed right-angle and rounded corners in eliminating flow dead zones and improving velocity uniformity. Considering the effects of channel width on mixing efficiency and flow resistance, the 0.10 mm arc-shaped structure was determined as the optimal configuration. The experimental results demonstrated that the fluorescence quenching efficiency (ΔF/F0) exhibited a good linear relationship with the logarithm of AFB1 concentration over the range of 5–100 ng∙mL−1, with a correlation coefficient R2 of 0.98871. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 1.2979 ng∙mL−1 and 2.2035 ng∙mL−1, respectively. The recoveries from spiked corn flour samples ranged from 96.15% to 103.97%, with relative standard deviations (RSD) of 2.97% to 4.92%. This study presents a promising portable detection scheme for on-site rapid screening and achieves a proof-of-concept validation.