Methylene blue-functionalized blue/red dual-emissive carbon dots for ratiometric fluorescence detection of sunset yellow in food.

Recently, excessive use of food colorings poses increasing threats to public health, particularly due to harmful effects on children. Sunset yellow (SY), a widely used synthetic colorant, necessitates reliable and efficient detection methods. Herein, a ratiometric fluorescent probe is constructed by grafting methylene blue (MB) onto nitrogen-doped carbon dots (N-CDs) for SY detection. With increasing SY concentration, the blue emission peak at 442 nm is significantly quenched via inner filter effect (IFE) and fluorescence resonance energy transfer (FRET), while the red emission at 694 nm shows comparably moderate attenuation. This sensor achieves a detection limit as low as 59 nM. Furthermore, a portable fluorescent sensing platform is developed for the on-site detection of SY in real samples, achieving recovery of 98.60%-103.10%. Therefore, this work provides a robust sensing strategy for SY monitoring, paving the way for rapid surveillance and enhanced control of food safety risks associated with colorant overuse.