Blue/yellow dual-emission carbon dot-based molecularly imprinted ratiometric fluorescence sensor combined with a smartphone for visual quantitative detection of vanillin in food

Ratiometric probe (blue/yellow CDs) offers visual color change and improved accuracy. • Molecularly imprinted polymers provide high selectivity against food interferents. • Smartphone with Color Picker App enables on-site visual quantitative detection. • Successfully applied to milk and ice cream with recoveries of 95.6–104.2%. A ratiometric fluorescence sensor (B-CDs@MIPs/Y-CDs) based on blue/yellow dual-emission carbon dots and molecularly imprinted polymers was constructed for visual detection of vanillin. The addition of vanillin resulted in selective quenching of the blue fluorescence of B-CDs at 438 nm via static quenching, whereas the yellow emission at 542 nm stayed constant, leading to a progressive color shift from blue to green and ultimately to yellow. Under optimized conditions, the linear range was 2.0–120.0 μM with a detection limit of 0.22 μM. Recoveries from spiked milk and ice cream samples ranged from 95.6% to 104.2% (RSD < 1.77%). Combined with a smartphone using the Color Picker App for RGB analysis, rapid visual detection was achieved. This method is low-cost, easy to operate, and sensitive, showing great potential for food safety monitoring. Download: Download high-res image (125KB) Download: Download full-size image