Green/red dual emissive carbon dots for ratiometric fluorescence detection of acid red 18 in food

Quantitative determination of hazardous synthetic colorants in food is quite essential for human health. Herein, a ratiometric fluorescence method is developed for sensitive and selective detection of acid red 18 (AR18) using green/red dual emissive carbon dots (g/r-CDs) as probes. The as-synthesized g/r-CDs exhibit two emission peaks at 508 and 610 nm under excitation of a UV light. When AR18 is added, the green fluorescence of g/r-CDs at 508 nm is quenched dramatically due to the strong inner filter effect; in contrast, the red fluorescence at 610 nm decreases much more mildly. The intensity ratio of I610/I508 has a good linearity with the AR18 concentration over the range of 0.05–8.00 μM. A detection limit of 16 nM is obtained, much lower than the most values reported by former analytical methods. Based on the g/r-CD sensor, accurate determination of AR18 in drinks and candy is successfully realized, demonstrating the good practicability of the proposed method for AR18 monitoring in real samples.