Fluorescent paper sensor based on green emissive carbon nanodots for visual detection of acid orange II in food samples

This work for the first time presents a visual fluorescence paper sensor for accurate and on-site detection of acid orange II (AO 2 ) in food matrix, where green-emissive carbon nanodots (G-CDs) were exploited. The as-synthesized G-CDs had an average particle size of 3.9 ± 0.7 nm and displayed green emission at 511 nm upon excitation at 450 nm. When there existed AO 2 , the G-CDs fluorescence was effectively suppressed via inner filter effect (IFE) and dynamic interaction. The as-prepared G-CDs probe achieved a 0.01–25.0 μM linear scope and a 36.5 nM limit of detection. Particularly, owing to a distinguishable reduction in G-CDs emission intensity by a smartphone application , a visual probing platform along with a nanopaper-based device were be developed for recognizing AO 2 . The corresponding detection limits were severally 0.61 μM and 1.39 μM. Success was achieved in applying our fluorescence approaches for detecting AO 2 in Yuba, chili powder, sunflower seeds, tomato paste and orange juice samples, attaining desirable results. The present work underlines the potential of smartphone-integrated nanopaper based on CDs as an encouraging candidate for on-site AO 2 recognition in food matrix.