Sensitivity fluorescent switching sensor for Cr (VI) and ascorbic acid detection based on orange peels-derived carbon dots modified with EDTA.

Orange peels were applied as precursors to synthesize carbon dots (CDs) via a one-step green hydrothermal method. The relationship between quantum yield and volatile oils in 14 different varieties of orange peels were investigated. The CDs showed strong blue fluorescence and were further modified with EDTA. Compared with the CDs, the CDs@EDTA exhibited higher sensitivity for Cr(VI) detection with a LOD of 10 nM. The CDs@EDTA was proved to be an effective fluorescent sensor element for Cr(VI) detection in water samples with recoveries ranged from 92.09% to 104.87% (RSD < 5%). Moreover, CDs@EDTA/Cr(VI) system was further developed as a fluorescent "off-on" sensor for ascorbic acid (AA) detection with a LOD of 0.1 µM. Further, the sensor had been successfully applied for the analysis of AA in fresh oranges and commercial orange juices. The recoveries of AA in fresh oranges and orange juices were 92.58-106.76% and 91.54-104.95%, respectively.