Ratiometric fluorescence detection of riboflavin based on fluorescence resonance energy transfer from nitrogen and phosphorus co-doped carbon dots to riboflavin

Fluorescent nitrogen and phosphorus co-doped carbon dots (NPCDs) were prepared via a hydrothermal method with citric acid and O-phosphorylethanolamine as precursors. The overlap between the absorption spectrum of riboflavin and the fluorescence emission spectrum of the NPCDs and the relative proximity of the NPCDs to riboflavin due to hydrogen bonding facilitated the formation of a NPCDs/riboflavin fluorescence resonance energy transfer (FRET) system. Thus, a ratiometric fluorescence method for the detection of riboflavin based on the formation of this NPCDs/riboflavin FRET system was developed. The method displayed a sensitive and selective response to riboflavin in the range 0.5–50 μmol/L with a detection limit of 0.17 μmol/L. It was also found to be suitable for the detection of riboflavin in milk and riboflavin pharmaceutical tablets.