Orange fluorescent dual-mode nanoprobe for selective and sensitive detection of amaranth based on S,N-Doped carbon dots

As one of the most widely used azo synthetic dyes, long-term consumption of excessive amaranthcan cause a threat to health. It is very urgent to establish high selective and sensitive method for amaranth detection. Orange fluorescent carbon dots utilizing l-methionine and o-phenylenediamine as raw materials, namely S,N-CDs, were prepared via one-step hydrothermal method. Dialysis, thin layer chromatography and chromatographic column were employed for further purification. The purified dual-mode nanoprobe based on fluorescent and UV absorption was successfully established. For fluorescent, excellent linear ranges of 5–70 μM and 110–195 μM were obtained, and low detection limit was 345.22 nM. For UV absorption, excellent linear ranges of 0–155 μM with low detection limit 12.70 nM. It revealed that inner filter effect and static quenching dominated in amaranth quenching the fluorescent of S,N-CDs. Furthermore, the dual-mode nanoprobe could be efficiently applied to determine amaranth in fruit juice, carbonated drink, and strawberry jam samples. It provided a new insight on the purification of carbon dots and detection of amaranth by dual-mode nanoprobe.