Food waste-driven N-doped carbon dots: Applications for Fe³⁺ sensing and cell imaging

We report highly fluorescent N-doped carbon dots (CDs) synthesized from food waste via one-step hydrothermal carbonization. To study the chemical transition of carbon dots from food wastes, the cat feed stocks driven from food waste were used as the waste model. In the model study, the core of the CDs was successfully self N-doped without extra pre- or post-treatments. The experimental results reveal that the nitrogen in the waste model played an important role in the formation of graphitic N and pyridinic N in the core and functional groups on the surface. Especially, high process temperature (≥180 °C) resulted in high quantum yield as 23% of the CDs from the waste model. To demonstrate the conversion of real food waste into CDs, the hamburger sandwich leftover was used as a precursor for CDs. The food waste driven CDs had similar chemical and fluorescent properties to that of the waste model, having quantum yield of 28%. This study exhibits the food waste driven carbon dots are excellent candidates for fluorescence probe to Fe³⁺ with high selectivity even under the interference of other metal, and for bio-imaging material with good cell viability over 80%.