One-step Hydrothermal Synthesis of N-doped Fluorescent Carbon Dots from Fermented Rice with Highly Selective Characteristics for Label-free Detection of Fe Ions and as Fluorescent Ink.

In our work, N-doped carbon dots (CDs) were synthesized by a facile hydrothermal method with fermented rice as the carbon source. The CDs show bright blue fluorescence, and the maximum emission wavelength was 380 nm with wavelength ranges from 320 to 560 nm. Interestingly, these as-prepared CDs show strong blue photoluminescent properties under the radiation with ultraviolet (UV) light. Moreover, it also exhibits good sensitive fluorescence detection for Fe ions; the detection limit is 0.1 μM, which is significant fluorescence quenching based on CDs. Other representative metal ions were further tested to verify their selectivity, which provides a solid underpinning for the practical use in Fe ions detection in real samples, e.g. underground water. In addition, the CDs work well as a fluorescent ink and can encrypt and store information.