Innovative linkage sensor based on bimodal excitation behavior nitrogen doped carbon dots for ratiometric and visual detection of fluoride ion in food

Fluoride ion (F − ), particularly an important substance for growth, development and bone metabolism, is one of the essential micronutrients in living organisms. Therefore, F − detection becomes one of the main problems that need to be addressed in ordinary living. Herein, an innovative bimodal excitation-based nitrogen-doped carbon dots (N-CDs) for ratiometric detection of fluoride ion (F − ) is developed by multistage response to curcumin and F − based on the localization of inner filter effect (L-IFE). Primarily, curcumin decreases the N-CDs fluorescence due to fluorescence resonance energy transfer. Subsequently, the cascade addition of F − changes the absorption band from 526 to 418 nm due to the generation of curcumin-F − complex. Thus, the L-IFE occurs, and uneven overlap between the curcumin-F − complex absorption and N-CDs excitation leads to the inverse variation in fluorescence signals under the illumination of 399 nm and 470 nm. This multistage sensing system exhibits excellent sensitivity toward F − , with a linear range from 0 to 50 µM and a low detection limit of 57 nM. Moreover, a smart-integrated sensing platform is designed for visual F − detection in practical samples. Thus, our work provides a novel guidance for F − detection in food environment.