Phenylalanine‐Doped Orange Peel‐Derived N‐CDs: Elucidating the Quenching Mechanism of Fe ³⁺ and Their Application in Cellular Imaging

In this study, we employed orange peel as a carbon source and phenylalanine as a nitrogen source, leading to the successful development of an economical and environmentally friendly approach for synthesizing fluorescent nitrogen‐doped carbon dots (N‐CDs) via a one‐step hydrothermal method. The morphology of the prepared N‐CDs was characterized using TEM, XPS, Raman, XRD, and FT‐IR techniques. The results indicate that N‐CDs exhibit a spherical structure with an average diameter of approximately 2.28 nm and are abundant in oxygen and nitrogen functional groups. When exposed to ultraviolet light, N‐CDs exhibit strong blue fluorescence with a peak emission wavelength at 414 nm. The fluorescence quantum yield is as high as 14.2%. Meanwhile, the fluorescence of N‐CDs could be selectively quenched by Fe 3+ , showing a linear correlation with Fe 3+ concentrations ranging from 66 to 300 µM and achieving a minimum detection limit of 0.42 µM. It is noteworthy that N‐CDs demonstrate excellent biocompatibility and low toxicity and have been successfully utilized for the detection of Fe 3+ in A549 cells. In conclusion, these fluorescent N‐CDs exhibit the potential to serve as highly sensitive probes for the detection of Fe 3+ ions in biological systems.