Fluorescent nitrogen-doped carbon dots (N-CDs) with excellent stability were prepared via single-step hydrothermal carbonization of citric acid (CA) and ethylenediamine (EDA). The as-prepared N-CDs emit blue fluorescence under the excitation of 365[Formula: see text]nm and have a size distribution of 2.80 ± 0.47[Formula: see text]nm with benign size effect. The structure and morphology were further characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. It was found that the surface of the N-CDs was successfully functionalized, which presented water solubility and chelation with Fe3+. XRD results display a diffraction peak at 23.9°C, which corresponds to the (002) interlayer spacing of a graphitic structure revealing an amorphous carbon phase. Furthermore, due to good sensitivity, N-CDs were used as probes for Fe3+ detection. The low limit of detection of 0.6[Formula: see text]μM as a fluorescence probe was successfully obtained based on the linear relationship between ([Formula: see text] and concentration of Fe3+ ions. Besides the satisfactory fluorescence, PVA/N-CDs membranes and fluorescent inks demonstrate potential for anti-counterfeiting applications due to its characteristic flexibility, transparency, removability and invisibility under ambient lighting.
Retraction of “Equipment-Free, Single-Step, Rapid, “On-Site” Kit for Visual Detection of Lead Ions in Soil, Water, Bacteria, Live Cells, and Solid Fruits Using Fluorescent Cube-Shaped Nitrogen-Doped Carbon Dots”