The sensitivity and specificity of carbon dot species on the detection of chromium metal ions

Rapid industrialization has brought about Cr 6+ pollution, and the excellent performance of carbon dots (CDs) provides a new idea for preparing environmentally friendly nanoprobes for Cr 6+ detection. In the present work, five spherical fluorescent CDs with an average diameter of 4 nm based on citric acid, citric acid and p-phenylenediamine, citric acid and octylamine, gelatin, and glutamic acid were synthesized by a one-step hydrothermal process. Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible (UV–Vis) absorption spectra and steady-state fluorescence spectroscopy were used to detect the fluorescence properties of CDs. A fluorescent “on–off” sensor was used to investigate the effects on Cr 6+ by using the fluorescence burst mechanism of CDs. The results indicate that Cr 6+ had a fluorescence burst effect assigned to CDs its chelation with the Cr(VI) on all the four CDs containing elemental nitrogen which facilitating charge transfer from the excited state of the CDs to Cr(VI). Among the other four CDs used for Cr(VI) detection, the gelatin-based CDs had a wide detection range and good linearity ( R 2  = 0.9873) for Cr(VI). There is a linear relationship between the degree of fluorescence burst and the Cr 6+ concentration, which provides a reference for the use of CDs in metal ion detection.