Controllable Functionalization of Carbon Dots as Selective and Sensitive Fluorescent Probes for Sensing Cu(II) Ions

Carbon dots (CDs) are efficient fluorescent probes for metal ion detection due to their high sensitivity, nontoxicity and stability, but their rich functional groups lead to simultaneous responses to multiple ions. So, how to realize highly selective detection for specific ions is still a challenging task. In this work, "bare CDs" were synthesized using the electrochemical stripping method, followed by grafting with hydroxyl and carboxyl groups following the hydrothermal method with boric acid. Transmission electron microscopy, an X-ray diffractometer, Fourier transform infrared spectroscopy, UV-visible spectrophotometers and a fluorescence spectrometer were used to characterize their morphology, surface functional groups and optical properties, respectively. The modified CDs exhibit a high sensitivity of 65% and selectivity towards Cu2+. Meanwhile, they also exhibited a short response time of less than 1 min and a good stability in terms of pH and ionic strength.