Highly fluorescent carbon dots as selective and visual probes for sensing copper ions in living cells via an electron transfer process

As an integral part of many important enzymes, Cu2+ is involved in a number of vital biological processes, which is linked to the oxidative damage and environmental contamination when Cu2+ is excessive. In this work, Cu2+ can be captured by the amino groups of carbon dots (CDs) to form complexes, resulting in a strong fluorescence quenching of CDs via a nonradiative electron transfer process, which offered a rapid, visual, and selective methodology for Cu2+ detection. The probe exhibited a wide response concentration range (0.01-2 mu M) to Cu2+ with a detection limit of 6.7 nM. Significantly, the CDs presented excellent biocompatibility and high photostability, which were applicable for the visualization of Cu2+ dynamic invasion into living cells and Tilapia mossambica. Furthermore, the toxicity of Cu2+ ions to living cells could be inhibited with CDs by the formation of complexes.