A novel highly fluorescent S, N, O co-doped carbon dots for biosensing and bioimaging of copper ions in live cells.

In this study, novel highly fluorescent sulfur, nitrogen, and oxygen co-doped carbon dots (S, N, O-CDs) were prepared from -phenylenediamine and sulfamide by using the hydrothermal method. The prepared S, N, O-CDs show high doping rate and fluorescence yield as well as long-term fluorescence stability. In addition, S, N, O-CDs show good fluorescence response towards Cu over a concentration range of 2-60 μM with a detection limit of 0.29 μM. Taking advantages of the properties of S, N, O-CDs including high selectivity and low cytotoxicity, S, N, O-CDs were successfully applied for Cu sensing and imaging in the cells and O˙-induced Cu increase in the cells was observed. Furthermore, on account of strong complexation between Cu and pyrophosphate ion (PPi) as well as specific hydrolysis ability of alkaline phosphatase (ALP) towards PPi, PPi and ALP were further detected with high selectivity based on S, N, O-CDs/Cu system. The prepared S, N, O-CDs showed good detection results for PPi and ALP with detection limits of 0.44 μM and 1.03 U L, respectively. Moreover, the developed method also realized PPi and ALP detection in real samples.