N,S co-doped carbon dots as a stable bio-imaging probe for detection of intracellular temperature and tetracycline

Stable bioimaging with nanomaterials in living cells has been a great challenge and of great importance for understanding intracellular events and elucidating various biological phenomena. Herein, we demonstrate that N,S co-doped carbon dots (N,S-CDs) produced by one-pot reflux treatment of C₃N₃S₃ with ethane diamine at a relatively low temperature (80 °C) exhibit a high fluorescence quantum yield of about 30.4%, favorable biocompatibility, low-toxicity, strong resistance to photobleaching and good stability. The N,S-CDs as an effective temperature indicator exhibit good temperature-dependent fluorescence with a sensational linear response from 20 to 80 °C. In addition, the obtained N,S-CDs facilitate high selectivity detection of tetracycline (TC) with a detection limit as low as 3 × 10^-10 M and a wide linear range from 1.39 × 10^-5 to 1.39 × 10^-9 M. More importantly, the N,S-CDs display an unambiguous bioimaging ability in the detection of intracellular temperature and TC with satisfactory results.