A novel method for the synthesis of carbon dots assisted by free radicals

Carbon dots (CDs) have gradually become a widely favored type of fluorescent nanomaterials with unlimited and promising applications. This work reports a means of breaking the shackle of method to develop new red and white CDs by introducing free radicals. The resulting white emissive CDs in this strategy are employed to demonstrate electroluminescent white-light-emitting diodes (WLEDs) and achieve a record-high external quantum efficiency (0.95%) of one-step-produced white CDs (WCD)-LEDs, which dramatically simplifies the whole fabrication processes of WLEDs. With additional passivation treatment, the red CDs (RCD2) with excellent properties such as N and S co-doping, bright (quantum yield = 49%) and stable photoluminescence (PL), large positive zeta potential (+20.5 mV), and two-photon fluorescence are obtained. Such RCD2 are used for rapid staining (5 min) of yeast cells. The two CDs synthesized via this method have outstanding performance in different aspects, which provides new promise of CDs for further functionalization and applications.