Rapid synthesis of nitrogen doped carbon dots with green fluorescent for bio-imaging

Abstract Carbon dots (CDs) are a class of fluorescence nanoparticles with a particle size less than 10 nm. Because of their excellent fluorescence properties, good biocompatibility and easy surface-modification, CDs have become an ideal fluorescent probe and drug carrier. In this work, novel green emitting CDs with good water solubility were synthesized within 15 min by one-step microwave-assisted hydrothermal method using pyrocatechol as carbon source and ethylenediamine as nitrogen dopant. The fluorescence quantum yield of CDs was optimized to 14.38% by tuning the reaction temperature and time. Considering good biocompatibility of the CDs demonstrated by flow cytometry, methyl thiazolyl tetrazolium and hemolytic analysis, we used CDs for cell imaging taking human liver cancer cells SMMC-7721 and HepG2 as the models. Intriguingly, the CDs were found to be able to enter not only the cytoplasm, but also the nucleus, after incubation of 2 h.