One-Step Fabrication of Functional Carbon Dots with 90% Fluorescence Quantum Yield for Long-Term Lysosome Imaging.

Compared with semiconductor quantum dots and organic chromophores, carbon dots (CDs)-based lysosome probe with strong emission, an intrinsic targeting ability and easy synthesis procedure was urgently desired in visualization imaging studies. Herein, we showed that it was possible to produce CDs with desired properties for lysosome imaging via a one-step hydrothermal treatment of commercial reagents, rose bengal (RB) and branched polyethyleneimine (bPEI). The prepared P-R CDs had a high fluorescence quantum yield (FLQY) of 90.49%, a narrow emission band of 30 nm, negligible phototoxicity and dark toxicity. Moreover, P-R CDs had an intrinsic lysosome targeting ability without any post-modification ligands. Long-term cell imaging displayed P-R CDs can anchor lysosomes for up to 48 h without leakage. In addition, experimental results confirmed that dehalogenation crosslinking and structural reorganization of reactants were the main causes of the ultrahigh photoluminescence efficiency, low cytotoxicity and passivated surface of the P-R CDs. This origin was attributed to the restricted intersystem crossing and nonradiative transition, the reduced production of singlet oxygen, and suitable -NH2 functional groups. Due to outstanding characteristics, P-R CDs may be developed for a promising tool in lysosome image. The concept of facile preparation will also pave a new avenue for developing ultrabright functional nanomaterial markers.