Time-resolved spectroscopic study of dual heteroatom-doped carbon dots

Abstract

Carbon dots (CDs) have a potential application in bioimaing due to their excellent photoluminescence (PL), nontoxicity, and excitation-dependent photoluminescence (PL). We studied time-resolved spectroscopic behavior of nitrogen-doped carbon dots (N-CD) and boron-nitrogen doped carbon dots (BN-CD) which were synthesized by one-step microwave pyrolysis. The PL quantum yield of BN-CD was found to be 80.8%, which is approximately twice that of N-CD (40.2%). Although several PL mechanisms of CDs have been proposed in many reports, the origin of the PL of CDs is still in debate. We investigated the origin of the PL of CDs by using a series of spectroscopic methods. The PL lifetimes were fitted by stretched exponential functions which can generally describe to surface-functional PL systems having a distribution of chromophoric states. As a result, we observed that both the CDs pose multiple surface-functional electronic states with a dominant molecular-like state. This study successfully demonstrates the application of stretched exponential functions in describing heterogeneous PL systems.