Integrative Approach toward Uncovering the Origin of Photoluminescence in Dual Heteroatom-Doped Carbon Nanodots

The pursuit of exceptionally high photoluminescence (PL) and stability is critical in the development of novel fluorophores for use in challenging bioimaging and optoelectronic devices. Carbon nanodots (CDs) doped with heteroatoms provide a particularly attractive means of effectively tailoring their intrinsic properties and exploiting new phenomena. Here, we report a one-step, scalable synthesis of boron-and-nitrogen co-doped CD (BN-CD) with outstanding optical properties unlike those of nitrogen-doped CD (N-CD) in solid state as well as solution. The detailed mechanistic framework was explored using a series of spectroscopic analyses and ultrafast spectroscopy coupled with density functional theory calculations, which all conclusively confirmed that the presence of more graphitic structures in the core and well-distributed surface states are responsible for the enhanced PL in BN-CD. Furthermore, single-molecule spectroscopy analysis demonstrated that a single BN-CD shows higher PL intensity and enhanced photobleaching time. We anticipate that this study will aid in uncovering the full potential of CDs in various fields.