Surface state modulation of blue-emitting carbon dots with high quantum yield and high product yield

In order to explore the surface state modulation mechanism of carbon dots (CDs) with high quantum yield (QY) and high product yield (PY), CDs were synthesized from different carbon sources with different contents of oxygen-containing functional groups and different silane coupling agents with nitrogen-containing functional groups. The highest QY of as-prepared CDs can reach 97.32% and the PY values of CDs are all high ranging from 46.33-58.76%. It is found that the high content of C=O and pyrrolic N on the surface of CDs can endow CDs with high QY. Moreover, the PY of CDs not only depends on whether CDs have the crosslinked structure, but also is closely and positively correlated with pyridinic N. Consequently, our findings suggest that raw materials rich in carboxyl groups and amino groups are beneficial to the synthesis of CDs with high QY, and whether CDs with crosslinked structure and high content of pyridinic N decide the high PY of CDs. This work provides a theoretical guidance for large-scale synthesis of CDs with high QY and high PY.