Advances on synthesis of highly luminescent carbon quantum dots by citric acid carbonization

This work describes a simple method to produce highly luminescent carbon quantum dots (CQDs) emitting blue or green light. The method consists of the carbonization of citric acid at 250 °C under ambient condition and a further surface functionalization. The UV-Vis spectrum of these carbon nanostructures exhibited a well-resolved absorption band at 320 nm which was attributed to the n-π* transition of C-O groups mainly attached to the graphene sheet edge. Transmission electron microscopy corroborated the presence of CQDs. Additionally, a mechanism for the formation of the CQDs is proposed.