Rapid Synthesis of highly luminescent Carbon Quantum Dots using Low-Pressurized Microwave Solvothermal Heating

Abstract

[EN] In this research, we ameliorated the problems of carbon quantum dots synthesis and luminescence (quantum yields) by the novel synthesis protocol using microwave chemistry. Specifically, we synthesized high quantum yields carbon quantum dots (61%) by utilizing a microwave chemical synthesis, synthesizing at low pressure condition (lower than 5 atom) and short reaction time (3 hrs). The achievement of this high quantum yields made it clear that the contribution of polyethylene glycol (PEG) shell to carbon quantum dots is large. It was confirmed from the DLS and TEM image that the particle size of the synthesized particles was 8 to 13 nm. On the other hand, the relationship between the polymerization degree of added PEG and the quantum yields to the addition amount is summarized. The quantum yields of carbon quantum dots without addition of PEG was 16.7 %, while it was improved at 61.1 % when 0.6 g of PEG 6000 (Molecular weight: 6000) was added. Furthermore, we compared microwave with conventional method, and it was revealed that higher luminescent and narrower sized carbon quantum dots were synthesized in microwave heating than conventional method. This result presumably comes from the nature of microwave selective heating of carbon precursor.