Advances in synthesis of the graphene quantum dots from varied raw materials

As a new type of carbon material, graphene quantum dots (GQDs) show potential application value in chemical catalysis, biomedicine, optoelectronics, energy and other related fields because of its stronger quantum confinement effect and edge effect. Therefore, the preparation and application of GQDs have become one of the hotspots in the research of graphene-based materials. From the published references on the synthesis and ap-plications of GQDs, it can been seen that the difference of raw materials is still one of the important factors which affects the size, functional groups, fluorescence properties, and yields of GQDs, in addition the methods. In order to reduce the preparation cost and develop efficient and green methods to obtain GQDs, this review emphasized the differences in size and fluorescence properties of GQDs prepared by different raw materials such as graphite, coal, coke, as well as organic small molecules and biomass, and the reasons for the differences. Specifically, the advantages and disadvantages of different raw materials related preparation methods of GQDs are compared. Finally, an outlook on the possible solutions to the existing problems and the future research directions on preparation methods of GQDs with high yield and quality is proposed.