Graphene quantum dot (GQD) synthesis: A review of the methods, challenges and future prospects

Unique properties of dimensionally confined nanoparticles are successfully utilized in improving the performance of numerous applications. The quantum confinement effect and related opening of bandgap can be used to engineer optoelectrical properties, thus broadening their applicability in various fields. From a materials standpoint, carbonaceous materials such as graphene have recently attracted much attention among researchers. Graphene quantum dots (GQDs), the newest member of the carbonaceous material family, is of particular interest due to their distinct electronic, optical, chemical, and mechanical properties. GQDs can be customized and optimized by varying the size and number of graphene layers, doping, attaching functional groups and heteroatoms, or making composites. Apart from band structure, GQDs possess many other favorable functional properties required for various applications. Some desirable features include tunable fluorescence, high quantum efficiency/ quantum confinement, higher chemical stability, edge effects, biocompatibility, low toxicity, photostability and water solubility. In this mini review, reliable GQD fabrication techniques are discussed, emphasizing the requirements, strengths, weaknesses and specialties of each technique. Further, challenges and future prospects of GQDs are also discussed