A review of coal-based carbon and graphene quantum dots: synthesis, properties, and applications

Carbon dots (CDs) as zero-dimensional carbon nanomaterials are research hotspots in carbon research. Their unique physicochemical and optical features make them potential candidates for different emerging applications. Over the past few years, distinct precursors have been utilized for synthesizing carbon quantum dots (CQDs) and graphene quantum dots (GQDs). However, coal is an excellent carbon precursor for preparing CQDs and GQDs because of its low-cost, earth-rich, and unique structural features. Substantial progress has been made in tailoring coal to CDs and elucidating the factors contributing to their physicochemical properties. This article reviews the recent advances in research on coal and related materials-based CDs, emphasizing their synthesis methods, structural and optical properties. Further, this article focuses on their applications in catalysis, energy storage, fluorescent films, light-emitting diodes, sensing, and bioimaging. Lastly, the challenges and prospects of the future development of coal-based CDs are also elucidated.