Coal-based carbon/graphene quantum dots: formation mechanisms and applications

Abstract The Carbon/graphene quantum dots (CQDs/GQDs) have received increasing attention as emerging zero-dimensional (0D) carbon nanomaterials. The CQDs/GQDs were endowed with significant potential in environmental and energy fields, due to the unique photoluminescence, good biocompatibility, excellent electron transfer capability, and low toxicity. Compared with graphite and hydrocarbons, coal and its derivatives are considered as alternative carbon sources for preparing CQDs/GQDs, as their low cost and abundant reserves. Thereby, the important issue of realization the deep processing and functional applications of coal is cracking the C–O bonds that connected the aromatic ring clusters in coal and its derivatives to obtain CQDs/GQDs. This article briefly reviews the synthesis methods and physicochemical properties of coal-based CQDs/GQDs in recent years, focusing on the formation mechanism of coal-based CQDs/GQDs and their functionalization. In addition, their applications in sensing, photocatalysis, electrochemistry and biomedicine are discussed, as well as the prospects for future research. Hopefully, this paper will provide significant support for the design of efficient coal-based carbon nanomaterials and sustainable options for overcoming bottlenecks in coal applications.