Co-production of carbon quantum dots and biofuels via hydrothermal conversion of biomass

As a new kind of carbon material, bio-based carbon quantum dots (CDs) have attracted increasing attention, attributed to their excellent properties and widespread applications. In particular, biomass hydrothermal conversion has become a popular technology for bio-based CDs production, due to its advantages in terms of friendliness to the environment, effective cost, and simple operation. This article reviews the formation mechanisms, properties, and applications of bio-based hydrothermal CDs comprehensively. The CDs formation mechanisms were summarized from the perspective of biomass (such as lignocellulosic biomass and algae) and its model compositions (such as carbohydrate, protein, and lignin). The properties of bio-based hydrothermal CDs including microstructure, chemical structure and composition, toxicity and biocompatibility, and optical performance were discussed. Meanwhile, the applications of bio-based CDs in biological imaging, sensor, photoelectric device, catalyst, and disease treatment were outlined as well. Furthermore, the co-production of CDs and value-added biofuels from biomass hydrothermal process is proposed and further related research directions were recommended.