Classification and synergy of biomass conversion to carbon dots: fully tapping the potential of biomass itself

Abstract

Carbon dots produced from a wide variety of biomass (B-CDs) had multifarious structures, poor repeatability, and low quantum yields. Most studies on certain biomass conversion to B-CDs were not of general guidance. Many chemical reagents were used to modify B-CDs, but they weaken the economic and eco-friendly advantages of B-CDs, especially affecting large-scale production. Given the above, we proposed a new classification research idea based on the key components to explore the general regularity of biomass conversion to B-CDs, thus fully tapping the potential of biomass itself to produce reproducible carbon dots with little or no chemical reagent. A first-stage systematic study along the way of key components—representing biomass—biomass synergy was carried out to investigate the differences in structure, properties, and suitable reaction conditions of B-CDs. Cellulose- and protein-based CDs showed different dominant luminescence centers. The optimum temperatures were given for preparing B-CDs from protein-rich (200℃) and cellulosic (260℃) biomass at the adaptive residence time of 1 ~ 4 h. B-CDs derived from biomass synergy were dominated by radiative recombination, indicating that protein-rich biomass as a nitrogen source is superior to some chemical reagents. The synergy resulted in higher ratios of nitrogen doping and C = O group, thus obtaining a higher quantum yield (from 2.95 to 22.64%) and a longer wave emission with less excitation energy. The classification research idea in this paper provides an effective way to maximize the potential of biomass itself and reference for the challenging work of establishing a general rule system for diverse biomass conversion into B-CDs.