Understanding the growth of carbon dots derived from bioresources via plasma-electrified synthesis

Carbon dots (CDs) have been the forefront of materials research owing to their unique size-dependent quantum confinement and carbon hybridization state-dependent physicochemical properties, rendering them useful for many applications, including imaging, sensing, energy conversion and storage, optoelectronics, and nanocatalysis. However, precise atomic-scale control of CDs with well-defined structures and properties is still challenging owing to inefficient synthesis methods and limited understanding of their growth mechanisms. Here, we utilize a direct current (DC) microplasma electrochemical reactor to convert various bioresources into CDs with controlled structures and carbon hybridization states in a rapid, catalyst-free, and environmentally friendly manner. Moreover, in situ optical emission and absorption spectroscopies were further integrated into the microplasma reactor to reveal growth mechanisms, providing a possible prediction over the synthesized products without time-consuming ex situ characterization. A high plasma current enhanced the ionization rate, which subsequently led to more water dissociation into OH radicals, more precursor fragmentation, and therefore higher CDs production. Our work provides insight into the synthesis of bioresource-derived CDs between the plasma parameters and structural properties of the synthesized CDs.