Ligand Mediated, Spatially Confined Carbonization of Biomass Forming High-Performance Colloidal Carbon Dots

Owing to their humble chemical composition, carbon dots (CDs) can be readily synthesized from biomass, transforming waste into luminescent nanomaterials. In reforming biomass into CDs, the choice of solvent plays a critical role in bottom-up degradation, emulsion formation, surface structuring, and the physiochemical and optical properties of the CDs. However, there is a lack of understanding on the effect of solvents, particularly in the context of solvent-dispersed CDs that are of interest to optoelectronics applications. Here, a spatially confined carbonization of laminarin using oleylamine (OLA) as the solvent, exploiting ligand-carbon interactions, resulted in uniform (3.6 ± 1.5 nm) colloidal CDs exhibiting single crystallinity. Uniquely, the OLA-capped CDs show distinctive multiple emissions from blue to green and red simultaneously under UV excitation, demonstrating the intricate electron transfer and trapping from carbon core/functional groups to surface bound-ligand multiple emissions. The OLA-CDs can be stably dispersed in various solvents and facilely fabricated into thin-film devices. This work establishes the versatility and tunability of ligand-induced, spatially confined carbonization in forming colloidal CDs for optoelectronic devices from crude biomass.