Abstract
Polymeric carbon dots (PCDs) are an astonishing class of fluorescent materials with distinctive structures, properties, and applications. However, the internal structures of PCDs are still unclear and are the subject of considerable debate due to their complexity. Herein, a new type of pure blue light-emitting PCDs was synthesized hydrothermally from ε-poly-l-lysine and citric acid. PCDs were observed by using scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS) on an atomically thin graphene surface to determine the internal structure and compositional gradients combined with other spectroscopic analyses. These methods revealed that PCDs have a spongy, porous structure with uniform element distribution, reflecting organic polymeric frameworks that embrace fluorescent aromatic moieties devoid of graphitic, inorganic carbon. The polymeric framework acts as …
