Unveiling the Photoluminescence Mechanism of Carbonized Polymer Dots: Evolution and Synergistic Photoluminescence of Multiple Molecular Fluorophores

Carbonized polymer dots (CPDs) are a class of exceptional fluorescent materials with diverse applications. However, their photoluminescence (PL) mechanism remained enigmatic and controversial, hindering further development and application. While molecular fluorophores explain primary fluorescence in some CPDs, the overall PL of CPDs still cannot be fully explained, such as their excitation-dependent behaviors, let alone the modulation of PL. Besides, the extracted molecular fluorophores are dissociative, raising questions including the purity of CPDs and whether the PL of CPDs nanoparticles come from these molecular fluorophores. Here, the emission around 510 nm of citric acid-ethylenediamine CPDs (CA-EDA CPDs) was proved to be contributed by a molecular fluorophore, which evolved from another molecular fluorophore following the quantum confinement effect. Further research revealed the whole PL mechanism of CA-EDA CPDs to be the evolution and synergistic PL of multiple molecular fluorophores linked on CPDs nanoparticle. The evolution of molecular fluorophores had also been observed in another two systems, indicating the universality of this mechanism, and a new approach for regulating the optical properties of CPDs was put forward inspired by this mechanism. This study not only refined the PL mechanism but also paved the way for future advancements of CPDs.