Evidence of the contribution of molecular fluorophores to the luminescence of carbon entities formed by solvothermal treatment of trinitropyrene.

Carbon dots are a subset of carbon nanomaterials with fluorescent properties that render them attractive for various potential applications such as bioimaging and sensing. The past years saw significant progress being made in the understanding of the formation and the underlying fluorescent property. Nevertheless, efforts are still necessary to unravel the formation of carbon dots and the origin of their luminescence, especially for new types of precursor material such as polycyclic aromatic compounds. Trinitropyrene, a nitroaromatic derivative of pyrene, is increasingly being used as an organic precursor for carbon dot synthesis by bottom-up method. This work aims to study the luminescent products obtained by microwave-assisted solvothermal treatment of trinitropyrene in a common organic solvent for nanoparticle synthesis, dimethylformamide. By employing flash chromatography, we isolated different fractions from which mainly stems the fluorescence observed from the crude sample obtained post solvothermal treatment. By performing structural and spectroscopic characterization techniques, we observed that they possess quiet similar chemical composition and luminescent properties but significant differences from a structural point of view. From these observations, we suggest that the fractions mainly consist of molecular derivatives of the precursor material. This study calls attention to the need of separation and purification techniques in order to better assess the properties of carbon dots.