Studying the emission complexity of conjugated molecules by manipulating the molecular aggregate state

We prepared quantum dots (QDs) based on a conjugated molecule (coumarin 6, C-6), which is considered to be a mesoscopic aggregate, to build a bridge linking the monodisperse state (solution state) and macroscopic aggregates (powder state). Their spectral features, including steady spectral data, dynamic features and fluorescence quantum yields, have been compared in detail. All dynamic data were modelled using the continuous rate distribution function. The final results showed that the fluorescence quantum yield of organic quantum dots based on C-6 gradually decreases as the size of the QDs increases, which may be attributed to enhancement of the rate of non-radiative relaxation, which originates from the aggregation. This is beneficial for further understanding the optical characteristics of conjugated molecules.