Homogeneous Resonant Energy Transfer within Clusters of Monodisperse Colloidal Quantum Dots

As fluorescent nanocrystals, colloidal quantum dots (QDs) are increasingly used for biosensing thanks to their ability to perform Forster resonant energy transfer (FRET). Especially, all-QD-based donor- acceptor systems offer promising approaches for the design of FRET biosensors. But contrary to molecular fluorophores, QD emission properties are highly conditioned by the size distribution of QDs, so it is possible to observe energy transfers between QDs coming from the same monodisperse population, when packed into clusters. Here, we characterize such homogeneous resonant energy transfer (homo-FRET) processes occurring between CdTe QDs clustered within an organosilane polymer matrix and develop a mathematical model to account for their efficiencies. We evidence the critical role of the statistical donor-acceptor polarization of the QD population and provide tools to quantify it. Interestingly, as QD-QD homo-FRET proves to only depend on size dispersion and Stokes shift, the conclusions of our study can be extended to any kind of QDs and our model can be used to predict their own homo-FRET efficiency.