Dual-color super-resolution imaging of quantum dot clusters

Semiconductor quantum dots (QDs) in small clusters can exchange excited state energy via various transfer mechanisms such as Forster resonant energy transfer (FRET). Such energy transfer enables excitons to move from larger bandgap donors to smaller bandgap acceptors. Clusters of mixed donor/acceptor QD species consequently have a spectral signature that is dependent on which QDs in the clusters are responsible for the emission. Using a dual-color super-resolution imaging approach, we report on the spectral characteristics of interacting QDs in clusters with nanometer spatial resolution. Higher emission intensities from clusters are shown to emanate from sub-regions of the clusters and have spectral signatures that indicate the emission is dominated by the acceptor region of the spectrum. Thus, energy transferring interactions among QDs in clusters funnel excitons primarily to acceptor particles. Acceptor particles are responsible for the majority of the emission from the clusters with an emission spectra corresponding to the spectral profiles of the acceptor species.