Designed long lived emission from CdSe quantum dots by reversible electronic energy transfer with a surface bound chromophore

The size-tunable emission of luminescent quantum dots (QDs) makes them highly interesting for applications that range from bioimaging to optoelectronics. For the same applications, engineering their luminescence lifetime – in particular, making it longer – would be as important; however, no rational methodology to reach this goal is available to date. Here we describe a strategy to prolong the emission lifetime of QDs by electronic energy shuttling to the triplet excited state of a surface-bound molecular chromophore. To implement this idea we made CdSe QDs of different sizes, and we self-assembled them with a pyrene derivative. We observed that the conjugates exhibit delayed luminescence, with emission decays that are prolonged by more than 3 orders of magnitude compared to the parent CdSe QDs (lifetimes up to 330 s). The mechanism invokes unprecedented reversible quantum dot-to-organic chromophore electronic energy transfer