Overcoming the Complex Excited-State Dynamics of Colloidal Cadmium Selenide Nanocrystals Involved in Energy Transfer Processes

Abstract

Semiconductor nanocrystals are often characterized by complex excited-state dynamics which reflect the inhomogeneous character of ensemble of nanocrystals. A new hybrid inorganic–organic donor–acceptor system involving CdSe nanocrystals and paramagnetic nitronyl nitroxide free radicals is shown to lead to efficient Forster (dipolar) resonance energy transfer. This transfer process, which is monitored by steady-state and time-dependent photoluminescence quenching experiments, occurs on a time scale similar to that of the intrinsic recombination in CdSe nanocrystals, allowing to unravel some of the complexity associated with the excited-state photophysics of semiconductor nanocrystals. A Stern–Volmer formalism that can handle the multiexponential nature of the time-dependent excited-state kinetics of CdSe nanocrystals is developed, leading to excellent agreement between steady-state and time-dependent photoluminescence data when a log-normal distribution model is used for the intrinsinc recombination rate c...