Surface effects in the fluorescence ultra-fast dynamics from CdSe nano-crystals

We investigated the ultra-fast photoluminescence (PL) and photoluminescence anisotropy (PLA) dynamics from colloidal CdSe nano-crystals (NCʹs). Both TOPO-capped and ZnS-capped NCʹs were excited high in the energy band for these investigations. The comparison between the PL dynamics from these two types of NCʹs shows that only the slow component of the PLA decay is influenced by surface treatment. We found that the decay of PA close to zero occurs on a time-scale of tens of femtoseconds. This rules out the contribution of intra-band energy relaxation to the polarization decay.