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 (NC's). Both T OPO-capped and ZnS-capped NC's were excited high in the energy band for the se investigations. The comparison between the PL dynamics from these two ty pes of NC's shows that only the slow component of the PLA decay is influenc ed 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 o f intra-band energy relaxation to the polarization decay. (C) 2001 Elsevier Science B.V. All rights reserved.