Blinking suppression and intensity recurrences in single CdSe-oligo (phenylene vinylene) nanostructures: experiment and kinetic model

Abstract

We report time-resolved single molecule fluorescence imaging of individual CdSe quantum dots that are functionalized with oligomeric conjugated organic ligands. The fluorescence intensity trajectories from these composite nanostructures display both a strong degree of blinking suppression and interesting intensity fluctuations with recurrence times on the order of 10-60 seconds (quantified by Fourier transform analysis). In addition, Time-Tagged-Time-Resolved (TTTR) fluorescence measurements of the fluorescence decay rate of individual hybrid nanostructures indicate significantly modified non-radiative decay rates relative to conventional ZnS-capped CdSe quantum dots. Modeling of fluorescence intensity trajectories using a diffusive reaction coordinate model shows that slow fluctuations in electron energies (1Se, 2Pe) can give rise to the recurrences via modified Auger-assisted hole-trapping rates. We briefly discuss a possible ligand-induced mechanism for such behavior.