Fluorescence blinking statistics from single CdSe nanorods

TL;DR

This study analyzes fluorescence blinking in single CdSe nanorods of various sizes and surface passivations, revealing that blinking statistics are largely unaffected by surface passivation but depend on aspect ratio and quantum confinement effects.

Contribution

It provides the first comprehensive comparison of blinking statistics across different nanorod sizes, surface passivations, and shapes, highlighting the influence of aspect ratio and quantum confinement.

Findings

Blinking off-time follows a power law distribution.

Blinking on-time follows a truncated power law.

Aspect ratio influences the crossover time linearly.

Abstract

We report fluorescence blinking statistics measured from single CdSe nanorods (NRs) of seven different sizes with aspect ratio ranging from 3 to 11. This study included core/shell CdSe/ZnSe NRs and core NRs with two different surface ligands producing different degrees of surface passivation. We compare the findings for NRs to our measurements of blinking statistics from spherical CdSe core and CdSe/ZnS core/shell nanocrystals (NCs). We find that for both NRs and spherical NCs, the off-time probability distributions are well described by a power law, while the on-time probability distributions are best described by a truncated power law. The measured crossover time is indistinguishable within experimental uncertainty for core and core/shell NRs, and for core NRs with different ligands, indicating that surface passivation does not affect the blinking statistics significantly. We find that at fixed excitation intensity, the inverse crossover time increases approximately linearly with increasing NR aspect ratio; for a given sample, the inverse crossover time increases very gradually with increasing excitation intensity. The measured per-particle absorption cross section for all samples indicates that the change in NR absorption cross-section with sample size can account for some but not all of the differences in crossover time. This suggests that the degree of quantum confinement may be partially responsible for the aspect ratio dependence of the crossover time.