Related Experiment Video
Updated: May 8, 2026
17:14
Compact Quantum Dots for Single-molecule Imaging
Published on: October 9, 2012
Size-dependent photoionization in single CdSe/ZnS nanocrystals
Kevin T Early1, David J Nesbitt
1JILA, National Institute of Standards and Technology and University of Colorado, Department of Chemistry and Biochemistry, University of Colorado Boulder , Boulder, Colorado 80309, United States.
Nano Letters
|September 12, 2013
Summary
Fluorescence blinking in semiconductor nanocrystals is better understood. Increasing nanocrystal size reduces the probability of photoionization from biexcitons, a key factor in blinking behavior.
Area of Science:
- Materials Science
- Quantum Dots
- Nanotechnology
Background:
- Single semiconductor nanocrystals exhibit fluorescence intermittency (blinking) following power-law statistics.
- Blinking's 'on' times show pump-power dependent truncation, suggesting biexciton photoionization.
Purpose of the Study:
- Investigate the effect of nanocrystal radius on the 'on' time truncation.
- Determine the relationship between nanocrystal size and biexciton photoionization probability.
Main Methods:
- Experimental measurements of fluorescence intermittency in CdSe/ZnS nanocrystals of varying radii.
- Theoretical effective mass calculations of exciton wave functions.
Main Results:
- Observed a decrease in per-pulse photoionization probability with increasing CdSe core radius (1.3 to 3.5 nm).
- Determined a radius scaling of P(ionize) proportional to 1/r(3.5(5)).
- Calculations show similar scaling for electron and hole probabilities in the ZnS shell.
Conclusions:
- Nanocrystal radius significantly influences biexciton photoionization probability.
- Surface-localized charge ejection mechanisms are proposed.
- Results provide insights into controlling blinking in quantum dots.
