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On/Off Flurescence Intermittency of Single Semiconductor Quantum Dots



M Kuno, D P. Fromm, H F. Hamann, Alan Gallagher, David Nesbitt


Single molecule confocal microscopy is used to investigate the detailed kinetics of fluorescence intermittency in colloidal II-VI (CdSe) semiconductor quantum dots. Two distinct modes of behavior are observed corresponding to (i) sustained on episodes (τon) of rapid laser absorption/fluorescence cycling, followed by (ii) sustained off episodes (τoff) where essentially no light is emitted despite continuous laser excitation. Both on-time and off-time probability densities follow an inverse power law, P (τon/off)varies as} l/τmon/off}, over more than seven decades in probability density and five decades in time. Such inverse power law behavior is an unambiguous signature of highlydistributed kinetics with rates varying over 105-fold, in contrast with models for switching between on and off configurations of the system via single rate constant processes. The unprecedenteddynamic range of the current data permits several kinetic models of fluorescence intermittency to be evaluated at the single molecule level and indicate the importance of fluctuations in the quantum dot environment.
Journal of Chemical Physics
No. 2


distributed kinetics, inverse power law, nanocrystallites, quantum dots, single molecule spectroscopy


Kuno, M. , Fromm, D. , Hamann, H. , Gallagher, A. and Nesbitt, D. (2001), On/Off Flurescence Intermittency of Single Semiconductor Quantum Dots, Journal of Chemical Physics (Accessed April 16, 2024)
Created June 30, 2001, Updated October 12, 2021