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Mechanisms of fluorescence blinking in semiconductor nanocrystal quantum dots

Tang, Jau and Marcus, R. A. (2005) Mechanisms of fluorescence blinking in semiconductor nanocrystal quantum dots. Journal of Chemical Physics, 123 (5). Art. no. 054704. ISSN 0021-9606. http://resolver.caltech.edu/CaltechAUTHORS:TANjcp05a

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Abstract

The light-induced spectral diffusion and fluorescence intermittency (blinking) of semiconductor nanocrystal quantum dots are investigated theoretically using a diffusion-controlled electron-transfer (DCET) model, where a light-induced one-dimensional diffusion process in energy space is considered. Unlike the conventional electron-transfer reactions with simple exponential kinetics, the model naturally leads to a power-law statistics for the intermittency. We formulate a possible explanation for the spectral broadening and its proportionality to the light energy density, the –3/2 power law for the blinking statistics of the fluorescence intermittency, the breakdown of the power-law behavior with a bending tail for the "light" periods, a lack of bending tail for the "dark" periods (but would eventually appear at later times), and the dependence of the bending tail on light intensity and temperature. This DCET model predicts a critical time tc (a function of the electronic coupling strength and other quantities), such that for times shorter than tc the exponent for the power law is –1/2 instead of –3/2. Quantitative analyses are made of the experimental data on spectral diffusion and on the asymmetric blinking statistics for the "on" and "off" events. Causes for deviation of the exponent from the ideal value of –3/2 are also discussed. Several fundamental properties are determined from the present experimental data, the diffusion correlation time, the Stokes shift, and a combination of other molecular-based quantities. Specific experiments are suggested to test the model further, extract other molecular properties, and elucidate more details of the light-induced charge-transfer dynamics in quantum dots.


Item Type:Article
Additional Information:©2005 American Institute of Physics (Received 8 April 2005; accepted 12 June 2005; published online 8 August 2005) We are pleased to acknowledge the support of the National Science Foundation and the Office of Naval Research. The authors would also like to acknowledge the support of one of the authors (J.T.) by the James W. Glanville Fellowship in Chemistry at the California Institute of California. One of the authors (R.A.M.) benefited considerably from the many interactions with Dr. Pavel Frantsuzov, and from calling his attention to several key articles. J.T. benefited from discussion with Ms. Chung and Prof. Bawendi on their recent work.
Subject Keywords:semiconductor quantum dots; nanostructured materials; photoluminescence; fluorescence; spectral line broadening
Record Number:CaltechAUTHORS:TANjcp05a
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:TANjcp05a
Alternative URL:http://dx.doi.org/10.1063/1.1993567
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1535
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:27 Jan 2006
Last Modified:26 Dec 2012 08:44

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