Web Release Date: November 30,
Saturation of Two-Photon Excitation Provides Insight into the Effects of a Quantum Dot Blinking Suppressant: A Fluorescence Correlation Spectroscopy Study
and
Department of Chemistry, 2500 University Drive NW, University of Calgary, Calgary, Alberta, Canada, T2N 1N4, and National Agency for New Technologies Energy and Environment (ENEA), Via Anguillarese 301, 00123 S. Maria di Galeria, Rome, Italy
Received: October 1, 2007
Abstract:
Quantum dots are now extensively used as luminescent tags for biological and chemical applications; however,
their propensity to display intermittent luminescence (aka blinking) has limited their use in quantitative assays.
Various surface active redox agents, such as 
-mercaptoethanol, have been posited as antiblinking agents to
help mitigate this challenge. We have examined the effect of -mercaptoethanol on the luminescence
intermittency of CdSe/ZnS quantum dots using fluorescence correlation spectroscopy. We find that
-mercaptoethanol lowers the quantum dot brightness and therefore lowers the probability of observing blinking
but does not otherwise inhibit intermittent luminescence. Based on changes in fluorescence correlation data
and excited-state lifetimes, we propose that the partitioning of -mercaptoethanol onto the quantum dot surfaces
increases nonradiative de-excitation rates. This behavior appears to be independent of the quantum dot surface
passivation layer or the solution contents.
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