Blinking and nonradiant dark fraction of water-soluble quantum dots in aqueous solution

We describe the nonradiant fraction and blinking of Qdot-streptavidin samples in solution

J. Yao; D. R. Larson; H. D. Vishwasrao; W. R. Zipfel; W. W. Webb


Scholarcy highlights

  • S emiconducting quantum dots have been shown to possess several photophysical properties that are superior to those of organic fluorophores: high-absorption cross sections, excellent photostability, broad excitation spectra, and narrow emission spectra
  • By confocal fluorescence coincidence analysis and two-photon cross-correlation fluorescence correlation spectroscopy, we measured the properties of bright qdots and dark qdots as they diffused through a femtoliter optical focal volume
  • We found that the bright fraction determined from single-particle measurements correlates with the ensemble quantum yield
  • Qdot655-SAv was obtained from Quantum Dot and was labeled with biotin-oligonucleotide-fluorescein
  • We used complementary methods, including CFCA and two-photon cross-correlation FCS on the qdot-dye conjugate freely diffusing in solution and wide-field epifluorescence imaging of unlabeled, gel-localized but locally mobile qdots
  • The brightness of qdots can be characterized in two distinct but complementary ways: the mean intrinsic brightness of single qdots in the β€˜β€˜on’’ state can be measured by action cross sections or count rate per dot and the bright fraction of the dot population that is capable of absorbing excitation light can be conveniently estimated from the ensemble QY
  • The very best batch has both the highest ensemble quantum yield and the highest on-time fraction

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