Determining the exact number of dye molecules attached to colloidal CdSe/ZnS quantum dots in Förster resonant energy transfer assemblies

Abstract

Semiconductor quantum dots functionalized with organic dye molecules are important tools for biological sensor applications. Energy transfer between the quantum dot and the attached dyes can be utilized for sensing. Though important, the determination of the real number of dye molecules attached per quantum dot is rather difficult. In this work, a method will be presented to determine the number of ATTO-590 dye molecules attached to CdSe/ZnS quantum dots based on time resolved spectral analysis. The energy transfer from the excited quantum dot to the attached ATTO-590 dye leads to a reduced lifetime of the quantum dot's excitons. The higher the concentration of dye molecules, the shorter the excitonic lifetime becomes. However, the number of dye molecules attached per quantum dot will vary. Therefore, for correctly explaining the decay of the luminescence upon photoexcitation of the quantum dot, it is necessary to take into account the distribution of the number of dyes attached per quantum dot. A Poisson distribution of the ATTO-590 dye molecules not only leads to excellent agreement between experimental and theoretical decay curves but also additionally yields the average number of dye molecules attached per quantum dot. In this way, the number of dyes per quantum dot can be conveniently determined.

Optical sensing by integration of analyte-sensitive fluorophore to particles

“…molecules, as shown in this Jablonski diagram. The images have been adopted from Kaiser et al [43,44].…”

“…On the other hand, in case of QD-fluorophore FRET assemblies, the effective fluorescence lifetime of the fluorophores will be similar to that of the donor particles (i.e. QDs) [44] [66]. Thus, by linking of fluorophores to the surface of QDs their effective lifetimes can be changed.…”

Capillary electrophoresis, a method for the determination of nucleic acid ligands covalently attached to quantum dots representing a donor of Förster resonance energy transfer

“…Thus, Kaiser et al. reliably determined the real number distribution of dye molecules attached to QDs by time‐resolved photoluminescence measurements . Clapp et al.…”

“…The higher is the number of acceptor molecules attached to a donor, the faster is the transfer of energy to luminescent dyes and the higher is FRET efficiency. Thus, Kaiser et al reliably determined the real number distribution of dye molecules attached to QDs by time-resolved photoluminescence measurements [29]. Clapp et al observed an increased FRET efficiency with increasing number of dye-labeled proteins immobilized on the QD surface during titration [30].…”

Predicting signatures of anisotropic resonance energy transfer in dye-functionalized nanoparticles

“…7–10 However, the anisotropic nature of dye–NP RET remains largely unnoticed either in theoretical or experimental accounts. 11–13 Note that, even in the case of spherical NPs, RET cannot be considered isotropic when the underlying lattice is anisotropic ( e.g. , in wurtzite structures).…”