Distance Dependence of Single-Fluorophore Quenching by Gold Nanoparticles Studied on DNA Origami

Physical and Theoretical Chemistry-NanoBioScience, TU Braunschweig, Hans-Sommer-Strasse 10, 38106 Braunschweig, Germany.
ACS Nano (Impact Factor: 12.88). 03/2012; 6(4):3189-95. DOI: 10.1021/nn2050483
Source: PubMed

ABSTRACT We study the distance-dependent quenching of fluorescence due to a metallic nanoparticle in proximity of a fluorophore. In our single-molecule measurements, we achieve excellent control over structure and stoichiometry by using self-assembled DNA structures (DNA origami) as a breadboard where both the fluorophore and the 10 nm metallic nanoparticle are positioned with nanometer precision. The single-molecule spectroscopy method employed here reports on the co-localization of particle and dye, while fluorescence lifetime imaging is used to directly obtain the correlation of intensity and fluorescence lifetime for varying particle to dye distances. Our data can be well explained by exact calculations that include dipole-dipole orientation and distances. Fitting with a more practical model for nanosurface energy transfer yields 10.4 nm as the characteristic distance of 50% energy transfer. The use of DNA nanotechnology together with minimal sample usage by attaching the particles to the DNA origami directly on the microscope coverslip paves the way for more complex experiments exploiting dye-nanoparticle interactions.

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    • "Most impressively, a five-fold overall enhancement of upconversion emission was demonstrated in NaYF4: Yb3+, Er3+ nanocrystals when coupled them with gold island films 17. However, all previously reported enhancement factors were less than 5-fold, and in many cases, quenching was unavoidable 18, 19, mainly due to the following reasons: (1) frequency mismatching between the localized plasmon resonance (usually determined by the used metal, their shape, size, the dielectric environment, and the spacer distance) and the used emission/excitation light, (2) a competition of a few processes including a increase of the excitation rate by the local field enhancement (LFE) 20, an enhancement of radiative decay rate by the surface plasmon-coupled emission (SPCE) and quenching that reduces the efficiency caused by the non-radiative energy transferring (NRET) from the upconversion material to the metal surfaces 21,22, all of which will be greatly dependent on the spacing distance between the upconversion material and the metal 23-26. "
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    • "The efficiency of quenching of fluorescence and fluorescence lifetime of the donor in the presence of AuNPs depends very much on the size of the nanoparticles as well as the distance of separation of the fluorophore from it. To have a control on the latter, people have adopted techniques like tagging DNA type spacers of definite lengths (tunable spacers) [19] [20] [22] [28] [29], sheathing the AuNPs by variable number of monomolecular films [30], etc. Singlemolecule spectroscopy has also been exploited to explore and understand the mechanism of AuNP induced quenching [31] [32] [33]. Although increase in the fluorescence is observed with smaller AuNPs (≤10 nm) which is rationalized from an enhanced local field induced by the nanoparticle [32], for larger nanoparticles (≥10 nm) quenching always dominates. "
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