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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: POSTERS Single Molecules, Biopolymers, Membranes

CPP 9.5: Poster

Montag, 25. Februar 2008, 16:45–19:00, Poster A

Measuring distance fluctuations by single pairs of gold nanoparticles — •Miriam Wähnert¹, Romy Radünz², and Frank Cichos³ — ¹Molecular Nanophotonics Group, University Leipzig, 04103 Leipzig — ²Molecular Nanophotonics Group, University Leipzig, 04103 Leipzig — ³Molecular Nanophotonics Group, University Leipzig, 04103 Leipzig

Single Molecule fluorescence resonance energy transfer (SMFRET) measures distance changes. This is heavily applied in biophysical studies. In combination with time resolved time tagged fluorescence detection it even allows the study of the dynamics of conformational fluctuations. However, the distance fluctuations accessible are limited to a range up to about 10 nm. Further, the technique suffers often from fluorescence blinking or bleaching of either donor or acceptor of the energy transfer dye couple.

We report on experiments, which employ the plasmon coupling between two gold nanoparticles to monitor distance fluctuations. The plasmon coupling of two gold particles is visible at distances up to a few 10 nm. Therefore it measures distance fluctuations on a much longer lengthscale than SMFRET. The interaction of the two plasmon oscillations shifts the extinction spectrum to longer wavelength. An optical signal off resonance of the single particle resonance is a measure for the particle distance. We use a photothermal detection technique to monitor the distance fluctuations between very small particles that are difficult to detect by optical scattering. First experimental results will be presented together with a numerical analysis of the technique.