Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: POSTERS Dynamics and Diffusion

CPP 15.14: Poster

Tuesday, March 24, 2009, 14:00–16:30, P3

Photothermal fluctuation spectroscopy on gold nanoparticle dimers — •Miriam Wähnert, Nils Neubauer, Romy Radünz, and Frank Cichos — Molecular Nanophotonics Group, University of Leipzig, Linnéstraße 5, 04103 Leipzig

To measure distance changes on the nanoscale, FRET (Fluorescence resonance energy transfer) is a heavily applied technique in biophysical studies. The upper limit of distance fluctuations being measured with this method is about 10 nm. Furthermore it suffers from photochemical degradation mechanisms like blinking and bleaching of the energy transferring dye molecules.

We report on recent experiments using pairs of gold nanoparticles as absorbing markers replacing dye molecules. Gold particles are strongly interacting with light, if they are excited near the plasmon resonance. The resulting dipoles of two closely spaced gold nanoparticles can couple to form a new rersonance, which appears in the absorption as a distinct feature. The strength of this absorption depends on the distance of the two particles and is visible up to a few 10 nm, which clearly exceeds the lengthscale of FRET. The gold nanoparticles are detected by photothermal heterodyne detection, using the release of heat from the absorbing particles to create a local refractive index change around them, which can be probed with a confocal laser scanning setup. Due to the plasmon coupling a fluctuating distance will result in a fluctuating photothermal signal. Numerical analyses of the spectra together with first experimental results will be presented.