Regensburg 2010 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster: Colloids and Complex Liquids
CPP 37.12: Poster
Mittwoch, 24. März 2010, 17:30–19:00, Poster B2
Photothermal Correlation Spectroscopy and Hot Brownian Motion — •Romy Radünz1, Daniel Rings2, Klaus Kroy2, and Frank Cichos1 — 1Molecular Nanophotonics Group, University of Leipzig — 2Soft Matter Theory Group, University of Leipzig
Photothermal correlation spectroscopy (PhoCS) is a recently developed tool to explore the diffusion of non-fluorescent tracers of only a few nanometers in size in solution in an equivalent way as it is done in fluorescence correlation spectroscopy. As a key feature of photothermal detection techniques the tracers and their intermediate surrounding are heated up. Although small temperature rises at the particles surface of a few Kelvin are sufficient to detect a single particle, in the case of gold nanoparticles surface temperature rises up to a few 100 K can be achieved with moderate heating intensities exploiting the high absorption cross sections near the plasmon resonance. To interpret the results of PhoCS correctly it is crucial to describe the diffusion of hot particles in a cold surrounding accurately. A model is presented for this Hot Brownian Motion that handles not only the influence of the inhomogeneous viscosity around the particle on the drag coefficient but gives also a first approach to quantify the impact of the non-uniform temperature distribution on the strength of thermal fluctuations that drives Brownian motion. To validate the theoretical description we have studied the diffusion of gold nanoparticles in water. Comparison with the theoretical estimates shows good agreement for temperature rises below 100 K leading to a robust basis for photothermal tracer techniques.