Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: Single Molecules

CPP 15.6: Vortrag

Dienstag, 26. Februar 2008, 18:15–18:30, C 230

Probing polymer dynamics by interfacial heat transfer at single gold nanoparticles — •Romy Radünz and Frank Cichos — Molecular Nanophotonics Group, University of Leipzig, Linnéstr. 5, 04103 Leipzig

A new time-resolved photothermal microscopy technique has been developed, which allows to follow the release of heat from a single nanoparticle to the local surrounding. Photothermal microscopy is based on the conversion of light absorbed by a single nanoparticle into heat, which is released into the polymer matrix and induces a local refractive index change on a length scale on the order of 100 nm. Finally, this refractive index change can be detected optically with a confocal microscope by heterodyne optical techniques. Within this all-optical setup gold nanoparticles with a diameter down to 10 nm can be detected. By following the temporal evolution of the photothermal signal we are able to probe heat transfer across nanoscale interfaces between single metal nanoparticle and polymer matrix, that depends on the interfacial heat transfer resistance and the heat conductivity of the polymer. Furthermore, it is possible to probe thermal properties of the polymer at various states of matter of the polymer. Temperatures even above melting temperatures of polymers are achievable due to the high absorption cross section and heat conversion efficiency of gold nanoparticles. The lengthscale on which these properties are probed can be controlled by applying an intensity modulated laser beam, since the heat diffusion length decreases with increasing modulation frequency.