Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Nanoparticles and Composite Materials

CPP 8.21: Poster

Monday, March 26, 2012, 17:30–20:00, Poster A

New Perspectives of Twin-Focus Photothermal Correlation Spectroscopy — •Romy Schachoff, Markus Selmke, Marco Braun, and Frank Cichos — Universität Leipzig, Exp. Phys. I, MONA

Photothermal microscopy has been used successfully for the detection of non-fluorescent nano-objects such as gold nanoparticles, quantum dots or carbon nanotubes. It employs a local temperature field around a laser excited absorber inducing a local refractive index change which is detected by a second laser. A careful investigation of the mechanisms and the origin of the photothermal signal has shown that the photothermal detection volume is in general a twin-focus with two well separated axial detection regions that differ in their signal phase. With the help of this clear spatial separation we are able to measure low axial flow velocities on a short length scale by a cross correlation analysis. We have investigated the diffusion of gold nanoparticles in water by means of this so called Twin-PhoCS. Radiation pressure induced flow velocities are extracted and the detection limits for velocities and small displacements are explored with the help of small gold nanoparticles in the twin-focus.