Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Nanoparticles and Composite Materials

CPP 8.4: Poster

Montag, 26. März 2012, 17:30–20:00, Poster A

Diffraction around a Single Heated Nanoparticle — •Markus Selmke, Marco Braun, and Frank Cichos — Universität Leipzig, Exp. Phys. I, molecular nanophotonics

Within the growing field of nano-sciences a fruitful new domain of metal nano-particles (NPs) has emerged: NPs of different shapes and composition have been used as markers, field-/ temperature-sources and sensors in many studies. Their unique and tunable absorptive properties are utilized in single particle photothermal (PT) detection which overcomes the scattering cross-section limitation of regular dark/wide-field and confocal microscopes. It is based on the (lock-in-)detected intensity-modulation of a probing laser beam caused by a particle-centered refractive index profile which is generated almost instantaneously through the absorption of a modulated heating laser. Thereby, even single molecules may be detected and a dispersion-like signature of the signal is obtained, which is what one would expect for a lens affecting the propagation of the gaussian probe beam. So far, no model exists which is able to describe the axial shape of the detected signal, nor does a quantitative theory for the signal magnitude exist at all. This gap, which so far separates this ultra-sensitive imaging technique from a quantitative tool, was bridged by the development of quantitative theories which are able to reproduce the full body of observed phenomena. One of them, the diffraction model presented here is shown to be particularly intuitive, quantitative and simple.