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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Transport and Confinement I

CPP 17.10: Vortrag

Dienstag, 1. April 2014, 12:30–12:45, ZEU 260

Gold Nano-Structure Assisted Thermophoretic Trapping of Single Nano-Objects — •Marco Braun and Frank Cichos — Molecular Nanophotonics, Fakultät für Physik und GeowissenschaftenUniversität Leipzig, Deutschland

Single molecule spectroscopy has become indispensable in todays soft-matter sciences. Brownian motion scaling with the molecules hydrodynamic radius lets it quickly disappear from the observation volume, which is why the molecule of interest is typically immobilized in a polymer matrix or by chemical interactions, generally accepted due to a lack of alternatives. Here, we present an all-optical technique to trap single nano-objects in solution which exploits highly localized thermal fields. The so-called thermophoretic trap exploits thermophoretic forces that act on a particle placed in a temperature gradient, which e.g. locally distorts the screening of the surface charges and by that induces a particle drift. In our approach the temperature field is generated by an optically heated gold nano-structure. Due to the small dimensions of the heat sources, even a small temperature increase introduces large temperature gradients causing a strong thermophoretic drift by which the motion of a Brownian particles can by manipulated. In our experiment an appropriate gold structure is heated locally by a focused laser beam with feedback to the Brownian particles position.