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BP: Fachverband Biologische Physik

BP 7: Poster I

BP 7.33: Poster

Monday, March 23, 2009, 17:45–20:00, P3

Tip-enhanced single molecule fluorescence near-field microscopy for nanobiophysics — •Heinrich Gotthard Frey, Jan Paskarbeit, and Dario Anselmetti — Experimental Biophysics and Applied Nanoscience, Fakultät für Physik, Universität Bielefeld, Universitätsstraße 25, 33615 Bielefeld

For nanobiophysical applications, scanning near-field optical microscopy (SNOM) of single fluorescent dye molecules must combine high electrical field intensities in the sample near-field with high optical and topographical resolution [1] and the ability to image surface-immobilized biomolecules in aqueous solution. We show, that theses requirements can be satisfied using the electric field enhancement at the tip of far-field illuminated silicon AFM probes in aperture-less SNOM.

Single ATTO-740 dye molecules have been imaged at an optical resolution of 20-25nm (separation of two dye molecules) under ambient conditions and in aqueous solution with commercial silicon AFM probes and sophisticated phase-sensitive single photon counting technology in dynamic AFM mode of operation. Two illumination modes have been tested successfully: a) back-illumination via evanescent fields in a total-internal-reflection-microscopy setup using an oil-immersion objective lens and b) direct top-illumination side. Although both optical setups gave similar results, they differ considerably with respect of potential experimental applications that will be discussed [2].

[1] H.G. Frey et al., Nanotechnology 17, 3105-3110, 2006 [2] H.G. Frey et al., in preparation 2008