Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 4: New Experimental Techniques

CPP 4.2: Talk

Monday, March 27, 2006, 14:30–14:45, ZEU Lich

Gold Nanorods as Novel Nonbleaching Plasmon-Based Sensors for Molecular Orientations and Local Refractive Index Changes — •Jan Becker and Carsten Sönnichsen — Nanobiotechnology group, Institute for Physical Chemistry, University of Mainz, Germany (www.nano-bio-tech.de)

Gold nanorods of typical dimensions of 25nm x 60nm can be observed in a darkfield microscope because of their strong light scattering at the plasmon resonance. The scattered light of these gold rods is strongly polarized along their long axis making them an ideal orientation probe. We study the rotations of single gold nanorods weakly bound to a glass surface by observing the intensity fluctuations in polarized light. We observe some fast rotating rods (10ms time scale) and some very slow rotating rods likely trapped in shallow surface potentials.

Furthermore, the wavelength of the plasmon depends on the volume and aspect ratio of the gold nanorod, but also on the refractive index of the local environment. We study this plasmon shift for different particle shapes to find the optimal local refractive index sensor using a novel automated acquisition setup. Nanorods are found to be more sensitive than spherical particles, triangles, cubes and hollow spheres.