Berlin 2001 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 2: Single Molecule Spectroscopy

CPP 2.6: Talk

Tuesday, April 3, 2001, 17:25–17:45, 110

Metal nanoparticles as optical nanosensors for concentrations of organic molecules — •S. Malkmus, T. Wilk, T. Franzl, C. Söennichsen, G. von Plessen, and J. Feldmann — Photonics and Optoelectronics Group, Physics Department and Center for Nanoscience (CeNS), University of Munich, Amalienstrasse 54, 80799 Muenchen, Germany

Gold and silver nanoparticles scatter light very efficiently at the particle plasmon frequency. The sensitive dependence of the plasmon resonance on the refractive index of the material in close vicinity (∼ 10nm) can be employed as a highly local sensor for the dielectric environment around the nanoparticle. By measuring spectra of individual nanoparticles in a microscope setup with a sensitive nitrogen cooled CCD camera, we detect the local concentration of saccharose molecules in water, as an example of an organic molecule in solution. We detected the plasmon resonance shift induced on individual silver particles with 60nm diameter down to saccharose concentrations of a few weight percent, which corresponds to less than 10 million molecules or 10 attomol within the local sensing volume of each nanoparticles. The sensitivity may be further increased by several orders of magnitude in a dedicated setup.