NANO-OPTICS Applied Research

Immunosensors based on Fluorescence Enhancement by Metal Nanoparticles*

In fluorophore-labeled immunoassays the signal level can be dramatically improved due to surface enhanced fluorescence. The electrodynamic interaction of the fluorophore molecule with a metal nanoparticle increases the effective fluorescence quantum yield. When using fluorophores with low intrinsic quantum efficiency the light emission is quasi "switched on” when the immunilogic part with its label-fluorophore is fixed close to the metal nanoparticle surface by immunological binding reactions. This high surface specificity of fluorescence emission enables improved surface-to-background signal discrimination. We develop this technique towards its applicability in a new generation of clinical equipment.

* In cooperation with the Institut für Biochemie und Molekulare Zellbiologie, University of Vienna

Color Effects of Thin Film Systems Containing Metallic Nanostructures

A metal nanoparticle array located at a fixed distance from a plane metal mirror (by, e.g., a dielectric spacer layer) shows a spectral band of suppressed reflection. The center wavelength of this band depends on the optical properties of the nanoparticles and their distance to the metal mirror. This optical phenomenon can be modeled theoretically by the stratified medium theory, which is usually applied for dielectric multilayers. Applications of such systems lie in the fields of novel color effects, in particular of highly reflecting metal surfaces (Al, Ag, Au, etc.) and chemical sensorics. In the latter case we apply the system as a transducer of chemically induced swelling/shrinking action of specific polymers used as the interlayer material to optical signals.

Last modified on 5.5.2007 J.R.Krenn