Label-free optical detection and tracking of single virions bound to their receptors in supported membrane bilayers.

We apply an interferometric optical detection scheme to image and track unlabeled single virions. Individual simian virus 40 virions and uninfectious virus-like particles were imaged on a glass substrate and on a supported membrane bilayer. Moreover, single unlabeled virions were tracked when bound to supported membrane bilayers via the viral receptor, the glycolipid GM1.

Measurement of the complex dielectric constant of a single gold nanoparticle.

A differential interference contrast microscopy technique that employs a photonic crystal fiber as a white-light source is used to measure both the real and the imaginary part of the complex dielectric constant of single 10 and 15 nm gold nanoparticles over a wavelength range of 480 to 610 nm. Noticeable deviations from bulk gold measurements are observed at short wavelengths and for individual particles even after taking into account finite-size surface damping effects.

Interferometric optical detection and tracking of very small gold nanoparticles at a water-glass interface.

We use an interferometric detection scheme to directly detect single gold nanoparticles with a diameter as small as 5 nm in an aqueous environment. We demonstrate both confocal and wide-field detection of nanoparticles and study signal strength as a function of particle size. Furthermore, we demonstrate a detection speed up to 2 micros.

Electrically conductive and optically transparent Sb-doped SnO2 STM-probe for local excitation of electroluminescence.

We demonstrate that an optically transparent and electrically conductive antimon-doped tin-oxide tip that is prepared in a sol-gel process can be used as a probe for scanning tunnelling microscopy (STM), yielding atomic vertical and nanometre lateral resolution. Emission of visible light from the tunnelling junction between gold particles and the tip is observed for bias voltages above 7 V. In contrast to the metallic tips generally used in STM, this tip does not significantly perturb the local optical response.

Reduced photobleaching of chromophores close to a metal surface.

The photobleaching of chromophores in front of a metal film is measured by recording the emitted fluorescence intensity from an ensemble of chromophores as a function of time. A strong dependence of the photostability on the distance from the metal surface is found. The experimental data are well described in a classical electromagnetic model with the additional assumption that photobleaching occurs at a constant rate from the excited state.