Optical trapping of single fluorescent molecules at the detection spots of nanoprobes.

We propose a scheme of optical trapping of fluorescent molecules, based on the strongly enhanced optical field due to surface plasmon resonances at laser illuminated metal tips or particles. A semiclassical approach is compared to a quantum-mechanical one. Attractive as well as repulsive forces are possible depending on the wavelength of the optical field. The trapping potential is shown to be strong enough to overcome the Brownian motion in water solution for common optical tweezer light inten-sities. Single molecule resonance Raman spectroscopy probes are particularly well suited for the trap-ping scheme. Finally we propose intracellular probing of the function of biomolecules as an application.