Dual optical microscope for visualization of single "transparent" nanoparticles

An experimental setup of a far-field optical microscope intended for simultaneous visualization of single nanoparticles by two different methods is described. The first method is based on a modified version of a surface plasmon resonance microscope, the second on a highly sensitive recording of fluorescent labels inserted into the observed nanoparticles. The created microscope allows visualizing nanoparticles that weakly absorb light in a selected wavelength range and are characterized by a refractive index close to its size in the surrounding liquid (polymeric nanoparticles, viruses, liposomes, intracellular microvesicles in aqueous medium). The combination of the two methods allows to increase the reliability of nanoparticles detection. The optical scheme of the dual microscope and its principle of operation are described, and examples of the registration of nanoparticles are given.