(462j) Far-Field Optical Nanoscopiy Based On Continuous Wave Laser Stimulated Emission Depletion (STED) for Nanofluidics

For electrophoresis in a nanochannel, measurement of concentration profile is desirable when Taylor dispersion is concerned. However, due to diffraction limit in optics, it is not possible to measure the concentration profile in a nanochannel with conventional optical method. Here we developed a stimulated emission depletion (STED) microscopy for future concentration profile measurement in nanochannels. STED is one of the breakthrough technologies that are far-field optical microscopy and can break the diffraction limit barrier and achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave (CW) lasers with different wavelengths, i.e. violet and green lasers for excitation and STED, respectively. Fluorescent dye coumarin 102 is used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a glass slide, which is coated with the nanoparticles, indicates that a spatial resolution of about 70 nm has so far been achieved. A two dimensional (2-D) image of the particles pattern of the STED system is constructed and compared with scanning confocal microscope. The present work has further extended the application of the STED microscopy into the blue regime.