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Near-field Scanning Optical Microscopy (NSOM)

Near-field Scanning Optical Microscopy (NSOM). Technique for chemical analysis. What is it? (Revised).

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Near-field Scanning Optical Microscopy (NSOM)

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  1. Near-field Scanning Optical Microscopy (NSOM) Technique for chemical analysis

  2. What is it? (Revised) • Near-field scanning optical microscopy (NSOM) is a type of microscopy where a sub-wavelength light source is used as a scanning probe. It is a near-surface technique to examine materials up close. • NSOM uses wavelengths smaller than the diffraction wavelength to attain more accuracy

  3. TP-NSOM Resolution • NSOM demonstrates sub-diffraction limited resolution. Line scan through the fluorescence image of a single molecule.  • NSOM can achieve resolution better than 1/2 the wavelength.

  4. NSOM Scanning • NSOM can scan high density systems such as encountered in in vivo experiments, and surfaces in solution. • NSOM uses spectroscopic techniques rather than imaging. • Detecting the emission of a dye molecule or the intrinsic fluorescence of the protein of interest can yield conformational information.  • Many problems in contemporary molecular biology require a detailed description of molecular conformational changes. 

  5. What can Near Optical Microscopy do? Simultaneous three-way fluorescence, transmission, and topography NSOM measurements have been used in conjunction with modeling to study the phase separation of polymer blends

  6. NSOM Schematic

  7. NSOM Schematic • In current experiments, a continuous wave 532 nm doubled Nd:YAG laser (Coherent Inc.) generates the light sent through a fiber tip.  Typical output power from the aperture is 10 - 100 nW. • Figure 2. Experimental configuration for near-field scanning optical microscope (NSOM).  Laser light coupled into a single mode optical fiber passes through a subwavelength aperture at the end of the fiber.  Transmitted light or laser induced fluorescence emission is collected by an objective and imaged onto a detector.  An image is formed by raster scanning the sample and recording the collected light intensity as a function of scan position. ENLARGED AREA (next slide)

  8. Enlarged diagram of dither piezo

  9. References • http://physics.nist.gov/Divisions/Div844/facilities/nsom/nsom.html • http://www.umich.edu/~protein/NSOM/Technique.html • http://www.physics.unc.edu/~rsuper/research/projects/nsom/

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