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Near-field Scanning Optical Microscopy (NSOM)

Near-field Scanning Optical Microscopy (NSOM). Technique for chemical analysis. What is it? (Revised). Near field scanning optical microscopy (NSOM) was developed in the mid 1980's as a means to break the diffraction limit on spatial resolution attainable with optical measurement. 

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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) was developed in the mid 1980's as a means to break the diffraction limit on spatial resolution attainable with optical measurement.  • Traditional NSOM utilizes a tapered, metal-coated optical fiber with a small aperture as either an excitation source or collection device.  • 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. Developments in NSOM • In the 1990s, they developed a new device. The idea was to spatially map an optical signal from the surface of a sample by scattering that signal with a solid probe.  • The challenge of the diffraction limit originates from the fact that it is impossible to focus light to a spot smaller than half its wavelength. • Typical spatial resolution for the fiber approach to NSOM is ~50-100 nm, though careful probe and sample preparation have yielded ~30 nm resolution.

  4. NSOM Scanning • NSOM can scan high density systems such as encountered in in vivo experiments, and surfaces in solution. • Many problems in contemporary molecular biology require a detailed description of molecular conformational changes. 

  5. Examples of NSOM Photography Image of Malaria-Infected Blood Cells Near-Field Image of Sperm Cell

  6. Examples of NSOM performed at NIST We present high-resolution images with near-field scanning optical microscopy to study phase separation in polymer films Transmission and transmitted fluorescence near-field scanning optical microscope images were taken for direct visualization of the intermediate steps of phase separation Simultaneous three-way fluorescence, transmission, and topography NSOM measurements have been used in conjunction with modeling to study the phase separation of polymer blends

  7. NSOM Schematic

  8. 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.

  9. 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)

  10. Enlarged schematic diagram of dither piezo

  11. Labs Currently Using NSOM Beckman Institute for Materials Science and Technology - A wide variety of excellent images created with a near field scanning optical microscope are included on the Beckman Institute • Groeber Lab of Optical Imaging Spectroscopy - Yale University researchers at the Groeber Lab in the Department of Applied Physics and Physics emphasize the combined use of optical spectroscopy and optical imaging as a tool for materials characterization. Haydon's Research Group at Iowa State University - Phil Haydon applies NSOM to biological samples in order to discover new insights into the regulation of ion channels and synaptic transmissions in neurons. Laboratory for Spectroscopic Imaging - The University of Texas research group, which is headed up by Paul Barbara, uses NSOM to image molecular semiconductor heterostructures and organic thin films. National Institute of Standards and Technology, Optical Technology Division - The Physics group at the NIST is extending measurements and standards to the nanoscale for the optical characterization of thin films and interfaces. National Renewable Energy Laboratory - NSOM - The NSOM instrument at the NREL in Golden, Colorado was designed for solid state spectroscopy and operates at either room temperature or in a cryostat. Superfine Group - The nanoscience research group, headed by Richard Superfine, at the University of North Carolina in Chapel Hill, conducts near-field research using polystyrene and magnetic particles as probes, rather than the traditional fiber optical probes. Ultra at Boston University - The Ultra research group, which is located in the Department of Physics, is involved in several near-field optical projects.

  12. Websites for More Information • 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/ • http://www.olympusmicro.com/primer/techniques/nearfield/nearfieldwebresources.html

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