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Project

Development of a new form of superresolution optical microscopy by combining Raman spectroscopy and plasmon waveguiding effect.

The objective of this proposal is to realize a novel scheme for high resolution Raman spectroscopy/microscopy method combining surface enhanced Raman scattering and the sub-diffraction limited plasmon waveguide effect. SERS is a promosing technique for bio/chemical imaging and sensing. Under specific condition, SERS can be detected even from individual single molecules, requiring a ~1014 - 1015 fold enhancement as compared to the typical Raman scattering cross sections of individual molecules (~10-29 - 10-31 cm2). Such huge enhancements are usually realized at coinage metal surfaces with nanoscale features (e.g. roughened electrodes, nanoparticles and aggregations of them), which can sustain collective oscillation of surface electrons resonant with typical visible/near IR optical excitation field. SERS enhancement strongly depends on the metal, size, and shape of the nanoscale structures of a the substrate. Minizturization of dielectric waveguides is limited by diffraction to about half the wavelength of light. The limitation strongly restricts the spatial resolution of subsequent optical imaging. Alternatively, the diffraction limit can be substantially broken by using metals instead of dielectrics as the waveguide materials. This is based on the coupling of free photons to electron excitations at a metal/air interface to form SPPs. It has been shown that SPPs modes propagate along nano-structures of metals over many microns. Photon energy can be easily confined and propagate along a nanostructure with a cross-section less than the wavelength/20. The unique combination of SERS with the concept of the plasmon waveguide effect in metals will be developed in this project to a new imaging mode with an optical resolution in the order of a few nanometers.
Date:1 Jul 2009 →  30 Sep 2012
Keywords:Surface plasmons, Microscopy, Raman spectroscopy, AFM, Waveguiding, Nano particles, Silver wires, Surface Enahnced Raman Spectroscopy
Disciplines:Condensed matter physics and nanophysics, Physical chemistry, Sustainable chemistry