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Design and Implementation of Near Field Excitation System for Spectroscopy of Biological Species

Sasanpour, Pezhman | 2010

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 40978 (48)
  4. University: Sharif University of Technology
  5. Department: Institute for Nanoscience and Nanotechnology
  6. Advisor(s): Rashidian, Bizhan; Vossoughi, Manouchehr; Shahrokhian, Saeed
  7. Abstract:
  8. The main goal of this project is analysis, design and implementation of scanning near field optical system for detection of biological species. The activities fall in two main category. Theoretical and experimental. In theoretical part, after studying different models describing near field interaction, we have developed software for computationally analysis of nonlinear interaction of light with nanostructures, considering third order nonlinear susceptibility and dispersion behavior of permittivity for metallic nanostructures. The software implements three dimensional finite difference time domain (FDTD) method for analysis of interaction of electromagnetic wave with matter. In developed software, dispersion behavior of permittivity has been incorporated using Drude and Lorentz models. Effect of third order nonlinear susceptibility has been added to system where by using Newton- Raphson method, nonlinear equations have been solved. Exploiting the developed software, we have analyzed below items. A) Analysis of electric field enhancement of gold mesotriangles deposited on glass substrate which are used as active substrates for surface enhanced raman spectroscopy (SERS). B) Analysis of third order nonlinear enhancement in gold nanostructures according to surface plasmon resonance and its potential applications. C) Analysis of our novel proposed method for cancer cell apoptosis using gold nanoparticles as localized UV source of radiation. D) Analysis of our proposed method of fluorescent microscopy based on using gold nanotraingles as nonlinear optical antenna. In experiment part, we have designed an omni-purpose near field imaging and spectroscopy system for analysis of biological species. Most of the subsystems including positioning, feedback, low noise amplifiers (LNA), direct digital synthesizer (DDS), calibration system for positioning and optical probes has been designed, implemented and tested accordingly. In addition, we have designed and implemented a biosensor for detection of antibodies. Biosensor system consists of quartz tuning fork crystals which are coated with antigens and according to lock&key properties of antibody-antigene, after forming chemical bond, the mass of tuning fork prongs and accordingly its resonance frequency will change. By detection of resonance frequency shift, Q-factor, amplitude and phase response of this resonator, existence of specific antibody can be detected.
  9. Keywords:
  10. Biosensor ; Scanning Near-Field Optical Microscope (SNOM) ; Finite Difference Method ; Third Order Nonlinearity ; Biophotonic ; Near Field Optic ; Nonlinear Plasmonic

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