High Sensitivity Surface Enhanced Raman Scattering Detection of Tryptophan

  • Author / Creator
    Kandakkathara, Archana A
  • Raman spectroscopy has the capability of providing detailed information about molecular structure, but the extremely small cross section of Raman scattering prevents this technique from applications requiring high sensitivity. Surface enhanced Raman scattering (SERS) on the other hand provides strongly increased Raman signal from molecules attached to metallic nanostructures and thus a promising technique for high sensitivity analytical applications. However, there are issues which have to be addressed in order to make SERS a reliable technique such as the optimization of conditions for any given analyte, understanding the kinetic processes of binding of the target molecules to the nanostructures and understanding the evolution and coagulation of the nanostructures, in the case of colloidal solutions. In the present thesis the goal was to develop very sensitive SERS techniques for the measurement of biomolecules of interest for analysis of the contents of cells. The techniques explored could be eventually be applicable to microfluidic systems with the ultimate goal of analyzing the molecular constituents of single cells. A high sensitivity detection system based on SERS has been developed and spectrum from tryptophan (Trp) amino acid at very low concentration (10^−8 M) has been detected. The concentration at which good quality SERS spectra could be detected from Trp is 4 orders of magnitude smaller than that previously reported in literature. A study on background electrolytes in the solution which has a significant role in SERS experiment has also been carried out. Optimization of electrolytes leads to the high enhancement reported in this thesis. The SERS detection has also been performed in microfluidic and flow cell geometries which enable a combination of high sensitivity of the SERS with the low volume requirements of microfluidic devices. A Teflon AF capillary was used for performing liquid core waveguide (LCW) SERS measurements and with this geometry the enhancement obtained was increased by a factor of 10. The enhanced sensitivity and better understanding of the optimum conditions for SERS developed in the thesis are important since they now could allow the possibility of assays of the chemical constituents of single cells in future microfluidic systems.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.