This paper reports a novel surface-enhanced Raman scattering (SERS)-active light waveguide method for ultrasensitive detection of a sample dissolved in a small volume of low refractive index liquid. The SERS-active light waveguide demonstrated in this study was constructed via the light-guiding silica capillary. The surface of its inner wall was modified with SERS-active silver nanoparticles that can remarkably enhance Raman signals. The capillary with the SERS-active modified layer was filled with the sample solution to form the SERS-active liquid core (LC) fiber. The incident laser beam travels through the waveguide in a totally reflective mode within the fiber wall and penetrates a small distance into the sample solution by the evanescent wave field. The Raman scattering of the analytes adsorbed onto the surface of the SERS-active modified layer can be excited by laser beam and refracted into the fiber wall. Thus, a sample dissolved in low refractive index liquid, e.g., methanol, can be quantitatively monitored by Raman spectroscopy and the detection limit of its concentration is lower than 10-9mol/L.
Weiqing Xu, Shuping Xu, Zhicheng Lü, Lei Chen, Bing Zhao, and Yukihiro Ozaki, "Ultrasensitive Detection of 1, 4-Bis(4-vinylpyridyl)phenylene in a Small Volume of Low Refractive Index Liquid by Surface-Enhanced Raman Scattering-Active Light Waveguide," Appl. Spectrosc. 58, 414-419 (2004)