Development of nanowire based surface-enhanced raman scattering sensor: optical properties and biomedical applications

Abstract

In 1977, Jeanmaire and Van Duyne and Albrecht and Creighton independently observed that adsorption of pyridine to electrochemically roughened silver surfaces could increase the Raman signals of pyridine by a factor of ~$10^6$.$^{1,2}$ This striking discovery was denoted Surface-enhanced Raman Scattering (SERS) effect and immediately became the subject of intensive study.$^3$ After its discovery more than 30 years ago, SERS was expected to have major impact as a sensitive analytical technique and tool for fundamental studies of surface molecules as well as biomedical applications. Unfortunately, the lack of reliable and reproducible SERS signals limited its applicability. In recent years, the synthesis of well-defined nanostructures, the discovery of single molecule SERS, and the design of SERS active platform that maximize the electromagnetic enhancement are driving the resurgence of this field in both fundamentals and applications. In this dissertation, we present the works on SERS using single crystalline noble metal nanowires (NWs). The Au and Ag NWs synthesized in vapor phase have atomically smooth surfaces and thus they can be used as well-defined and well-characterized SERS active platforms. Initially, the optical properties of noble metal NWs were discussed in conjunction with theoretical calculations. This allows us to find simple and reproducible SERS active nanostructures. Secondly, the NW based SERS active platforms were used for molecular detection. These nanostructures enable to detect various analytes such as avidin and various metal ions. Last, the biomedical applications of NW based SERS sensors were presented. The multiplex pathogen DNAs sensing and single nucleotide polymorphism (SNP) detection were possible using these SERS sensors. The abstracts for each chapter are as follows. $\emph{Chapter 1. Optical Properties of Well-defined Surface-enhanced Raman Scattering Active Nanostructures}$ Well-defined SERS active systems were fabricated by ...