Hybrid Plasmonic Nanostructures for Chemical Sensors

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopic technique, which enables sensitive detection down to single-molecule level and provides its specific fingerprints. The design of SERS systems have been great attention to overcome the traditional drawback of Raman scattering - its intrinsic weakness of Raman signals. Recently, plasmonic systems based on metal nanoparticles on a metal film have generated great interest for ultrasensitive SERS chemical sensors. Particle-on-film plasmonic systems can provide the precise gap regions between metal nanoparticles and metal films which can provide reproducible hot spots with large SERS enhancements. This thesis presents fabrication of plasmonic nanostructures and provides chemical applications. Firstly, Chapter 1 present brief introduction of surface plasmon (SP), SERS and hybrid plasmonic nanostructures for sensitive SERS chemical sensor. Chapter 2, we present high-density GNS assemblies on Ag film for ultrasensitive SERS chemical sensors with an attomole level of detection capability of explosive molecules. In Chapter 3, we suggested pH-responsive plasmonic systems for modulate gap distances between the silver nanoparticle and silver films, leading to great change in particle-film plasmon couplings. In Chapter 4, we present a new design platform based on the 3D antireflective metal/semiconductor heterojunction nanostructures. In this design, our SERS system enables molecular level of detection capability of benzenethiol (100 zeptomole), rhodamine 6G (10 attomole), and adenine (10 attomole) molecules. Finally, in Chapter 5, we introduce a hybrid plasmonic architecture utilizing combined plasmonic effects of particle-film gap plasmons and silver film over nanosphere (AgFON) substrates. When gold nanoparticles (AuNPs) are assembled on AgFON substrates with controllable particle-film gap distances, the AuNP-AgFON system supports multiple plasmonic couplings from interparticle, particle-film, and crevice gaps, resulting in a huge SERS effect.