Resonant Localized Surface Plasmon Resonance Spectroscopy: Fundamentals and ApplicationsPublic Deposited
The work presented here describes investigations into the interaction of resonant molecules with metallic nanoparticles by localized surface plasmon resonance (LSPR) spectroscopy. The contents of this thesis include the study of the coupling mechanism between molecular resonance and plasmon resonance from experimental and theoretical perspectives and applications of this mechanism to biological sensing. From these studies, LSPR spectroscopy is shown to be a powerful tool to study the electronic structures of resonant molecules adsorbed on nanostructured metallic surfaces. In studies of the dye molecule Rhodamine 6G on Ag nanoparticles, we find that Rhodamine 6G is prone to aggregation on the Ag nanoparticle surface, leading to electronic structure changes that can be detected by LSPR and simulated by electrodynamics and density functional theory. It is further shown that resonant LSPR spectroscopy is able to detect the electronic resonance changes in heme-containing proteins caused by small molecules binding to the protein. Moreover, for the resonant analyte tris(bipyridine)ruthenium(II) with two electronic resonances polarized in different directions, the LSPR couples strongly to only one of the electronic resonances that is in-plane with the plasmon resonance. The correlation between the molecular resonance, LSPR and the wavelength-scanned surface-enhanced resonance Raman scattering (WS-SERRS) excitation profile is investigated using the tris(bipyridine)ruthenium(II)/Ag nanoparticle system. In combination with electrodynamics modeling, it is demonstrated that the WS-SERRS excitation profiles involve multiplicative electromagnetic and resonance Raman enhancement. Lastly, the optical properties of new plasmonic materials are explored by a numerical electrodynamics method and compared with experimental results. LSPR of truncated tetrahedral copper and aluminum nanoparticles of different sizes and in different media are studied by the discrete dipole approximation method. Since copper and aluminum are very active and prone to oxidize, the effect of oxides on the LSPR nanoparticles is also examined.