Influence of the Local Dielectric Environment and its Spatial Symmetry on Metal Nanoparticle Surface Plasmon Resonances

This project examines how the collective oscillation of electrons in optically excited metal nanoparticles ( diameter \u3c 100 nm) is affected by the presence of different dielectric environments. When coupled with material polarization, these collective oscillations are known as a Surface Plasmon Polaritons (SPPs), which preferentially absorb and scatter light at a specific frequency satisfying the Local Surface Plasmon Resonance (LSPR) condition. Surface plasmons on metal nanoparticles are widely studied for use in optical labeling, ultrasensitive biodetection, and thermally activated tissue treatment. In general Mie theory can be used to accurately model the optical behavior of ideal spherical particles in a homogeneous environment. However, many experiments involving LSPRs deal with metal nanoparticles in inhomogeneous environments; a typical experimental procedure involves the deposition of a colloidal suspension of metal nanoparticles directly onto a substrate. This project explains how the LSPR of nanoparticles deposited onto planar substrates depends upon the polarization of incident radiation, and demonstrates evidence of resonance tuning by comparing the optical response in various dielectric environments