Plasmonics Research at the Plasmonics and Nanosensing Laboratory is currently focused on the development of plasmon-based sensors that exploit electrodynamically generated local surface plasmon resonances at the surface of noble metal nanoparticles. Our research activities has four primary branches: Nanofabrication of metal nanoparticles and nanostructured surfaces, theoretical modeling of local surface plasmon resonances and nanogap plasmon resonances, far-field optical characterization of local surface plasmon resonance, and applications of metal nanoparticle local surface plasmon resonances, such as surface enhanced Raman spectroscopy and dark-field scattering spectroscopy.

Surface enhanced Raman scattering

Raman spectroscopy is a powerful technique for chemical and biological analysis because it can provide a chemical fingerprint of probed molecules and the measurement is not affected by an aqueous environment, which is a limitation for infrared spectroscopy. The chemical fingerprint represents the vibrational structure of the probed molecules, which is measured from inelastically scattered photons from the polarizable bonds of the molecules in the probe region of the collection optics. However, inelastic light scattering is a weak process, e.g. a typical inelastic scattering process generates several orders of magnitude fewer photon fluxes than optical absorption processes used in infrared and fluorescence spectroscopies. Almost forty years ago, the surface enhanced Raman scattering (SERS) effect was discovered when the inelastic, or Stokes, scattered emission from molecules adsorbed in close proximity to nanogaps located between metal nanostructures was strongly enhanced due primarily to an electromagnetic enhancement effect. An enhancement factor of ten million drastically increases photon emission compared to a conventional Raman scattering process. SERS is emerging as a powerful and important analytical technique that can provide a chemical fingerprint of small quantities of surface adsorbed species, surface reactions and their intermediate species.