Light scattering from gold nanoshells
Oldenburg, Steven Jay
Halas, Naomi J.
Doctor of Philosophy
Gold nanoshells consist of a dielectric core surrounded by an ultra thin shell of gold. By adjusting the ratio between the radius of the core and the thickness of the shell the plasmon resonance of the nanoshell can be placed at any wavelength from 500 nm--2500 nm. As the dimensions of the nanoshell approaches the wavelength of incident light, the extinction spectrum becomes a superposition of the multipole plasmon resonances. Adjustments to the core:shell ratio centered either the dipole or quadrupole mode at 830 mn. The distinct far field scattering distribution from each multipolar mode agreed well with calculations. The plasmon resonance condition and the local surface roughness give rise to intense local fields at the surface of the particle. When mercaptoaniline was absorbed onto nanoshells that had a plasmon resonance in the near IR, enhancements of the Raman signal by more than five orders of magnitude were recorded.
Inorganic chemistry; Optics