1 research outputs found
Tuning of Spectral and Angular Distribution of Scattering from Single Gold Nanoparticles by Subwavelength Interference Layers
Localized surface plasmon resonance
(LSPR) as the resonant oscillation
of conduction electrons in metal nanostructures upon light irradiation
is widely used for sensing as well as nanoscale manipulation. The
spectral resonance band position can be controlled mainly by nanoparticle
composition, size, and geometry and is slightly influenced by the
local refractive index of the near-field environment. Here we introduce
another approach for tuning, based on interference modulation of the
light scattered by the nanostructure. Thereby, the incoming electric
field is wavelength-dependent modulated in strength and direction
by interference due to a subwavelength spacer layer between nanoparticle
and a gold film. Hence, the wavelength of the scattering maximum is
tuned with respect to the original nanoparticle LSPR. The scattering
wavelength can be adjusted by a metallic mirror layer located 100–200
nm away from the nanoparticle, in contrast to near-field gap mode
techniques that work at distances up to 50 nm in the nanoparticle
environment. Thereby we demonstrate, for the first time at the single
nanoparticle level, that dependent on the interference spacer layer
thickness, different distributions of the scattered signal can be
observed, such as bell-shaped or doughnut-shaped point spread functions
(PSF). The tuning effect by interference is furthermore applied to
anisotropic particles (dimers), which exhibit more than one resonance
peak, and to particles which are moved from air into the polymeric
spacer layer to study the influence of the distance to the gold film
in combination with a change of the surrounding refractive index