Demonstrated herein is a simple method for the induction of J-aggregate formation in a colloidal solution of gold nanoparticles through the use of pseudoisocyanine (PIC) and polyvinyl sulfate. The plasmon-exciton coupling of the nanoparticle J-aggregate complex results in a split lineshape absorption spectrum with upper and lower plexcitonic branches. The use of nanoparticles with various plasmon resonances causes a shift in the upper plexcitonic band while the lower plexcitonic band remains at the same wavelength.
Analytical expressions for the plasmon resonance frequencies of prolate and oblate spheroids and their dependence on ellipticity are derived, and approximate bounds on these frequencies established. These formulas may be useful in tuning the plasmon resonance within certain limits. With increasing aspect ratio, the prolate spheroid resonance is red shifted relative to a sphere with no lower limit under the assumptions of a Drude dispersion model. On the other hand, the oblate resonances are blue shifted as the spheroid becomes increasingly flat, but up to a limit.
While phase variation due to ultrasonic modulation of coherent light has been extensively studied in acousto-optical
imaging, fewer groups have studied non-phase mechanisms of ultrasonic modulation, which may be important in
exploring ultrasonic modulation of incoherent light for imaging. We have developed a versatile Monte Carlo based
method that can model not only phase variation due to refractive index changes and scatterer displacement, but also
amplitude and exit location variations due to the changes in optical properties and refractive index under ultrasonic
modulation, in which the exit location variation has not been modeled previously to our knowledge. Our results show
that the modulation depth due to the exit location variation is one to two orders of magnitude higher than that due to
amplitude variation, but two to three orders of magnitude lower than that due to phase variation for monochromatic light.
Furthermore, it is found that the modulation depth in reflectance due to the exit location variation is larger than that in
transmittance for small source-detector separations.
Plasmon resonances are computed for prolate spheroidal nanoshells. Both longitudinal and transverse resonances are
investigated as a function of aspect ratio. Formulas for the surface charge density on the outside and inside shell surfaces