  We systematically investigated and quantified how gold (Au) metal
nanoparticles (NPs) optical spectra change upon introduction into biological
tissue phantoms environment, in which the AuNPs can agglomerate. Quantitative
knowledge of how the AuNPs spectra and plasmon resonance wavelength change
inside a phantom environment can provide many in-vitro and in-vivo plasmonic
NPs-mediated applications. Because the plasmonic properties of metal NPs are
dependent on their size, morphology, concentration and local environment,
tuning the incident photon wavelength may increase the AuNPs plasmonic
properties, on which applications such as plasmonic photothermal therapy and
photonic gene circuits are based. Quantitatively analyzing optical absorption
and scattering data, we were able to observe changes in the resonance peak
positions and breadths, which are related to the distribution of the spherical
AuNPs within the chitosan phantoms as a function of the particles size and
concentration.
