The absolute magnitude of the optical cross-section does
not provide a reliable measure for the optical properties of an
ensemble of nanoparticles employed in real-life biomedical
applications because smaller particles can be loaded in a given
volume in greater numbers as compared to particles of a larger
size. Therefore, a more meaningful property for comparison
across a range of sizes is the size-normalized cross-section or
volumetric coefficient C/V where V is the particle volume.36
The volumetric coefficients expressed in units of µm-1 give us
the per micron absorption coefficient µa and scattering coefficient
µs of the nanoparticles. Values of µa and µs have been
tabulated (Table 1) for the different nanoparticle configurations.
It can be seen from Table 1 that the nanoshell configuration
used by Hirsch et a