  The optical and morphological properties of hollow gold nanoparticles (HGNPs)
can be finely modified by employing Poly-L-Lysine hydrobromide (PLL), an homo
poly aminoacid of the L-lysine, used as reducer and stabilizer. We investigate
locally the plasmonic response of these nanostructures by electron energy loss
spectroscopy (EELS). The plasmon excitations are interpreted by discrete
dipolar approximation (DDA) simulations. We demonstrate that this controlled
top-down morphological modification a fine tuning of the optical response is
possible. Unlike the traditional lithographic techniques, this has been
achieved in a controlled manner using wet chemistry, enabling the potential use
of these nanostructures for a broad range of plasmonic applications, including
biomedicine, catalysis and quantum communications.
