  Optical properties of polymer capped gold nanoparticles of various sizes
(diameter 3-6 nm) have been studied. We present a new scheme to extract size
dependent variation of total dielectric function of gold nanoparticles from
measured UV-Vis absorption data. The new scheme can also be used, in principle,
for other related systems as well. We show how quantum effect, surface atomic
co - ordination and polymer - nanoparticle interface morphology leads to a
systematic variation in inter band part of the dielectric function of gold
nanoparticles, obtained from the analysis using our new scheme. Careful
analysis enables identification of the possible changes to the electronic band
structure in such nanoparticles.
