ABSTRACT
The intense research in the field of nanoparticles by chemists, physicists, and material scientists has
gained tremendous momentum because of the search for new materials of dimension less than 100 nm
to further miniaturize electronic devices [1-6]. Although nanomaterials are fascinating, the fundamental
question of how molecular electronic properties evolve with increasing size in this intermediate region
between molecular and solid-state physics becomes intriguing. The collective electronic, optical, and
magnetic properties of organized assemblies of size-selective monodispersed nanocrystals are increas-
ingly becoming the subjects of investigation [7]. Control over the spatial arrangement of these building
blocks often leads to new materials with chemical, mechanical, optical, or electronic properties distinctly
different from their bulk component [8]. A variety of metal [9], metal oxide [10], semiconductor [11]
nanoparticles and nanorods, and carbon nanotubes [12] have been synthesized and proposed as
potential entities for optical and electronic devices [12-13]. Recently, metallic clusters with fractal
structures have sparked much interest because of the localization of dynamical excitations in these
fractal objects, which plays important roles in many physical processes [14]. In particular, the localiza-
tion of resonant dipolar eigenmodes can lead to a dramatic enhancement of many optical effects in
fractals [14]. Their origin is attributed to the collective oscillation of the free conduction electrons
induced by an interacting electromagnetic field. These resonances are also denoted as surface plasmons.
Mie [15] was the first to explain this phenomenon by applying classical electrodynamics to spherical
particles and solved Maxwell’s equations for the appropriate boundary conditions. The explanation
looks apparently much simpler for monometallics, but becomes more complicated when one moves to a
system containing two metals with definite interaction in the closest proximity.
