Size Dependent Optical Properties of Spherical ZnO@Cu and ZnO@Au Core/Shell Nanostructures
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Date
2022-02-19
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Addis Ababa University
Abstract
In this work, we studies the effect of size and thickness variation on the optical
properties of a system that consists of spherical ZnO@Cu and ZnO@Au core-shell
composite nanostructures embedded in a dielectric host matrix. The effective dielectric
function, refractive index, and absorbance of the composite nanostructures are
determined using the Maxwell-Garnett effective medium theory within the framework
of the electrostatic approximation. The numerical simulation using nanoinclusions of
radii 30 nm shows interesting behavior in the optical responses of the ensemble. In
particular, it is shown that for different values of volume fraction and filling factor
the refractive index and optical absorbance of the ensemble exhibited two sets
of resonance peaks; the first set located around 515 nm and 490 nm and the second
set found above 635 nm and 605 nm spectral regions for a system of ZnO@Cu
and ZnO@Au nanoparticles, respectively. These peaks are attributed to the surface
plasmon resonance of copper and gold at the core@metal and metal@host-matrix interface.
Moreover, when the Cu and Au shell thickness is increased, the observed
resonance peaks are enhanced; accompanied with slight red shifts for the first set
of peaks and a blue shifts for the second set of peaks. In brief, it is seen that the
optical properties of spherical ZnO@Cu and ZnO@Au core-shell nanoinclusions embedded
in vacuum can be tuned by varying the shell thickness, filling factor, and/or
volume fraction of the nanocomposites. The results obtained may be used in various
applications such as sensors and nano-optoelectronics devices in optimizing material
parameters to the desired values.
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Keywords
Size Dependent, Optical Properties, Spherical ZnO@Cu and ZnO@Au Core, Shell Nanostructures