Size Dependent Optical Properties of Spherical ZnO@Cu and ZnO@Au Core/Shell Nanostructures

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Addis Ababa University


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.



Size Dependent, Optical Properties, Spherical ZnO@Cu and ZnO@Au Core, Shell Nanostructures