S Farjami Shayesteh
Articles written in Pramana – Journal of Physics
Volume 85 Issue 6 December 2015 pp 1245-1255
In this work, we present the effect of refractive index of an embedding medium, core and shell having various sizes of metallic nanoshells on the surface plasmon resonance (SPR) properties in the spherical dielectric–metal core–shell nanoparticles based on the quasistatic approaches and Mie theory. For the metallic nanoshell with dimensions comparable to the wavelength of light, the quasistatic approximation shows good agreement with the Mie theory results. However, for large nanoparticles the quasistatic approximation is not appropriate and Mie theory illustrates SPR due to dipole and quadrupole in extinction cross-section. The typical cross-section calculations show two peaks that related to inner and outer surfaces. The dimensional dependence of optical constant in the Drude model leads to a decrease in plasma absorption in metal core–shell. By increasing the shell radius and therefore increasing the metal content the SPR at the outer surface shifts to higher energy and the weaker peak (at inner surface) shifts to lower energy. Also, depending on the metal shell materials SPR occurs in different energy regions and therefore can be tuned the SP frequency at higher energy by changing the shell materials. In addition, SPR frequency is sensitive to variation in refractive index of the environment of core-shell.
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