Effect of gold plasmonic shell on nonlinear optical characteristics and structure of iron based nanoparticles

Growth of the gold plasmonic shells on the iron based nanoparticles could enhance the linear and nonlinear optical properties of the iron based nanostructures, due to the coupling of the localized surface plasmon (LSP) modes on the inner and outer surface of each Au-shell. We have fabricated the iron based nanoparticles via arc discharge technique in water that is a cost effective and simple single-step synthesis route. Then, the gold shells have been grown chemically on the iron-based cores. The structural properties of core-shell nanoparticles have been investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD measurements have exposed the existence of three phases of iron (oxides) including pure iron, magnetite, and wustite within the cores. TEM images have shown that the average core-shell size with the size distribution in the range of 10 to 80 is 25 +/- 10 nm. The UV-visible optical and closed-aperture Z-scan measurements have verified the coupling LSP modes coupling between the inner and outer surfaces of the Au-shells covering the iron based cores. The experimentally obtained UV-visible spectra have qualitatively verified the numerical results obtained using the finite element simulation method.