The designer optical resonances of metal nanoshells

Abstract

Metal nanoshells consist of a dielectric or semiconducting core coated with a metallic layer of nanometer scale dimensions. Gold nanoshells with silica cores were fabricated by first attaching gold colloid to the surface of the silica spheres and then developing the attached gold into a complete shell. This technique formed continuous gold shells approximately 10 nm thick. By varying the relative dimensions of the core and the shell, the optical resonance of these nanoparticles can be varied over hundreds of nanometers in wavelength, extending from the visible into the infrared region of the spectrum. For a gold nanoshell with a 340 nm core, at shell thicknesses exceeding 15 nm, additional peaks appeared in the UV-visible spectrum. Calculations based on a vector basis solution to Maxwell's equations matched both the position and relative magnitude of these secondary peaks