Plasmonic Core/Shell Nanorod Arrays:  Subattoliter Controlled Geometry and Tunable Optical Properties

Abstract

The fabrication and optical properties of a nanostructured system consisting of free-standing metallic nanorods surrounded by a dielectric nanoshell are reported. The adjustable core−shell geometry allows the resonant optical properties of the system to be tuned throughout the visible spectrum in the 500−900 nm range. The shell presents a tubular geometry of uniform thickness that can be varied from a fraction of a nanometer to a few tens of nanometers. This creates a well-defined subattoliter volume for the integration of a substance to be excited or probed. To exemplify such an application, the sensitivity of the nanostructured system to the variation of the shell's index of refraction is studied as a function of shell thickness and nanorod aspect ratio. The spectral sensitivity of the longitudinal resonance of the structure was found to be about 100 nm per refractive index unit with a figure of merit (sensitivity/line-width) of about 1.

Optical Transmission Properties and Electric Field Distribution of Interacting 2D Silver Nanorod Arrays

“…[27,28] MMP allows for 3D calculations both in the electromagnetic near-and far-field, and hence sheds light on both aspects. Note that previously reported theoretical calculations using the finite element and Maxwell-Garnett theory focused either on the near-field [29,30] or the far-field [26] aspects only. MMP offers a concise and scale independent converging theoretical approach for modeling the nanorod array structures presented here.…”

Optical and electrical properties of gold nanowires synthesized by electrochemical deposition

“…23 The SPR is very sensitive to the kind, size, shape, crystal structure, and dielectric constant of the metal and surrounding medium (here: polycarbonate). 8,21,[24][25][26][27] In the case of Fig. 4, as schematically illustrated by Fig.…”

Optics of Metallic Nanostructures

“…Both the spectral position of this collective plasmonic resonance and the associated electromagnetic field distribution in the nanorod array strongly depend on the inter-rod coupling strength; this behavior differs from the dipolar response of isolated nanorods from which they originate. These unique properties therefore demonstrate strong potential for the use of oriented metallic nanorod assemblies in the manipulation of light in nanoscale waveguide applications, sensing and nonlinearity enhancement applications, as well as in subwavelength imaging [38,120].…”

“…This behavior is illustrated in Figure 24(b) in the particular case of a varying rod diameter; however, it is also observed when the rod length is varied. The inter-rod distance can also be varied in order to tune the spectral position of the resonances in the array throughout the visible spectrum [38,120]. The spectral position of this resonance for a given nanorod aspect ratio is not, however, consistent with that of the localized surface plasmon resonances of an isolated rod or even for geometries involving dimers, for which the longitudinal resonance is expected to appear at a much longer wavelength [23,24,122,123].…”