Surfaces enhanced with film-coupled silver nanopolyhedrons for optical transmittance

Abstract

A metallic nanoparticle positioned over a metal film offers enormous advantages as a highly controllable system relevant for probing field-enhancement and designing controlled-emissivity surfaces for thermophotovoltaic devices. The film-coupled silver (Ag) nanoparticle is of particular interest due to the formation of waveguide cavity-like modes between the NPs and film. The ability of individual nanopolyhedron (NP) patch antennas, consisting of Ag NP separated from gold (Au) film by a dielectric spacer layer spacer, to act as efficient and tunable absorption elements is demonstrated. The size and shape of the gap between the nanoparticle and film can be precisely controlled using relatively simple, bottom-up fabrication approaches. We show that the film-coupled NPs provide a transmission spectrum that can be tailored by varying the geometry (the size of the NPs and/or the thickness of the spacer). We perform both experimental spectroscopy and numerical simulations of individual NPs positioned over Au film, finding excellent agreement between experiment and simulation. The waveguide mode description serves as a starting point to explain the optical properties observed.

Layered Assembly of Silver Nanocubes/Polyelectrolyte/Gold Film as an Efficient Substrate for Surface-Enhanced Raman Scattering

“…Ag nanocubes were assembled on the PE layer surface without using any additional process to control their spatial arrangement. − An accurate distance between as-deposited Ag nanocubes and underlying Au films was fabricated by a layer-by-layer deposition of PE layers. Remarkable enhancement in SERS signals was experimentally achieved through the rationally designed SERS substrate and probe molecules (rhodamine 6G and crystal violet) due to the coupling of multiple LSP and SPP resonances. − A high degree of morphological, size, and distance control facilitates a better understanding of the enhancement mechanisms in SERS and search for optimal conditions. The electromagnetic enhancement was further investigated by the finite-difference time-domain simulations.…”