Controlling the Plasmonic Properties of Supported 2D Arrays of Gold Nanocages
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Controlling the Plasmonic Properties of Supported 2D Arrays of Gold Nanocages Alyssa Staff1, Sandrine Lepinay1,2, Jacques Albert2, Antaoli Ianoul1 1
Chemistry, Carleton University, Ottawa, ON, Canada.
2
Electronics, Carleton University, Ottawa, ON, Canada.
ABSTRACT The enhancement of the plasmonic signatures, indicated by the shifting of the localized surface plasmon resonances, of three-dimensional, hollow, gold nanocages with respect to substrate nature and cage density is reported. The effect of substrate nature was investigated using absorbance, reflection, and transmission by ultraviolet-visible and near-infrared spectrophotometry. The gold nanocages were deposited on substrates as monolayers primarily by Langmuir-Blodgett technique. The density of the deposited monolayers and the nature of the surface of the substrates were determined using AFM and SEM/TEM imaging. The position of the LSPR signatures, primarily the dipolar plasmonic resonances, with respect to changing environment and nanostructure characteristics determined the tuneability of the plasmonic enhancements.
INTRODUCTION Noble metal nanostructures are of particular interest for a wide range of applications. The unique plasmonic properties of noble metal nanostructures, based on the variance of the localized surface plasmon resonance (LSPR) signatures with varying size, shape, and arrangement, allow for use in sensor, catalysis, imaging, and surface-enhanced Raman scattering (SERS) applications [1]. The structure, size, and density of the assembled nanostructures, as well as the nature of the environment surrounding them greatly affects the plasmonic interactions of the noble metal nanostructures, most clearly seen by a shifting of the dipolar plasmon peak when analyzed by ultraviolet-visible (UV-vis) or near-infrared (NIR) spectrophotometry. Investigations of silver nanostructures, especially nanocubes or nanospheres, have been extensively covered [2,3,4], as well as many other noble metals or metal alloys of various shapes and conformations. Thus far, gold nanocages are of key consideration for theranostic applications [5]. However, the ability to control the plasmonic signature of gold nanocages by varying the substrate nature as well as the size of the nanocages and the density of the deposited layer allows for further potential applications in optics, including sensors and fibre optic applications. In this investigation, the dipolar plasmon intereactions of the gold nanocage assemblies were monitored by ultraviolet-visible and near-infrared spectrophotometry. The gold nanocages were capped with polyvinylpyrrolidone (PVP) through the routine synthesis of gold nanocages. Select samples were further functionalized with hexadecanethiol (HDT) to improve the hydrophobicity of the nanocages before deposition by Langmuir-Blodgett technique. The two-dimensional assemblies under investigation were prepared by Langmuir-Blodgett technique, followed by analysis of the densities of the assemblies, as well as the structure and size of the gold nanocages
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