Manipulating the confinement of electromagnetic field in size-specific gold nanoparticles dimers and trimers.

Sudip Kumar Pal,Sujit Kumar Ghosh,Hirak Chatterjee

doi:10.1039/c9ra07346a

Abstract

The intriguing light–matter interactions can be governed by controlling the particle size and shape, electromagnetic interactions and dielectric properties and local environment of the metal nanostructures. Amongst the different approaches that have been engendered to manipulate light at the nanoscale, the self-assembly of metallic nanostructures with controllable interparticle distances and angular orientations, which strongly impact their optical attributes, is one of the viable avenues to exploit their utility in a diverse range of niche applications. The simplest geometrical architectures that enable such modulations are dimers with changeable interparticle distances and trimers with an additional degree of angular orientation to correlate the plasmonic observables with the observed spectral characteristics. Wet chemical approaches have been adopted in this study for the synthesis of size-selective gold nanoparticles, and appropriate organic linkers have judiciously been employed to induce plasmonic interactions amongst the gold nanoparticles in close proximity to each other. The combination of experimental observations and electromagnetic simulations adopted to probe the plasmonic interactions revealed that the electrodynamic coupling effect was very sensitive to particle size, interparticle distances and angular orientations in these simple nanoassemblies. The capability to precisely manipulate the electric field at the junctions between these plasmon-coupled nanoparticles could pave the way for the application of these nanoassemblies in surface-enhanced spectroscopies and sensing applications.

Highlights

The collective properties of an ensemble of plasmonic nanostructures are signi cantly altered than the algebraic sum of all their individual properties, and this leads to the emergence of communal properties in the system.[1]
While tuning the band maximum to the desired wavelength is necessary for the ampli cation of the extinction cross-sections and optical elds in the preferred regions of the electromagnetic spectrum, the collective optical properties of the aggregates of metallic nanoparticles can be modulated by controlling the geometric arrangements, such as the interparticle distances and relative orientations, of the assembly.[2,3,4,5]
Gold nanoparticles were prepared by the Frens' citrate reduction procedure, and due to the adsorption of the negatively-charged citrate anions onto the gold surface, the particles carried a residual surface charge that stabilised them.[55]

Summary

Introduction

The collective properties of an ensemble of plasmonic nanostructures are signi cantly altered than the algebraic sum of all their individual properties, and this leads to the emergence of communal properties in the system.[1]. While tuning the band maximum to the desired wavelength is necessary for the ampli cation of the extinction cross-sections and optical elds in the preferred regions of the electromagnetic spectrum, the collective optical properties of the aggregates of metallic nanoparticles can be modulated by controlling the geometric arrangements, such as the interparticle distances and relative orientations, of the assembly.[2,3,4,5] exploring the fundamental nature of plasmon coupling by spatially controlling the interparticle distance and/or angle is of immense signi cance from both the theoretical and experimental perspectives

Objectives

Methods

Results

Conclusion