A Study on the Plasmonic Properties of Silver Core Gold Shell Nanoparticles: Optical Assessment of the Particle Structure

Abstract

This paper reports a qualitative comparison between the optical properties of a set of silver core, gold shell nanoparticles with varying composition and structure to those calculated using the Mie solution. To achieve this, silver nanoparticles were synthesized in aqueous phase from a silver hydroxide precursor with sodium acrylate as dual reducing-capping agent. The particles were then coated with a layer of gold with controllable thickness through a reduction-deposition process. The resulting nanoparticles reveal well defined optical properties that make them suitable for comparison to ideal calculated results using the Mie solution. The discussion focuses on the correlation between the synthesized core shell nanoparticles with varying Au shell thickness and the Mie solution results in terms of the optical properties. The results give insight in how to design and synthesize silver core, gold shell nanoparticles with controllable optical properties (e.g., SPR band in terms of intensity and position), and has implications in creating nanoparticle materials to be used as biological probes and sensing elements.

Structure of Gold–Silver Nanoparticles

“…This is attributable to an increase in gold character; while redshift of the LSPR can also be caused by an increase in particle size, since the TEM data shows a ca. 5 nm decrease in the diameter of the Au@Ag@Au _More Au sample compared to the Au@Ag@Au _Less Au sample (see Figure ), the observed redshift must be a result of the difference in composition. , The LSPR peak for these systems does not lie between the LSPR peaks of monometallic silver and gold on the above plot (as would be expected with silver, gold, and bimetallic nanoparticles of comparable size) as the large size of the silver nanoparticles (diameter 77 nm) substantially redshifts the silver LSPR peak. To confirm the stability of the colloids, UV–vis spectra were recorded again, one month after synthesis; these spectra are shown in Figure S5 (Supporting Information).…”

“…Multishell bimetallic nanostructures, such as Au@Ag@Au (core@shell@shell), are desired for their optical properties. , Here, the Ag middle layer displays optimal localized surface plasmon resonance (LSPR) properties with the outer Au shell providing increased stability in biological environments . In addition, the Au core stabilizes the Ag middle layer against the galvanic replacement reaction; the galvanic replacement would take place if pure Ag nanoparticles were used as cores and Au were to be deposited directly onto them .…”

A Review on the Development of Gold and Silver Nanoparticles-Based Biosensor as a Detection Strategy of Emerging and Pathogenic RNA Virus

“…The optical and electrochemical properties of Ag-Au bimetallic nanoparticles have been widely studied due to the beneficial coupling of both metals [ 60 ]. The Ag core-Au shell nanoparticles (Ag@AuNPs) have demonstrated the desired optical properties calculated using the Mie solution [ 61 ]. In the study, the optical properties of a set of Ag@AuNPs were dependent on the amount of Au added in the coating procedure i.e., 5%, 15%, and 25% Au atomic feeding ratios.…”

Analysis of surface plasmon resonance in the composite core(Au)/interlayer/shell(Ag) nanoparticles

“…Xu et al [2] have discussed the SPR properties of separate core/shell nanostructures, whose core and shell are separated by vacuum cavity, and found a cavity resonance enhancement effect and new absorption bands due to more interfaces and the consequent plasmon coupling. Mott et al [21] synthesized nanoparticles similar to Ag/Cavity/Au core/shell structure and found the amount of gold added in the coating procedure has a large impact on the structure of the nanoparticles and the resulting optical properties. The cavity provides the separate core/shell system with the opportunity to cooperate with the other functional materials, which may endow the system with remarkable properties.…”