Plasmonic responses of Cu–Ag bimetallic system: Influence of distinctiveness and arrangements

Highlights

• Cu–Ag system was studied by the combination of theory and experiment.

• Systematical study on the plasmonic properties of Cu–Ag system.

• Cu–Ag nano-corncob liked were firstly investigated here.

Abstract

In this article, the effect of the distinctiveness and arrangements on the plasmonic resonance of Cu–Ag system were studied by finite element method, and the effect of morphologies on the plasmonic properties of Cu@Ag core@shell NPs and Cu–Ag corn-cob liked NPs was investigated by experiment. For Cu@Ag core-shell structure, as the fixed thickness of Ag-shell at 10 nm, the dipole plasmon resonance gradually blue-shifts with increasing the radius of Cu core, and as the fixed radius of Cu-core at 50 nm, the feature peak shows a red-shift and broadening with increasing the thickness of Ag shell. For Cu–Ag corn-cob structure, the feature for different Ag coverage are similar to each other and most of the them follow the blue-shifted tendency with the increase the degree of Ag-coverage. Furthermore, as the regular-shaped structure increases (form trigonal to spherical), the plasmon resonance gradually blue shifts, and finally, we use two parameters to describe the different idealized Cu–Ag structure: separation, exterior contact, intersection and core@shell. The combined information from our simulation and experiment will give guidelines for choosing adequate particles when aiming at certain plasmonic properties.

Introduction

In the last few years, the various material systems focused on the combination of experiment and theoretical simulation in order to further understanding the evolution of the complexity and providing an essential description for physicochemical processes. Localized surface plasmon resonances (LSPRs) of bimetallic nanoparticles (NPs) have been well investigated due to their potential application in catalysis, nano-waveguides or sensor [[1], [2], [3], [4]].

Cu–Ag bimetallic NPs have attracted extensive interest in such fields as catalysis and printed electronics. Additionally, the plasmon resonance of Cu–Ag system can be significantly modified by nano-sized and nano-shaped alloys or intermetallics [5]. Zhang et al. [6]. reported LSPRs of Au-core@Ag-shell nanorods by changing the thickness of Ag shell, the finite-different-time-domain (FDTD) calculations showed that the band of Ag SPR became predominate as the thickness of the Ag shell increases, and this trend was evident from their experiments. Shang et al. [7] showed that the geometrical effects of Cu@Ag NPs on the Cu concentration in liquid solder during soldering by using a finite element method (FEM), and they found that Cu@Ag NPs doped flux enhanced the spreading of Sn solder at the constant volume by reducing central height and increasing effective width. Srihari et al. [8] investigated the mechanical behavior of lamellar Cu–Ag composites with different size via finite element simulation, the results showed that the stress-strain behavior had a small deviation at strains <3% but was in good accordance with experiment at strains above 3%.

Cu–Ag bimetallic systems have been well investigated in the previous works [[9], [10], [11], [12], [13]]. However, in most of these cases, the reports describe only one structure or interface under an implicit equilibrium condition [[14], [15], [16], [17]]. Here, we use galvanic exchange method, which produce two structural configurations: Cu@Ag core-shell and Cu–Ag nano-corn-cob (NC) liked (as tiny-sized Ag loaded onto the surface of Cu). We also investigate that the experimental results have been compared with the FEM simulation to ensure the Cu–Ag model's correctness and reliability. Furthermore, the evolution of the plasmonic and interband absorption as a function of various condition, including the shell thickness or core radius of Cu@Ag NPs, surface Ag-coverage of Cu–Ag NCs and multiple surface configurations of Cu@Ag NPs were studied. These include the formation of Cu–Ag NCs and the systematic simulation of Cu–Ag bimetallic nanoparticles, to the best of our knowledge, have not been reported before [[18], [19], [20]].