Synthesis of Cu@Ag core–shell nanoparticles for characterization of thermal stability and electric resistivity

Abstract

A two-step synthetic method has been utilized to prepare copper–silver (Cu@Ag) core–shell particles with thin Ag shell coated over a Cu core of initial diameter of 80 ± 5 nm. The formation of core–shell particles is characterized by transmetallation reaction on the surface of the Cu particles, where copper atoms function as the reducer for silver ions. The morphological characterization of Cu@Ag reveals that excess supply of Ag-based reagent produces nanostructures with enhanced core–shell diameter, increased shell thickness, and agglomeration of Ag in the bulk surface, whereas limited supply of Ag species results in nanoparticles with imperfect enveloping of Cu core—making them susceptible to oxidation. Experiments with TGA and DSC verify that thermal stability of core–shell nanoparticles is achieved for the specimen undisturbed by agglomeration and imperfect enveloping effects. Though the electrical resistivity of Cu@Ag nanoparticles increases in general with larger molar proportion of Cu, its increment rate is small for the limit [Cu]:[Ag]=4:1 and then higher beyond it. The sample with [Cu]:[Ag]=4:1, characterized by higher thermal stability, slowest oxidation speed, lower electric resistivity( 64.24 $\mu \Omega$ cm), and negligible agglomeration effect, is recommended for industrial applications.