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

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 cm), and negligible agglomeration effect, is recommended for industrial applications.