Ultrafine Ag-coated Cu (Cu@Ag) nanoparticles (NPs) less than 20 nm in diameter were prepared. After synthesizing ultrafine Cu NPs using a solvothermal method to serve as the core particles, Cu@Ag NPs were fabricated with different initial Ag precursor concentrations, resulting in different thicknesses, densities, and uniformities of Ag shells. The average thickness and density of the Ag shell increased with increasing initial Ag precursor concentration in a Cu:Ag atomic ratio from 6:1 to 1:1. However, excessive Ag precursor concentrations induced homogeneous nucleation and growth of surplus fine pure NPs. Ag dewetting behavior and Cu oxidation in the Cu-4@Agi(1) NPs were observed, they occurred during heating at 200 and 250 degrees C, respectively. The electrical resistivities of sintered Cu-4@Ag-1 films decreased with increasing temperature from 200 to 240 degrees C. The resistivity after washing the OA and sintering for 60 min at 240 degrees C in air was measured to be 4.96 x 10(-3) Omega cm. The film was sintered in nitrogen using the ink containing non-washed Cu-4@Ag-1 NPs indicated the lower resistivity of 2.70 x 10(-3) Omega cm owing to the non-oxidation atmosphere, although the chemically capped oleylamine in the core-shell NPs hindered the sintering behavior. (C) 2016 Elsevier B.V. All rights reserved.