The current work introduces a simple, convenient, and novel method for the synthesis of surface oxide free copper (Cu) nanoparticles. Electrical explosion of Cu wire in n-hexane containing oleic acid produced pure Cu nanoparticles smaller than 15 nm in diameter. The X-ray diffraction (XRD) patterns revealed that the oleic add-coated Cu nanoparticles maintained a highly pure Cu phase with no oxides for over three months after the synthesis. Analyses of Fourier transform infrared (FTIR) spectra indicated that the oleic acid was chemisorbed on the Cu surface via its oxygen atoms. In particular, an aggregation problem of the Cu nanoparticles with an increasing number of wire explosions was resolved by applying in-situ sonication process during the wire explosion. (C) 2014 Elsevier B.V. All rights reserved.