In this paper, the effect of ambient gas species on the characteristics of the produced nanoparticles in wire explosion process is reported. Cu wires with a diameter of 125 mu m and length of 6.1 cm were exploded in different ambiances of Ar and admixtures of Ar and N-2 at 500 mbar pressure. Immediate formation of arc plasma is observed for Ar ambiance. On the other hand, considerable delay in formation of arc plasma is observed for the admixtures of Ar and N-2. The arc plasma formation time is found to increase with increasing N-2 concentration in the admixture. Transmission electron microscope and X-ray diffraction were used to characterize the produced nanoparticles. Among the nanoparticles produced in different ambient gas species, the nanoparticles produced in Ar ambiance have higher particle size compared to admixtures of Ar and N-2. The particle size is found to reduce with increasing N-2 concentration in the ambiance. Difference in arc plasma formation time is probably the factor that gives rise to the difference in the particle sizes. (C) 2012 Elsevier B.V. All rights reserved.