The nitrogen-doped ZnO nanoparticles (NPs) were successfully synthesized by using an RF thermal plasma process which would be a promising technique to the massive production. XRD measurements revealed that the formation of the hexagonal ZnO wurtzite structure. The synthesized nitrogen-doped ZnO NPs showed the nitrogen and carbon concentrations of 3.1-4.6 x 1020 cm(-3) and 1.1-1.2 x 10(20) cm(-3). The hole injection was confirmed by evaluating band edge electroluminescence from the LED structures using nitrogen doped ZnO NPs as a p-type layer. (C) 2016 Elsevier Ltd. All rights reserved.