This paper reports the deposition of ZnO nanoparticles with controlled sizes and different particle densities and their structural, composition and optical properties. They were deposited by means of a DC magnetron based vacuum nanoparticle source onto different substrates (GaAs, Si and Ti/SiO2/Si). We believe that this is the first time that such nanoparticles have been produced using this unique technique. Zinc was used as sputtering target to produce zinc nanoparticles which were oxidized in-line using molecular oxygen. The structural properties and chemistry of the ZnO were studied by transmission electron microscopy. An average particle size of 6(+/- 2) nm was produced with uniform size distribution. The particle density was controlled using a quartz crystal monitor. Surface densities of 2.3x10(11)/cm(2), 1.1x10(13)/cm(2) and 3.9x10(13)/cm(2) were measured for three different deposition runs. The ZnO particles were found to be single crystalline having hexagonal structure. Photoluminescence measurements of all samples were performed at room temperature using a cw He-Cd laser at 325nm excitation. The UV emission around 375nm at room temperature is due to excitonic recombination and the broad emission centered at 520nm may be attributed to intrinsic point defects such as oxygen interstitials. (C) 2010 Elsevier B.V. All rights reserved.