A process and apparatus prepares and collects metal nanoparticles by forming a vapor of aluminum or copper metal that is solid at room temperature, the vapor of the metal being provided in an inert gaseous carrying medium. At least some of the metal is solidified within the gaseous stream. The gaseous stream and metal material is moved in a gaseous carrying environment into or through a dry mechanical pumping system. While the particles are within the dry mechanical pumping system or after the nanoparticles have moved through the dry pumping system, the vaporized metal material and nanoparticles are contacted with an inert liquid collecting medium.