We have developed two techniques for preventing the oxidation of nickel nanoparticles upon their removal from the gas phase reactor into the air atmosphere. In the first method the nickel particles are collected in an organic liquid, where they have no contact with air, by using a trapping apparatus connected to the reactor. In the second approach the nickel particles are coated with an organic solid which prevents their contact with oxygen in the air. We confirmed that the surfaces of nickel nanoparticles coated with stearic acid at a thickness of 23 nm were not oxidized after exposure to air for 77 d.