Catalytically active magnetic nanoparticles in the Cu-O system

Cu-O nanoparticles 11 to 215 nm in average size have been prepared by a levitation-jet process in a He flow with air additions and characterized by scanning electron microscopy, X-ray diffraction, BET measurements, vibrating-sample magnetometry, and optical spectroscopy in the UV, visible, and IR spectral regions. The nanoparticles were pseudospherical in shape and consisted predominantly of Cu 2 O and CuO. Magnetization measurements showed that the nanoparticles exhibited soft-magnetic ferromagnetic behavior (up to 0.06 A m 2 /kg in terms of maximum magnetization). The nanoparticles were also investigated in a high-temperature air flow reactor as a promising catalytic material for propane oxidation to CO 2 . In the case of two-phase nanoparticles, the total conversion temperature was found to decrease by 70 K as the nanoparticle size decreased from 110 to 51 nm, with a minimum temperature of 450 K for single-phase Cu 2 O particles 29 nm in size. The increase in catalytic activity seems to be related to the behavior of localized electron states on the CuO/Cu 2 O interface, which are responsible for the room-temperature ferromagnetism of the nanoparticles.