We report a new method for preparing functionalized superparamagnetic Fe3O4@SiO2 possessing high saturation magnetization. Magnetite particles were prepared by simple co-precipitation method in aqueous medium, and then Fe3O4@SiO2 nanosphere was synthesized by using nano Fe3O4 as the core, TEOS as the silica source and polyethylene glycol (PEG 1000) as the surfactant. Then, the silica-coated Fe3O4 nanoparticles were covered with ligand complex of Cu(II). The functionalized magnetic core shell nanoparticles (MNPs) were investigated by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, dynamic light scattering and N-2 adsorption/desorption. Also, its Cu content was determined by inductively coupled plasma (ICP) analyzer. Then, the immobilized copper complex was used as an efficient catalyst for synthesis of 1- and 5-substituted 1H-tetrazoles from nitriles and amines in good to excellent yields. The results show that the supported catalyst could be conveniently recovered through the use of an external magnetic field and reused for subsequent reactions for at least 6 times with less deterioration in catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.