Core-shell Ni-Fe@ferrite nanoparticles with an average diameter of 14 nm and shell thickness of 3 run were synthesized through a redox-transmetalation process. The alloy core and spinel oxide shell were verified by X-ray photoelectron spectroscopy. X-ray diffraction, and transmission electron microscopy. The hydrophobic oleylamine molecules on the Surface were replaced by hydrophilic meso-2,3-Dimercaptosuccinic acid to make the nanoparticles to be water-soluble. X-ray diffraction study of the as-prepared core-shell nanoparticles indicates that they remained face centered cubic alloy core and spinel shell form in air. Magnetic measurements indicate that the core-shell nanoparticles exhibit superparamagnetic and exchange bias characteristics at 300 K and 5 K. respectively. (C) 2008 Elsevier Ltd. All rights reserved.