Gold/manganese oxide nanocomposites have been synthesized by seed-mediated epitaxial growth of manganese oxide on the surface of gold nanoparticles under hydrothermal condition. The architectures of the nanocomposites were varied by tuning the composition of the solvent employed in the reaction medium. The particles have been characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopic (XPS) techniques. Magnetic measurements show that there are no significant changes in the magnetic moment and coercivity of Mn3O4 nanoparticles upon conjugation with the gold nanoparticles. These bifunctional nanoconjugates have been found to serve as efficient electrocatalysts in comparison with their individual counterparts for the oxygen reduction reaction. The differences in the structure-function relationship of the Au-Mn3O4 composites arise from distinct surface properties of the catalysts. (C) 2013 Elsevier B.V. All rights reserved.