Size-conti oiled PtRu nanoparticles embedded in TiO2 were prepared by simultaneous multi-gun sputtering from pure targets of Pt Ru and TiO2 The mean diameter of the PtRu nanoparticles as confirmed by their high-resolution transmission electron microscopic images can be varied from 1 8 to 3 7 nm by changing the RF power ratio of PtRu and TiO2 The transmission electron diffraction and grazing incidence wide angle X-ray scattering patterns of the PtRu nanoparticles embedded in TiO2 confirmed that the PtRu exists as a mixed alloy structure consisting of both fcc and hcp phases whereas the TiO2 matrix is present as an amorphous phase The size-controlled PtRu/TiO2 electrodes were found to exhibit unique electronic propel ties depending on their size which affected the potential of zero total charge and methanol oxidation reaction The mass activity of PtRu/TiO2 for methanol oxidation was determined by the interplay of the surface electronic factors at the metal-solution-interface and the value of the oxophilicity of the nanoparticles was increased by decreasing the particle size (C) 2010 Elsevier Ltd All rights reserved