  We use hexagonal mesophases made of oil-swollen surfactant-stabilized tubes
arranged on a triangular lattice in water and doped with metallic salts as
templates for the radiolytic synthesis of nanostructures. The nanostructures
formed in this type of soft matrix are bimetallic palladium-platinum porous
nanoballs composed of 3D-connected nanowires, of typical thickness 2.5 nm,
forming hexagonal cells. We demonstrate using electron microscopy and
small-angle X-ray scattering that the pore size of the nanoballs is directly
determined by the diameter of the oil tube of the doped mesophases, which we
have varied in a controlled fashion from 10 to 55 nm. Bimetallic nanostructures
comprising various proportions of palladium and platinum can be synthesized.
Their alloy structure was evidenced by X-ray photoelectron spectroscopy,
energy-dispersive X-ray spectroscopy, and high-angular dark field scanning
transmission electron microscopy experiments. Our templating approach allows
therefore the synthesis of bimetallic nanoballs of tunable porosity and
composition.
