An in situ real-time x-ray diffraction study of phase segregation in Au—Pt nanoparticles

摘要

In situ real-time x-ray diffraction was used to study phase segregation and coarsening of Au–Pt nanoparticles supported on silica powder, and porous alumina membranes. Contrary to the expectations from the bulk phase diagram, silica supported Au–Pt nanoparticles have an alloyed structure that is preserved even after extensive annealing at temperatures as high at 700 °C. In stark contrast, alumina supported Au–Pt nanoparticles exhibit a rich phase behaviour that is sensitive to alloy composition and the details of the synthesis process. In particular, low-density as-prepared Au_(41)Pt_(59) nanoparticles exhibit the signature of incipient phase segregation that develops into full phase separation during annealing at high temperature.