Simulation of MEIS Spectra for Quantitative Understanding of Average Size, Composition, and Size Distribution of Pt–Rh Alloy Nanoparticles

We have newly developed a medium-energy ion scattering (MEIS) simulation program for the analysis of alloy nanoparticles. The program was applied to the composition and average particle size analysis of Pt–Rh/α-Al2O3 treated in oxidative and reductive atmospheres. It was found that the Pt concentration near the surface decreased after oxidative treatment at 800°C and returned to its original value after reductive treatment at the same temperature. It was shown that Pt particle average sizes less than 10 nm can be evaluated quantitatively. Also, this technique gives some insight into particle size distribution in the initial stage of particle sintering, which has been quite out of the reach of conventional analytical tools.