Size and composition for 1-5 nm Ø PtRu alloy nano-particles from Cu Kα X-ray patterns

X-ray diffraction (XRD) studies on PtRu clusters with a range of diameters are reported. It is shown that for clusters smaller than 5 nm, Scherrer's formula is not adequate for the simultaneous interpretation of the size and composition of the clusters from their diffraction patterns. The theoretically and computationally developed approach is based on Debye's exact formula for scattering by randomly oriented molecules applied here to atomic models for the clusters. The novel approach interprets plausibly the same XRD patterns that Scherrer's formula could not. Pt1−x-Rux nano-particles are synthesized with a modified polyol method and their size and composition are found from the interpretation of Cu Kα diffraction patterns using Debye's formula. The obtained results are consistent with both the chemical information and with previously reported results from other methods of investigation. Experimental profiles are shown to be affected here by non-uniformity of particle sizes.