Determination of Single- and Multi-Component Nanoparticle Sizes by X-ray Absorption Spectroscopy

An approach to estimate the size of quasi-spherical nanoparticle systems composed of atoms crystalizing in face centered cubic lattice using the data from X-ray absorption spectroscopy is introduced. For monoatomic clusters, the number of atomic layers surrounding the X-ray-absorbing atom m is evaluated from the coordination numbers, and the size of the particle calculated as the diameter of a sphere having the same volume as the cuboctahedron with the edge length of m atoms, assuming complete atomic layer structure. The particle size estimated by the approach agrees well with the experimental data obtained by other methods for clusters up to 5 nm. For bimetallic systems, coordination numbers of one component to the other in various inner-structured mixtures were derived. The interatomic distance of the solid solution is approximated to the weighted mean of the two constituents' lattice parameters and these mean values were used to estimate the particle size. The method could be applied to core-shell structures of bimetallic systems, as well as to three-component particles using reasonable approximations, and the particle sizes are estimated in a similar manner. The diameters of polyatomic clusters estimated by this approach were shown to closely follow the experimental data obtained by independent techniques.