Analysis of the contrast in icosahedral gold nanoparticles

When observing nanoparticles with the transmission electron microscope very often we observe a contrast that can be interpreted at first sight as coming from a some kind of a quasicrystalline array, i.e. with order but not periodicity. In the case of icosahedral particles their structure has been well studied by many years and their contrast explained in terms of twins. In this work we present the analysis of the quasi-periodic contrast observed in icosahedral gold nanoparticles along the five-fold direction, which resembles the contrasts of a quasicrystalline structures. A detailed analysis led us to demonstrate that it could correspond to a Moire´ -pattern artifact produced in an array of Mackay icosahedra.