SIMULATION OF THE EXPERIMENTAL HRTEM CONTRAST OF ICOSAHEDRAL GOLD NANOPARTICLES OF DIFFERENT SIZES

Experimental contrasts of high-resolution transmission electron microscope (HRTEM) of icosahedral gold nanoparticles with 2.8, 4, 9 and 15 nm in diameter are simulated in this work, mainly those close to the five-fold axis. Experimentally it has been shown that the contrast shown by these particles around the five-fold axis consists of ten-spots rosettes and pentagonal motifs. Sometimes, a central defect consisting of a line crossing the particle along its diameter is also observed. In this work we use Mackay icosahedral particles together with image simulation to interpret the main features of their HRTEM contrast. We demonstrate that particle size and a slight tilt from the exact fold axis produces most of these features through moire effects but not all.