Tracking iridium atoms with electron microscopy: first steps of metal nanocluster formation in one-dimensional zeolite channels.

Using aberration-corrected scanning transmission electron microscopy (STEM), we imaged iridium atoms in isolated iridium complexes in the one-dimensional nonintersecting 14-ring channels of zeolite SSZ-53. STEM allows tracking of the movement of atoms in the channels, demonstrating the interaction of iridium with the zeolite framework (channel confinement) and providing a direct visualization of the initial steps of metal nanocluster formation. The results demonstrate how STEM can be used to help design improved catalysts by identifying the catalytic sites and observing how they change in reactive atmospheres.