Optical and X-ray diffraction study of AgI clusters incorporated into zeolite LTA

Abstract

AgI clusters are incorporated into cages of zeolite LTA. The loading density of AgI is systematically changed from 0.2 to 4.0 molecules per α-cage. The electronic states and structures of the AgI clusters, with regard to their optical absorption spectra and X-ray powder diffraction patterns, are discussed. At a dilute loading, a notable absorption band, assigned to the AgI molecule, appears at 5.6 eV. With increasing loading densities, new absorption bands appear at 4.7, 4.2, 4.1, and 3.6 eV. These bands show that (AgI) n (n = 2 − 4) clusters with larger sizes are formed with increasing loading density. These clusters seem to exist in α-cages. The X-ray diffraction (XRD) patterns exhibit superlattice reflections at high loading densities. The appearance of the extra reflections has a correlation with the formation of (AgI)3 and (AgI)4 clusters. The Ag and I atoms of the cluster seem to be situated at the position of tetrahedral-based symmetry in the α-cage.