Abstract :
The stability and decay of silver clusters characterized by absorption bands 320 and 285 nm incorporated in mordenites
with different SiO2rAl2O3molar ratios were studied under ambient conditions. Significantly different rates of disappearance
of these two bands were the basis for assigning them to different silver species. Oxidation converts the clusters peaking
at 320 and 285 nm into other silver clusters characterized by absorption bands at 310 and 240 nm, respectively. The
oxidation of silver clusters peaking at 285 nm is significantly faster than that at 320 nm. The stability of both original
clusters decreases with acid site strength that, in its turn, depends on Si02rAl2O3molar ratio. The minimum lifetime of
clusters peaking at 320 and 285 nm equal to ca. 40 and 20 days, respectively, was observed for mordenite characterized by
the strongest acid sites. For mordenites possessing weaker acid sites, the lifetime of these clusters is found to be more than
50 months. The oxidation of silver clusters is reversible, and re-reduced silver clusters were revealed to possess the same
electron structure as original ones. q1999 Published by Elsevier Science B.V. All rights reserved.
