Pulsed EPR for studying silver clusters

• Published in: Radiation physics and chemistry (1993) Vol. 47; no. 1; pp. 75 - 81
• Main Authors: Michalik, J., Wasowicz, T., Sadlo, J., Reijerse, E.J., Kevan, L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 1996; Elsevier
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Radiation chemistry; Metal cluster; Transition metal Ions; Ionic cluster; EPR spectrometry; Radiolysis; Zeolite; Silver Ions; Experimental study; Molecular sieve
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/0969-806X(95)00085-C

The cationic silver clusters of different nuclearity have been produced by radiolysis of zeolite A and SAPO molecular sieves containing Ag + as exchangeable cations. The pulsed EPR spectroscopy has been applied for studying the local environment of silver cluster in order to understand the mechanism of cluster formation and stabilization. The electron spin echo modulation (ESEM) results on Ag 6 n+ cluster in dehydration zeolite A indicate that the hexameric silver is stabilized only in sodalite cages which are surrounded by α-cages containing no water molecules. Trimeric silver clusters formed in hydrated A zeolites strongly interact with water, thus the paramagnetic center can be considered as a cluster-water adduct. In SAPO-molecular sieves, silver clusters are formed only in the presence of adsorbed alcohol molecules. From ESEM it is determined that Ag 4 n+ in SAPO-42 is stabilized in α-cages, where it is directly coordinated by two methanol molecules. Dimeric silver, Ag 2 + in SAPO-5 and SAPO-11 is located in 6-ring channels and interacts with three CH 3OH molecules, each in different 10-ring or 12-ring channels. The differences of Ag 2 + stability in SAPO-5 and SAPO-11 are also discussed.