INTRAZEOLITE SEMICONDUCTORS - NA-23 MAS NMR, TL+ LUMINESCENCE QUENCHING, AND FAR-IR STUDIES OF ACID-BASE PRECURSOR CHEMISTRY IN ZEOLITE-Y

1991-11-01
MCMURRAY, L
HOLMES, AJ
KUPERMAN, A
OZIN, GA
Özkar, Saim
Proton-loaded zeolites, prepared from fully dehydrated zeolites and gaseous, anhydrous Bronsted acids, represent an important step in the synthesis of intrazeolite semiconductor quantum supralattices. Adsorption-induced Na-23 MAS NMR chemical shifts, far-IR Na+ and Tl+ translatory mode frequency shifts, and Tl+ luminescence quenching effects were chosen as probes of cation-anion interaction in these materials. Samples of zeolite Y with various loadings of Tl+ were prepared via aqueous ion-exchange techniques. The samples were characterized by powder X-ray diffraction and far-IR spectroscopy. Luminescence measurements revealed Tl+ excitation and emission bands in the UV spectral region. Exposure of thallium Tl(I) zeolite Y to anhydrous HBr quenched the luminescence intensity. The intensity quenching followed Stern-Volmer quenching kinetics. Preliminary luminescence lifetime studies of this system supported a static ion pair quenching model. Compelling additional evidence in favor of cation-anion pair formation comes from the observation of alpha-cage site-specific Na-23 MAS NMR chemical shifts in HBr/Na56Y compared to virgin Na56Y. The relevance of these observations for proton-loaded zeolite Y to the acid-base precursor chemistry involved in the synthesis of semiconductor nanostructures encapsulated in zeolite Y is critically discussed.
Citation Formats
L. MCMURRAY, A. HOLMES, A. KUPERMAN, G. OZIN, and S. Özkar, “INTRAZEOLITE SEMICONDUCTORS - NA-23 MAS NMR, TL+ LUMINESCENCE QUENCHING, AND FAR-IR STUDIES OF ACID-BASE PRECURSOR CHEMISTRY IN ZEOLITE-Y,” pp. 9448–9456, 1991, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/69957.