| Autor: |
Enderle, B. A., Labouriau, A., Ott, K. C., Gates, B. C. |
| Zdroj: |
Nano Letters; November 2002, Vol. 2 Issue: 11 p1269-1271, 3p |
| Abstrakt: |
Platinum nanoclusters and mononuclear platinum complexes in zeolite KLTL were characterized by 129Xe NMR spectroscopy at temperatures from 100 to 296 K; the chemical shift increased with decreasing temperature, consistent with xenon's increasingly strong interactions with the platinum. The room-temperature chemical shift of xenon characterizing the zeolite containing the platinum clusters was 148.7 ppm, but that of the zeolite containing the platinum complexes was only 98.3 ppm, slightly greater than the value representing the bare zeolite, 95.4 ppm. These data, combined with literature data characterizing similar samples, indicate that the 129Xe chemical shift increases with the size of the metal species in the zeolite, up to the point at which entry of the Xe atom into the space containing the metal is constrained by the geometry of the metal species and the zeolite cage; in the limiting case, the chemical shift is substantially reduced because a Xe atom interacts with an encaged nanocluster only through a cage window. |
| Databáze: |
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