EXAFS study of silver clusters in zeolites

The EXAFS measurements on Ag K-edge have been carried out at 298 K on compl etely Ag+-exchanged zeolite 4A(Ag-4A) with different dehydration treatments . In the Fourier transforms F(r) of EXAFS spectra there: appear two distinc t peaks. By two-shell curve-fitting analysis it is found that the Ag ion-fr amework oxygen and Ag-Ag contact distances decrease as the color of Ag-4A c hanges from white (fully hydrated) to brown (fully dehydrated). The coordin ation number of Ag atom(Ag-0) around a central Ag-0, 9.0 +/- 0.5, for brown Ag-4A suggests a formation of a silver cluster with Ag-0-Ag-0 contact dist ance of 2.81 Angstrom.