Comparison of the O Kα x-ray emission bands in micro- and mesoporous silica materials and in α-quartz
- chair: Khyzhun, O. / Strunskus, T. / Wöll, Ch. / Gies, H. / Staemmler, V. (2008)
J. Chem. Phys. 129 (2008), 8, 084711
- Date: 2008
Khyzhun, O. / Strunskus, T. / Wöll, Ch. / Gies, H. / Staemmler, V. (2008): "Comparison of the O Kα x-ray emission bands in micro- and mesoporous silica materials and in α-quartz". In: J. Chem. Phys. 129 (2008), 8, 084711
X-ray emission spectroscopy (XES) at the O Kα threshold has been used to investigate the electronic structure of a microporous pure calcined zeolite with the crystal structure of the MFI-type framework (silicalite), a deboronated MFI zeolite (DB-MFI), a pure mesoporous cubic MCM-48 material, a MCM-48 loaded with copper and zinc oxide nanoparticles (Cu/ZnO-MCM-48), and a crystalline layered silicic acid H-RUB-18.
For comparison, the XES O Kα spectrum of pure α-quartz has also been recorded. In the nonresonant energy regime the XES O Kα spectra for all these compounds look very similar indicating that the electronic structure of the micro- and mesoporous silica materials is very similar to that of quartz.
In the resonant regime, however, the spectra exhibit significant differences. In all the materials under study, the resonant XES O Kα spectra recorded at photon energies close to the positions of the O K edges show Raman-type inelastic peaks with an energy loss of 11 eV, originating from electronic excitations within these insulating materials. The prominent features in the XES O Kα spectra of α-quartz and H-RUB-18 are analyzed by means of quantum chemical ab initio cluster calculations.