Extended x-ray absorption fine-structure determinations of coordination numbers: Limitations

1980 ◽  
Vol 22 (8) ◽  
pp. 3551-3562 ◽  
Author(s):  
P. Eisenberger ◽  
B. Lengeler
Keyword(s):  
Fine Structure ◽  
X Ray ◽  
Coordination Numbers ◽  
Absorption Fine ◽  
Structure Determinations ◽  
X Ray Absorption

scholarly journals X-Ray Absorption Spectroscopy from H-Passivated Porous Si and Oxidized Si Nanocrystals

1994 ◽  
Vol 375 ◽  
Author(s):  
S. Schuppler ◽  
S. L. Friedman ◽  
M. A. Marcus ◽  
D. L. Adler ◽  
Y.-H. Xie ◽  
...  
Keyword(s):  
Fine Structure ◽  
Quantum Confinement ◽  
Ir Absorption ◽  
X Ray ◽  
Coordination Numbers ◽  
Absorption Fine ◽  
Visible Luminescence ◽  
Si Nanocrystals ◽  
Wide Range ◽  
X Ray Absorption

AbstractQuantum confinement in nanoscale Si structures is widely believed to be responsible for the visible luminescence observed from anodically etched porous silicon (por-Si), but little is known about the actual size or shape of these structures. Extended x-ray absorption fine structure data from a wide variety of por-Si samples show significantly reduced average Si coordination numbers due to the sizable contribution of surface-coordinated H. (The H/Si ratios, as large as 1.2, were independently confirmed by ir-absorption and α-recoil measurements.) The Si coordinations imply very large surface/volume ratios, enabling the average Si structures to be identified as crystalline particles (not wires) whose dimensions are typically <15 Å. Comparison of the size-dependent peak luminescence energies with those of oxidized Si nanocrystals, whose shapes are known, shows remarkable agreement. Furthermore, near-edge x-ray absorption fine structure measurements of the nanocrystals shows the outer oxide and interfacial suboxide layers to be constant over a wide range of nanocrystal sizes. The combination of these results effectively rules out surface species as being responsible for the observed visible luminescence in por-Si, and strongly supports quantum confinement as the dominant mechanism occurring in Si particles which are substantially smaller than previously reported or proposed.

Synthesis and characterization of 1,2,3,4 tetrahydroquinoline intercalated into MoS2 in search of cleaner fuels

2007 ◽  
Vol 22 (10) ◽  
pp. 2747-2757 ◽  
Author(s):  
Karina Castillo ◽  
Felicia Manciu ◽  
J.G. Parsons ◽  
Russell R. Chianelli
Keyword(s):  
Fine Structure ◽  
Infrared Spectroscopy ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers ◽  
Absorption Fine ◽  
Diffraction Patterns ◽  
X Ray Absorption

Two different morphologies of MoS2 (short and long sheets) were utilized to elucidate the intercalation mechanism of 1,2,3,4 tetrahydroquinoline (THQ). MoS2 (short sheets) and molybdenite (MB) (long sheets) were exfoliated and restacked in the presence of THQ. The x-ray diffraction patterns of both samples show a new reflection in the 001 plane, which implies a lowering of symmetry and corresponds to an expansion of the layers by approximately 12.3 Å. In the MoS2-THQ sample, 80% of the MoS2 was intercalated and 20% remained stacked. In the MB-THQ sample, 30% of MB was intercalated while 70% remained stacked. X-ray absorption structure (XAS) studies showed changes in atomic geometry and coordination. The x-ray absorption near-edge spectra showed shifts in the geometry of the intercalated MoS2 and MB sample compared to the unintercalated samples. Extended x-ray absorption fine structure studies showed lower coordination numbers compared to the untreated samples. Infrared spectroscopy characterization of these same samples suggests intercalation and partial dehydrogenation of the THQ.

Structure of magnetic thin films and nanostructures studied by extended X-ray absorption fine structure

2000 ◽  
Vol 454-456 ◽  
pp. 723-728 ◽  
Author(s):  
H. Magnan ◽  
P. Le Fèvre ◽  
A. Midoir ◽  
D. Chandesris ◽  
H. Jaffrès ◽  
...  
Keyword(s):  
Thin Films ◽  
Fine Structure ◽  
Magnetic Thin Films ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption
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