Title of article :
The interactions of thiophene with polycrystalline UO2
Author/Authors :
Hedhili، نويسنده , , M.N. and Yakshinskiy، نويسنده , , B.V. and Schlereth، نويسنده , , T.W. and Gouder، نويسنده , , T. and Madey، نويسنده , , T.E.، نويسنده ,
Issue Information :
هفته نامه با شماره پیاپی سال 2005
Pages :
17
From page :
17
To page :
33
Abstract :
We have studied the adsorption and desorption of thiophene on polycrystalline UO2 as function of coverage, over the temperature range 100–640 K, using X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and electron stimulated desorption (ESD). Thiophene is found to adsorb molecularly on stoichiometric UO2. C 1s and S 2p XPS spectra are measured at different thiophene exposures and at different temperatures; they show no evidence for the presence of dissociation fragments, confirming that thiophene adsorbs and desorbs molecularly on a polycrystalline stoichiometric UO2 surface. The variation of the S 2p and C 1s intensity as function of exposure, together with ESD measurements of O+ as function of exposure, can be connected to the growth mode of a thiophene film on UO2; the thiophene film converts from a flat-lying configuration to an inclined structure as coverage increases. The effects of X-rays, UV, and electron irradiation on thiophene films have been studied in two different coverage regimes, monolayer and multilayer. Irradiation leads to a modification of thiophene films, and appreciable concentrations of species stable to 640 K are present on the surface for both regimes. The XPS results suggest that irradiation induces polymerization and oligomerization, as well as formation of thiolates and dissociation fragments of thiophene. The adsorption and reactivity of thiophene on defective UO2 surfaces have also been studied. The O vacancies and defects in the oxide surface cause cleavage of C–H and C–S bonds leading to the dissociation of thiophene at temperatures as low as 100 K. These results illustrate the important role played by O vacancies in the chemistry of thiophene over an oxide surface.
Keywords :
Thiophene , Surface defects , X-Ray Photoelectron Spectroscopy (XPS) , Temperature programmed desorption (TPD) , sputtering , Uranium oxide , Chemisorption , Polycrystalline surfaces
Journal title :
Surface Science
Serial Year :
2005
Journal title :
Surface Science
Record number :
1682565
Link To Document :
بازگشت