| 1. |
- O'Shea, James N, et al.
(författare)
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Molecular damage in bi-isonicotinic acid adsorbed on rutile TiO2(110)
- 2008
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 602:9, s. 1693-1698
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Tidskriftsartikel (refereegranskat)abstract
- Here we present the characteristic signatures in X-ray absorption and photoemission spectroscopy for molecular damage in adsorbed monolayers of bi-isonicotinic acid on a rutile TiO2(110) surface. Bi-isonicotinic acid is the anchor ligand through which many important inorganic complexes are bound to the surface of TiO2 in dye-sensitized solar cells. The nature of the damage caused by excessive heating of the adsorbed monolayer is consistent with splitting the molecule into two adsorbed isonicotinic acid molecular fragments. The effect on the lowest unoccupied molecular orbitals (involved in electron transfer in the molecule) can be understood in terms of the adsorption geometry of the reaction products and their nearest neighbor interactions.
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| 2. |
- Taylor, John B., et al.
(författare)
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Charge transfer dynamics at model metal-organic solar cell surfaces
- 2007
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:44, s. 16646-16655
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Tidskriftsartikel (refereegranskat)abstract
- The "core-hole clock" implementation of resonant photoemission has been used to investigate the charge-transfer dynamics of bi-isonicotinic acid molecules (4,4'-dicarboxy-2,2'-bipyridine) adsorbed on a rutile TiO2(110) surface containing varying densities of gold islands. In the presence of, nominally, a few monolayers of gold there exists a strong coupling between the adsorbed molecules and the surface. This is derived from the measurement of a <3 fs charge-transfer time for the injection of a core-excited electron into the substrate. This ultrafast charge-transfer time is quenched for a fraction of the molecules upon the addition of only a few further monolayers of gold. There is evidence to suggest that this effect derives from a change in the bonding configuration of bi-isonicotinic acid molecules. However, results also support the occurrence of ultrafast back-transfer from Au states to core-excited unoccupied molecular states.
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| 3. |
- Taylor, John B., et al.
(författare)
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The adsorption and charge transfer dynamics of bi-isonicotinic acid on Au(111)
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:13
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of bi-isonicotinic acid (4,4[prime]-dicarboxy-2,2[prime]-bipyridine) with the Au(111) surface has been investigated using electron spectroscopic techniques. Near edge x-ray absorption fine structure (NEXAFS) spectra show that monolayers of the molecule lie flat to the surface and also reveal that the monolayer is sensitive to the preparation conditions employed. Core level x-ray photoelectron spectroscopy (XPS) shows that the adsorbed molecule does not undergo deprotonation upon adsorption. The “core-hole clock” implementation of resonant photoemission has been used to probe the coupling between molecule and substrate. This technique has revealed the possibility of ultrafast backtransfer from the substrate into the molecule upon resonant excitation of a N 1s core level electron. This is supported by a NEXAFS and XPS investigation of energy level alignments in the system. ©2007 American Institute of Physics
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| 4. |
- Swarbrick, Janine C, et al.
(författare)
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High energy resolution X-ray absorption spectroscopy of environmentally relevant lead(II) compounds
- 2009
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Ingår i: Inorganic chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 48:22, s. 10748-10756
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Tidskriftsartikel (refereegranskat)abstract
- The determination of the chemical environment of Pb in natural samples is a challenge of great importance in environmental and health physics. We report a high energy resolution fluorescence detection (HERFD) X-ray absorption near-edge spectroscopy (XANES) study at the Pb L(3) and L(1) absorption edges to determine the chemical environment of Pb in a series of model and environmentally relevant compounds. HERFD spectroscopy can reveal increased spectral detail due to an apparent reduction in the core hole lifetime broadening. HERFD spectra of model Pb(II) compounds were compared to FEFF 8.4 multiple scattering calculations with reduced peak broadening parameters, and density of state (DOS) simulations, to determine the origins of the spectral features. A pre-edge in the L(3) XANES is revealed which is shown to arise from hybridization between the Pb p and d states. HERFD spectra of Pb(II)-containing environmentally relevant solutions were compared to model spectra and calculations. The results presented in this paper show that the chemical environment of Pb can be identified from spectral features resolved in HERFD spectroscopy at the Pb L(3) edge. The technique provides information that is complementary to conventional extended X-ray absorption fine structure (EXAFS) spectroscopy.
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