| 21. |
- He, J. J., et al.
(författare)
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Phthalocyanine-sensitized nanostructured TiO2 electrodes prepared by a novel anchoring method
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:9, s. 2743-2747
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Tidskriftsartikel (refereegranskat)abstract
- A novel method for anchoring phthalocyanines substituted with ester groups onto nanostructured TiO2 films is described. Such phthalocyanines did not adsorb on nanostructured TiO2 film by the ordinary methods. In our new method, the TiO2 film is pretreated with (CH3)(3)COLi to change the surface hydroxyl groups (-OH) into oxygen anions (-O-), thus making the surface more reactive toward the ester functionalities of the dye. The dye can then be anchored onto the semiconductor surface through the produced carboxylate group(s). The amount of anchored dye on the semiconductor shows a dependence on both the time of base treatment and the time of dye treatment. Electrodes treated with the free base phthalocyanine and zinc phthalocyanine were characterized by absorption spectroscopy, photocurrent action spectroscopy, and photocurrent-photovoltage measurements. The homogeneous blue-green color and the absorption bands in the far-red region are indicative of an attachment of the dye on TiO2 film. A monochromatic incident photo-to-current conversion efficiency of 4.3 % was achieved at 690 nm for a cell where the base-treated electrode was treated with ZnPcBu.
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| 22. |
- He, Jianjun, et al.
(författare)
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Modified phthalocyanines for efficient near-IR sensitization of nanostructured TiO2 electrode
- 2002
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 124:17, s. 4922-4932
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Tidskriftsartikel (refereegranskat)abstract
- A zinc phthalocyanine with tyrosine substituents (ZnPcTyr), modified for efficient far-red/near-IR performance in dye-sensitized nanostructured TiO2 solar cells, and its reference, glycine-substituted zinc phthalocyanine, (ZnPcGly), were synthesized and characterized. The compounds were studied spectroscopically, electrochemically, and photoelectrochemically. Incorporating tyrosine groups into phthalocyanine makes the dye ethanol-soluble and reduces surface aggregation as a result of steric effects. The performance of a solar cell based on ZnPcTyr is much better than that based on ZnPcGly. Addition of 3alpha,7alpha-dihydroxy-5beta-cholic acid (cheno) and 4-tert-butylpyridine (TBP) to the dye solution when preparing a dye-sensitized TiO2 electrode diminishes significantly the surface aggregation and, therefore, improves the performance of solar cells based on these phthalocyanines. The highest monochromatic incident photo-to-current conversion efficiency (IPCE) of similar to24% at 690 nm and an overall conversion efficiency (eta) of 0.54% were achieved for a cell based on a ZnPcTyr-sensitized TiO2 electrode. Addition of TBP in the electrolyte decreases the IPCE and eta considerably, although it increases the open-circuit photovoltage. Time-resolved transient absorption measurements of interfacial electron-transfer kinetics in a ZnPoTyr-sensitized nanostructured 702 thin film show that electron injection from the excited state of the dye into the conduction band of TiO2 is completed in similar to500 fs and that more than half of the injected electrons recombines with the oxidized dye molecules in similar to300 ps. In addition to surface aggregation, the very fast electron recombination is most likely responsible for the low performance of the solar cell based on ZnPcTyr.
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| 23. |
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| 24. |
- Johansson, A., et al.
(författare)
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Synthesis and photophysics of one mononuclear Mn(III) and one dinuclear Mn(III,III) complex covalently linked to a ruthenium(II) tris(bipyridyl) complex
- 2003
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42, s. 7502-7511
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-1).
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| 25. |
- Johansson, O., et al.
(författare)
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Electron donor-acceptor dyads based on ruthenium(II) bipyridine and terpyridine complexes bound to naphthalenediimide
- 2003
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42:9, s. 2908-2918
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Tidskriftsartikel (refereegranskat)abstract
- Two series of photosensitizer-electron acceptor complexes have been synthesized and fully characterized: ruthenium(11) tris(bipyridine) {[Ru-II(bpy)(2)(bpy-X-NDI)], where X = -CH2-, tolylene, or phenylene, bpy is 2,2'-bipyridine, and NDI is naphthalenediimide} and ruthenium(II) bis(terpyridine) {[Ru-II(Y-tpy)(tpy-X-NDI)], where Y = H or tolyl and X = tolylene or phenylene, and tpy = 2,2':6',2-terpyridine}. The complexes have been studied by cyclic and differential pulse voltammetry and by steady state and time-resolved absorption and emission techniques. Rates for forward and backward electron transfer have been investigated, following photoexcitation of the ruthenium(II) polypyridine moiety. The terpyridine complexes were only marginally affected by the linked diimide unit, and no electron transfer was observed. In the bipyridine complexes we achieved efficient charge separation. For the complexes containing a phenyl link between the ruthenium(II) and diimide moieties, our results suggest a biphasic forward electron-transfer reaction, in which 20% of the charge-separated state was formed via population of the naphthalenediimide triplet state.
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| 26. |
- Johansson, O., et al.
(författare)
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Intramolecular charge separation in a hydrogen bonded tyrosine-ruthenium(II)-naphthalene diimide triad
- 2004
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :2, s. 194-195, s. 194-195
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Tidskriftsartikel (refereegranskat)abstract
- Long-lived charge-separated states in the ns to mus range were observed upon laser flash excitation of a donor-chromophore-acceptor triad based on tris(bipyridine) ruthenium(II) as photosensitizer, naphthalene diimide as acceptor; and a hydrogen bonded phenol as donor.
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| 27. |
- Li, P., et al.
(författare)
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Influence of tertiary phosphanes on the coordination configurations and electrochemical properties of iron hydrogenase model complexes : Crystal structures of (mu-S2C3H6)Fe-2(CO)(6-n)L-n (L = PMe2Ph, n=1, 2; PPh3 P(OEt)(3), n=1)
- 2005
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :12, s. 2506-2513
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Tidskriftsartikel (refereegranskat)abstract
- A series of mono- and disubstituted diiron complexes [(mu-pdt)-Fe-2(CO)(5)L] [pdt = 1,3-propanedithiolato; L = PMe3 (2), PMe2Ph (3), PPh3 (4), P(OEt)(3) (5)] and [(mu-pdt)Fe-2(CO)(4)L-2] [L = PMe2Ph (6), PPh3 (7), P(OEt)3 (8)] were prepared as Fe-only hydrogenase-active-site models by controllable CO displacement of [(mu-pdt)Fe-2(CO)(6)] by tertiary phosphanes. The coordination configurations of 3-6 were characterized by X-ray crystallography. Disubstituted diiron complex 6 features an apical/apical coordination mode, instead of the typical transoid basal/basal configuration. The electrochemistry of 2-6 and 8 was studied by cyclic voltammetry to evaluate the effects of different tertiary phosphane ligands on the redox properties of the iron atoms of model complexes.
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| 28. |
- Lomoth, R., et al.
(författare)
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Synthesis and characterization of a dinuclear manganese(III,III) complex with three phenolate ligands
- 2002
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Ingår i: European Journal of Inorganic Chemistry. - 1434-1948 .- 1099-1948. ; 2002:11, s. 2965-2974
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Tidskriftsartikel (refereegranskat)abstract
- A dinuclear manganese complex ([Mn2L(mu-OAc)(2)]PF6) has been synthesized, where L is the trianion of 2,6-bis{[(2-hydroxy-3,5-di- tert-butylbenzyl) (2-pyridylmethyl) amino] methyl)-4-methylphenol, a ligand with three phenolate groups. The two pseudo-octahedrally coordinated Mn ions are bridged via the two bidentate acetate ligands and the 4-methylphenolate group of the ligand. We have characterized the complex with electrochemistry, spectroelectrochemistry and EPR spectroscopy. Electrochemically the Mn-2(III,III) complex undergoes two metal-centered quasi-reversible one-electron reduction steps (E-1/2 = 0.04 and -0.32 V vs. SCE). Reduction to the Mn-2(II,III) state results in transformation into a modified complex with slightly different redox properties. One-electron oxidation (E-1/2 = 0.96 V vs. SCE) affords the Mn-2(III,IV) state while further one-electron oxidation (E-1/2 = 1.13 V vs. SCE) presumably involves ligand oxidation. High valent Mn complexes involving Mn-IV or Mn-V centers are of particular interest as intermediates in catalytic water oxidation. The redox potentials of [Mn2L(mu-OAC)(2)](+) show the expected stabilization of higher manganese oxidation states compared with the related complex, [Mn-2(bpmp)(mu-OAc)(2)](+).
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| 29. |
- Niburg, M., et al.
(författare)
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A complete sub-system of parallel optical interconnects for telecom applications
- 1996
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Ingår i: 1996 Proceedings 46th Electronic Components and Technology Conference. ; , s. 259-263
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Konferensbidrag (refereegranskat)abstract
- Increased throughput and flexibility requirements in large-scale electronic equipment create needs for increased interconnection density capacity and re-configurability. The growing demand for new broadband interactive telecom and computer services is expected to enforce this development, which presents a challenge to traditional electronic interconnection techniques and an opportunity for new optical solutions, provided that the cost of introduction of the optical technology is affordable for both system operators and service users. The authors describe a complete sub-system of parallel optical interconnects (i.e., a total solution including the link itself and the equipment practice supporting the link) which exhibits both cost and performance benefits compared to a pure electrical or a serial optical solution.
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| 30. |
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