| 1. |
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| 2. |
- Wilson, J., et al.
(författare)
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Base Pair Sensitivity and Enhanced ON/OFF Ratios of DNA-Binding: Donor-Acceptor-Donor Fluorophores
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 117:40, s. 12000-12006
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Tidskriftsartikel (refereegranskat)abstract
- The photophysical properties of two recently reported live cell compatible, DNA-binding dyes, 4,6-bis(4-(4-methylpiperazin-1-yl)phenyl)pyrimidin-2-ol, 1, and [1,3-bis[4-(4-methylpiperazin-1-yl)phenyl]-1,3-propandioato-kappa O, kappa O']difluoroboron, 2, are characterized. Both dyes are quenched in aqueous solutions, while binding to sequences containing only AT pairs enhances the emission. Binding of the dyes to sequences containing only GC pairs does not produce a significant emission enhancement, and for sequences containing both AT and GC base pairs, emission is dependent on the length of the AT pair tracts. Through emission lifetime measurements and analysis of the dye redox potentials, photoinduced electron transfer with GC pairs is implicated as a quenching mechanism. Binding of the dyes to AT-rich regions is accompanied by bathochromic shifts of 26 and 30 nm, respectively. Excitation at longer wavelengths thus increases the ON/OFF ratio of the bound probes significantly and provides improved contrast ratios in solution as well as in fluorescence microscopy of living cells.
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| 3. |
- Abrahamsson, Maria, 1975, et al.
(författare)
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High Extinction Coefficient Ru-Sensitizers that Promote Hole Transfer on Nanocrystalline TiO2
- 2014
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 15:6, s. 1154-1163
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Tidskriftsartikel (refereegranskat)abstract
- Two series of Ru-II polypyridyl compounds with formulas [(bpy)(2)RuL](PF6)(2) and [(deeb)(2)RuL](PF6)(2), where bpy is 2,2-bipyridine, deeb is 4,4-diethylester-2,2-bpy, and L is one of several substituted 9-(1,3-dithiole-2-ylidene)-4,5-diazafluorene ligands, were studied as potential photosensitizers for TiO2. These compounds possess notably high extinction coefficients (40000M(-1)cm(-1) @470 nm) which are shown by time-dependent density functional theory (TD-DFT) calculations to result from overlapping metal-to-ligand charge transfer (MLCT) and ligand-localized transitions. Low-temperature absorption and photoluminescence measurements were suggestive of a short-lived MLCT excited state. When adsorbed onto TiO2 thin films, both the free ligands (L) and their corresponding [(deeb)(2)RuL](2+) complexes exhibited rapid excited-state electron injection into TiO2; in the case of the complexes, this was followed by rapid (k>10(8) s(-1)) hole transfer from Ru-III to the 1,3-dithiole ring of the L ligand. Observation of diffusion-limited reductive quenching of the [Ru(bpz)(3)](2+)* (bpz is 2,2-bipyrazine) excited state by the L ligands in solution supported the occurrence of intramolecular hole transfer following electron injection by the TiO2-anchored complexes.
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| 4. |
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| 5. |
- Abrahamsson, Maria, 1975
(författare)
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Solar energy conversion using iron polypyridyl type photosensitizers - A viable route for the future?
- 2017
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Ingår i: Photochemistry. - Cambridge : Royal Society of Chemistry. - 0556-3860 .- 1465-1947. - 9781782625438 ; 44, s. 285-295
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Tidskriftsartikel (refereegranskat)abstract
- In this chapter, recent advances on the use of environmentally friendly iron-based photosensitizers are reviewed and compared with earlier investigations of similar compounds. The photophysical consequences of ligand design is considered together with theoretical approaches to establishing the detailed structure-property relationships.
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| 6. |
- Abrahamsson, Maria, 1975-
(författare)
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Tuning of the Excited State Properties of Ruthenium(II)-Polypyridyl Complexes
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Processes where a molecule absorbs visible light and then converts the solar energy into chemical energy are important in many biological systems, such as photosynthesis and also in many technical applications e.g. photovoltaics. This thesis describes a part of a multidisciplinary project, aiming at a functional mimic of the natural photosynthesis, with the overall goal of production of a renewable fuel from sun and water. More specific, the thesis is focused on design and photophysical characterization of new photosensitizers, i.e. light absorbers that should be capable of transferring electrons to an acceptor and be suitable building blocks for supramolecular rod-like donor-photosensitizer-acceptor arrays. The excited state lifetime, the excited state energy and the geometry are important properties for a photosensitizer. The work presented here describes a new strategy to obtain longer excited state lifetimes of the geometrically favorable Ru(II)-bistridentate type complexes, without a concomitant substantial decrease in excited state energy. The basic idea is that a more octahedral coordination around the Ru will lead to longer excited state lifetimes. In the first generation of new photosensitizers a 50-fold increase of the excited state lifetime was observed, going from 0.25 ns for the model complex to 15 ns for the best photosensitizer. The second generation goes another step forward, to an excited state lifetime of 810 ns. Furthermore, the third generation of new photosensitizers show excited state lifetimes in the 0.45 - 5.5 microsecond region at room temperature, a significant improvement. In addition, the third generation of photosensitizers are suitable for further symmetric attachment of electron donor and acceptor motifs, and it is shown that the favorable properties are maintained upon the attachment of anchoring groups. The reactivity of the excited state towards light-induced reactions is proved and the photostability is sufficient so the new design strategy has proven successful.
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| 7. |
- Amombo Noa, Francoise Mystere, 1988, et al.
(författare)
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A unified topology approach to dot-, rod-, and sheet-MOFs
- 2021
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Ingår i: Chem. - : Elsevier BV. - 2451-9294 .- 2451-9308. ; 7:9, s. 2491-2512
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Tidskriftsartikel (refereegranskat)abstract
- Metal-organic frameworks made from multi-metal-ion units in the shape of clusters and rods (termed dot-MOFs and rod-MOFs) are well known. Here, we introduce MOFs with multi-metallic units in the form of sheets-sheet-MOFs. We show exemplars of all three types of units based on structures containing Y3+, Ce3+, or Gd3+ linked by benzene1,2,4,5-tetracarboxylate to give crystals of a dot-MOF in H2NMe2[Y(b-tec)(H2O)] CTH-14, a sheet-MOF in [Ce-3(btec)(Hbtec)(OAc)(HCO2)] CTH-15, and a rod-MOF in 4,4'-azopyridinium[Gd-2(btec)(2)] CTH-16. Cyclic voltammetry shows that CTH-15 stabilizes Ce(IV). Given the fact that sheet-MOFs represent an intellectual advance in the evolution of MOFs, a unified approach is proposed for the topological classification of dot-, rod-, and sheet-MOFs. It is suggested that the stability ofMOFs follow in the trend dot < rod < sheet. For CTH-14-16, the sheet- and the rod-MOF have higher thermal stability. We suggest sheet-MOFs as an additional strategy for making robust MOFs.
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| 8. |
- Andersson, Johanna, 1983, et al.
(författare)
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Lifetime Heterogeneity of DNA-Bound dppz Complexes Originates from Distinct Intercalation Geometries Determined by Complex-Complex Interactions
- 2013
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:2, s. 1151-1159
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Tidskriftsartikel (refereegranskat)abstract
- Despite the extensive interest in structurally explaining the photophysics of DNA-bound [Ru(phen)(2)dppz](2+) and [Ru(bpy)(2)dppz](2+), the origin of the two distinct emission lifetimes of the pure enantiomers when intercalated into DNA has remained elusive. In this report, we have combined a photophysical characterization with a detailed isothermal titration calorimetry study to investigate the binding of the pure Delta and Lambda enantiomers of both complexes with [poly(dAdT)](2). We find that a binding model with two different binding geometries, proposed to be symmetric and canted intercalation from the minor groove, as recently reported in high-resolution X-ray structures, is required to appropriately explain the data. By assigning the long emission lifetime to the canted binding geometry, we can simultaneously fit both calorimetric data and the binding-density-dependent changes in the relative abundance of the two emission lifetimes using the same binding model. We find that all complex complex interactions are slightly unfavorable for Delta-[Ru(bpy)(2)dppz](2+), whereas interactions involving a complex canted away from a neighbor are favorable for the other three complexes. We also conclude that Delta-[Ru(bpy)(2)dppz](2+) preferably binds isolated, Delta-[Ru(phen)(2)dppz](2+) preferably binds as duplets of canted complexes, and that all complexes are reluctant to form longer consecutive sequences than triplets. We propose that this is due to an interplay of repulsive complex complex and attractive complex-DNA interactions modulated by allosteric DNA conformation changes that are largely affected by the nature of the ancillary ligands.
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| 9. |
- Barbosa de Mattos, Deise Fernanda, 1985, et al.
(författare)
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Covalent incorporation of diphenylanthracene in oxotriphenylhexanoate organogels as a quasi-solid photon upconversion matrix
- 2020
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 153:21
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Tidskriftsartikel (refereegranskat)abstract
- Triplet-triplet annihilation photon upconversion (TTA-UC) in solid state assemblies are desirable since they can be easily incorporated into devices such as solar cells, thus utilizing more of the solar spectrum. Realizing this is, however, a significant challenge that must circumvent the need for molecular diffusion, poor exciton migration, and detrimental back energy transfer among other hurdles. Here, we show that the above-mentioned issues can be overcome using the versatile and easily synthesized oxotriphenylhexanoate (OTHO) gelator that allows covalent incorporation of chromophores (or other functional units) at well-defined positions. To study the self-assembly properties as well as its use as a TTA-UC platform, we combine the benchmark couple platinum octaethylporphyrin as a sensitizer and 9,10-diphenylanthracene (DPA) as an annihilator, where DPA is covalently linked to the OTHO gelator at different positions. We show that TTA-UC can be achieved in the chromophore-decorated gels and that the position of attachment affects the photophysical properties as well as triplet energy transfer and triplet-triplet annihilation. This study not only provides proof-of-principle for the covalent approach but also highlights the need for a detailed mechanistic insight into the photophysical processes underpinning solid state TTA-UC.
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| 10. |
- Bettucci, Ottavia, et al.
(författare)
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Organic dye-sensitized solar cells containing alkaline iodide-based gel polymer electrolytes: Influence of cation size
- 2018
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 20:2, s. 1276-1285
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Tidskriftsartikel (refereegranskat)abstract
- The electrolyte used in dye-sensitized solar cells (DSSCs) plays a key role in the process of current generation, and hence the analysis of charge-transfer mechanisms both in its bulk and at its interfaces with other materials is of fundamental importance. Because of solvent confinement, gel polymer electrolytes are more practical and convenient to use with respect to liquid electrolytes, but in-depth studies are still necessary to optimize their performances. In this work, gel polymer electrolytes of general formulation polyacrylonitrile (PAN)/ethylene carbonate (EC)/propylene carbonate (PC)/MI, where M + is a cation in the alkaline series Li-Cs, were prepared and used in DSSCs. Their ionic conductivities were determined by impedance analysis, and their temperature dependence showed Arrhenius behavior within the experimental window. FT-IR studies of the electrolytes confirmed the prevalence of EC coordination around the cations. Photo-anodes were prepared by adsorbing organic sensitizer D35 on nanocrystalline TiO 2 thin films, and employed to build DSSCs with the gel electrolytes. Nanosecond transient spectroscopy results indicated a slightly faster dye regeneration process in the presence of large cations (Cs + , Rb + ). Moreover, a negative shift of TiO 2 flat-band potential with the decreasing charge density of the cations (increasing size) was observed through Mott-Schottky analysis. In general, results indicate that cell efficiencies are mostly governed by photocurrent values, in turn depending on the conductivity increase with cation size. Accordingly, the best result was obtained with the Cs + -containing cell, although in this case a slight reduction of photovoltage compared to Rb + was observed.
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