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| 2. |
- Albinsson, Bo, 1963, et al.
(författare)
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Electron and energy transfer in donor-acceptor systems with conjugated molecular bridges
- 2007
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 9:44, s. 5847-5864
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Tidskriftsartikel (refereegranskat)abstract
- Electron and energy transfer reactions in covalently connected donor-bridge-acceptor assemblies are strongly dependent, not only on the donor-acceptor distance, but also on the electronic structure of the bridge. In this article we describe some well characterised systems where the bridges are π-conjugated chromophores, and where, specifically, the interplay between bridge length and energy plays an important role for the donor-acceptor electronic coupling. For any application that relies on the transport of electrons, for example molecule based solar cells or molecular scale electronics, it will be imperative to predict the electron transfer capabilities of different molecular structures. The potential difficulties with making such predictions and the lack of suitable models are also discussed. © the Owner Societies.
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| 3. |
- Albinsson, Bo, 1963, et al.
(författare)
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Long-range electron and excitation energy transfer in donor-bridge-acceptor systems
- 2008
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Ingår i: Journal of Photochemistry and Photobiology C: Photochemistry Reviews. - : Elsevier BV. - 1389-5567. ; 9:3, s. 138-155
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Tidskriftsartikel (refereegranskat)abstract
- Donor-bridge-acceptor (D-B-A) systems, either as supermolecules or on surfaces, have been extensively studied with respect to long-range electron (ET) and excitation energy (EET) transfer. In more recent years, the main research objective has been to develop knowledge on how to construct molecular-based devices, with predetermined electron transfer properties, intended for application in electronics and photovoltaics. At present, such construction is in general hampered for several reasons. Most importantly, the property of a D-B-A system is not a simple linear combination of properties of the individual components, but depends on the specific building blocks and how they are assembled. An important example is the ability of the bridge to support the intended transfer process. The mediation of the transfer is characterized by an attenuation factor, beta, often viewed as a bridge specific constant but which also depends on the donor and the acceptor, i.e. the same bridge can either be poorly or strongly conducting depending oil the donor and acceptor. This review gives an account of the experimental exploration of the attenuation factor beta in a series of bis(porphyrin) systems covalently linked by bridges of the oligo(phenyleneethynylene) (OPE) type. Attenuation factors for ET as well as for both singlet and triplet EET are discussed. A report is also given on the dependence of the transfer efficiency on the energy-gap between the donor and bridge states relevant for the specific transfer process. The experimental variation of beta with varying donor and acceptor components is shown fora range of conjugated bridges by representative examples from the literature. The theoretical rationalization for the observed variation is briefly discussed. Based on the Gamow tunneling model, the observed variations in beta-values with varying donors and acceptors for the same bridges is simulated Successfully simultaneously as the observed energy-gap dependence is modelled. (C) 2008 Elsevier B.V. All rights reserved.
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| 4. |
- Andreasson, Joakim, 1973, et al.
(författare)
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All-photonic molecular half-adder
- 2006
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 128:50, s. 16259-16265
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Tidskriftsartikel (refereegranskat)abstract
- One molecule acts as both an AND and an XOR Boolean logic gate that share the same two photonic inputs. The molecule comprises a half-adder, adding two binary digits with only light as inputs and outputs, and consists of three covalently linked photochromic moieties, a spiropyran and two quinolinederived dihydroindolizines. The AND function is based on the absorption properties of the molecule, whereas the XOR function is based on an off-on-off response of the fluorescence to the inputs that results from interchromophore excited-state quenching interactions. The half-adder is simple to operate and can be cycled many times.
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| 5. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Molecular AND logic gate based on electric dichroism of a photochromic dihydroindolizine
- 2005
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 44:46, s. 7591-7594
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Tidskriftsartikel (refereegranskat)abstract
- (Chemical Equation Presented) Very ANDy: A photochromic molecular switch has been found to act as an AND Boolean logic gate. The switch takes as input both UV light, which causes photo-isomerization of a dihydroindolizine to an open, dipolar form, and an electric field, which aligns this isomer in solution (see scheme). The output of the gate is read as the electric linear dichroism response of the open isomer. The gate can be reset with visible light. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.
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| 6. |
- Börjesson, Karl, 1982, et al.
(författare)
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A membrane anchored DNA-based energy/electron transfer assembly
- 2008
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Ingår i: Nucleic acids symposium series (2004). - 1746-8272. ; :52, s. 691-691
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Tidskriftsartikel (refereegranskat)abstract
- In this work the trapping and conversion of visible light energy into chemical energy is examined using a supramolecular assembly. This consists of a light absorbing antenna and a porphyrin redox centre both covalently attached to a DNA strand, which in turn is bound to a lipid membrane. The excitation energy is finally trapped as a benzoquinone radical anion that could potentially be used in subsequent chemical reactions.
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| 7. |
- Börjesson, Karl, 1982, et al.
(författare)
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Characterization and use of tricyclic fluorescent nucleic acid base analogues
- 2008
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Ingår i: Nucleic acids symposium series (2004). - 1746-8272. ; :52, s. 3-4
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Tidskriftsartikel (refereegranskat)abstract
- The two recently developed nucleic acid probe molecules tC and tC(O) both have unique properties compared to other molecules in the family of fluorescent base analogues.(1-5) These tricyclic base analogues both form very stable base pairs with guanine and give minimal perturbations to the native structure of DNA.(2) We have found that tC(O) is the brightest fluorescent base analogue reported(4) and that tC also is very bright and has a fluorescence quantum yield that is virtually insensitive to its surrounding microenvironment within the nucleic acid(3). These base analogues have so far been used in FRET-studies of a DNA-polymerase system(6) and in initial anisotropy-studies of DNA-containing systems(4).
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| 8. |
- Börjesson, Karl, 1982, et al.
(författare)
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Membrane-Anchored DNA Assembly for Energy and Electron Transfer
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:8, s. 2831-2839
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Tidskriftsartikel (refereegranskat)abstract
- In this work we examine the trapping and conversion of visible light energy into chemical energy using a supramolecular assembly. The assembly consists of a light-absorbing antenna and a porphyrin redox center, which are covalently attached to two complementary 14-mer DNA strands, hybridized to form a double helix and anchored to a lipid membrane. The excitation energy Is finally trapped In the lipid phase of the membrane as a benzoquinone radical anion that could potentially be used In subsequent chemical reactions. In addition, In this model complex, the hydrophobic porphyrin moiety acts as an anchor into the liposome positioning the DNA construct on the lipid membrane surface. The results show the suitability of our system as a prototype for DNA-based light-harvesting devices, In which energy transfer from the aqueous phase to the interior of the lipid membrane Is followed by charge separation. © 2009 American Chemical Society.
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| 9. |
- Börjesson, Karl, 1982, et al.
(författare)
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Nucleic Acid Base Analog FRET-Pair Facilitating Detailed Structural Measurements in Nucleic Acid Containing Systems
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:12, s. 4288-4293
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Tidskriftsartikel (refereegranskat)abstract
- We present the first nucleobase analog fluorescence resonance energy transfer (FRET)-pair. The pair consists of tC O , 1,3-diaza-2- oxophenoxazine, as an energy donor and the newly developed tC nitro , 7-nitro-1,3-diaza-2-oxophenothiazine, as an energy acceptor. The FRET-pair successfully monitors distances covering up to more than one turn of the DNA duplex. Importantly, we show that the rigid stacking of the two base analogs, and consequently excellent control of their exact positions and orientations, results in a high control of the orientation factor and hence very distinct FRET changes as the number of bases separating tC O and tCnitro is varied. A set of DNA strands containing the FRET-pair at wisely chosen locations will, thus, make it possible to accurately distinguish distance- from orientation-changes using FRET. In combination with the good nucleobase analog properties, this points toward detailed studies of the inherent dynamics of nucleic acid structures. Moreover, the placement of FRET-pair chromophores inside the base stack will be a great advantage in studies where other (biomacro)molecules interact with the nucleic acid. Lastly, our study gives possibly the first truly solid experimental support to the dependence of energy transfer efficiency on orientation of involved transition dipoles as predicted by the Forster theory. © 2009 American Chemical Society.
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| 10. |
- Czolkos, Ilja, 1980, et al.
(författare)
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Platform for Controlled Supramolecular Nano-Assembly
- 2009
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 9:6, s. 2482-2486
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Tidskriftsartikel (refereegranskat)abstract
- We here present a two-dimensional (2D) micro/nano-fluidic technique where reactant-doped liquid−crystal films spread and mix on micro- and nanopatterned substrates. Surface-supported phospholipid monolayers are individually doped with complementary DNA molecules which hybridize when these lipid films mix. Using lipid films to convey reactants reduces the dimensionality of traditional 3D chemistry to 2D, and possibly to 1D by confining the lipid film to nanometer-sized lanes. The hybridization event was observed by FRET using single-molecule-sensitive confocal fluorescence detection. We could successfully detect hybridization in lipid streams on 250 nm wide lanes. Our results show that the number and density of reactants as well as sequence of reactant addition can be controlled within confined liquid crystal films, providing a platform for nanochemistry with potential for kinetic control.
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