| 1. |
- Chaignon, Frederique, et al.
(author)
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Photoinduced electron transfer in ruthenium(II) trisbipyridine complexes connected to a naphthalenebisimide via an oligo(phenyleneethynylene) spacer
- 2009
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In: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 33:2, s. 408-416
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Journal article (peer-reviewed)abstract
- The preparation and the characterization of three new dyads composed of a ruthenium trisbipyridine complex linked to a naphthalene bisimide electron acceptor via a phenyleneethynylene spacer of different length (one or two units) are reported. The dyads also differ by the anchoring position of the spacer on the bipyridine, which is appended either at the 4-position or the 5-position. Cyclic voltammetry and the UV-Vis absorption spectroscopy suggested that the spacer linked at the 5-position ensures a longer pi-conjugation length but the electron transfer rates indicate a lower electronic coupling, than in 4-position. Photoinduced emission yields indicate a significant quenching of the MLCT excited-state of the ruthenium complex in these dyads. Except for the dyad linked in 5 position with one phenyleneethynylene unit, the transient absorption spectroscopy of all the other dyads evidences that the MLCT excited-state decays almost exclusively by electron transfer to form the charge-separated state Ru-III-NBI-. This state could not be observed, presumably because the subsequent recombination to the ground state was much faster than its formation. In the dyad linked in 5 position with only one phenyleneethynylene unit, at room temperature, the (MLCT)-M-3* state is in equilibrium with the (NBI)-N-3* state, and it also decays via electron transfer. The notable feature of these dyads is first the occurrence of a relatively long-range electron transfer reaction via a bis(phenylethynylene) linking unit anchored at the 5 position. Secondly, we show within these series of compounds that subtle variations in the structure of the dyads (length of the spacer and anchoring position on bipy) have a strong impact on the rates and in the mechanism of decay of the (MLCT)-M-3* state. The photophysical properties of the dyads can be explained in terms of energy proximity of different excited states and magnitude of the electronic coupling according to the anchoring position.
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| 4. |
- Falkenström, Magnus, et al.
(author)
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Laser ultrasonics for process control in the metal industry
- 2011
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In: Nondestructive Testing and Evaluation. - : Informa UK Limited. - 1058-9759 .- 1477-2671. ; 26, s. 237-252
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Research review (peer-reviewed)abstract
- Laser ultrasonic (LUS) techniques show great promise for online measurement of material structures and properties during the processing of steels and other metals due to their high information content combined with their ability to operate in difficult environments. Laboratory-scale experiments are presented together with theoretical background showing how LUS can provide insight into the phenomena of recrystallisation, grain growth and phase transformation based on the measurements of velocities for different wave types and on their attenuation. This technique is unique in allowing dynamic observations of such phenomena at elevated temperatures. As microstructure is the most important factor governing the strength of metals, it follows that LUS signals are closely correlated with strength properties in many cases. The LUS equipment has been applied in several industrial trials to successfully evaluate mechanical properties of the product materials. It is also shown how absolute measurements of dimensions such as plate thickness can be made without physical contact and without the need for any calibration factors. © 2011 Taylor & Francis.
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| 5. |
- Falkenström, Magnus, et al.
(author)
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Light-induced charge separation in ruthenium based triads : New variations on an old theme
- 2007
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In: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693 .- 1873-3255. ; 360:3, s. 741-750
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Research review (peer-reviewed)abstract
- Success with artificial photosynthesis requires control of the photoinduced electron transfer reactions leading to charge-separated states. In this review, some new ideas to optimize such charge-separated states in ruthenium(II) polypyridyl based three-component systems with respect to: (1) long lifetimes and (2) ability to store sufficient energy for catalytic water splitting, are presented. To form long-lived charge-separated states, a manganese complex as electron donor and potential catalyst for water oxidation has been used. The recombination reaction is unusually slow because it occurs deep down in the Marcus normal region as a consequence of the large bond reorganization following the manganese oxidation. For the creation of high energy charge-separated states, a strategy using bichromophoric systems is presented. By consecutive excitations of the two chromophores, the formation of charge-separated states that lie higher in energy than either of the two excited states could in theory be achieved, the first results of which will be discussed in this review.
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| 6. |
- Fortage, Jerome, et al.
(author)
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Charge-Transfer State and Large First Hyperpolarizability Constant in a Highly Electronically Coupled Zinc and Gold Porphyrin Dyad
- 2009
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 15:36, s. 9058-9067
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Research review (peer-reviewed)abstract
- We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state (+ZnP-AuP center dot) that displays a particularly long lifetime (tau=4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100 x 10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.
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| 7. |
- Fortage, Jerome, et al.
(author)
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Charge transfer state and large first hyperpolarizability in a highly electronically coupled zinc and gold porphyrin dyad
- 2009
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In: Chemistry - A European Journal. - 1521-3765 .- 0947-6539. ; 15:36, s. 9058-9067
-
Journal article (peer-reviewed)abstract
- We report the synthesis and the characterizations of a novel dyad composed of a zinc porphyrin (ZnP) linked to a gold porphyrin (AuP) through an ethynyl spacer. The UV/Vis absorption spectrum and the electrochemical properties clearly reveal that this dyad exhibits a strong electronic coupling in the ground state as evidenced by shifted redox potentials and the appearance of an intense charge-transfer band localized at lambda = 739 nm in dichloromethane. A spectroelectrochemical study of the dyad along with the parent homometallic system (i.e., ZnP-ZnP and AuP-AuP) was undertaken to determine the spectra of the reduced and oxidized porphyrin units. Femtosecond transient absorption spectroscopic analysis showed that the photoexcitation of the heterometallic dyad leads to an ultrafast formation of a charge-separated state (+ZnP-AuP center dot) that displays a particularly long lifetime (tau=4 ns in toluene) for such a short separation distance. The molecular orbitals of the dyad were determined by DFT quantum-chemical calculations. This theoretical study confirms that the observed intense band at lambda = 739 nm corresponds to an interporphyrin charge-transfer transition from the HOMO orbital localized on the zinc porphyrin to LUMO orbitals localized on the gold porphyrin. Finally, a Hyper-Rayleigh scattering study shows that the dyad possesses a large first molecular hyperpolarizability coefficient (beta = 2100 x 10(-30) esu at lambda = 1064 nm), thus highlighting the valuable nonlinear optical properties of this new type of push-pull porphyrin system.
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| 9. |
- Gurell, Jonas, et al.
(author)
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IR-teknik för direkt mätning av ämnestemperatur och ugnsatmosfär i värmningsugnar
- 2012
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Reports (peer-reviewed)abstract
- Infraröd(IR) strålning är elektromagnetisk(EM) strålning i våglängdsintervallet 0,75– 1000μm. Omedelbart under detta område har vi synligt ljus, omedelbart ovanför mikrovågor som är de mest kortvågiga av det område som benämns radiovågor. All materia avger (emitterar) och absorberar IR-strålning, och såväl emissions- som absorptionsspektra är starkt temperaturberoende. Det är därför vanligt med kontaktlös temperaturmätning baserad på IR–teknik. Under senare år har en betydande teknisk utveckling skett, både av optiska system och detektorer. För höga temperaturer är den vanligaste mättekniken s.k. pyrometri, vilken är baserad på mätning av emission från mätobjektet. Ursprungligen var detta en teknik enbart för mätning av mycket heta fasta föremål med strålning i det synliga området, baserat på att man visuellt jämförde objektets färg med en glödtråd som hettats upp successivt. Med utvecklingen av känsliga IR–detektorer har pyrometrin expanderat till IR–området. All emission av EM strålning beskrivs av kvantmekaniken, som säger att varje fysikaliskt system endast kan anta ett begränsat antal diskreta energitillstånd. Fasta kroppar har ett mycket stort antal s.k. frihetsgrader, och därmed också ett närmast oändligt antal möjliga energitillstånd. Fördelningen av energitillstånd följer den s.k. Boltzmann-statistiken. Ju högre temperatur, desto högre energitillstånd populeras, vilket i sin tur innebär att EM strålning med allt kortare våglängd emitteras.
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| 10. |
- Gurell, J., et al.
(author)
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Laser induced breakdown spectroscopy for fast elemental analysis sorting of metallic scrap pieces using certified reference materials
- 2012
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In: Spectrochimica Acta Part B: Atomic Spectroscopy. - : Elsevier BV. - 0584-8547. ; 74, s. 46-50
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Journal article (peer-reviewed)abstract
- A setup utilizing laser induced breakdown spectroscopy (LIBS) for performing elemental analysis in order to classify metallic samples is currently under construction. The setup uses short laser pulses to locally ablate the sample create luminous plasmas. The emitted light is analyzed spectroscopically for instantaneous determination of the elemental composition. A table-top system based on a compact CCD spectrometer has been constructed combined with fast software in order to test the concept of remote, single shot material classification with LIBS. Certified reference materials with known elemental compositions were used in the laboratory tests. We report on successful laboratory tests in which samples were classified using an analysis based on optical emission following a single laser pulse with an operating distance of approximately 1 m. Details regarding field tests of this versatile promising technique are discussed.
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