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441.
Rasmus Ringstrm Fredrik Edhborg Zachary W. Schroeder Lan Chen Michael J. Ferguson Rik R. Tykwinski Bo Albinsson 《Chemical science》2022,13(17):4944
Three pentacene dimers have been synthesized to investigate the effect of molecular rotation and rotational conformations on singlet fission (SF). In all three dimers, the pentacene units are linked by a 1,4-diethynylphenylene spacer that provides almost unimpeded rotational freedom between the pentacene- and phenylene-subunits in the parent dimer. Substituents on the phenylene spacer add varying degrees of steric hindrance that restricts both the rotation and the equilibrium distribution of different conformers; the less restricted conformers exhibit faster SF and more rapid subsequent triplet-pair recombination. Furthermore, the rotational conformers have small shifts in their absorption spectra and this feature has been used to selectively excite different conformers and study the resulting SF. Femtosecond transient absorption studies at 100 K reveal that the same dimer can have orders of magnitude faster SF in a strongly coupled conformer compared to a more weakly coupled one. Measurements in polystyrene further show that the SF rate is nearly independent of viscosity whereas the triplet pair lifetime is considerably longer in a high viscosity medium. The results provide insight into design criteria for maintaining high initial SF rate while suppressing triplet recombination in intramolecular singlet fission.In this study we show that one molecule can have vastly different singlet fission and triplet recombination rates depending on its rotational freedom and the relative orientation of the pentacene moieties. 相似文献
442.
Jonas Hedman David Nilebo Dr. Elin Larsson Langhammer Dr. Fredrik Björefors 《ChemSusChem》2020,13(21):5731-5739
The interaction between a fibre optic evanescent wave sensor and the positive electrode material, lithium iron phosphate, in a battery cell is presented. The optical–electrochemical combination was investigated in a reflection-based and a transmission-based configuration, both leading to comparable results. Both constant current cycling and cyclic voltammetry were employed to link the optical response to the charge and discharge of the battery cells, and the results demonstrated that the optical signal changed consistently with lithium ion insertion and extraction. More precisely, cyclic voltammetry showed that the intensity increased when iron was oxidised during charge and then decreased as iron was reduced during discharge. Cyclic voltammetry also revealed that the optical signal remained unchanged when essentially no oxidation or reduction of the electrode material took place. This shows that optical fibre sensors may be used as a way of monitoring state of charge and electrode properties under dynamic conditions. 相似文献
443.
Yu Cao Mats Delin Fredrik Kullenberg Lars Nyborg 《Surface and interface analysis : SIA》2020,52(12):1066-1070
Electron beam melting is an additive manufacturing technology in vacuum that suits Ti-6Al-4V parts, which has a high affinity with oxygen. Since the high cost of the feedstock powder, the un-melted powder is often recycled in the subsequent process. In this study, the influence of powder reuse on the surface characteristics of Ti-6Al-4V powder is examined using a variety of technology including scanning electron microscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The modification of surface morphology and chemistry either generally or locally are revealed and discussed, which helps the creation of powder recycling strategy. Compared with fresh virgin powder, “worn” and rougher powder particles are observed after recycling. Meanwhile, the average oxide thickness is slightly increased, and less Al enrichment was found at the surface. Locally varied chemistry/oxide thickness on different powder particles or different location on the same particle is observed. 相似文献
444.
Prof. David A. Leigh Lucian Pirvu Dr. Fredrik Schaufelberger Dr. Daniel J. Tetlow Liang Zhang 《Angewandte Chemie (International ed. in English)》2018,57(33):10484-10488
We report on a rotaxane‐like architecture secured by the in situ tying of an overhand knot in the tris(2,6‐pyridyldicarboxamide) region of the axle through complexation with a lanthanide ion (Lu3+). The increase in steric bulk caused by the knotting locks a crown ether onto the thread. Removal of the lutetium ion unties the knot, and when the axle binding site for the ring is deactivated, the macrocycle spontaneously dethreads. When the binding interaction is switched on again, the crown ether rethreads over the 10 nm length of the untangled strand. The overhand knot can be retied, relocking the threaded structure, by once again adding lutetium ions. 相似文献
445.
Jakob Lindberg Johan Nilvebrant Per-ke Nygren Fredrik Lehmann 《Molecules (Basel, Switzerland)》2021,26(19)
We review drug conjugates combining a tumor-selective moiety with a cytotoxic agent as cancer treatments. Currently, antibody-drug conjugates (ADCs) are the most common drug conjugates used clinically as cancer treatments. While providing both efficacy and favorable tolerability, ADCs have limitations due to their size and complexity. Peptides as tumor-targeting carriers in peptide-drug conjugates (PDCs) offer a number of benefits. Melphalan flufenamide (melflufen) is a highly lipophilic PDC that takes a novel approach by utilizing increased aminopeptidase activity to selectively increase the release and concentration of cytotoxic alkylating agents inside tumor cells. The only other PDC approved currently for clinical use is 177Lu-dotatate, a targeted form of radiotherapy combining a somatostatin analog with a radionuclide. It is approved as a treatment for gastroenteropancreatic neuroendocrine tumors. Results with other PDCs combining synthetic analogs of natural peptide ligands with cytotoxic agents have been mixed. The field of drug conjugates as drug delivery systems for the treatment of cancer continues to advance with the application of new technologies. Melflufen provides a paradigm for rational PDC design, with a targeted mechanism of action and the potential for deepening responses to treatment, maintaining remissions, and eradicating therapy-resistant stem cells. 相似文献
446.
Fredrik Weiland Muhammad Saad Qureshi Jonas Wennebro Christian Lindfors Taina Ohra-aho Hoda Shafaghat Ann-Christine Johansson 《Molecules (Basel, Switzerland)》2021,26(23)
Petrochemical products could be produced from circular feedstock, such as waste plastics. Most plants that utilize syngas in their production are today equipped with entrained flow gasifiers, as this type of gasifier generates the highest syngas quality. However, feeding of circular feedstocks to an entrained flow gasifier can be problematic. Therefore, in this work, a two-step process was studied, in which polypropylene was pre-treated by pyrolysis to produce a liquid intermediate that was easily fed to the gasifier. The products from both pyrolysis and gasification were thoroughly characterized. Moreover, the product yields from the individual steps, as well as from the entire process chain, are reported. It was estimated that the yields of CO and H2 from the two-step process were at least 0.95 and 0.06 kg per kg of polypropylene, respectively, assuming that the pyrolysis liquid and wax can be combined as feedstock to an entrained flow gasifier. On an energy basis, the energy content of CO and H2 in the produced syngas corresponded to approximately 40% of the energy content of the polypropylene raw material. This is, however, expected to be significantly improved on a larger scale where losses are proportionally smaller. 相似文献
447.
The structural battery electrolyte (SBE) is a crucial component for the structural battery, which is an innovative energy storage device. While the SBE must allow for ion transport, it must also contribute to the structural integrity of the battery. In this contribution, we study the electro‐chemical properties of the SBE using finite element analysis. For the governing equations, we use Ampere's law in terms of a balance equation, and also the mass continuity equation of ions, which in the end results in a fully coupled transient multiphysics problem. Due to the strong heterogeneities in the SBE microstructure, a multi‐scale approach is adopted. 相似文献
448.
In this paper a mixed velocity‐pressure variational formulation is adopted for the subscale modeling of sintering stemming from micropores with surface tension. The macroscopic response is obtained from variationally consistent homogenization. As to the driving force for sintering, the model framework allows for a non‐spherical sintering stress, derived via the homogenization procedure, which contrasts traditional macroscopic modeling. The proposed method can seamlessly handle the transition from macroscopically compressible to incompressible response. For the Representative Volume Elements (RVEs) the weakly periodic, Neumann, and Dirichlet type boundary conditions are established, and it is shown that the Hill‐Mandel condition is satisfied. The numerical examples show the transient behavior of a 2D unit‐cell subjected to free sintering. Effective macroscale properties pertinent to different boundary conditions are compared for a 3D microstructure. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
449.
Aqueous solutions of proteins and oppositely charged polyelectrolytes were studied at different polyelectrolyte chain length, ionic strength, and protein-protein interaction potential as a function of the polyelectrolyte concentration. One of the protein models used represented lysozyme in aqueous environment. The model systems were solved by Monte Carlo simulations, and their properties were analyzed in terms of radial distribution functions, structure factors, and cluster composition probabilities. In the system with the strongest electrostatic protein-polyelectrolyte interaction the largest clusters were formed near or at equivalent amount of net protein charge and polyelectrolyte charge, whereas in excess of polyelectrolyte a redissolution appeared. Shorter polyelectrolyte chains and increased ionic strength lead to weaker cluster formation. An inclusion of nonelectrostatic protein-protein attraction promoted the protein-polyelectrolyte cluster formation. 相似文献
450.