| 1. |
- Spassky, Dmitry, et al.
(författare)
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Influence of the Sc cation substituent on the structural properties and energy transfer processes in GAGG:Ce crystals
- 2020
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 22:15, s. 2621-2631
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the Sc cation substituent on the structural and luminescence properties of GAGG:Ce crystals was studied. Unit cell parameters and space groups were obtained using XRD analysis. The chemical compositions of the crystals were determined using SEM-EDX and TEM-EDX techniques. Structures were refined by the Rietveld method and the distribution of Al/Ga/Sc cations between octahedral and tetrahedral sites was obtained. The influence of Sc on the electronic band structure and the energy of the 4f and 5d Ce3+ levels is shown. The modification of the band structure induced by the Sc electronic states results in the suppression of Gd emission and enhancement of Ce3+ emission at low temperatures. The Ce3+ emission decay is accelerated under high-energy excitation of the Sc-containing GAGG compound.
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| 2. |
- Dods, Robert, 1989, et al.
(författare)
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Ultrafast structural changes within a photosynthetic reaction centre.
- 2021
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 1476-4687 .- 0028-0836. ; 589:7841, s. 310-314
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic reaction centres harvest the energy content of sunlight by transporting electrons across an energy-transducing biological membrane. Here we use time-resolved serial femtosecond crystallography1 using an X-ray free-electron laser2 to observe light-induced structural changes in the photosynthetic reaction centre of Blastochloris viridis on a timescale of picoseconds. Structural perturbations first occur at the special pair of chlorophyll molecules of the photosynthetic reaction centre that are photo-oxidized by light. Electron transfer to the menaquinone acceptor on the opposite side of the membrane induces a movement of this cofactor together with lower amplitude protein rearrangements. These observations reveal how proteins use conformational dynamics to stabilize the charge-separation steps of electron-transfer reactions.
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| 3. |
- Morozov, Anatolii V., et al.
(författare)
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Retardation of Structure Densification by Increasing Covalency in Li-Rich Layered Oxide Positive Electrodes for Li-Ion Batteries
- 2022
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 34:15, s. 6779-6791
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Tidskriftsartikel (refereegranskat)abstract
- Because of the outstanding discharge capacity provided by oxygen redox activity, Li-rich layered oxide positive electrode materials for Li-ion batteries attract tremendous attention. However, there is still no full consensus on the role that the ionocovalency of transition metal (TM)–oxygen (O) chemical bonding plays in the reversibility of the oxygen redox as well as on both local crystal and electronic structure transformations. Here, we managed to tune the cationic/anionic redox contributions to the overall electrochemical activity using the xLi2RuO3-(1 – x)Li1.2Ni0.2Mn0.6O2 solid solutions as a model system possessing the same crystal structure and morphology as Li-rich layered oxides. We conclusively traced the whole cascade of events from increasing the covalency of the TM–O bond, suppressing irreversible oxygen oxidation to the generation of the reduced Mn species toward retarding the structure “densification” in the Li-rich layered oxides. The results demonstrate that enhancing the degree of covalency of the TM–O bonding is vitally important for anchoring the reversibility of the charge compensation mechanism occurring through partial oxygen oxidation.
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| 4. |
- Spassky, Dmitry, et al.
(författare)
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Temperature dependent energy transfer to Eu3+ emission centres in K5Eu(MoO4)4 crystals
- 2024
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Ingår i: CrystEngComm. - 1466-8033. ; 26:8, s. 1106-1116
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Tidskriftsartikel (refereegranskat)abstract
- Luminescence properties of a palmierite-type K5Eu(MoO4)4 crystal were studied in a wide temperature range of 7-650 K. Eu3+ ions are shown to occupy at least three non-equivalent positions in the palmierite-type structure, forming emission centres with slightly different characteristics due to an incommensurate modulated disordering. The relative intensity of the Eu3+ emission bands originating from the 5D0 and 5D1 terms is shown to depend on excitation energy and the origin of the observed differences is discussed. It is shown that quenching temperature of the Eu3+ emission depends on excitation energy that is explained by energetical overlap of the 4f-4f Eu3+ transitions with the Urbach tail of the fundamental absorption region. Energy transfer processes to the Eu3+ emission centres were studied using the methods of time resolved spectroscopy.
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| 5. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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