| 1. |
- Adalsteinsson, Sigurbjörn Már, et al.
(författare)
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Correlating chemical composition and optical properties of photochromic rare-earth oxyhydrides using ion beam analysis
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : ELSEVIER. - 0168-583X .- 1872-9584. ; 485, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- We relate the photochromic response of rare-earth oxyhydride thin films (YHO, NdHO, GdHO and DyHO) synthesized by reactive magnetron sputtering to chemical composition. Depth profiles of the sample composition are extracted by a multi-method ion beam analysis approach. The total areal density of the thin films is deduced from Rutherford Backscattering Spectrometry while coincidence Time-of-Flight/Energy Elastic Recoil Detection Analysis provides depth-profiles of the film constituents. High-resolution depth profiles of the concentration of light species, i.e. hydrogen and oxygen, are additionally extracted from Nuclear Reaction Analysis and Elastic Backscattering Spectrometry, respectively. The photochromic response of the films is measured by optical transmission spectroscopy before and after illumination. We report photochromic properties for YHO, NdHO, GdHO and DyHO for chemical compositions described by the formula REH2-delta O delta in the range of 0.45 < 6 < 1.5.
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| 2. |
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| 3. |
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| 4. |
- Baba, Elbruz Murat, et al.
(författare)
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Preferential Orientation of Photochromic Gadolinium Oxyhydride Films
- 2020
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Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 25:14
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Tidskriftsartikel (refereegranskat)abstract
- We report preferential orientation control in photochromic gadolinium oxyhydride (GdHO) thin films deposited by a two-step process. Gadolinium hydride (GdH2-x) films were grown by reactive magnetron sputtering, followed by oxidation in air. The preferential orientation, grain size, anion concentrations and photochromic response of the films were strongly dependent on the deposition pressure. The GdHO films showed a preferential orientation along the [100] direction and exhibited photochromism when synthesized at deposition pressures of up to 5.8 Pa. The photochromic contrast was larger than 20% when the films were deposited below 2.8 Pa with a 0.22 H-2/Ar flow ratio. We argue that the relation of preferential orientation and the post deposition oxidation since oxygen concentration is known to be a key parameter for photochromism in rare-earth oxyhydride thin films. The experimental observations described above were explained by the decrease of the grain size as a result of the increase of the deposition pressure of the sputtering gas, followed by a higher oxygen incorporation.
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| 5. |
- Carstensen, Hauke, et al.
(författare)
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Self-assembly and percolation in two dimensional binary magnetic colloids
- 2022
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 18:33, s. 6222-6228
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Tidskriftsartikel (refereegranskat)abstract
- We study the self-assembly of branching-chain networks and crystals in a binary colloidal system with tunable interactions. The particle positions are extracted from microscopy images and order parameters are extracted by image processing and statistical analysis. With these, we construct phase diagrams with respect to particle density, ratio and interaction. In order to draw a more complete picture, we complement the experiments with computer simulations. We establish a region in the phase diagram, where bead ratios and interactions are symmetric, promoting percolated structures.
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| 6. |
- Dennison, Andrew J. C., et al.
(författare)
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Graphite intercalation compound (GIC) crystal monochromators for cold neutron instruments : Characterization of KC24 by time-of-flight neutron diffraction
- 2021
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 92:2
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Tidskriftsartikel (refereegranskat)abstract
- Graphite intercalation compounds (GICs) are a group of layered materials that are suitable as monochromators for cold neutrons. KC24 is a particularly interesting compound in this regard as it features a large c-axis lattice spacing of 8.74 angstrom, high reflectivity, and the possibility to produce large crystals with mosaicity that matches the beam divergence of cold neutron guides. GICs can be synthesized with different levels of intercalation, known as the stage of the compounds. Each stage displays a specific d-spacing. Impure GIC-monochromators containing multiple stages produce mixing of neutron wavelengths, which complicates data analysis on neutron reflectometers. We discuss the implications of GIC crystal purity and stage contamination for neutron reflectometry and show how GIC crystals can be characterized by time-of-flight neutron diffraction providing an efficient and quantifiable measure of the reflected wavelength spectrum. This allows taking into account multiple wavelength contaminations and ascertains the robustness of reflectometry measurements.
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| 7. |
- Droulias, S. A., et al.
(författare)
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Influence of deuterium-induced volume changes on optical transmission in Fe/V (001) and Cr/V (001) superlattices
- 2022
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 105:19
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Tidskriftsartikel (refereegranskat)abstract
- The deuterium-induced changes of the optical transmission in Fe/V (001) and Cr/V (001) superlattices are found experimentally to be dominated by the volume changes of the vanadium layers and thus indirectly linked to concentration. The deuterium-induced expansion is 67% larger in Cr/V 2/14 monolayers (ML) as compared to Fe/V 2/14 ML. This large difference can be explained by a difference in the site of deuterium from tetrahedral in Fe/V to octahedral in Cr/V. First-principles calculations based on this assumption give quantitative agreement with both the measured optical transmission and the deuterium-induced expansion coefficient. Placing hydrogen in the middle of the vanadium layers results in total energies at 0 K that favor tetrahedral occupancy at low concentrations, although the energy difference is of the order of the thermal energy available in the experiments. Hence small changes in strain, defect concentration, and/or vibrational spectrum of the superlattices may tip the balance to octahedral occupancy at low concentrations. Given this link to concentration and the linear scaling, optical transmission can, therefore, be used in a straightforward way to obtain pressure-composition isotherms also in thin metal films that do not undergo metal-insulator transitions upon hydrogenation.
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| 8. |
- Forooqi Motlaq, Vahid, et al.
(författare)
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Dissolution mechanism of supported phospholipid bilayer in the presence of amphiphilic drug investigated by neutron reflectometry and quartz crystal microbalance with dissipation monitoring
- 2022
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier. - 0005-2736 .- 1879-2642. ; 1864:10
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Tidskriftsartikel (refereegranskat)abstract
- The influence and interaction of the ionizable amphiphilic drug amitriptyline hydrochloride (AMT) on a 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) phospholipid bilayer supported on a silica surface have been investigated using a combination of neutron reflectometry and quartz crystal microbalance with dissipation monitoring. Adding AMT solutions with concentrations 3, 12, and 50 mM leaves the lipid bilayer mainly intact and we observe most of the AMT molecules attached to the head-group region of the outer bilayer leaflet. Virtually no AMT penetrates into the hydrophilic head-group region of the inner leaflet close to the silica surface. By adding 200 mM AMT solution, the lipid bilayer dissolved entirely, indicating a threshold concentration for the solubilization of the bilayer by AMT. The observed threshold concentration is consistent with the observation that various bilayer structures abruptly transform into mixed AMT-DOPC micelles beyond a certain AMT-DOPC composition. Based on our experimental observations, we suggest that the penetration of drug into the phospholipid bilayer, and subsequent solubilization of the membrane, follows a two-step mechanism with the outer leaflet being removed prior to the inner leaflet.
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| 9. |
- Gvaramia, Manuchar, et al.
(författare)
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Neutron spin echo spectroscopy with a moving sample
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Neutron spin echo spectroscopy is a high resolution inelastic neutron scattering method probing nanosecond dynamics. It is well suited to study the atomistic motion in polymer systems and contributes to our understanding of viscoelasticity. However, for samples under shear, or moving samples in general, Doppler scattering has to be considered. We compare the measured phase shift and depolarisation due to Doppler scattering from a rotating graphite disk to numerical and analytical calculations and find excellent agreement. This allows to take into account Doppler scattering during the data processing and makes longer Fourier times as well as higher shear rates and Q ranges possible with neutron spin echo spectroscopy, enabling for example the study of polymers under high shear.
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| 10. |
- Hans, Marcus, et al.
(författare)
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Photochromic Mechanism and Dual-Phase Formation in Oxygen-Containing Rare-Earth Hydride Thin Films
- 2020
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Ingår i: Advanced Optical Materials. - : WILEY-V C H VERLAG GMBH. - 2162-7568 .- 2195-1071. ; 8:19
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Tidskriftsartikel (refereegranskat)abstract
- The phase formation of a photochromic Gd-0.31(H0.55O0.45)(0.69)thin film, grown by reactive magnetron sputtering, is critically evaluated. Oxygen is preferably incorporated into the underdense columnar grain boundaries, when the as-deposited gadolinium hydride film is exposed to ambient conditions. Two phases, Gd(2)O(3)and GdH2, are formed with significant compressive residual stress of 5.9 +/- 1.5 GPa. These findings, extracted from transmission electron microscopy, X-ray diffraction and atom probe tomography, provide a straightforward explanation for the photochromic effect. The mechanism can be understood as photon-induced hydrogen transfer between the two phases, identical in nature to the photochromic effect in bulk yttrium hydride at high pressure.
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