| 1. |
- Bannenberg, Lars J., et al.
(author)
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Direct Comparison of PdAu Alloy Thin Films and Nanoparticles upon Hydrogen Exposure
- 2019
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In: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 11:17, s. 15489-15497
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Journal article (peer-reviewed)abstract
- Nanostructured metal hydrides are able to efficiently detect hydrogen in optical sensors. In the literature, two nanostructured systems based on metal hydrides have been proposed for this purpose each with its own detection principle: continuous sub-100 nm thin films read out via optical reflectance/transmittance changes and nanoparticle arrays for which the detection relies on localized surface plasmon resonance. Despite their apparent similarities, their optical and structural response to hydrogen has never been directly compared. In response, for the case of Pd 1-y Au y (y = 0.15-0.30) alloys, we directly compare these two systems and establish that they are distinctively different. We show that the dissimilar optical response is not caused by the different optical readout principles but results from a fundamentally different structural response to hydrogen due to the different nanostructurings. The measurements empirically suggest that these differences cannot be fully accounted by surface effects but that the nature of the film-substrate interaction plays an important role and affects both the hydrogen solubility and the metal-to-metal hydride transition. In a broader perspective, our results establish that the specifics of nanoconfinement dictate the structural properties of metal hydrides, which in turn control the properties of nanostructured devices including the sensing characteristics of optical hydrogen sensors and hydride-based active plasmonic systems.
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| 2. |
- Caselli, Lucrezia, et al.
(author)
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Interaction of nanoparticles with lipid films : the role of symmetry and shape anisotropy
- 2022
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:5, s. 2762-2776
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Journal article (peer-reviewed)abstract
- The bioactivity, biological fate and cytotoxicity of nanomaterials when they come into contact with living organisms are determined by their interaction with biomacromolecules and biological barriers. In this context, the role of symmetry/shape anisotropy of both the nanomaterials and biological interfaces in their mutual interaction, is a relatively unaddressed issue. Here, we study the interaction of gold nanoparticles (NPs) of different shapes (nanospheres and nanorods) with biomimetic membranes of different morphology, i.e. flat membranes (2D symmetry, representative of the most common plasma membrane geometry), and cubic membranes (3D symmetry, representative of non-lamellar membranes, found in Nature under certain biological conditions). For this purpose we used an ensemble of complementary structural techniques, including Neutron Reflectometry, Grazing Incidence Small-Angle Neutron Scattering, on a nanometer lengthscale and Confocal Laser Scanning Microscopy on a micrometer length scale. We found that the structural stability of the membrane towards NPs is dependent on the topological characteristic of the lipid assembly and of the NPs, where a higher symmetry gave higher stability. In addition, Confocal Laser Scanning Microscopy analyses highlighted that NPs interact with cubic and lamellar phases according to two distinct mechanisms, related to the different structures of the lipid assemblies. This study for the first time systematically addresses the role of NPs shape in the interaction with lipid assemblies with different symmetry. The results will contribute to improve the fundamental knowledge on lipid interfaces and will provide new insights on the biological function of phase transitions as a response strategy to the exposure of NPs.
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| 3. |
- Chien, Yu-Chuan, 1990-, et al.
(author)
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Correlations between precipitation reactions and electrochemical performance of lithium-sulfur batteries probed by operando scattering techniques
- 2022
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In: Chem. - : Elsevier. - 2451-9294. ; 8:5
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Journal article (peer-reviewed)abstract
- A comprehensive description of electrochemical processes in the positive electrode of lithium-sulfur batteries is crucial for the utilization of active material. However, the discharge mechanisms are complicated due to various reactions in multiple phases and the tortuosity of the highly porous carbon matrix. In this work, simultaneous measurements of small-angle and wide-angle scattering and cell resistance are performed on operating lithium-sulfur cells. Results indicate that precipitates grow mostly in number, not in size, and that the structure of the carbon matrix is not affected. The comparison of the small-angle and wide-angle scattering reveals the amorphous discharge products found at a low discharge rate. Further analysis demonstrates the correlation between the diffusion resistance and the compositional change of electrolyte in the mesopores at the end of discharge, which suggests that Li-ion deficiency is the limiting factor for sulfur utilization at a medium discharge rate.
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| 4. |
- Chien, Yu-Chuan, 1990-, et al.
(author)
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Mechanistic Insights on the Mesoscale in the Positive Electrode of Lithium–Sulfur Batteries
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Other publication (other academic/artistic)abstract
- A comprehensive description of the electrochemical processes in the positive electrodeof lithium–sulfur batteries is critical to the enhancement of sulfur utilization. However,the discharge mechanisms are complicated due to the various reactions in multiplephases and the tortuosity of the highly porous carbon matrix. While previous studieshave focused on the precipitation of Li2S, the effect of the limited mass transport insidethe micro-/mesopores of an electrode with optimized surface area have largely beenneglected. In this work, operando small-angle scattering with three different contrasts,and wide-angle scattering, has been performed with simultaneous resistance measure-ment of internal and diffusion. The results indicate that both electrode passivation andcomplete pore blockage are unlikely since the precipitates are surrounded by the elec-trolyte and grow mostly in number, not in size. The difference between the small- andwide-angle scattering reveals the amorphous discharge products at a low C-rate. Furtheranalyses demonstrate the correlation between the diffusion resistance and the contrastin the mesopores at the end of discharge, which suggests that Li-ion deficiency is thelimiting factor of sulfur utilization at a medium C-rate.
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| 5. |
- Dabkowska, Aleksandra P., et al.
(author)
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Non-lamellar lipid assembly at interfaces : controlling layer structure by responsive nanogel particles
- 2017
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In: Interface Focus. - : ROYAL SOC. - 2042-8898 .- 2042-8901. ; 7:4
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Journal article (peer-reviewed)abstract
- Biological membranes do not only occur as planar bilayer structures, but depending on the lipid composition, can also curve into intriguing three-dimensional structures. In order to fully understand the biological implications as well as to reveal the full potential for applications, e.g. for drug delivery and other biomedical devices, of such structures, well-defined model systems are required. Here, we discuss the formation of lipid non-lamellar liquid crystalline (LC) surface layers spin-coated from the constituting lipids followed by hydration of the lipid layer. We demonstrate that hybrid lipid polymer films can be formed with different properties compared with the neat lipid LC layers. The nanostructure and morphologies of the lipid films formed reflect those in the bulk. Most notably, mixed lipid layers, which are composed of glycerol monooleate and diglycerol monooleate with poly(N-isopropylacrylamide) nanogels, can form films of reverse cubic phases that are capable of responding to temperature stimulus. Owing to the presence of the nanogel particles, changing the temperature not only regulates the hydration of the cubic phase lipid films, but also the lateral organization of the lipid domains within the lipid self-assembled film. This opens up the possibility for new nanostructured materials based on lipid-polymer responsive layers.
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| 6. |
- Ukleev, Victor, et al.
(author)
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Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru]10 multilayers
- 2024
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In: Science and Technology of Advanced Materials. - : Taylor & Francis. - 1468-6996 .- 1878-5514. ; 25:1
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Journal article (peer-reviewed)abstract
- We report investigations of the magnetic textures in periodic multilayers [Pt(1 nm)/(CoFeB(0.8 nm)/Ru(1.4 nm)]10 using polarised neutron reflectometry (PNR) and small-angle neutron scattering (SANS). The multilayers are known to host skyrmions stabilized by Dzyaloshinskii-Moriya interactions induced by broken inversion symmetry and spin–orbit coupling at the asymmetric interfaces. From depth-dependent PNR measurements, we observed well-defined structural features and obtained the layer-resolved magnetization profiles. The in-plane magnetization of the CoFeB layers calculated from fitting of the PNR profiles is found to be in excellent agreement with magnetometry data. Using SANS as a bulk probe of the entire multilayer, we observe long-period magnetic stripe domains and skyrmion ensembles with full orientational disorder at room temperature. No sign of skyrmions is found below 250 K, which we suggest is due to an increase of an effective magnetic anisotropy in the CoFeB layer on cooling that suppresses skyrmion stability. Using polarised SANS at room temperature, we prove the existence of pure Néel-type windings in both stripe domain and skyrmion regimes. No Bloch-type winding admixture, i.e. an indication for hybrid windings, is detected within the measurement sensitivity, in good agreement with expectations according to our micromagnetic modelling of the multilayers. Our findings using neutron techniques provide valuable microscopic insights into the rich magnetic behavior of skyrmion-hosting multilayers, which are essential for the advancement of future skyrmion-based spintronic devices.
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