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Applications of electron energy measurement based on resonant spin depolarization at BESSY II
Get PDFAn electron energy measurement based on resonant spin depolarization has been running permanently at BESSY II for several years. This high precision energy measurement was set up primarily for users of synchrotron radiation for meteorological applications from the Physikalisch Technische Bundesanstalt PTB . Recent investigations have led to a better understanding of the method and the possibility of shortening the measurement time. This allows for new observations and the use of the energy measurement for different applications such as the model free measurement of the natural chromaticity, the momentum compaction factor or synchrotron sideband
Lichtgetriebener Elektronentransfer durch Phospholipid Doppelschichten in anaerober und aerober Atmosphäre
Get PDFIn der natürlichen Photosynthese ermöglicht der lichtgetriebene Elektronentransfer durch die Thylakoidmembran eine effiziente Ladungstrennung und die Kompartimentierung von Reaktionsräumen zur Erzeugung von NADPH und CO2 sowie die Oxidation von Wasser. Diese Reaktionen sind komplementäre Redoxreaktionen und erfordern jeweils unterschiedliche Reaktionsbedingungen für optimale Leistungsfähigkeit. Derzeitige Studien zur künstlichen Photosynthese werden hauptsächlich in Lösung durchgeführt und die Komponenten sind empfindlich gegenüber Sauerstoff, was ihre Anwendbarkeit an Luft und unter wasserspaltenden Bedingungen einschränkt. In diesem Artikel berichten wir über den lichtgetriebenen Elektronentransfer durch eine Lipid Doppelschichtmembran von Liposomen mittels eines starren oligoaromatischen molekularen Drahtes, der es ermöglicht, eine Oxidations und eine Reduktionsreaktion, die durch die Membran räumlich getrennt sind, elektronisch zu verbinden. Der molekulare Draht hat ein einfaches, symmetrisches, leicht zu synthetisierendes Design auf der Basis von Benzothiadiazol und Fluoren Einheiten und absorbiert Licht im sichtbaren Spektrum, wodurch er sich für die Umwandlung von Sonnenenergie eignet. Die Modellreaktionen in dieser Studie sind die lichtgetriebene NADH Oxidation im inneren wässrigen Kompartiment der Liposomen und die lichtgetriebene Reduktion eines organischen wasserlöslichen Farbstoffs in der äu eren wässrigen Hauptphase. Darüber hinaus ist das System sowohl in aerober als auch in anaerober Atmosphäre aktiv, was vielversprechend ist für zukünftige Reaktionen an Luft und für Reaktionen, bei denen Sauerstoff erzeugt wird, wie beispielsweise die solarbetriebene Wasserspaltung im Kontext der künstlichen Photosynthes
Fluorine Free Ion Exchange Membranes for Photo electrochemical Applications
Get PDFThe increasing global demand for sustainable energy solutions has driven significant advancements in photoelectrochemical PEC technologies, particularly for hydrogen production and biomass valorization. A key challenge for PEC cells is the selection of ion exchange membranes IEMs that ensure efficient product separation between anode and cathode half cells while enabling efficient ion transport. Moreover, these membranes also need to show long term stability. Traditionally, perfluorinated membranes such as Nafion have been widely used due to their high proton conductivity and chemical resilience. However, their high cost, environmental concerns, and the impending regulatory restrictions on per and polyfluoroalkyl substances necessitate the development of fluorine free alternatives. This review explores the latest advancements in fluorine free IEMs for photo electrochemical applications, highlighting their synthesis, physicochemical properties, appropriate characterization methods, and performance metrics. We discuss emerging materials that offer comparable ionic conductivity, durability, and operational efficiency while addressing recyclability and environmental impact. By assessing the potential of these next generation membranes, we aim to provide insights into their role in advancing photo and electrochemical systems toward a more sustainable and economically viable futur
Above Room Temperature Ferromagnetism in Large Scale Epitaxial Fe3GaTe2 Graphene van der Waals Heterostructures
Get PDFFe3GaTe2 FGaT , a two dimensional 2D layered ferromagnetic metal, exhibits a high Curie temperature TC of amp; 8764;360 K along with strong perpendicular magnetic anisotropy PMA , making it a promising material candidate for next generation energy efficient magnetic devices. However, the vast majority of studies on FGaT to date have been limited to millimeter sized bulk crystals and exfoliated flakes, which are unsuitable for practical applications and integration into device processing. Also, its combination with other 2D materials to form van der Waals vdW heterostructures has only been achieved by flake stacking. Consequently, the controlled large area growth of FGaT and related heterostructures remains largely unexplored. In this work, we demonstrate the high quality, large area growth of epitaxial FGaT thin films on single crystalline graphene SiC templates using molecular beam epitaxy. Structural characterization confirms the high crystalline quality of the continuous FGaT graphene vdW heterostructures. Temperature dependent magnetization and anomalous Hall measurements reveal robust PMA with an enhanced TC well above room temperature, reaching up to 400 K. Furthermore, X ray absorption and X ray magnetic circular dichroism spectra provide insight into the spin and orbital magnetic moment contributions, further validating the high TC and robust PMA. These findings are highly significant for the future development of high performance spintronic devices based on 2D heterostructures, with potential applications in next generation data storage, logic processing, and quantum technologie
Structure Guided Engineering of a Versatile Urethanase Improves Its Polyurethane Depolymerization Activity
Get PDFPolyurethane PUR , the fifth most prevalent synthetic polymer, substantially contributes to the global plastic waste problem. Biotechnology based recycling methods have recently emerged as innovative solutions to plastic waste disposal and sparked interest among scientific communities and industrial stakeholders in discovering and designing highly active plastic degrading enzymes. Here, the ligand free crystal structure of UMG SP2, a metagenome derived urethanase with depolymerization activities, at 2.59 resolution, as well as its co structures bound to a suicide hydrolase inhibitor and a short chain carbamate substrate at 2.16 and 2.40 resolutions, respectively, is reported. Structural analysis and molecular dynamics simulations reveal that the flexible loop L3 consisting of residues 219 226 is crucial for regulating the hydrolytic activity of UMG SP2. The semi rational redesign of UMG SP2 reveals superior variants, A141G and Q399A, exhibiting over 30.7 and 7.4 fold increased activities on polyester PUR and a methylene diamine derivative of PUR, respectively, compared to the wild type enzyme. These findings advance the understanding of the structure function relationship of PUR hydrolyzing enzymes, which hold great promise for developing effective industrial PUR recycling processes and mitigating the environmental footprint of plastic wast
The use of a dynamic solvent system as a novel approach to sustainable MOF crystallization
No full textHerein, we report a novel and green synthetic approach for pyrazolate based metal organic frameworks MOFs as demonstrated by the three prominent examples of this material class [Ni bdp ]n and two supramolecular isomers [Zn bdp ]n and BUT 58 H2bdp 1,4 bis 1H pyrazol 4 yl benzene . The replacement of dimethylformamide DMF with a dynamic solvent system DSS a reactive mixture of 1 butanol and acetic acid in the synthesis allows us to avoid toxic chemicals, as well as precisely control the crystal size and morphology of the products. Unlike DMF, which decomposes into lower value byproducts during synthesis, DSS produces a value added ester butyl acetate . Furthermore, a sustainable washing procedure fully eliminates the need for DMF, while ensuring a high porosity product. Improved material crystallinity leads to a more pronounced breathing behavior during nitrogen physisorption. Moreover, flexibility modulation through crystal size engineering becomes within reach. Due to the accessibility to highly crystalline materials, single crystal X ray diffraction on the pristine crystals could be performed to elucidate the preferred adsorption sites in the studied framework
Moon photovoltaics utilizing lunar regolith and halide perovskites
Get PDFPowering future Moon settlements requires reliable and cost effective energy generation with high specific power. Here, we propose halide perovskite photovoltaics PV fabricated on regolith based moonglass that could be produced on the Moon, thereby saving 99 of material transport weight. This enables effective specific power ratios, over 22 50 W g, a factor of 20 100 higher compared to traditional space PV solutions, while not compromising radiation shielding, reliability, and mechanical stability as done until now. Using anorthosite high glass forming regolith simulant, we achieve transparent moonglasses that allow depositing high quality perovskites. We achieve performances on par with references, revealing the potential of perovskite based Moon photovoltaics, and propose routes to achieve power conversion efficiencies of 23 . The moonglass exhibits high tolerance to high energetic proton irradiation, which, when combined with the radiation tolerance of perovskites, allows highly radiation tolerant, reliable devices paving the way to future sustainable lunar energy solution
Pattern Matching Based Denoising for Images with Repeated Sub Structures
Get PDFIn electron microscopy, obtaining low noise images is often difficult, especially when examining biological samples or delicate materials. Therefore, the suppression of noise is essential for the analysis of such noisy images. State of the art image denoising methods are dominated by supervised Convolution neural network CNN based methods. However, supervised CNNs cannot be used if a noise free ground truth is unavailable. To address this problem, we propose a method that uses re occurring patterns in images. Our proposed method does not require noise free images for the denoising task. Instead, it is based on the idea that averaging images with the same signal having independent noise suppresses the overall noise. In order to evaluate the performance of our method, we compare our results with other state of the art denoising methods that do not require a noise free image. We show that our method is the best for retaining fine image structures. Additionally, we develop a confidence map for evaluating the denoising quality of the proposed method. Furthermore, we analyze the time complexity of the algorithm to ensure scalability and optimize the algorithm to improve the runtime efficienc
Breaking Barriers Centimeter Sized Single Layer WSe2 by Gold Mediated Exfoliation for Ambipolar Field Effect Transistors at Ultra Low Voltages
Get PDFTransition Metal Dichalcogenides TMDCs are promising semiconductor alternatives to silicon in CMOS technology. Their layered nature allows scaling to a single layer 1L without degrading electrical performance, enabling further miniaturization of field effect transistors FETs . TMDCs like WSe2 exhibit ambipolar transport, allowing fabrication of both p type and n type devices on a single flake, simplifying circuit design. Ambipolar, large area, high quality 1L WSe2 is therefore highly desirable. Here, centimeter scale exfoliated 1L WSe2 is achieved, reaching 1L areas of up to 20 mm2 via thermally activated gold mediated TMDC exfoliation using large, high quality WSe amp; 8322; parent crystals. The quality of 1L WSe2 is comprehensively investigated via Raman spectroscopy, photoluminescence, X ray, and ultraviolet photoelectron spectroscopy, as well as electronic transport measurements. For the latter, 1L WSe2 based FETs are fabricated on lithium ion conducting glass ceramic substrates serving as both supporting substrate and high performance gate. Subthreshold slopes as steep as 30 and 50 mV dec amp; 8722;1, maximum mobilities of 15 and 18 cm2 V amp; 8315; s amp; 8315; , and ON OFF ratios of amp; 8776;108 and 109 for electron and hole currents, respectively, are achieved at ultra low gate voltages amp; 8776;2 V . The performance, demonstrated across 15 devices, suggests that 1L WSe2 in this device architecture can pave the way toward providing an alternative to conventional silicon based CMOS technology for innovative, further miniaturized device
Local solid state processes adjust the selectivity in catalytic oxidation reactions on cobalt oxides
Get PDFTransition metal oxides are excellent catalysts for selective oxidation reactions, which are a prominent source of industrially relevant chemicals. However, these reactions suffer from multiple competing reaction pathways, limiting the selectivity. Thus, it is essential to gain an understanding of the underlying processes occurring on the catalyst that affect its performance. Here we synergistically combine operando X ray spectroscopy and operando transmission electron microscopy to unravel a network of solid state processes that controls the catalytic properties of Co3O4 in the oxidation of 2 propanol towards acetone. These include exsolution, diffusion and defect formation, which strongly distort the catalyst lattice at lower temperatures. Ultimately, they also lead to a maximum in acetone selectivity when the catalyst is trapped in a frustrated or metastable state at the onset of crystallization of the exsolved particles to CoO and void formation, which coincides with the maximum in surface cobalt oxidation state in the spine