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Capturing ultrafast molecular motions and lattice dynamics in spin crossover film using femtosecond diffraction methods
Full text linkA comprehensive insight into ultrafast dynamics of photo switchable materials is desired for efficient control of material properties through light excitation. Here, we study a polycrystalline spin crossover thin film as a prototypical example and reveal the sequential photo switching dynamics, from local molecular rearrangement to global lattice deformation. On the earliest femtosecond timescale, the local molecular structural rearrangement occurs within a constant unit cell volume through a two step process, involving initial Fe amp; 8722;ligand bond elongation followed by ligand rotation. The highly oriented structure of the nanocrystalline films and the experimental geometry enables resolving the full anisotropic lattice structural dynamics in and out of the sample plane separately. While both molecular switching and lattice heating influence lattice volume, they exert varying degrees of impact at disparate time scales following photoexcitation. This study highlights the opportunities provided by Mega electron volt electron and X ray free electron laser to advance the understanding of ultrafast dynamics of photo switchable material
Seasonality in Perovskite Solar Cells Insights from 4 Years of Outdoor Data
Full text linkInsights are reported from a 4 year outdoor study in Berlin using encapsulated p i n perovskite solar cells with the structure ITO 2PACz Cs0.15FA0.85PbI2.55Br0.45 bandgap of 1.65 eV C60 SnO2 Cu. Peak summer performance showed little to no degradation during the first two summers and only amp; 8776;2 absolute drop in outdoor power conversion efficiency from the first to fourth summer. Despite good stability, the devices exhibit significant seasonality, with winter performance up to 30 lower than in summer during the first year, increasing with aging. The factors contributing to this seasonality are separated into four categories I solar spectrum, II device temperature, III maximum power point tracking losses, and IV metastability effects. Among these, metastability particularly light soaking behavior is the largest contributing factor that sets perovskite technology apart from conventional photovoltaics. It was found that in cold, low light winter conditions, voltage gains from light soaking remain unsaturated, leading to reduced performance. Full saturation requires more than 24 h of continuous illumination, indicating that device performance depends on more than a single diurnal cycle. This comprehensive analysis highlights the complexity of seasonal behavior and the importance of long term, real world testing for accurate forecasting of perovskite photovoltaic energy yiel
Operando monitoring of the functional role of tetrahedral cobalt centers for the oxygen evolution reaction
No full textThe complexity of the intrinsic oxygen evolution reaction OER mechanism, particularly the precise relationships between the local coordination geometry of active metal centers and the resulting OER kinetics, remains to be fully understood. Herein, we construct a series of 3 amp; 8201;d transition metal incorporated cobalt hydroxide based nanobox architectures for the OER which contain tetrahedrally coordinated Co II centers. Combination of bulk and surface sensitive operando spectroelectrochemical approaches reveals that tetrahedral Co II centers undergo a dynamic transformation into highly active Co IV intermediates acting as the true OER active species which activate lattice oxygen during the OER. Such a dynamic change in the local coordination geometry of Co centers can be further facilitated by partial Fe incorporation. In comparison, the formation of such active Co IV species is found to be hindered in CoOOH and Co FeOOH, which are predominantly containing [CoIIIO6] and [CoII FeIIIO6] octahedra, respectively, but no mono amp; 956; oxo bridged [CoIIO4] moieties. This study offers a comprehensive view of the dynamic role of local coordination geometry of active metal centers in the OER kinetic
A new conservation material for gold in heritage wall paintings polymer stabilized nanogold gels NGGs
No full textGilded wall paintings such as those in Petra Jordan undergo deterioration processes such as delamination and loss of the gold layer. The aim of this work is to produce a functioning long lasting adhesive that compensates for binder and gold loss while stabilising the gold layer. Polymer stabilised gold nanoparticles AuNPs as a conservation material for gilded heritage paintings Nano Gold Gel NGG were synthesised using two facile and affordable synthesis approaches. AuNPs enhance the stability of the adhesive polymer over time and introduce mass conservation to the gold layer. Two natural polymers and one synthetic polymer, frequently used in conservation as adhesives, were used as reducing agents and stabilisers for the nanoparticles. The chemical alteration of the polymers and the Au polymer interaction at the molecular level were investigated with FTIR spectroscopy, while the chemical environment of gold was investigated with X ray absorption spectroscopy XANES EXAFS . The synthesized NGG was applied on the replica samples to reattach the gold layer to its support. Characterisation results indicate that the formation of AuNPs stabilised by the three polymers did not alter the chemical structure of the polymers. The applied NGG successfully achieved re adhesion and exhibited appropriate optical and chemical properties for use as a conservation materia
Thermal evolution of sol gel synthesized 8YSZ thin films insights from coupled in situ synchrotron diffraction and electrical conductivity measurements
No full textThe thin film approach for Solid Oxide Cell SOC electrolytes offers a pathway to reduce the high fabrication and operating temperatures of these devices. In this work, we present a detailed ex situ and in situ study of 8 mol yttria stabilized zirconia 8YSZ nanostructured dense thin films with a thickness of 100 nm. These films were synthesised through the sol gel method and deposited by dip coating on fused glass. The microstructural and crystalline evolution in the 300 800 C range was studied by synchrotron Grazing Incidence X ray Diffraction GIXRD . Crystallisation of the 8YSZ films was observed to start at 343 C with 4 5 nm crystallites consisting only of the cubic phase. With increasing temperature, this phase is maintained and the crystallite size reaches 38 nm at 800 C. Additionally, the evolution of the lattice parameter was studied, which allowed us to determine the variation of the thermal expansion coefficient TEC of the films during both heating and cooling. The TEC as a function of temperature has three linear regions during heating and two during cooling, with values between 9.6 10 amp; 8722;7 K amp; 8722;1 and 3.7 10 amp; 8722;5 K amp; 8722;1. These findings provide valuable insights into the structural response of the material under thermal cycling, relevant to the performance and stability of SOC devices. Coupled with the crystallographic characterisation, the electrical properties of the thin films were studied through conductivity measurements, obtaining conductivities about 1.5 to 5 times higher than the conductivity of 8YSZ bulk samples, with values of 0.06 S cm amp; 8722;1 at 700 C. Thus, the conjunction of a reduced electrolyte thickness with the enhanced conductivity of nanostructured 8YSZ makes these films attractive for intermediate temperature SOC application
A Crystalline Bismuth II Radical Anion Synthesis, Characterization, and Reactivity
No full textWe report the synthesis of a planarized tris amidobismuthane supported by a rigid, bulky NNN pincer ligand, which enforces a T shaped geometry at the bismuth center. The Bi NNN complex features a low lying LUMO with distinct Bi 6p orbital character as shown by DFT calculations. Cyclic voltammetry reveals a fully reversible one electron reduction at E1 2 1.85 V versus Fc0 in THF. Chemical reduction with KC8 in the presence of 4,7,13,16,21,24 hexaoxa 1,10 diazabicyclo[8.8.8]hexacosane 222 crypt enables the isolation of an unprecedented Bi II radical anion in high isolated yields. Multi frequency EPR, X ray absorption spectroscopy and SQUID magnetometry complemented by theoretical calculations confirm localization of the unpaired electron on the bismuth center. Preliminary reactivity studies display radical reactivity as shown by single electron transfer chemistry and radical coupling reaction
Mechanistic insights into the structure based design of a CspZ targeting Lyme disease vaccine
No full textBorrelia burgdorferi Bb causes Lyme disease LD , one of the most common vector borne diseases in the Northern Hemisphere. Here, we solve the crystal structure of a mutated Bb vaccine antigen, CspZ YA that lacks the ability to bind to host complement factor H FH . We generate point mutants of CspZ YA and identify CspZ YAI183Y and CspZ YAC187S to trigger more robust bactericidal responses. Compared to CspZ YA, these CspZ YA mutants require a lower immunization frequency to protect mice from LD associated inflammation and bacterial colonization. Antigenicity of wild type and mutant CspZ YA proteins are similar, as measured using sera from infected people or immunized female mice. Structural comparison of CspZ YA with CspZ YAI183Y and CspZ YAC187S shows enhanced interactions of two helices adjacent to the FH binding sites in the mutants, consistent with their elevated thermostability. In line with these findings, protective CspZ YA monoclonal antibodies show increased binding to CspZ YA at a physiological temperature 37 amp; 8201; C . In summary, this proof of concept study applies structural vaccinology to enhance intramolecular interactions for the long term stability of a Bb antigen while maintaining its protective epitopes, thus promoting LD vaccine developmen
Topological modeling of metallic foams
Full text linkUnderstanding material s micro and macrostructure is key to linking inner structure information to large scale physical properties and function. An improvement of the microstructure during production processes can lead to materials with enhanced physical properties or even to the development of new classes of materials. In this paper, we develop an accurate topological model to describe the dual neighborhood structure of foams and other cellular materials e.g. plant cell clusters or polycrystalline materials like steel, rocks, and ceramics obtained by x ray tomography, adhering to Plateau s rules four pores meet at a vertex, and three meet along an edge. While the degree of non convexity in the pores is a priori unknown, our approach is designed for structures without extreme geometric irregularities e.g. tangled pores . It provides meaningful combinatorial numerical validation in such cases but may not extend reliably to more complex geometries. To illustrate our method, we analyze a sample of aluminum foam comprising 1911 pores. The resulting abstract combinatorial foam structure partially aligns with that of the associated power diagram sharing 51.45 of the tetrahedra in the dual complex but also reveals significant deviation
Development of Aluminum Scandium Alloys for Hydrogen Storage Valves
Full text linkFor the development of aluminum scandium alloys to produce a hydrogen storage valves, various aluminum alloy series with different Sc and Zr contents are tested. The alloys are mainly characterized by hardness measurements and tensile tests. The hardening curves are recorded for different temperatures and compositions, and the selected parameters are validated with the corresponding mechanical tests. The alloys 5083 amp; 8201; amp; 8201;0.2 Sc and AlSi16Mg1Sc0.4 are selected for the production of hydrogen valves by forging and additive manufacturin
Converting experiment data to NeXus application definitions at BESSY II
Full text linkIn our efforts to achieve FAIR data practices at BESSY II, we are leveraging the NeXus standard [1], a common data exchange format for data obtained in the fields of neutron, muon, and X ray science. Two core components of this standard are its base classes and application definitions. NeXus base classes serve as building blocks, offering community agreed names and data structures for all devices required to run an experiment, including those on the beamline. Built upon these base classes, NeXus application definitions specify the minimal required structures and data elements necessary to represent a given experimental technique. In this work, we present preliminary results from the development of an application definition for a multi modal experiment conducted at the mySpot beamline of BESSY II. This versatile beamline supports measurements with multiple techniques XRD, SAXS, XRF, EXAFS, and XANES performed simultaneously under in operando conditions. For the data conversion process, we use pynxtools [2], a tool designed to facilitate FAIR experimental data. Additionally, we discuss the perspective of this development for the Bluesky NeXus package [3], developed at BESSY II, which enables the automated export of NeXus compliant HDF5 files for Blueksy based experiments and beamlines. [1] https www.nexusformat.org [2] https github.com FAIRmat NFDI pynxtools [3] https codebase.helmholtz.cloud hzb bluesky core source blueskynexu