Microporous and Mesoporous Materials 398 (2025): 113832

https://doi.org/10.1016/j.micromeso.2025.113832

The recent synthetic accessibility of aluminosilicate and all-silica zeolites with extremely large pore sizes opens new opportunities in materials science. Beyond their catalytic applications, these novel materials uniquely enable the adsorption of very large molecules—a capability previously unrealized with conventional zeolites due to pore size restrictions, which consequently hindered adsorption studies of such compounds. This work explores new use cases for these materials by investigating the adsorption of various antibiotics, with molar masses up to 900 g/mol, in hydrophobic extra-large pore zeolites. We highlight the significant potential of these advanced zeolites for critical applications, like the removal of antibiotics from wastewater and the development of novel drug delivery systems. Employing classical forcefield-based simulations, we explain the main molecular structure-topology relationships that govern the formation of strongly interacting combinations between specific antibiotics and extra-large pore zeolite frameworks.

 © 2025 The Authors. Published by Elsevier Inc.

npj Microgravity 11 (2025): 1-9

https://doi.org/10.1038/s41526-025-00521-9

The long-term goal of establishing a sustained human presence on Mars requires the capacity to produce essential consumables on-site. To this end, we develop strategies for processing inorganic oxidic powders and biomass into highly particle-filled composites using direct ink writing (DIW) 3D printing. Our approach relies on a simulant of a Martian regolith unit rich in hydrated clay minerals and food-grade spirulina, used as proxies for local regolith and cyanobacterial biomass, respectively. The composites are further reinforced through crosslinking with the plant-based molecule genipin. Detailed rheological analysis was performed for the 3D printing feedstocks, while the printed composites were characterized using thermal gravimetric analysis (TGA), surface area porosity analysis (BET), microscopy and mechanical tests. Dissolution tests demonstrated that genipin effectively crosslinks the cyanobacterial biomass. The outcome is a highly porous, lightweight material with adaptable, complex morphology, which has significant potential for use in the resource-constrained environments of long-duration Mars missions.

 © 2025 The Author(s)

Nature Chemistry  (2025): 1-7

https://doi.org/10.1038/s41557-025-01890-0

Since the early days of space exploration, the efficient production of oxygen and hydrogen via water electrolysis has been a central task for regenerative life-support systems. Water electrolysers are, however, challenged by the near-absence of buoyancy in microgravity, resulting in hindered gas bubble detachment from electrodes and diminished electrolysis efficiencies. Here we show that a commercial neodymium magnet enhances water electrolysis with current density improvements of up to 240% in microgravity by exploiting the magnetic polarization of the electrolyte and the magnetohydrodynamic force. We demonstrate that these interactions enhance gas bubble detachment and displacement through magnetic convection and achieve passive gas–liquid phase separation. Two model magnetoelectrolytic cells, a proton-exchange membrane electrolyser and a magnetohydrodynamic drive, were designed to leverage these forces and produce oxygen and hydrogen at near-terrestrial efficiencies in microgravity. Overall, this work highlights achievable, lightweight, low-maintenance and energy-efficient phase separation and electrolyser technologies to support future human spaceflight architectures

 © 2025 Attribution 4.0 International ( CC BY 4.0 )

Bioresource Technology 427 (2025): 132383

https://doi.org/10.1016/j.biortech.2025.132383

A sustained presence on Mars requires the production of food on site, but farming is limited by the local availability of suitable nutrients. Cyanobacteria can feed on Martian resources, and we hypothesized that the nutrients they mobilize could be extracted through anaerobic digestion and used as crop fertilizer.We therefore tested the abilities of three microbial communities to digest the biomass of Anabaena sp. in minimal medium, 200 g L^-1 Mars regolith simulant (MGS-1), and water.All communities produced ammonium and removed organic carbon in all media, especially in minimal medium and 200 g L^-1 MGS-1. However, MGS-1 also adsorbed organics and reduced the phosphate and ammonium recovery efficiency. A taxonomic analysis revealed a syntrophic fermentative community and hydrogenotrophic methanogens in minimal medium, but methanogens were outcompeted in MGS-1 by sulfate-reducing bacteria.Overall, this study suggests the viability of a bioprocess which could support crop production from Martian resources.

 © 2025, Attribution 4.0 International (CC BY 4.0)

Journal of Power Sources 640 (2025): 236630

https://doi.org/10.1016/j.jpowsour.2025.236630

The interplay between bubble release dynamics and surface wettability profoundly influences the performance of water dissociation systems; a topic not well understood. To systematically study the effect of electrode geometry and wettability, we have employed additive manufacturing to fabricate textured 316L-stainless steel electrodes composed of well-arranged pillars with different geometries and hydrophilicity. Through combined experimental and simulation approaches using bubbly flow models, we demonstrate that geometrically-induced wettability significantly affects hydrogen bubble dynamics, transitioning from gas-filled to liquid-filled states, and modulates bubble growth and detachment mechanisms. It is shown that the kinetics of bubble release and the surface coverage on hemispherical-topped pillars can finely be tuned to reduce the transport overpotential by 68.8 % and to increase the Faradaic efficiency (FE) by 191.5 % at −300 mA cm⁻² relative to untextured electrodes. These findings delineate a pragmatic approach toward the design of textured electrodes for efficient gas-evolving reactions.

 © 2025 Elsevier B.V. All rights are reserved

Materials Today Communications 46 (2025): 112734

https://doi.org/10.1016/j.mtcomm.2025.112734

Through adaption of the process parameters during additive manufacturing, the microstructure of Ti-6Al-4V parts can be tailored through in-situ heat treatment and post processes. The influence of the energy input, described by the line and the volume energy density as well as the influence of the laser power on microstructural features and the resulting fundamental mechanical properties is shown. Higher energy inputs and laser power leading to higher β-phase contents up to 7.4 vol.-% in as-built state and a very fine bimodal to fully lamellar microstructure combining high strength of 1183 MPa with a high ductility of 11.4 % but a low impact toughness of 118 kJ m^-2. Beyond this, hot-isostatic pressing is applied as a secondary heat treatment step, to close low-density defects and tune the properties even further. By adapting the energy inputs during additive manufacturing, the final volume content of precipitation-hardened β-phase and α-morphology can be controlled by adjusting the initial as-built mircostrucutre and the oversaturation of the phases due to in-situ heat treatment of the laser additive manufacturing process. This leads to an increase of the material strength of 11 % to 1095 MPa in combination with an elongation of 12 % and a high impact toughness of 348 kJ m^-2. This shows the potential of additive manufacturing as a preliminary heat treatment step for hot-isostatic pressing, allowing defect-free locally adjusted microstructures, which could combine high strength, ductility and toughness.

 © 2025 The Author(s). Published by Elsevier Ltd.

Nature Physics  (2025): 1-7

https://doi.org/10.1038/s41567-025-02889-7

Floquet engineering—the coherent dressing of matter via time-periodic perturbations—is a mechanism to realize and control emergent phases in materials out of equilibrium. However, its applicability to metallic quantum materials and semimetals such as graphene is an open question. The report of light-induced anomalous Hall effect in graphene remains debated, and a time-resolved photoemission experiment has suggested that Floquet effects might not be realizable in graphene and other semimetals with relatively short decoherence times. Here we provide direct spectroscopic evidence of Floquet effects in graphene through electronic structure measurements. We observe light–matter-dressed Dirac bands by measuring the contribution of Floquet sidebands, Volkov sidebands and their quantum path interference to graphene’s photoemission spectrum. Our results demonstrate that Floquet engineering in graphene is possible, even though ultrafast decoherence processes occur on the timescale of a few tens of femtoseconds. Our approach offers a way to experimentally realize Floquet engineering strategies in metallic and semimetallic systems and for the coherent stabilization of light-induced states with potentially non-trivial topological properties.

 © 2025 The Author(s)

Nature Communications 16(2025): 3209

https://doi.org/10.1038/s41467-025-58402-4

Structural disorder can be used to tune the properties of functional materials and is an important tool that can be employed for the development of complex framework materials, such as metal-organic frameworks. Here we show the synthesis and structural characterization of a metal-organic framework, UoB-100(Dy). Average structure refinements indicate that the node is disordered between two orientations of the nonanuclear secondary building unit (SBU). By performing 3D diffuse scattering (DS) analysis and Monte Carlo (MC) simulations, we confirm the presence of strong correlations between the metal clusters of UoB-100(Dy). These nodes assemble into a complex nanodomain structure. Quantum mechanical calculations identify linker strain as the driving force behind the nanodomain structure. The implications of such a nanodomain structure for the magnetic, gas storage, and mechanical properties of lanthanide MOFs are discussed.

 © 2025 The Author(s)

Advanced Energy and Sustainability (2025): 2400448

https://doi.org/10.1002/aesr.202400448

Lithium-ion batteries (LIBs) are indispensable in modern electronic instruments and electric vehicles because of their high energy density and long cycle life. However, the performance of traditional LIBs is constrained by limited theoretical specific capacities and structural stabilities, failing to meet the demands of next-generation high-performance applications. Transition metal sulfides are emerging as promising electrode materials due to their low cost, high theoretical capacities, and superior intrinsic properties. Compared to oxides, metal sulfides exhibit enhanced electrical conductivity, faster ion diffusion, and multi-electron transfer capabilities, which collectively enable higher energy density, better rate performance, and improved cycling stability. Flame spray pyrolysis (FSP) offers a scalable, cost-effective method for synthesizing functional structured electrode materials. This one-step process facilitates precise control over particle composition, and morphology, enabling complex modifications such as doping, homogeneous mixing, coating, and noble metal promotion/functionalization. FSP also produces metastable nanoparticle phases and allows direct deposition of materials onto electrodes without binders or solvents, streamlining electrode fabrication. The integration of FSP synthesis with electrode production in a continuous process chain holds immense potential for large-scale manufacturing of LIB electrodes. This approach is anticipated to revolutionize energy storage technologies, addressing the challenges of cost, performance, and scalability.

 © 2025, Attribution 4.0 International (CC BY 4.0)

Small (2025): 2409993

https://doi.org/10.1002/smll.202409993

The objective of this study is to investigate the influence of various process parameters, such as the fuel-to-oxygen ratio, precursor flow rate, co-flow rate, and different metal-to-sulfur ratios on the properties of metal sulfide particles synthesized via flame spray pyrolysis (FSP). The particle size increases with increasing dispersion oxygen flow and copper sulfide is obtained only when the fuel-to-oxygen ratio is equal to or higher than 1.5. The temperature of the flame rises with an increasing precursor flow rate and copper sulfide is formed at a precursor flow rate of 5 mL min⁻¹ or lower, while contamination occurs above 5 mL min⁻¹. A Co-flow rate above 100 L min⁻¹ is required to cool the aerosol stream before deposition on the filter. A pure copper sulfide phase is produced when sulfur is more than 5 times in molar ratio compared to Cu in the liquid solution and particle size decreases with increasing sulfur concentration. This research will contribute to a better understanding of the fundamental formation process of metal sulfides under oxygen-lean gas-phase conditions and serve as a milestone in optimizing synthesis parameters for various applications.

 © 2025 Attribution 4.0 International (CC BY 4.0)

The Journal of Physical Chemistry C 129 (2025): 4383-4397

https://doi.org/10.1021/acs.jpcc.5c00220

This study establishes a theoretical framework to elucidate the impact of gas bubble evolution dynamics on the reaction overpotentials in electrolytic hydrogen and oxygen production. By distinguishing between ohmic, activation, and concentration overpotentials, we formulate governing equations to determine the influence of gas bubble growth and detachment on each overpotential component. Additionally, we employ SHapley Additive exPlanations (SHAP) analysis to interpret the patterns identified by a regression neural network trained on our analytical equations. Our findings indicate that gas bubble evolution dynamics impact reaction overpotentials to different degrees, leading to divergent escalation rates and requiring targeted improvement strategies. We therefore systematically investigate the impact of key parameters influencing the gas bubble evolution dynamics such as the electrode surface wettability, the electrolyte concentration and the temperature on mitigating reaction overpotentials. Measures, such as enhancing the electrode hydrophilicity from 90 to 160°, reduces the activation and concentration overpotentials by up to 54.0% and 79.3%, respectively. Moreover, by increasing the electrolyte molarity from 0.5 to 1 M, ohmic and concentration overpotentials can be reduced by 47.1% and 72.1%, respectively, with diminishing performance returns beyond 2 M. Higher temperatures result in mild to moderate decreases across all overpotential components by improving electrolyte conductivity and mass transfer. In summary, this analysis provides valuable insights not only for optimizing electrolytic hydrogen and oxygen production devices, but it also offers the opportunity to transfer gained insights into other gas-evolving electrochemical systems and supports their optimization toward higher energy conversion efficiencies.

 © 2025 The Authors. Published by American Chemical Society

Acta Materialia 283 (2025): 120488

https://doi.org/10.1016/j.actamat.2024.120488

Additively manufactured components are generally heat treated to remove the undesired microstructure formed during the repeated heating-cooling cycles inherent to the process, known as intrinsic heat treatment (IHT). Recently, the IHT has been explored as a driving force for precipitation hardening in steels which can potentially shorten the manufacturing chain of AM components. However, the mechanisms behind the formation of secondary phase precipitates during the complex thermal history remains unclear. In this work, a combination of in situ high energy X-ray diffraction, atom probe tomography, scanning and transmission electron microscopy were used to reveal the precipitation sequence in an X40CrMoV5–1 tool steel during laser-directed energy deposition (L-DED). V-rich MCN and V₈CN₇ carbonitrides, as well as, Fe-Cr-rich M₃C and M₇C₃ carbides were formed at different stages of the L-DED. Their evolution and resulting chemical stoichiometry was correlated to the exact phase transformation occurring in the microstructure during the IHT over different regions along the built direction. Finally, the combined results from the in situ and ex situ experiments enabled us to retrace the history of the full microstructure during the L-DED process. The findings lead to the conclusion that secondary hardening effect in tool steel is, as expected, sensitive to the severity of the IHT, and if limited, can result in a tempered microstructure comparable to the ones conventionally obtained after tempering heat treatments.

 © 2025 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc.

IUCrJ 11 (2024): 977-990

https://doi.org/10.1107/S2052252524009722

Regolith draws intensive research attention because of its importance as the basis for fabricating materials for future human space exploration. Martian regolith is predicted to consist of defect-rich crystal structures due to long-term space weathering. The present report focuses on the structural differences between defect-rich and defect-poor forsterite (Mg₂SiO₄) – one of the major phases in Martian regolith. In this work, forsterites were synthesized using reverse strike co-precipitation and high-energy ball milling (BM). Subsequent post-processing was also carried out using BM to enhance the defects. The crystal structures of the samples were characterized by X-ray powder diffraction and total scattering using Cu and synchrotron radiation followed by Rietveld refinement and pair distribution function (PDF) analysis, respectively. The structural models were deduced by density functional theory assisted PDF refinements, describing both long-range and short-range order caused by defects. The Raman spectral features of the synthetic forsterites complement the ab initio simulation for an in-depth understanding of the associated structural defects.

 © 2024 Attribution 4.0 International (CC BY 4.0)

Advanced Electronic Materials (2024): 2400481

https://doi.org/10.1002/aelm.202400481

Artificial Neural Networks (ANN) require a better platform to reduce their energy consumption and achieve their full potential. Electrochemical devices like the Electrochemical Neuromorphic Organic Device (ENODe) stand out as a potential building block for ANNs, due to their lower energy demand, in addition to their biocompatibility and access to multiple and stable memory levels. However, the non-volatile effect observed in these devices is not yet fully understood. Hence, here we propose a 2D drift-diffusion model that is capable to reproduce the device behavior. The model relies on the assumption of trapping sites for cations, which are increasingly filled or emptied during subsequent pre-synaptic pulses. The model is verified by experiments on devices with varying post-synaptic dimensions. Overall, the results provide a framework to discuss ENODe operation and design strategies for ENODes with well-controlled memory states.

© 2024 The Author(s). Advanced Electronic Materials published by Wiley-VCH GmbH

Journal of the American Ceramic Society (2024): e20170

https://doi.org/10.1111/jace.20170

We report on temperature-dependent structural and spectroscopic properties of two new members of the mullite-type ceramics SnAlBO₄ and SnGaBO₄. In-situ X-ray powder diffraction (XRPD) demonstrates positive thermal expansion behavior for all orthorhombic lattice parameters between 13 and 840 K. The lattice thermal expansion is modeled by Grüneisen first-order approximation, where the vibrational energy is calculated by the Debye–Einstein–anharmonicity (DEA) approach. Although the thermal changes of the metric parameters do not show any discontinuity, the double-Debye model and low-temperature thermal analysis leave hints for subtle displacive changes. Splitting of the tin-doublets of the ¹¹⁹Sn Mössbauer spectra at low temperature is assumed to be associated with structural modulation although the temperature-dependent Raman spectra could not support these findings. The modulation could either be dynamic which requires much longer thermal equilibration than the speed of the data collection for XRPD and Raman spectroscopy. Selective Raman mode frequencies are analyzed using a modified Klemens model, which helps to understand the thermal anharmonic behaviors of the SnO₄, MO₆, and BO₃ polyhedra as a function of temperature.

© 2024 The Author(s). Journal of the American Ceramic Society published by Wiley Periodicals LLC on behalf of American Ceramic Society

Macromolecular Rapid Communications (2024): 2400557

https://doi.org/10.1002/marc.202400557

Bisfunctional benzoxazine and polyether diamine-based polymers show Arrhenius-like stress-relaxation varying with stoichiometry and polymerization temperatures proving vitrimeric behavior. Molecular structural investigations reveal the presence of different aminoalkylated phenols occurring at varying ratios depending on polymer composition and polymerization conditions. The vitrimeric mechanism is found to involve an amine exchange reaction of aminoalkylated phenols in an equilibrium reaction like a nucleophilic substitution reaction. As determined by molecular studies and dissolution experiments in reactive solvents, aliphatic and aromatic primary as well as aliphatic secondary amines in the polybenzoxazine structure can act as nucleophiles in reaction with electrophilic methylene bridges. Thus, aminoalkylated phenols proved to be a relevant structural motif resulting in a vitrimeric polybenzoxazine due to amine exchange reaction.

© 2024 The Author(s). Macromolecular Rapid Communications published by Wiley-VCH GmbH

Advanced Functional Materials 35 (2024)

doi: https://doi.org/10.1002/adfm.202411521

The innovative development of reactive-spray systems for gas-phaseproduction of metal sulfides are potential materials for next-generationtechnologies. These flame-synthesized sulfides (doped, functionalized, andheterogeneously mixed derivatives) hold significant potential as photocatalystsfor water splitting. The knowledge acquired from nonaqueous precursor-solvent and high-temperature aerosol chemistries, optimal process parametersare established to generate In 2-(4/3)x Snx S3 , solid-solutions. The thermally drivenreducing gas-phase reactions are controlled through fuel/oxygen ratio. Particlescharacterizations (X-ray diffraction, transmission electron microscopy (TEM)and imaging) revealed structural stability and crystallinity. The In2-(4/3)x Snx S3 ,at higher Sn doping had enhanced photoexcitation. Donor-acceptor levelswithin the material facilitated electron-hole pair trapping, crucial for redoxreactions. With suitable band gap energies for water oxidation (1.9-1.1 eV)closely matched flat band potentials (4.38-4.67 eV) for redox reactions. Thepowder characterization showed 8% In 2 O3 in InSn0.75 S3 after photocatalysisdue to S-degradation in the initial light “on/off cycles”. The pioneeringprocess of employing oxygen-deficient reducing flame enabled a seriesof photo-catalytically active metal sulfide nanoparticles with work functionenergies in the range of 5.19-5.37 eV. This synthesis strategy holds the potentialfor impactful advancements in both industry and R&D, addressing the urgentneed for new materials capable of inducing water oxidation under visible light.

© 2024 The Author(s). Advanced Functional Materials published by Wiley-VCH GmbH

ACS Omega 9 (2024): 41480-41490

Doi: https://doi.org/10.1021/acsomega.4c05019

Silica aerogels are highly porous materials with unique properties such as high specific surface area, high thermal insulation, and high open porosity. These characteristics make them attractive for several applications in closed microfluidic channels such as BioMEMS, catalysis, and thermal insulation. However, aerogel-filled microchannels have not been reported in the literature yet because of the complexity of creating a process that controls the integration, shrinkage, and mechanical stability of these materials inside a closed channel. In this work, a process is presented to integrate aerogels in microchannels with reproducibility, mechanical stability, and no shrinkage. This protocol is based on the filling of channels during the gelation, which is crucial to avoid shrinkage, CO₂ supercritical drying, and mechanical additives (polyethylene glycol and carbon nanotubes). Furthermore, the influence of polyethylene glycol and carbon nanotubes on the compressive strength, porosity, and specific surface area is investigated. Following the suggested process protocol, the integration of different aerogel compositions (with and without reinforcement) is successfully achieved in the microchannels without shrinkage and cracks. This research opens up new possibilities for the use of different aerogels in microfluidics with structural integrity and enhanced functionality.

© 2024 The Authors. Published by American Chemical Society

Journal of Environmental Chemical Engineering  12  (2024) : 113071

doi: https://doi.org/10.1016/j.jece.2024.113071

Integrating microbial electrolysis cells (MEC) with anaerobic digestion (AD) would offer different synergistic advantages to these technologies. The MEC bioanode could be immersed in the AD reactor, stabilizing the process, or operated as an independent cell, further removing organic matter. However, up to now, bioanodes operated in anaerobic digestion conditions present low current production and tend to deactivate over time. In the present work, we conducted a comparison of six carbon-based and metal-based electrode materials, including novel options such as stainless steel wool (SSW) and carbon nanofibers (ES300), never tested before under these conditions. The electrodes were evaluated using two inoculation procedures, operating simultaneously in the same electrolyte with different feeding media. The bioanodes produced double the current densities when fed with undigested corn silage compared to anaerobic digester effluent, showing the potential for direct integration into anaerobic digesters without pre-fermentation. Unprecedented stable current densities, up to 0.4 mA cm−2, were obtained over 60 days of operation in real anaerobic digestion conditions by Geobacter-dominated bioanodes on SSW and ES300, outperforming state-of-the-art bioanodes and avoiding the dramatic deactivation previously reported. Microbial community analysis of SSW and ES300 elucidated how the microbial composition in the bioanodes was mostly depending on the electrode material, rather than the inoculation procedure. The results achieved with these bioanodes pave the way for scaling up and commercializing integrated AD-MEC systems.

 © 2024 The Authors ( CC BY 4.0 )

Science 385 (2024): 318-321

doi:  10.1126/science.adp4963

Nitrenes are a highly reactive, yet fundamental, compound class. They possess a monovalent nitrogen atom and usually a short life span, typically in the nanosecond range. Here, we report on the synthesis of a stable nitrene by photolysis of the arylazide M ^S FluindN ₃  ( 1 ), which gave rise to the quantitative formation of the arylnitrene M ^S FluindN ( 2 ) (M ^S Fluind is dispiro[fluorene-9 ,3′-(1′,1′,7′,7′-tetramethyl-s-hydrindacen-4′-yl)-5′,9′′-fluorene]) that remains unchanged for at least 3 days when stored under argon atmosphere at room temperature. The extraordinary life span permitted the full characterization of  2  by single-crystal x-ray crystallography, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry, which supports a triplet ground state. Theoretical simulations suggest that in addition to the kinetic stabilization conferred by the bulky M ^S Fluind aryl substituent, electron delocalization across the central aromatic ring contributes to the electron stabilization of  2 .

© 2024, The Authors and American Association for the Advancement of Science

Scientific Reports 35 (2024): 16491

doi:  10.1038/s41598-024-67030-9

Separation and classification are important operations in particle technology, but they are still limited in terms of suspended particles in the micrometer and nanometer size-range. Electrical fields can be beneficial for sorting such particles according to material properties. A mechanism based on strong and inhomogeneous fields is dielectrophoresis (DEP). It can be used to separate microparticles according to their material properties, such as conductivity and permittivity, by selectively trapping one particle type while the other can pass the separator. Conventional DEP separators show either a limitation in throughput or frequency bandwidth. A low throughput limits the economical feasibility in many cases. A lower frequency bandwidth limits the variety of materials that can be sorted by DEP. To separate semiconducting particles from a mixture containing particles with higher conductivity according to their material, high frequencies are required. Possible applications are the separation of semiconducting and metallic carbon nanotubes or the separation of carbon-coated lithium iron phosphate particles from graphite in the recycling process of spent lithium-ion batteries. In this publication, we aim to display how to tune the electrical impedance of a high-throughput DEP separator based on custom-designed printed circuit boards to increase its frequency bandwidth. By adding inductors to the electrical circuit, we were able to increase the frequency bandwidth from 500 kHz to over 11 MHz. The experiments in this study act as proof-of-principle. Furthermore, a non-deterministic way to increase the impedance of the setup is shown, yielding a maximum frequency of 39.16 MHz.

© 2024, The Author(s)

2D Materials  11 (2024): 025031

doi:  https://doi.org/ 10.1088/2053-1583/ad3134

MoS₂  and WS₂  mono- and multilayers were grown on SiO₂ /Si substrates. Growth by atomic layer deposition (ALD) at fast growth rates is compared to sub-ALD, which is a slow growth rate process with only partial precursor surface coverage per cycle. A Raman spectroscopic analysis of the intensity and frequency difference of the modes reveals different stages of growth from partial to full surface layer coverage followed by layer-by-layer formation. The initial layer thickness and structural quality strongly depend on the growth rate and monolayers only form using sub-ALD. Optical activity is demonstrated by photoluminescence (PL) characterization which shows typical excitonic emission from MoS₂  and WS₂  monolayers. A chemical analysis confirming the stoichiometry of MoS₂  is performed by x-ray photoelectron spectroscopy. The surface morphology of layers grown with different growth rates is studied by atomic force microscopy. Plan-view transmission electron microscopy analysis of MoS₂  directly grown on freestanding graphene reveals the local crystalline quality of the layers, in agreement with Raman and PL results.

 © 2024 IOP Publishing Ltd.

Wiley Interdisciplinary Reviews: Computational Molecular Science 14  (2024): e1708

doi:  https://doi.org/10.1002/wcms.1708

The field of liquid-phase and solid-state high-pressure chemistry has exploded since the advent of the diamond anvil cell, an experimental technique that allows the application of pressures up to several hundred gigapascals. To complement high-pressure experiments, a large number of computational tools have been developed. These techniques enable the simulation of chemical systems, their sizes ranging from single atoms to infinitely large crystals, under high pressure, and the calculation of the resulting structural, electronic, and spectroscopic changes. At the most fundamental level, computational methods using carefully tailored wall potentials allow the analytical calculation of energies and electronic properties of compressed atoms. Molecules and molecular clusters can be compressed either via mechanochemical approaches or via more sophisticated computational protocols using implicit or explicit solvation approaches, typically in combination with density functional theory, thus allowing the simulation of pressure-induced chemical reactions. Crystals and other periodic systems can also be routinely simulated under pressure, both statically and dynamically, to predict the changes of crystallographic data under pressure and high-pressure crystal structure transitions. In this review, the theoretical foundations of the available computational tools for simulating high-pressure chemistry are introduced and example applications demonstrating the strengths and weaknesses of each approach are discussed. This article is categorized under: Structure and Mechanism > Computational Materials Science Electronic Structure Theory > Ab Initio Electronic Structure Methods Software > Simulation Methods.

 © 2024 The Authors 

Scientific Reports 14 (2024): 8559

https://doi.org/10.1038/s41598-024-59027-1

The interaction of rarefied gases with functionalized surfaces is of great importance in technical applications such as gas separation membranes and catalysis. To investigate the influence of functionalization and rarefaction on gas flow rate in a defined geometry, pressure-driven gas flow experiments with helium and carbon dioxide through plain and alkyl-functionalized microchannels are performed. The experiments cover Knudsen numbers from 0.01 to 200 and therefore the slip flow regime up to free molecular flow. To minimize the experimental uncertainty which is prevalent in micro flow experiments, a methodology is developed to make optimal use of the measurement data. The results are compared to an analysis-based hydraulic closure model (ACM) predicting rarefied gas flow in straight channels and to numerical solutions of the linearized S-model and BGK kinetic equations. The experimental data shows that if there is a difference between plain and functionalized channels, it is likely obscured by experimental uncertainty. This stands in contrast to previous measurements in smaller geometries and demonstrates that the surface-to-volume ratio of 0.4 μμm⁻¹ seems to be too small for the functionalization to have a strong influence and highlights the importance of geometric scale for surface effects. These results also shed light on the molecular reflection characteristics described by the TMAC.

 © 2024 Attribution 4.0 International (CC BY 4.0)

Cell  187 (2024): 11296-1311.e26

doi:   https://doi.org/10.1016/j.cell.2024.01.034

Most membrane proteins are modified by covalent addition of complex sugars through N- and O-glycosylation. Unlike proteins, glycans do not typically adopt specific secondary structures and remain very mobile, shielding potentially large fractions of protein surface. High glycan conformational freedom hinders complete structural elucidation of glycoproteins. Computer simulations may be used to model glycosylated proteins but require hundreds of thousands of computing hours on supercomputers, thus limiting routine use. Here, we describe GlycoSHIELD, a reductionist method that can be implemented on personal computers to graft realistic ensembles of glycan conformers onto static protein structures in minutes. Using molecular dynamics simulation, small-angle X-ray scattering, cryoelectron microscopy, and mass spectrometry, we show that this open-access toolkit provides enhanced models of glycoprotein structures. Focusing on N-cadherin, human coronavirus spike proteins, and gamma-aminobutyric acid receptors, we show that GlycoSHIELD can shed light on the impact of glycans on the conformation and activity of complex glycoproteins.

 © 2024 Attribution 4.0 International (CC BY 4.0)

Additive Manufacturing  80  (2024): 103988

doi: https://doi.org/ 10.1016/j.addma.2024.103988

Smart alloying enables local modification of the chemical composition of metallic components within additive manufacturing processes. In the example of laser based powder bed fusion (PBF-LB/M), this new technology uses suspensions to place alloying elements precisely at every requested point of the printed area. It allows a tailor-made change of the local microstructure and properties. High chromium-containing stainless steel and carbon as the alloying element serves as a demonstration example. Microprobe and EBSD analyses confirm a locally increasing carbon content, which leads to the formation of fine martensitic structures with chromium-rich carbides at the grain boundaries of the ferritic base material. The associated change in microstructure regarding grain size and phase composition results in modified mechanical properties. Indentation tests carried out show a corresponding locally increased indentation hardness. This decisive influence of even individual alloying elements paves a new way for functional grading of metallic components in additive manufacturing.

 © 2024 The Authors ( CC BY 4.0 )

Advanced Functional Materials   34  (2023): 2303324

doi:  https://doi.org/10.1002/adfm.202303324

The gradual channel approximation forms the foundation for the analysis of field-effect transistors. It has been used to discuss transistors that are not necessarily based on the field effect as well, such as the organic electrochemical transistor (OECT). Here, the applicability of the gradual channel approximation for OECTs is studied by a 2D drift-diffusion model. It is found that OECT switching can be described by two separate effects—a doping/dedoping mechanism and the formation of an electrostatic double layer at the interface between the mixed conductor and the electrolyte. The balance between these two mechanisms is determined by the morphology of the mixed conductor, in particular the question whether ions move in the same phase and electric potential as the holes, or if separate ion and hole phases are formed. It is argued that the gradual channel approximation can only be used to describe electrostatic switching at the mixed conductor/electrolyte interface (the two-phase model), but cannot be employed to analyze devices operating on a doping/de-doping mechanism (the one -phase model). 

© 2024 The Authors. 

Materials and Design  237 (2024): 112603

doi:  https://doi.org/10.1016/j.matdes.2023.112603

Knowledge representation in the Materials Science and Engineering (MSE) domain is a vast and multi-faceted challenge: Overlap, ambiguity, and inconsistency in terminology are common. Invariant (consistent) and variant (context-specific) knowledge are difficult to align cross-domain. Generic top-level semantic terminology often is too abstract, while MSE domain terminology often is too specific. In this paper, an approach how to maintain a comprehensive MSE-centric terminology composing a mid-level ontology–the Platform MaterialDigital Core Ontology (PMDco)–via MSE community-based curation procedures is presented. The illustrated findings show how the PMDco bridges semantic gaps between high-level, MSE-specific, and other science domain semantics. Additionally, it demonstrates how the PMDco lowers development and integration thresholds. Moreover, the research highlights how to fuel it with real-world data sources ranging from manually conducted experiments and simulations with continuously automated industrial applications.

 © The Authors ( CC BY 4.0 )

Electrochemical Acta 473  (2024): 143473

doi: https://doi.org/ 10.1016/j.electacta.2023.143473

The electron-transfer reaction is of pivotal importance not only in electrochemistry, but also in other scientific disciplines, such as catalysis, biochemistry and biology. The kinetics of such reactions have been thoroughly investigated under ideal conditions (Butler and Volmer or Marcus theories) considering the Frumkin effects; However, the electron transfer in concentrated electrolytes still lacks a general theory. Here we discuss the effect of the concentration of the supporting electrolyte (an inert salt) on the kinetics of three redox couples with different nominal charge: hexaammineruthenium, ferricyanide and ferrocenemethanol. The redox couples are diluted but the supporting electrolyte concentration is high enough that significant deviations of the formal electrode potential from the ideality are observed; the kinetics are also altered. We propose a model in which the electrostatic interactions are described as a complexation between the redox active species and the counter-ions of the supporting electrolyte, in analogy with the treatment of the ion pairs. The model correctly fits the dependence of the formal potential and of the charge transfer resistance on the concentration, thus suggesting that the ion-transfer accompanying an electron-transfer plays a significant role in the overall reaction kinetics. This finding enables a more realistic description of the complex electron-transfer reactions occurring in electrocatalysis and catalysis, bioelectrochemistry and biochemistry, and electrochemical energy storage.

© 2023 The Author(s)

Nature Communications 14 (2023)

doi: 10.1038/s41467-023-41934-y

Structure-property relationships in ordered materials have long been a core principle in materials design. However, the introduction of disorder into materials provides structural flexibility and thus access to material properties that are not attainable in conventional, ordered materials. To understand disorder-property relationships, the disorder – ie, the local ordering principles – must be quantified. Local order can be probed experimentally by diffuse scattering. The analysis is notoriously difficult, especially if only powder samples are available. Here, we combine the advantages of three-dimensional electron diffraction – a method that allows single crystal diffraction measurements on sub-micron sized crystals – and three-dimensional difference pair distribution function analysis (3D-ΔPDF) to address this problem. In this work, we compare the 3D-ΔPDF from electron diffraction data with those obtained from neutron and x-ray experiments of yttria-stabilized zirconia (Zr _0.82 Y _0.18 O _1.91 ) and demonstrate the reliability of the proposed approach.

 © 2023 The Author(s) ( CC BY 4.0 )

Physics 16(2023)

doi: https://physics.aps.org/articles/v16/151

A new set of equations captures the dynamical interplay of electrons and vibrations in crystals and forms a basis for computational studies.

Although a crystal is a highly ordered structure, it is never at rest: its atoms are constantly vibrating about their equilibrium positions—even down to zero temperature. Such vibrations are called phonons, and their interaction with the electrons that hold the crystal together is partly responsible for the crystal’s optical properties, its ability to conduct heat or electricity, and even its vanishing electrical resistance if it is superconducting. Predicting, or at least understanding, such properties requires an accurate description of the interplay of electrons and phonons. This task is formidable given that the electronic problem alone—assuming that the atomic nuclei stand still—is already challenging and lacks an exact solution. Now, based on a long series of earlier milestones, Gianluca Stefanucci of the Tor Vergata University of Rome and colleagues have made an important step toward a complete theory of electrons and phonons.

At a low level of theory, the electron–phonon problem is easily formulated. First, one considers an arrangement of massive point charges representing electrons and atomic nuclei. Second, one lets these charges evolve under Coulomb’s law and the Schrödinger equation, possibly introducing some perturbation from time to time. The mathematical representation of the energy of such a system, consisting of kinetic and interaction terms, is the system’s Hamiltonian. However, knowing the exact theory is not enough because the corresponding equations are only formally simple. In practice, they are far too complex—not least owing to the huge number of particles involved—so that approximations are needed. Hence, at a high level, a workable theory should provide the means to make reasonable approximations yielding equations that can be solved on today’s computers.

One way to reduce the complexity of the problem is to step back from the picture of individual particles in favor of one of effective quasiparticles specific to the system at hand. An early example of a quasiparticle in the literature is the phonon: instead of focusing on the atomic nuclei that could, in principle, be located anywhere in space, one considers their collective vibration about their positions in a predefined crystal structure. Scientists have studied such “elastic waves” for almost a century [2], often resorting to two famous approximations: the Born-Oppenheimer approximation, which assumes that the electrons respond instantaneously to displacements of the nuclei; and the harmonic approximation, which posits that this response results in restoring forces proportional to the displacements.

Stefanucci and colleagues’ work builds on studies made in the middle of the last century that analyzed the interaction between quasiparticles by borrowing tools from quantum field theory. In 1961, Gordon Baym published a corresponding theory of electrons and phonons, in which the phonon field assigns a displacement to points in space and time [3]. One of the aforementioned tools is the technique of Feynman diagrams, which represent interaction processes graphically (Fig. 1) and can be translated into mathematical formulas through simple rules. By combining such diagrams into sets of equations that recursively depend on each other, one can account for all possible processes occurring in physical reality. In 1965, Lars Hedin presented examples of such equations, which completely describe systems of interacting electrons [4]. In a 2017 review, Feliciano Giustino merged these approaches and coined the term Hedin-Baym equations in the context of state-of-the-art materials simulations—answering many, but not all, open questions [5].

Stefanucci and colleagues have addressed several of the remaining issues [1]. First, they imposed requirements on the electron–phonon Hamiltonian, avoiding the mistake of trying to solve a problem not properly formulated in the first place. They emphasized that the equilibrium state around which the theory is built is not known in advance, making setting up and evaluating the Hamiltonian an iterative procedure. They also stressed that this Hamiltonian cannot generally be written in terms of physical phonons, contrary to what is often supposed. Second, the team generalized Giustino’s work [5] to systems driven out of equilibrium at any temperature—a key advance because this scenario reflects experimental and technological conditions. Mathematically, this generalization allows time to take on complex values. Third, the researchers carefully derived the corresponding rules for Feynman diagrams and provided the first complete set of diagrammatic Hedin-Baym equations. Such equations form the basis of systematic approximations, in which certain diagrams are neglected, and provide a criterion [3] for the resulting dynamics to respect fundamental conservation laws. Whereas the effects of electrons on phonons and vice versa are well studied separately [5], here it is crucial that both occur simultaneously.

Nowadays, parameter-free simulations of electrons and phonons rely heavily on so-called density-functional perturbation theory [6], which is based on the Born-Oppenheimer and harmonic approximations. By contrast, diagrammatic techniques are often—but not always [7]—used in combination with parameterized model Hamiltonians. Efforts to bring both approaches together have led to so-called downfolding methods, which already exist for the electron–phonon problem [8]. The insights gained by Stefanucci and colleagues will certainly help to further bridge the different strategies. Moreover, the advancements beyond thermal equilibrium will be of utmost importance because such an extension is needed to explain the latest time-resolved spectroscopy experiments and to design better photovoltaics. Finally, given that the team’s results apply to any fermion–boson system, such as an interacting light–matter system, many fields will benefit from this seminal work.

Chemical Science 14(2023)

doi: https://doi.org/10.1039/D3SC02202A

The most advanced structure prediction methods are powerless in exploring the conformational ensemble of disordered peptides and proteins and for this reason the “protein folding problem” remains unsolved. We present a novel methodology that enables the accurate prediction of spectroscopic fingerprints (circular dichroism, infrared, Raman, and Raman optical activity), and by this allows for “tidying up” the conformational ensembles of disordered peptides and disordered regions in proteins. This concept is elaborated for and applied to a dodecapeptide, whose spectroscopic fingerprint is measured and theoretically predicted by means of enhanced-sampling molecular dynamics coupled with quantum mechanical calculations. Following this approach, we demonstrate that peptides lacking a clear propensity for ordered secondary-structure motifs are not randomly, but only conditionally disordered. This means that their conformational landscape, or phase-space, can be well represented by a basis-set of conformers including about 10 to 100 structures. The implications of this finding have profound consequences both for the interpretation of experimental electronic and vibrational spectral features of peptides in solution and for the theoretical prediction of these features using accurate and computationally expensive techniques. The here-derived methods and conclusions are expected to fundamentally impact the rationalization of so-far elusive structure–spectra relationships for disordered peptides and proteins, towards improved and versatile structure prediction methods.

© 2023 The Author(s). Published by the Royal Society of Chemistry

Advanced Materials 35 (2023), 2208220

doi: 10.1002/adma.202208220

Determination of crystal structures of nanocrystalline or amorphous compounds is a great challenge in solid-state chemistry and physics. Pair distribution function (PDF) analysis of X-ray or neutron total scattering data has proven to be a key element in tackling this challenge. However, in most cases, a reliable structural motif is needed as a starting configuration for structure refinements. Here, an algorithm that is able to determine the crystal structure of an unknown compound by means of an on-the-fly trained machine learning model, which combines density functional theory calculations with comparison of calculated and measured PDFs for global optimization in an artificial landscape, is presented. Due to the nature of this landscape, even metastable configurations and stacking disorders can be identified. © 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.

© 2023 The Authors. Advanced Materials published by Wiley-VCH Gmb

Nature Chemistry 15 (2023), 848 - 855

doi: 10.1038/s41557-023-01186-1

Continuous-rotation 3D electron diffraction methods are increasingly popular for the structure analysis of very small organic molecular crystals and crystalline inorganic materials. Dynamical diffraction effects cause non-linear deviations from kinematical intensities that present issues in structure analysis. Here, a method for structure analysis of continuous-rotation 3D electron diffraction data is presented that takes multiple scattering effects into account. Dynamical and kinematical refinements of 12 compounds—ranging from small organic compounds to metal–organic frameworks to inorganic materials—are compared, for which the new approach yields significantly improved models in terms of accuracy and reliability with up to fourfold reduction of the noise level in difference Fourier maps. The intrinsic sensitivity of dynamical diffraction to the absolute structure is also used to assign the handedness of 58 crystals of 9 different chiral compounds, showing that 3D electron diffraction is a reliable tool for the routine determination of absolute structures.

© 2023, The Author(s).

Advanced Materials Interfaces 10 (2023)

doi: 10.1002/admi.202300207

This work presents porous zirconia-toughened alumina ceramics functionalized with Au@Pd/Au@Pt core–shell nanoparticle (NP) for in situ monitoring of catalytic reactions via surface-enhanced Raman scattering (SERS) which is augmented by the open cell foam structure of the ceramic support. In this respect, the porous ceramic enables efficient light trapping and propagation onto the coated surface, which provides good accessibility of the catalyst, while the core–shell particles are equipped with a catalytically active shell and a plasmonic core which enables SERS sensing. The metallic hybrid core–shell NPs are synthesized by the Au-seed mediated method and colloidally deposited onto the open porous ceramic matrix prepared via the polymer replica method. The Au@Pt NP functionalized porous ceramic show a Raman enhancement factor up to 10⁶, which is significantly higher than that of non-porous samples. In situ reaction monitoring via SERS is demonstrated by the Pt-catalyzed reduction of 4-nitrothiophenol to 4-aminothiophenol, showing high specificity for analysis of reactants and products. This multifunctional material concept featuring ceramics-augmented SERS and catalytic activity could be extended beyond real-time, sensitive reaction monitoring toward high temperature reactions, photothermal catalysis, bioprocessing and -sensing, green energy conversion, and related applications.

© 2023 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.

Rapid Prototyping Journal 29 (2023)

doi: 10.1108/RPJ-06-2022-0181

Purpose: This study aims at compensating for sintering deformation of components manufactured by metal binder jetting (MBJ) technology. Design/methodology/approach: In the present research, numerical simulations are used to predict sintering deformation. Subsequently, an algorithm is developed to counteract the deformations, and the compensated deformations are morphed into a CAD model for printing. Several test cases are designed, compensated and manufactured to evaluate the accuracy of the compensation calculations. A consistent accuracy measurement method is developed for both green and sintered parts. The final sintered parts are compared with the desired final shape, and the accuracy of the model is discussed. Furthermore, the effect of initial assumptions in the calculations, including green part densities, and green part dimensions on the final dimensional accuracy are studied. Findings: The proposed computational framework can compensate for the sintering deformations with acceptable accuracy, especially in the directions, for which the used material model has been calibrated. The precise assumption of green part density values is important for the accuracy of compensation calculations. For achieving tighter dimensional accuracy, green part dimensions should be incorporated into the computational framework. Originality/value: Several studies have already predicted sintering deformations using numerical methods for MBJ parts. However, very little research has been dedicated to the compensation of sintering deformations with numerical simulations, and to the best of the best of the authors' knowledge, no previous work has studied the effect of green part properties on dimensional accuracy of compensation calculations. This paper introduces a method to omit or minimize the trial-and-error experiments and leads to the manufacturing of dimensionally accurate geometries.

© 2022, Emerald Publishing Limited.

Advanced Materials  35 (2023), 2211104 

doi: 10.1002/adma.202211104

The development of a novel reactive spray technology based on the well-known gas-phase metal oxide synthesis route provides innumerable opportunities for the production of non-oxide nanoparticles. Among these materials, metal sulfides are expected to have a high impact, especially in the development of electrochemical and photochemical high-surface-area materials. As a proof-of-principle, MnS, CoS, Cu₂S, ZnS, Ag₂S, In₂S₃, SnS, and Bi₂S₃ are synthesized in an O₂-lean and sulfur-rich environment. In addition, the formation of Cu₂S in a single-droplet combustion experiment is reported. The multiscale approach combining flame sprays with single-droplet combustion is expected to pave the way toward a fundamental understanding of the gas-phase formation of metal sulfides in the future. The knowledge acquired can open the possibility for the development of a next-generation gas-phase technology facilitating the scalable synthesis of functional binary/ternary metal sulfides.

© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.

Materials Characterization 199 (2023), 112812

doi: https://doi.org/10.1016/j.matchar.2023.112812

The investigation of Li containing materials is of crucial importance for a number of material applications, including aerospace engineering. The aluminum alloy (AA) 2050, containing 2.7–5.0 at.% of Li, exhibits a lower density as well as excellent mechanical properties, due to the variety of phases that can form, including metastable ones. The high chemical composition sensitivity and near-atomic spatial resolution in three-dimensions of atom probe tomography make it a powerful technique to accurately assess solute partitioning and phase composition in particular at structural defects such as dislocations and grain boundaries. However, Li quantification is not straightforward due to its fast diffusion. Here, specimen preparation and Li electric field driven migration during atom probe analysis are investigated separately to better address the challenges associated with the experimental investigation of Li content in Li containing Al-alloys. We demonstrate a striking effect of Ga on Li distribution, which turns out to be significantly more critical than the electric field induced migration of Li during the atom probe tomography analysis.

© 2023 Published by Elsevier Inc.

Materials and Design, 227 (2023), 111745

doi: 10.1016/j.matdes.2023.111745

Acoustic emission (AE) is a well-established technique for in-situ damage analysis of composite materials. The main challenge, however, is to be able to correlate the measured AE signals with their respective damage mechanism sources. Hence, an innovative approach to classify AE signals based on supervised machine learning is presented in this work. At first, the constituents of a composite (fiber, matrix and interface) are characterized separately and fingerprint information regarding the characteristic AE features of each damage mechanism is gathered. This dataset is then used to train a model based on the k-nearest neighbors algorithm. Model accuracy is calculated to be 88%. Subsequently, AE signals measured during tensile tests of commercial composites are classified by the trained model. The analysis provides important information regarding location, time, frequency and intensity of each damage mechanism. Matrix cracking and fiber debonding are the most frequent damage mechanisms representing around 40% and 20% of the measured AE hits. Nevertheless, fiber breakage is the mechanism that dissipates the most AE energy (40%) for the studied composite. Furthermore, the presented method can also be applied together with other techniques like computer tomography, delivering a powerful approach to understand different multi-phase materials.

 © 2023 Attribution 4.0 International (CC BY 4.0)

Particle and Particle Systems Characterization 40 (2023)

doi: https://doi.org/10.1002/ppsc.202300048

Hetero-contacts are interfaces between different materials at the nanoscale leading to novel functional properties. In hetero-aggregates, primary particles of at least two different materials are mixed at primary particle or cluster level. Double flame spray pyrolysis (DFSP) is a versatile technique for the controlled synthesis of such materials. Characterization of hetero-aggregates by scanning transmission electron microscopy (STEM) requires acquisition and evaluation of many aggregate images in order to derive statistically significant results. Usually, STEM energy dispersive X-ray spectroscopy (EDXS) is used to acquire elemental maps providing the material distribution of the primary particles within hetero-aggregates. However, the acquisition of a single EDXS map takes up to several minutes. For this reason, determination of material types of primary particles from the intensity in high-angle annular dark field STEM images alone is desirable. These images can be acquired within a couple of seconds. In the present work, a method is suggested which allows for achieving this objective. It can be applied to distinguish materials with a significant difference in their atomic number and hence sufficient material contrast in the STEM images.

© 2023 The Authors. Particle & Particle Systems Characterization published by Wiley-VCH GmbH.

Science Advances 8 (2022)

doi: 10.1126/sciadv.abp9561

The breakup of drops and bubbles in turbulent fluids is a key mechanism in many environmental and engineering processes. Even in the well-studied dilute case, quantitative descriptions of drop fragmentation remain elusive, and empirical models continue to proliferate. We here investigate drop breakup by leveraging a novel computer code, which enables the generation of ensembles of experiments with thousands of independent, fully resolved simulations. We show that in homogeneous isotropic turbulence breakup is a memoryless process whose rate depends only on the Weber number. A simple model based on the computed breakup rates can accurately predict experimental measurements and demonstrates that dilute emulsions evolve through a continuous fragmentation process with exponentially increasing time scales. Our results suggest a nonvanishing breakup rate below the critical Kolmogorov-Hinze diameter, challenging the current paradigm of inertial drop fragmentation.

© 2022 The Authors.

Chemical Reviews 123 (2023), 6716 - 6792 

doi: 10.1021/acs.chemrev.2c00751

Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

© 2023 American Chemical Society. All rights reserved.

RSC Advances, 13 (2023), 15805 - 15809

doi: 10.1039/d3ra02988c

Diazocines are azobenzene derived macrocyclic photoswitches with well resolved photostationary states for the (E)- and (Z)-isomers, which improves their addressability by light. In this work, effective procedures for the stannylation and borylation of diazocines in different positions are reported. Their use in Stille cross-coupling and Suzuki cross-coupling reactions with organic bromides is demonstrated in yields of 47-94% (Stille cross-coupling) and 0-95% (Suzuki cross-coupling), respectively.

© 2023 The Royal Society of Chemistry.

Life Sciences in Space Research 36 (2023), 86 - 89 

doi: https://doi.org/10.1016/j.lssr.2022.08.009

The Moon and Mars Base Analog (MaMBA) is a concept for an extraterrestrial habitat developed at the Center of Applied Space Technology and Microgravity (ZARM) in Bremen, Germany. The long-term goal of the associated project is to create a technologically functioning prototype for a base on the Moon and on Mars. One key aspect of developing such a prototype base is the integration of a bioregenerative life support system (BLSS) and its testing under realistic conditions. A long-duration mission to Mars, in particular, will require BLSS with a reliability that can hardly be reached without extensive testing, starting well in advance of the mission. Standards exist for comparing the capabilities of various BLSS, which strongly focus on technological aspects. These, we argue, should be complemented with the use of facilities that enable investigations and optimization of BLSS prototypes with regard to their requirements on logistics, training, recovery from failure and contamination, and other constraints imposed when humans are in the loop. Such facilities, however, are lacking. The purpose of this paper is to present the MaMBA facility and its potential usages that may help close this gap. We describe how a BLSS (or parts of a BLSS) can be integrated into the current existing mock-up at the ZARM for relatively low-cost investigations of human factors affecting the BLSS. The MaMBA facility is available through collaborations as a test platform for characterizing, benchmarking, and testing BLSS under nominal and off-nominal conditions.

© 2022 The Committee on Space Research (COSPAR)

Acta Astronautica Article 210 (2023) ,162-175

doi:https://doi.org/10.1016/j.actaastro.2023.05.021, preprint available open access https://arxiv.org/abs/2305.15415

Astronaut crews and ground control support teams are highly interdependent teams that need to communicate effectively to achieve a safe mission - despite being separated by large distances. Team communication quality with its facets clarity of objectives and information flow, is a key coordination process to achieve high team performance and task satisfaction. Especially in interdependent teams working in extreme environments with time-delayed communications, the team's success is threatened if communication is ineffective. In this study, we hypothesized that communication quality affects two key team outcomes, performance and task satisfaction, and that these effects can be explained by increases in workload (effort and frustration). Hypotheses were tested during the AMADEE-20 analog Mars mission hosted by the Austrian Space Forum. The analog astronauts (AA) were supported by an On-Site-Support (OSS) team and a remote Mission-Support-Centre (MSC) team. The MSC was the only contact line for both AA and OSS, and the communication between them had a one-way time delay of 10 min. Our study consisted of three runs in which members across the three different multiteam systems had to exchange information to solve an interdependent task. We measured communication quality, effort and frustration, task satisfaction, and team performance. Results show that clarity of objectives and information flow positively impacted multiteam system performance. Furthermore, clarity of objectives reduced experienced effort and this in turn enhances team performance. High levels of information flow reduced experienced frustration, which in turn enhanced task satisfaction. Our findings show that these facets of communication quality are essential for multiteam systems that work separated from each other by a distance. We stress that specific (team) communication training for astronauts and support personnel will be key to effective teamwork during future Mars missions, and thus to overall mission success.

© 2023 IAA. Published by Elsevier Ltd. All rights reserved.

preprint licensed under CC BY-NC-SA 4.0

This publication is a result of the Humans on Mars Initiative.

Materials 16 (2023), 4170

doi: https://doi.org/10.3390/ma16114170, preprint available open access: doi:https://www.preprints.org/manuscript/202304.1169/v1

Once on Mars, maintenance and repair will be crucial for humans as supply chains including Earth andMars will be very complex. Consequently, the raw material available on mars must be processed and used. Factors such as the energy available for material production play just as important a role as the quality of the material that can be produced and the quality of its surface. With the aim of developing and technically implementing a process chain that meets the challenge of producing spare parts from oxygen-reduced Mars regolith, this paper addresses the issue of low-energy handling. Expected statistically distributed high roughnesses of sintered regolith analogs are approximated in this work by parameter variation in the PBF-LB/M process. For low-energy handling, a dry-adhesive microstructure is used. Investigations are carried out to determine the extent to which the rough surface resulting from the manufacturing process can be smoothed by deep rolling in such a way that the microstructure adheres and enables samples to be transported. For the investigated AlSi10Mg samples (12 mm x 12 mm x 10 mm), the surface roughness varies in a wide range from Sa 7.7 µm to Sa 64 µm after the additive manufacturing process, pull-off stresses of up to 6.99 N/cm² could be realized after deep rolling. This represents an increase in pull-off stresses by a factor of 392.94 compared to the pull-off stresses before deep rolling, enabling handling of even larger specimens. It is noteworthy that specimens with roughness values that were previously difficult to handle can be treated post-deep rolling, indicating a potential influence of additional variables that describe roughness or ripples and are associated with the adhesion effect of the microstructure of the dry adhesive.

© The Authors 2023 licensed under CC BY 4.0

This publication is a result of the Humans on Mars Initiative.

Science, 379  (2023), 6630

doi:  10.1126/science.ade5239

When tiles decorated to lower their symmetry are joined together, they can form aperiodic and labyrinthine patterns. Such Truchet tilings offer an efficient mechanism of visual data storage related to that used in barcodes and QR codes. We show that the crystalline metal–organic framework [OZn ₄ ][1,3-benzenedicarboxylate] ₃  (TRUMOF-1) is an atomic-scale realization of a complex three-dimensional Truchet tiling. Its crystal structure consists of a periodically arranged assembly of identical zinc-containing clusters connected uniformly in a well-defined but disordered fashion to give a topologically aperiodic microporous network. We suggest that this unusual structure emerges as a consequence of geometric frustration in the chemical building units from which it is assembled.

 © 2023 Attribution 4.0 International ( CC BY 4.0 )

Philosophical Transactions A  379 (2021) , 2188

doi: 10.1098/rsta.2019.0568

There is strong interest in lunar exploration from governmental space agencies, private companies and the public. NASA is about to send humans to the lunar surface again within the next few years, and ESA has proposed the concept of the Moon Village, with the goal of a sustainable human presence and activity on the lunar surface. Although construction of the infrastructure for this permanent human settlement is envisaged for the end of this decade by many, there is no definite mission plan yet. While this may be unsatisfactory for the impatient, this fact actually carries great potential: this is the optimal time to develop a forward-looking science input and influence mission planning. Based on data from recent missions (SMART-1, Kaguya, Chang’E, Chandrayaan-1 and LRO) as well as simulation campaigns (e.g. ILEWG EuroMoonMars), we provide initial input on how astronomy could be incorporated into a future Moon Village, and how the presence of humans (and robots) on the Moon could help deploy and maintain astronomical hardware.

 This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

© 2020 The Author(s) Published by the Royal Society. All rights reserved.

This publication is a result of the Humans on Mars Initiative.

npj Microgravity 8 (2022), 43

https://doi.org/10.1038/s41526-022-00240-5

The sustainability of crewed infrastructures on Mars will depend on their abilities to produce consumables on site. These abilities may be supported by diazotrophic, rock-leaching cyanobacteria: from resources naturally available on Mars, they could feed downstream biological processes and lead to the production of oxygen, food, fuels, structural materials, pharmaceuticals and more. The relevance of such a system will be dictated largely by the efficiency of regolith utilization by cyanobacteria. We therefore describe the growth dynamics of Anabaena sp. PCC 7938 as a function of MGS-1 concentration (a simulant of a widespread type of Martian regolith), of perchlorate concentration, and of their combination. To help devise improvement strategies and predict dynamics in regolith of differing composition, we identify the limiting element in MGS-1 – phosphorus – and its concentration-dependent effect on growth. Finally, we show that, while maintaining cyanobacteria and regolith in a single compartment can make the design of cultivation processes challenging, preventing direct physical contact between cells and grains may reduce growth. Overall, we hope for the knowledge gained here to support both the design of cultivation hardware and the modeling of cyanobacterium growth within.

© The Authors, https://doi.org/10.1038/s41526-022-00240-5  licensed under CC BY 4.0

This publication is a result of the Humans on Mars Initiative.

Journal of Catalyst 413 (2022), 1123

https://doi.org/10.1016/j.jcat.2022.08.020

Since the first studies reporting on its surprising catalytic properties, nanoporous gold (npAu) has emerged as a novel and ever since intensively investigated type of Au based catalyst. To judge its genuine catalytic potential and to be able to optimize its use in applications, it is mandatory, however, to quantify the influence of mass transport in the porous structure on the observed catalytic rates, i.e., to study the interplay between diffusion and reaction. To this end, we used pulsed field gradient (PFG) NMR for the first time to directly determine the diffusivities of reaction gases in a nanoporous metal – in this case for CO and CO₂ as species involved in low temperature CO oxidation efficiently catalyzed by npAu. By comparing the diffusion coefficients within the 20 nm pores of the material with the values in the bulk gas phase, the tortuosity of npAu’s pore system was assessable as the central geometrical parameter describing the extent to which diffusive transport in the pore system is slowed down. This knowledge allowed us in the following to disentangle the contributions of mass transport and the kinetics of the surface reaction (microkinetics). In particular, we were able to determine the rate constant and turnover frequency for low-temperature CO oxidation without previous ambiguities arising from potential transport limitations and to compare the results with other reported values. Based on the results, it was furthermore possible to predict optimized dimensions of the catalyst, resulting in minimized or even suppressed diffusion limitations. These predictions could be successfully verified, using np-Au platelets with lateral dimensions in the range of a few hundred microns. In this way, the catalytic conversion could be ramped up by 50 % and an activity level advanced which reflected the microkinetic potential of np-Au.

© The Authors, https://doi.org/10.1016/j.jcat.2022.08.020, licensed under CC BY-NC-ND 4.0

Material Research Letters 10 (2022),12, 824 

https://doi.org/10.1080/21663831.2022.2109941

Nanoporous gold as obtained by corrosion of alloys of gold and a less noble metal is a system with manifold applications. The process of dealloying, however, can result in partially porous samples, when dealloying conditions are not optimized with respect to composition and pre-treatment of the master alloy. In the present work, we investigate the dealloying interface between porous material and non-porous alloy in two samples, in which dealloying either stopped automatically or was interrupted manually. Reasons for unintended termination of dealloying in the former case are suggested.

© The Authors licensed under CC BY 4.0

Nature Communications 13 (2022) , 4692.

https://doi.org/10.1038/s41467-022-32370-5

Huntington’s disease is a neurodegenerative disease caused by an expanded polyQ stretch within Huntingtin (HTT) that renders the protein aggregation-prone, ultimately resulting in the formation of amyloid fibrils. A trimeric chaperone complex composed of Hsc70, DNAJB1 and Apg2 can suppress and reverse the aggregation of HTTExon1Q₄₈. DNAJB1 is the rate-limiting chaperone and we have here identified and characterized the binding interface between DNAJB1 and HTTExon1Q₄₈. DNAJB1 exhibits a HTT binding motif (HBM) in the hinge region between C-terminal domains (CTD) I and II and binds to the polyQ-adjacent proline rich domain (PRD) of soluble as well as aggregated HTT. The PRD of HTT represents an additional binding site for chaperones. Mutation of the highly conserved H244 of the HBM of DNAJB1 completely abrogates the suppression and disaggregation of HTT fibrils by the trimeric chaperone complex. Notably, this mutation does not affect the binding and remodeling of any other protein substrate, suggesting that the HBM of DNAJB1 is a specific interaction site for HTT. Overexpression of wt DNAJB1, but not of DNAJB1^H244A can prevent the accumulation of HTTExon1Q₉₇ aggregates in HEK293 cells, thus validating the biological significance of the HBM within DNAJB1.

© The Authors, https://doi.org/10.1038/s41467-022-32370-5  licensed under CC BY 4.0

44th COSPAR Scientific Assembly, Athens, Greece, 2022: abstract PEX.2-0002-22.

Leading space agencies have the intention to bring humans to Mars in the next decades, and some private companies are pushing for sooner deadlines. In fact, promises and plans to land humans on Mars have recurrently been announced since the end of the Apollo era, but have remained largely incomplete or even abandoned. At the University of Bremen, we are convinced that human Mars exploration will happen and that it will have a huge impact on both humankind and on the Martian environment. Given that even optimists do not see humans on Mars before the 2030s, we believe that now is the right moment to research possible scenarios for human Mars exploration and settlement, and to study the consequences for Earth, Mars and humankind. To this end, we have formed a new research initiative "Humans on Mars - Pathways to a long-term sustainable human presence" at the University of Bremen. Our approach to human Mars exploration is transdisciplinary and human-centered. On one hand, humankind has experienced tremendous progress and increase in welfare since the Apollo era. On the other hand, we see unambiguously the immense impact of increasing population and welfare on the environmental pollution and associated climate changes. In a nutshell, while the development of new technologies has been the main driver of progress, it has also put Earth in danger. We here argue that human Mars exploration can be instrumental in leading a change from a technology-centered toward a human-centered society, thereby solving our most pressing problems on Earth. Specifically, the thin CO2 Martian atmosphere, the scarcity of energy sources and water, the difficulties to produce food and consumables, and the need for cooperative human-robotic crews, pose challenges whose solutions will enormously benefit Earth. In short, the mindset emerging from thinking under the severe constraints on Mars could be the key to making our presence on Earth sustainable. In this talk, we will present our vision and report on the progress made in selected areas, starting with the shifts in experience and demands on new ways of interaction which come with humankind's expansion to Mars. These include the interactions of the humans on Mars with the humans on Earth on one hand and their habitat and swarm of robots on the other. We will present our efforts in in-situ resource utilization, which focus on sustainable bioproduction, the extraterrestrial fabrication of metal alloys, the production with impure materials and the harvesting of energy from space radiation.

 © 44th COSPAR Scientific Assembly ( CC BY 4.0 )

Advanced Energy Materials12 (2022), 28

https://doi.org/10.1002/aenm.202200657

Although isolated nonhexagonal carbon rings in graphene are associated with strain relaxation and curvature, dense and ordered arrangements of four-, five-, and eight-membered rings with strained carbon–carbon bonds can tile 2D planar layers. Using the Boltzmann transport equation formalism in combination with density functional theory calculations, how the presence of nonhexagonal rings impacts the thermal conductivity of three 2D carbon allotropes: T-graphene (four and eight rings), biphenylene (four, six, and eight rings), and net-graphene (four, six, and eight rings), is investigated. The phonon thermal conductivity (κ_ph), which captures three-phonon, four-phonon, and phonon–electron interactions, is significantly lowered with respect to pristine graphene. In compensation, the electron thermal conductivity (κ_e), which captures electron–phonon interactions, is enhanced to record high values, such that the room-temperature total thermal conductivity κ_total = κ_ph + κ_e approaches the values of pristine graphene. 2D carbon allotropes could be of interest for applications requiring thermal energy transfer by a combination of diffusion of electrons and phonon vibrations.

© The Authors, https://doi.org/10.1002/aenm.202200657, licensed under CC BY 4.0

Chemical Engineering Journal  433 (2022), 133583

https://doi.org/10.1016/j.cej.2021.133583

In the last decade, in-situ studies using nuclear magnetic resonance (NMR) showed the possibility to monitor local transport phenomena of gas-phase reactions inside opaque structures. While spatial species concentration is known to be accessible operando during heterogeneously catalyzed gas-phase reactions, the spatial acquisition of gas temperatures has proven to be challenging. So far, temperature information is gathered by auxiliary liquid-filled capillaries with temperature-dependent NMR-properties. Here, we present a method for spatially resolved temperature and density measurements of gases using the temperature dependence of the signal amplitude and the longitudinal relaxation time (T₁). In order to support the proposed method, temperature measurements of methane-filled tubes are carried out and compared to state-of-the-art temperature measurements using glycerol-filled capillaries. To demonstrate the applicability of the method during heterogeneously catalyzed gas-phase reactions, we measured the temperature operando inside a catalytically active honeycomb structure at standard pressure. The results show that direct temperature measurements of gases are possible, even though the low pressure inside the methane-filled tubes led to a low signal-to-noise ratio which compromised the accuracy of the data yielding relative errors of up to 7 %. This study focusses on temperature measurements of pure methane only. When applied to mixtures of gases, however, the proposed method has the potential to measure gas temperature and concentration at the same time.

© The Authors, https://doi.org/10.1016/j.cej.2021.133583, licensed under CC BY 4.0

Angewandte Chemie International Edition  61 (2022), 29

https://doi.org/10.1002/anie.202201925

The most pristinematerialof the Solar Systemis assumedto be preservedin cometsin the form of dust and iceas refractorymatter.ESA’smissionRosettaand its landerPhilaehad been developedto investigatethe nucleusof comet67P/Churyumov–Gerasimenkoin situ. Twenty-fiveminutesafter the initial touchdownof Philaeon the surfaceof comet67P in November2014, a mass spectrumwas recordedby the time-of-flightmass spectrometerCOSAConboardPhilae.The new characterizationof this mass spectrumthroughnon-negativeleast squaresfittingand MonteCarlo simulationsrevealsthe chemicalcompositionof comet67P. A suite of 12 organicmolecules,9 of whichalso foundin the originalanalysisof this data, exhibithigh statisticalprobabilityto be presentin the grainssampledfrom the cometarynucleus.Thesevolatilemoleculesare amongthe most abundantin the comet’schemicalcompositionand representan inventoryof the first raw materialspresentin the early Solar System.

© The Authors, https://doi.org/10.1002/anie.202201925, licensed under CC BY-NC-ND 4.0

Advanced Energy Materials 12 (2022), 22

https://doi.org/10.1002/aenm.202103842

The exploitation of renewable low temperature heat sources below 100 °C can significantly contribute to the transition to a low-carbon economy, in particular if applied to small and household scale. The scientific community has taken on the challenge to develop alternative techniques for the exploitation of such sources. Several innovative methods have been recently proposed; among them, many are based on electrochemistry. Here, the various techniques are discussed and a general thermodynamic analysis that allows to compare the performances and to identify the most promising technique is provided. The thermodynamic analysis is then extended to find the possible research lines in material science that could lead to improvements of the performances of the various techniques.

© The Authors, https://doi.org/10.1002/aenm.202103842, licensed under CC BY 4.0

Materials & Design  216 (2022), 110490

https://doi.org/10.1016/j.matdes.2022.110490

Sintering, as a post-processing step in metal binder jetting (MBJ), often results in distortion. Numerical simulations can predict sintering distortion and minimize costly trial-and-error experiments. The present paper implements a numerical approach based on a phenomenological model of sintering to capture the creep deformation during free sintering. To qualify and calibrate the material model for MBJ, metallographic studies, dilatometry experiments, and viscosity measurements are carried out instead of empirical models for viscosity and sinter stress. Using the calibrated material model, final sintering distortions are predicted in two industry-relevant parts. The reproducibility of MBJ products is illustrated by manufacturing seven specimens for each geometry, and a statistical method to evaluate the simulations’ accuracy is suggested. The predictions have a good agreement with experimental results, particularly for specimens with a lower build height. As the build height increases in MBJ specimens, the number of interlayer gaps in the build direction grows, resulting in anisotropic densification. This causes a lower prediction accuracy under isotropic shrinkage assumption, especially in overhang areas. Consideration of anisotropic shrinkage and heterogeneous density distribution of green parts in sintering simulation is essential to improve the accuracy of sintering predictions for MBJ components.

© The Authors, https://doi.org/10.1016/j.matdes.2022.110490, licensed under CC BY 4.0

Scientific Reports12 (2022), 2057

https://doi.org/10.1038/s41598-022-05871-y

Molecular diameters are an important property of gases for numerous scientific and technical disciplines. Different measurement techniques for these diameters exist, each delivering a characteristic value. Their reliability in describing the flow of rarefied gases, however, has not yet been discussed, especially the case for the transitional range between continuum and ballistic flow. Here, we present a method to describe gas flows in straight channels with arbitrary cross sections for the whole Knudsen range by using a superposition model based on molecular diameters. This model allows us to determine a transition diameter from flow measurement data that paves the way for generalized calculations of gas behaviour under rarefied conditions linking continuum and free molecular regime.

© The Authors, https://doi.org/10.1038/s41598-022-05871-y, licensed under CC BY 4.0

Nature Communications 13 (2022) , 687

https://doi.org/10.1038/s41467-022-28381-x

Aqueous zinc-ion batteries are realistic candidates as stationary storage systems for power-grid applications. However, to accelerate their commercialization, some important challenges must be specifically tackled, and appropriate experimental practices need to be embraced to align the academic research efforts with the realistic industrial working conditions for stationary storage. Within this commentary article, both the open challenges and the good experimental practices are discussed in relation to their impact on the future development of the aqueous Zn-ion technology.

© The Authors, https://doi.org/10.1038/s41467-022-28381-x, licensed under CC BY 4.0

Composites Part A 152 (2021), 106714

https://doi.org/10.1016/j.compositesa.2021.106714

Surface-initiated ring-opening (SI-ROP) polymerization of ɛ-caprolactone is known as possible modification method to increase the hydrophobicity of cellulosic substrates. In this study SI-ROP of ɛ-caprolactone is applied on native and mercerized flax yarn. By use of triazabicyclodecene as catalyst, SI-ROP at room temperature was possible and poly-ɛ-caprolactone (PCL) was linked with a weight content of 4–10% to flax yarns. Besides a lower hydrophilicity an increased surface energy was achieved for PCL modified flax yarn. Furthermore, the positive effect of PCL linkage on the fibers surface regarding adhesion potential to an epoxy matrix was shown via conducting fiber-pull-out tests. After SI-ROP of ɛ-caprolactone on flax fiber surface a reduction of fiber pull-out up to 33% was achieved, evoked by physical improvement e.g. better wettability of fiber with epoxy matrix as well as enhanced crosslinking between the hydroxyl groups of the surface grafted PCL and the epoxy resin.

© 2021 Elsevier Ltd. All rights reserved.

Advances in Space Research (2021) 68 (6), 2565-2599

https://doi.org/10.1016/j.asr.2021.04.047

© 2021 COSPAR. Published by Elsevier B.V., https://doi.org/10.1016/j.asr.2021.04.047

This publication is a result of the Humans on Mars Initiative.

Scientific Reports (2021) 11, 16861

https://doi.org/10.1038/s41598-021-95404-w

Separation of (biological) particles (≪10 μm≪10 μm) according to size or other properties is an ongoing challenge in a variety of technical relevant fields. Dielectrophoresis is one method to separate particles according to a diversity of properties, and within the last decades a pool of dielectrophoretic separation techniques has been developed. However, many of them either suffer selectivity or throughput. We use simulation and experiments to investigate retention mechanisms in a novel DEP scheme, namely, frequency-modulated DEP. Results from experiments and simulation show a good agreement for the separation of binary PS particles mixtures with respect to size and more importantly, for the challenging task of separating equally sized microparticles according to surface functionalization alone. The separation with respect to size was performed using 2 μμm and 3 μμm sized particles, whereas separation with respect to surface functionalization was performed with 2 μμm particles. The results from this study can be used to solve challenging separation tasks, for example to separate particles with distributed properties.

© The Authors, https://doi.org/10.1038/s41598-021-95404-w, licensed under CC BY 4.0

Angewandte Chemie International Edition (2021) 60, 19133-19138

https://doi.org/10.1002/anie.202107975

Carbenes and their analogues have constantly enthralled chemists with their intriguing reactivity of ambiphilic character stemming from their electronic structures. Phosphenium and arsenium ions are fiercely reactive cationic species, the stabilization of which has been so far achieved in the condensed phase by dispersing the positive charge through electromeric conjugation with at least one electron-rich substituent (frequently amido groups). Although observed in the gas phase, the isolation of dicoordinate phosphenium and arsenium ions lacking such stabilizing ligands has eluded chemists for decades. Herein we show that by judicious choice of aromatic substituents, dicoordinate, donor-free, Lewis-superacidic phosphenium and arsenium ions can be kinetically stabilized. They feature singlet electronic ground states possessing a vacant p-orbital and an electron lone pair with predominantly s-character.

© The Authors, https://doi.org/10.1002/anie.202107975, licensed under CC BY 4.0

Journal of Hazardous Materials (2021) 417, 5

https://doi.org/10.1016/j.jhazmat.2021.126005

The era of advanced computer simulations in materials science enables a great potential to design in silico computational experiments for (nano-)material performance. The adsorption efficiency of nanoparticles in various environments can be unveiled by atomistic models and computer simulations. Arsenic (As) is one of the important globally distributed contaminants with a hazardous impact on human health and environment, and it can strongly bind with iron nanocrystals (e.g., hematite (Fe₂O₃)) depending on their shape and size. Here, we developed a novel Kinetic Monte Carlo (KMC) model capable of exploring and delineating shape-efficiency dependence for Fe₂O₃ nanocrystals in contact with arsenate-contaminated water. This newly designed model demonstrated the performance of nanocrystals for removal of toxic (As) ions on their surface. The current model opens new avenues for designing further advanced KMC models for nanoparticles-toxic ions interactions, under varying environmentally relevant situations, e.g., groundwater, wetlands, and water treatment systems. In addition to bidentate adsorption complexes, implemented in the model presented, monodentate and outer-sphere adsorption complexes should be incorporated into the KMC model. Detailed environmental controls can be addressed by implementation of pH and background ions.

© The Authors, https://doi.org/10.1016/j.jhazmat.2021.126005, licensed under CC BY-NC-ND 4.0

Advances in Space Research (2021) 67 (9), 2688-2695

https://doi.org/10.1016/j.asr.2020.09.026

All currently considered solar sail designs require the deployment of a thin reflective membrane. This membrane is stowed using some folding technique and sometimes coiled onto a spool. The temperature of the deployed sail membrane is a critical aspect for solar sail design. Depending on the geometry of the imprinted folding lines, sunlight may be reflected inside folding lines which would locally increase the temperature of the membrane. The analysis presented here aims for a quantification of that temperature increase. Microscope images of a thick polyimide membrane reveal the geometry of folding lines for different tensioning states. In addition, the opening of folding lines are analysed with a finite-element beam model. After the determination of the geometry as a function of the tensioning state, it is analysed how many reflections may appear in a folding line depending on its opening angle for a sail that is oriented perpendicular to the Sun. Two cases are investigated, deep space and low-Earth orbit. It is shown that, even for small tensioning states, the membrane geometry does not allow more than only two reflections. Depending on the material, this can cause a slight temperature increase that also depends on the investigated case (deep space or low-Earth orbit).

© The Authors, https://doi.org/10.1016/j.asr.2020.09.026, licensed under CC BY-NC-ND 4.0

American Chemical Society (2021) 13 (20), 24130-24137

https://doi.org/10.1021/acsami.1c04056

Acta Astronautica (2021) 182, 160-178.

https://doi.org/10.1016/j.actaastro.2021.01.049

Analog environments for simulating aspects of spaceflight are being utilized for studying the psychological effects of the projected journey to Mars. In 2016, a series of three analog missions concluded at the Hawaii Space Exploration Analog and Simulation (HI-SEAS) facility. Three crews, each with six volunteers per mission, completed consecutive missions of increasing duration, simulating the isolation and confinement of a Mars exploration mission. The durations of the analog missions were 4 months, 8 months, and 12 months, respectively. In this paper, former crew members of these three missions compare how each crew organized their schedules with regard to work routines and social activities. We outline group-living habits that evolved similarly in the independent crews, and we discuss where social norms differed, leading to idiosyncratic policies for group-living during each mission. This information may serve as a reference to mission planners of both simulated and actual human spaceflight missions and also offers insights for psychology researchers that could motivate future studies of team cohesion and performance.

© The Authors, https://doi.org/10.1016/j.actaastro.2021.01.049, licensed under CC BY-NC-ND 4.0

This publication is a result of the Humans on Mars Initiative.

Journal of Materials Processing Technology (2021) 289, 116960. 

https://doi.org/10.1016/j.jmatprotec.2020.116960

The material and its microstructure define the behaviour of a part in a deformation process. A single particle deformation process is introduced as a rapid material characterization method extending already existing approaches. Particle-oriented peening is performed with spherical micro samples of the low carbon steel 100Cr6 (AISI 52100) and the martensitic stainless steel X46Cr13 (AISI 420). Three different diameters (0.6 mm, 0.8 mm and 1.0 mm) were chosen to investigate the impact of the material and the surface to volume ratio. By processing single particles, the mechanical and geometrical properties of the particle before and after the impact can be linked to the deformation behaviour during the peening process. The elastic and plastic material properties are revealed by studying the remaining plastic deformation of the particle and the velocity reduction as a result of the impact. Instrumented universal micro hardness measurements are carried out to determine the hardness of the particles and to correlate it with the behavior of the particles during the particle-oriented peening process. The plastic deformation work as a characteristic value of micro hardness measurements of the different material states is discussed. It is conceivable that the consideration of different material behaviour related values (so-called descriptors) may replace conventional material testing in the future. Using short-term characterization methods like the particle-oriented peening a fast determination of material properties is possible.

© 2020 Elsevier B.V., https://doi.org/10.1016/j.asr.2020.09.026

Front. Microbiol. (2021).

doi: 10.3389/fmicb.2021.611798

Press release ZARM

ZDF Heute feature

The leading space agencies aim for crewed missions to Mars in the coming decades. Among the associated challenges is the need to provide astronauts with life-support consumables and, for a Mars exploration program to be sustainable, most of those consumables should be generated on site. Research is being done to achieve this using cyanobacteria: fed from Mars's regolith and atmosphere, they would serve as a basis for biological life-support systems that rely on local materials. Efficiency will largely depend on cyanobacteria's behavior under artificial atmospheres: a compromise is needed between conditions that would be desirable from a purely engineering and logistical standpoint (by being close to conditions found on the Martian surface) and conditions that optimize cyanobacterial productivity. To help identify this compromise, we developed a low-pressure photobioreactor, dubbed Atmos, that can provide tightly regulated atmospheric conditions to nine cultivation chambers. We used it to study the effects of a 96% N₂, 4% CO₂ gas mixture at a total pressure of 100 hPa on Anabaena sp. PCC 7938. We showed that those atmospheric conditions (referred to as MDA-1) can support the vigorous autotrophic, diazotrophic growth of cyanobacteria. We found that MDA-1 did not prevent Anabaena sp. from using an analog of Martian regolith (MGS-1) as a nutrient source. Finally, we demonstrated that cyanobacterial biomass grown under MDA-1 could be used for feeding secondary consumers (here, the heterotrophic bacterium E. coli W). Taken as a whole, our results suggest that a mixture of gases extracted from the Martian atmosphere, brought to approximately one tenth of Earth's pressure at sea level, would be suitable for photobioreactor modules of cyanobacterium-based life-support systems. This finding could greatly enhance the viability of such systems on Mars.

This publication is a result of the Humans on Mars Initiative.

Nano Letters (2021) 21, 1871-1878

https://doi.org/10.1021/acs.nanolett.0c05080

© 2021 American Chemical Society, https://doi.org/10.1021/acs.nanolett.0c05080

ACS Earth Space Chem. (2021) 5, 391-408

https://doi.org/10.1021/acsearthspacechem.0c00250

More hot articles on electron-induced chemistry from the Swiederek group can be found here: https://www.uni-bremen.de/fb2/news/detailansicht/heisse-forschung-zu-elektronen-induzierter-chemie

Article:

• Mechanisms of methyl formate production during electron-induced processing of methanol–carbon monoxide ices, F. Schmidt, P. Swiderek, J. H. Bredehöft, Phys. Chem. Chem. Phys. 23, 11649-11662 (2021). https://doi.org/10.1039/D1CP01255J
• Role of low-energy electrons in the solubility switch of Zn-based oxocluster photoresist for extreme ultraviolet lithography M. Rohdenburg, N. Thakur, R. Cartaya, S. Castellanos, P. Swiderek, Phys. Chem. Chem. Phys. 23, 16646-16657 (2021). https://doi.org/10.1039/D1CP02334A

Nat. Nanotechnol. (2020).

doi: 10.1038/s41565-020-00791-2

Press release of the University of Bremen

Conical intersections (CoIns) of multidimensional potential energy surfaces are ubiquitous in nature and control pathways and yields of many photo-initiated intramolecular processes. Such topologies can be potentially involved in the energy transport in aggregated molecules or polymers but are yet to be uncovered. Here, using ultrafast two-dimensional electronic spectroscopy (2DES), we reveal the existence of intermolecular CoIns in molecular aggregates relevant for photovoltaics. Ultrafast, sub-10-fs 2DES tracks the coherent motion of a vibrational wave packet on an optically bright state and its abrupt transition into a dark state via a CoIn after only 40 fs. Non-adiabatic dynamics simulations identify an intermolecular CoIn as the source of these unusual dynamics. Our results indicate that intermolecular CoIns may effectively steer energy pathways in functional nanostructures for optoelectronics.

ADVANCED MANUFACTURING: POLYMER & COMPOSITES SCIENCE (2020)

doi: 10.1080/20550340.2020.1838224

Current wind turbine rotor blades have a significant impact on the cost of the turbine, which is mainly a consequence of the manual process steps involved in blade production. The manual, labour-intensive production process leads to high tolerances and requires high safety and reliability factors. Especially in the case of offshore turbines with current and upcoming blade dimensions, automation will make the blades cost effective, quicker to produce and guarantees a higher quality. Here, we analyse the current blade structure and production processes and present a technical review of the existing automation approaches for the textile build-up process in industry and academia. Thereby we classify these approaches according to the different techniques based on the rotor blade structure parts.

npj Quantum Materials (2020) 5, Article number: 79

doi: 10.1038/s41535-020-00277-3

The interplay of electronic correlations, spin–orbit coupling and topology holds promise for the realization of exotic states of quantum matter. Models of strongly interacting electrons on honeycomb lattices have revealed rich phase diagrams featuring unconventional quantum states including chiral superconductivity and correlated quantum spin Hall insulators intertwining with complex magnetic order. Material realizations of these electronic states are, however, scarce or inexistent. In this work, we propose and show that stacking 1T-TaSe₂ into bilayers can deconfine electrons from a deep Mott insulating state in the monolayer to a system of correlated Dirac fermions subject to sizable spin–orbit coupling in the bilayer. 1T-TaSe₂ develops a Star-of-David charge density wave pattern in each layer. When the Star-of-David centers belonging to two adyacent layers are stacked in a honeycomb pattern, the system realizes a generalized Kane–Mele–Hubbard model in a regime where Dirac semimetallic states are subject to significant Mott–Hubbard interactions and spin–orbit coupling. At charge neutrality, the system is close to a quantum phase transition between a quantum spin Hall and an antiferromagnetic insulator. We identify a perpendicular electric field and the twisting angle as two knobs to control topology and spin–orbit coupling in the system. Their combination can drive it across hitherto unexplored grounds of correlated electron physics, including a quantum tricritical point and an exotic first-order topological phase transition.

Scientific Reports (2020) 10 (1), art. no. 17890

doi: 10.1038/s41598-020-74434-w

Scanning transmission electron microscopy (STEM) allows to gain quantitative information on the atomic-scale structure and composition of materials, satisfying one of todays major needs in the development of novel nanoscale devices. The aim of this study is to quantify the impact of inelastic, i.e. plasmon excitations (PE), on the angular dependence of STEM intensities and answer the question whether these excitations are responsible for a drastic mismatch between experiments and contemporary image simulations observed at scattering angles below ∼ 40 mrad. For the two materials silicon and platinum, the angular dependencies of elastic and inelastic scattering are investigated. We utilize energy filtering in two complementary microscopes, which are representative for the systems used for quantitative STEM, to form position-averaged diffraction patterns as well as atomically resolved 4D STEM data sets for different energy ranges. The resulting five-dimensional data are used to elucidate the distinct features in real and momentum space for different energy losses. We find different angular distributions for the elastic and inelastic scattering, resulting in an increased low-angle intensity (∼ 10–40 mrad). The ratio of inelastic/elastic scattering increases with rising sample thickness, while the general shape of the angular dependency is maintained. Moreover, the ratio increases with the distance to an atomic column in the low-angle regime. Since PE are usually neglected in image simulations, consequently the experimental intensity is underestimated at these angles, which especially affects bright field or low-angle annular dark field imaging. The high-angle regime, however, is unaffected. In addition, we find negligible impact of inelastic scattering on first-moment imaging in momentum-resolved STEM, which is important for STEM techniques to measure internal electric fields in functional nanostructures. To resolve the discrepancies between experiment and simulation, we present an adopted simulation scheme including PE. This study highlights the necessity to take into account PE to achieve quantitative agreement between simulation and experiment. Besides solving the fundamental question of missing physics in established simulations, this finally allows for the quantitative evaluation of low-angle scattering, which contains valuable information about the material investigated.

ACS Applied Nano Materials (2020) 3 (8), 7490-7498.

doi:10.1021/acsanm.0c01104

Beilstein J. Nanotechnology (2020) 11, 991–999.

doi:10.3762/bjnano.11.83

Helical structures can be found in nature at various length scales ranging from the molecular level to the macroscale. Due to theirability to store mechanical energy and to optimize the accessible surface area, helical shapes contribute particularly to motion-driven processes and structural reinforcement. Due to these special features, helical fibers have become highly attractive forbiotechnological and tissue engineering applications. However, there are only a few methods available for the production ofbiocompatible helical microfibers. Given that, we present here a simple technique for the fabrication of helical chitosan microfiberswith embedded magnetic nanoparticles. Composite fibers were prepared by wet-spinning and coagulation in an ethanol bath.Thereby, no toxic components were introduced into the wet-spun chitosan fibers. After drying, the helical fibers had adiameter of approximately 130 μm. Scanning electron microscopy analysis of wet-spun helices revealed that the magnetic nanopar-ticles agglomerated into clusters inside the fiber matrix. The helical constructs exhibited a diameter of approximately 500 μm withone to two windings per millimeter. Due to their ferromagnetic properties they are easily attracted to a permanent magnet. Theresults from the tensile testing show that the helical chitosan microfibers exhibited an average Young’s modulus of 14 MPa. Bytaking advantage of the magnetic properties of the feedstock solution, the production of the helical fibers could be automated. Thefabrication of the helical fibers was achieved by utilizing the magnetic properties of the feedstock solution and winding theemerging fiber around a rotating magnetic collector needle upon coagulation. In summary, our helical chitosan microfibers are veryattractive for future use in magnetic tissue engineering or for the development of biocompatible actuator syste

PNAS (2020) 117, 11233-11239

https://doi.org/10.1073/pnas.1913716117

Pulsating flows through tubular geometries are laminar provided that velocities are moderate. This in particular is also believed to apply to cardiovascular flows where inertial forces are typically too low to sustain turbulence. On the other hand, flow instabilities and fluctuating shear stresses are held responsible for a variety of cardiovascular diseases. Here we report a nonlinear instability mechanism for pulsating pipe flow that gives rise to bursts of turbulence at low flow rates. Geometrical distortions of small, yet finite, amplitude are found to excite a state consisting of helical vortices during flow deceleration. The resulting flow pattern grows rapidly in magnitude, breaks down into turbulence, and eventually returns to laminar when the flow accelerates. This scenario causes shear stress fluctuations and flow reversal during each pulsation cycle. Such unsteady conditions can adversely affect blood vessels and have been shown to promote inflammation and dysfunction of the shear stress-sensitive endothelial cell layer.

Advanced Engineering Materials (2020) 22, 2000352

https://doi.org/10.1002/adem.202000352

This article is also featured on advanced science news:
https://www.advancedsciencenews.com/3d-printing-with-nanoparticles/

To translate the exceptional properties of colloidal nanoparticles (NPs) to macroscale geometries, assembly techniques must bridge a 10⁶‐fold range of length. Moreover, for successfully attaining a final mechanically robust nanocomposite macroscale material, some of the intrinsic NPs’ properties have to be maintained while minimizing the density of strength‐limiting defects. However, the assembly of nanoscale building blocks into macroscopic dimensions, and their effective macroscale properties, are inherently affected by the precision of the conditions required for assembly and emergent flaws including point defects, dislocations, grain boundaries, and cracks. Herein, a direct‐write self‐assembly technique is used to construct free‐standing, millimeter‐scale columns comprising spherical iron oxide NPs (15 nm diameter) surface functionalized with oleic acid (OA), which self‐assemble into face‐centered cubic (FCC) supercrystals in minutes during the direct‐writing process. The subsequent crosslinking of OA molecules results in nanocomposites with a maximum strength of 110 MPa and elastic modulus up to 58 GPa. These mechanical properties are interpreted according to the flaw size distribution and are as high as newly engineered platelet‐based nanocomposites. The findings indicate a broad potential to create mechanically robust, multifunctional 3D structures by combining additive manufacturing with colloidal assembly.

Acta Materialia (2020) 188, 733-739

https://doi.org/10.1016/j.actamat.2020.02.058

Laser based powder bed fusion is a promising manufacturing method that can be used for the fabrication of hard magnets such as NdFeB with nearly any given geometrical shape. However, the weak performance, e.g., low coercivity, of the 3D-printed magnets currently hinder their application. In this work, we demonstrated a proof-of-concept of powder bed additive manufacturing of heavy rare earth free NdFeB magnets with technologically attractive coercivity values. The 3D-printed NdFeB magnets exhibit the highest (up-to-date for the additively manufactured magnets without heavy rare earth metals) coercivity values reaching μ₀H_c = 1.6 T. The magnets were synthesized using a mixture of the NdFeB-based and the low-melting eutectic alloy powders. The essential function of the eutectic alloy, along with binding of the NdFeB-based magnetic particles, is the significant improvement of their coercivity by the in-situ grain boundary (GB) infiltration. The fundamental understanding of the magnetization reversal processes in these 3D-printed magnets leads to the conclusion that the excellent performance of the additively manufactured hard magnets can be achieved through the delicate control of the intergrain exchange interaction between the grains of the Nd₂Fe₁₄B phase.

Materials Advances(2020) 1, 86-98

DOI: 10.1039/d0ma00025f

A number of experimental studies have evaluated the potential of hydrophobic high-silica zeolites for the adsorptive removal of emerging organic contaminants, such as pharmaceuticals and personal care products, from water. Despite the widespread use of molecular modelling techniques in various other fields of zeolite science, the adsorption of pharmaceuticals and related pollutants has hardly been studied computationally. In this work, inexpensive molecular simulations using a literature force field (DREIDING) were performed to study the interaction of 21 emerging contaminants with two all-silica zeolites, mordenite (MOR topology) and zeolite Y (FAU topology). The selection of adsorbents and adsorbates was based on a previous experimental investigation of organic contaminant removal using high-silica zeolites (A. Rossner et al., Water Res., 2009, 43, 3787–3796). An analysis of the lowest-energy configurations revealed a good correspondence between calculated interaction energies and experimentally measured removal efficiencies (strong interaction – high removal), despite a number of inherent simplifications. This indicates that such simulations could be used as a screening tool to identify promising zeolites for adsorption-based pollutant removal prior to experimental investigations. To illustrate the predictive capabilities of the method, additional calculations were performed for acetaminophen adsorption in 11 other zeolite frameworks, as neither mordenite nor zeolite Y remove this pharmaceutical efficiently. Furthermore, the lowest-energy configurations were analysed for selected adsorbent-adsorbate combinations in order to explain the observed differences in affinity.

ACS Catalysis (2020) 10, 3164-3174

https://doi.org/10.1021/acscatal.9b05175

Software X (2020) 11, 100395

https://doi.org/10.1016/j.softx.2019.100395

We present nsCouette, a highly scalable software tool to solve the Navier–Stokes equations for incompressible fluid flow between differentially heated and independently rotating, concentric cylinders. It is based on a pseudospectral spatial discretization and dynamic time-stepping. It is implemented in modern Fortran with a hybrid MPI-OpenMP parallelization scheme and thus designed to compute turbulent flows at high Reynolds and Rayleigh numbers. An additional GPU implementation (C-CUDA) for intermediate problem sizes and a version for pipe flow (nsPipe) are also provided.

Desalination (2020) 475, 114192

DOI: 10.1016/j.desal.2019.114192

Lithium is becoming an important raw material due to the expansion of the market of lithium-ion batteries, required for electric vehicles and for stationary energy storage. The current method of lithium extraction is slow, inefficient and it has a strong environmental impact. In the last decade a new technology, called “electrochemical ion pumping”, based on the electrochemical selective capture of lithium cations from the brine, followed by the release of the ions into a so-called “recovery solution”, was proposed. In this work, we developed a flow-through-electrodes reactor, with which it was possible to capture lithium from a diluted solution containing 1 mM LiCl and 1 M NaCl, and concentrate it in a recovery solution. After 9 cycles, it was possible to produce 5 mL of 100 mM LiCl solution with 94% purity starting from more than one liter source solution. We have estimated the energy required by the process, finding that the major contribution is given by the hydraulic energy for pumping the electrolyte through the cell. The evaluation shows that the technology is economically feasible and it can enable a sustainable future production of lithium.

Chemical Engineering Journal (2020) 388 124234

https://doi.org/10.1016/j.cej.2020.124234

A micro-scale analysis of mass transport in ceramic foams that are used as catalyst supports in gas phase reactions is of high interest. Although the effects of flow rate and foam parameters on the radial and axial dispersion are known for liquid flows, no pore-scale experimental analysis has been yet reported to correlate the mechanical and diffusional dispersion of gas flows to the geometry of open-cell foams. Here, a spatially resolved Pulsed Field Gradient NMR method is applied to determine dispersion coefficients of thermally polarized gas along axial and transversal directions of open-cell foams. The comparative study of three commercial foam samples with different morphologies shows the effect of open porosity, window size, and flow rate on gas dispersion. Additionally, the influence of mechanical and diffusional dispersion at each flow rate is investigated for individual samples. By observing the transition from diffusional dispersion to mechanically driven dispersion of gas, it is found that diffusional dispersion plays an important role, even at higher flow rates after a transition from Darcy to Darcy-Forchheimer regime occurs. The measured values for dispersion coefficients of methane can be directly used in pseudo-heterogeneous models for the methanation reaction.

Angewandte Chemie - International Edition (2020) 59, 1828-1836

https://doi.org/10.1002/anie.201912312

The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. As low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purposes (carrier and drug) with a direct chemical composition–biological functionality relationship. Model-based dissolution kinetics of CuO NPs in the cellular interior at post-exposure conditions were controlled through Fe-doping for intra/extra cellular Cu²⁺ and biological outcome. Through controlled ion release and reactions taking place in the cellular interior, tumors could be treated selectively, in vitro and in vivo. Locally administered NPs enabled tumor cells apoptosis and stimulated systemic anti-cancer immune responses. We clearly show therapeutic effects without tumor cells relapse post-treatment with 6 % Fe-doped CuO NPs combined with myeloid-derived suppressor cell silencing.

ACS Applied Nano Materials (2020) 3, 699-710.

https://doi.org/10.1021/acsanm.9b02231

Angewandte Chemie-International Edition (2020) 59, 1581-1584

https://doi.org/10.1002/anie.201913081

The bis(ferrocenyl)phosphenium ion, [Fc₂P]⁺, reported by Cowley et al. (J. Am. Chem. Soc. 1981, 103, 714–715), was the only claimed donor-free divalent phosphenium ion. Our examination of the molecular and electronic structure reveals that [Fc₂P]⁺ possesses significant intramolecular Fe⋅⋅⋅P contacts, which are predominantly electrostatic and moderate the Lewis acidity. Nonetheless, [Fc₂P]⁺ undergoes complex formation with the Lewis bases PPh₃ and IPr to give the donor–acceptor complexes [Fc₂P(PPh₃)]⁺ and [Fc₂P(IPr)]⁺ (IPr=1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene).

Advanced Materials (2019) 1906160

https://doi.org/10.1002/adma.201906160

Controlling the feature sizes of 3D bicontinuous nanoporous (3DNP) materials is essential for their advanced applications in catalysis, sensing, energy systems, etc., requiring high specific surface area. However, the intrinsic coarsening of nanoporous materials naturally reduces their surface energy leading to the deterioration of physical properties over time, even at ambient temperatures. A novel 3DNP material beating the universal relationship of thermal coarsening is reported via high-entropy alloy (HEA) design. In newly developed TiVNbMoTa 3DNP HEAs, the nanoporous structure is constructed by very fine nanoscale ligaments of a solid-solution phase due to enhanced phase stability by maximizing the configuration entropy and suppressed surface diffusion. The smallest size of 3DNP HEA synthesized at 873 K is about 10 nm, which is one order of magnitude smaller than that of conventional porous materials. More importantly, the yield strength of ligament in 3DNP HEA approaches its theoretical strength of G/2π of the corresponding HEA alloy even after thermal exposure. This finding signifies the key benefit of high-entropy design in nanoporous materials—exceptional stability of size-related physical properties. This high-entropy strategy should thus open new opportunities for developing ultrastable nanomaterials against its environment.

Physical Review Letters (2019) 123, 206403

https://doi.org/10.1103/PhysRevLett.123.206403

We investigate the effects of external dielectric screening on the electronic dispersion and the band gap in the atomically thin, quasi-two-dimensional (2D) semiconductor WS2 using angle-resolved photoemission and optical spectroscopies, along with first-principles calculations. We find the main effect of increased external dielectric screening to be a reduction of the quasiparticle band gap, with rigid shifts to the bands themselves. Specifically, the band gap of monolayer WS2 is decreased by about 140 meV on a graphite substrate as compared to a hexagonal boron nitride substrate, while the electronic dispersion of WS2 remains unchanged within our experimental precision of 17 meV. These essentially rigid shifts of the valence and conduction bands result from the special spatial structure of the changes in the Coulomb potential induced by the dielectric environment of the monolayer.

Nano Letters (2019) 19(11), pp. 8630-8637

https://doi.org/10.1021/acs.nanolett.9b03194

Small (2019), Volume 15, Issue 50

https://doi.org/10.1002/smll.201904906

The adoption of graphene in electronics, optoelectronics, and photonics is hindered by the difficulty in obtaining high-quality material on technologically relevant substrates, over wafer-scale sizes, and with metal contamination levels compatible with industrial requirements. To date, the direct growth of graphene on insulating substrates has proved to be challenging, usually requiring metal-catalysts or yielding defective graphene. In this work, a metal-free approach implemented in commercially available reactors to obtain high-quality monolayer graphene on c-plane sapphire substrates via chemical vapor deposition is demonstrated. Low energy electron diffraction, low energy electron microscopy, and scanning tunneling microscopy measurements identify the Al-rich reconstruction (√31×√31)R±9° of sapphire to be crucial for obtaining epitaxial graphene. Raman spectroscopy and electrical transport measurements reveal high-quality graphene with mobilities consistently above 2000 cm² V⁻¹ s⁻¹. The process is scaled up to 4 and 6 in. wafers sizes and metal contamination levels are retrieved to be within the limits for back-end-of-line integration. The growth process introduced here establishes a method for the synthesis of wafer-scale graphene films on a technologically viable basis.

Journal of Physical Chemistry Letters (2019), Volume 10, Issue 22, 21 November 2019, Pages 6973-6982

https://doi.org/10.1021/acs.jpclett.9b02646

Nano letters (2019) 19 (9) , pp. 6554-6563. 

https://doi.org/10.1021/acs.nanolett.9b02798

The corresponding press release and TV contribution can be found here:

https://www.uni-bremen.de/mapex/aktuelles-und-veranstaltungen/neuigkeiten/news/news/detail/News/biologische-pflaster-koennte-bei-der-wundheilung-helfen/

Acta Crystallographica Section A: Foundations and Advances (2019) 75, pp. 705-717. 

doi.org/10.1107/S2053273319008027

Quantum crystallographic refinement of heavy-element-containing compounds is a challenge, because many physical effects have to be accounted for adequately. Here, the impact and magnitude of relativistic effects are compared with those of electron correlation, polarization through the environment, choice of basis set and treatment of thermal motion effects on the structure factors of diphenylmercury(II) [Hg(Ph)₂] and dicyanomercury(II) [Hg(CN)₂]. Furthermore, the individual atomic contributions to the structure factors are explored in detail (using Mulliken population analysis and the exponential decay of atomic displacement parameters) to compare the contributions of lighter atoms, especially hydrogen atoms, against mercury. Subsequently, relativistic Hirshfeld atom refinement (HAR) is validated against theoretical structure factors of Hg(Ph)₂ and Hg(CN)₂, starting from perturbed geometries, to test if the relativistic variant of HAR leads to multiple solutions. Generally, relativistic HAR is successful, leading to a perfect match with the reference geometries, but some limitations are pointed out.

Advanced Materials (2019) 1807747 

doi.org/10.1002/adma.201807747

Living beings have an unsurpassed range of ways to manipulate objects and interact with them. They can make autonomous decisions and can heal themselves. So far, a conventional robot cannot mimic this complexity even remotely. Classical robots are often used to help with lifting and gripping and thus to alleviate the effects of menial tasks. Sensors can render robots responsive, and artificial intelligence aims at enabling autonomous responses. Inanimate soft robots are a step in this direction, but it will only be in combination with living systems that full complexity will be achievable. The field of biohybrid soft robotics provides entirely new concepts to address current challenges, for example the ability to self‐heal, enable a soft touch, or to show situational versatility. Therefore, “living materials” are at the heart of this review. Similarly to biological taxonomy, there is a recent effort for taxonomy of biohybrid soft robotics. Here, an expansion is proposed to take into account not only function and origin of biohybrid soft robotic components, but also the materials. This materials taxonomy key demonstrates visually that materials science will drive the development of the field of soft biohybrid robotics.

Bioinformatics (Oxford, England) (2019) 35 (11), pp.1940-1947

https://dx.doi.org/10.1093/bioinformatics/bty909

MOTIVATION: Non-negative matrix factorization (NMF) is a common tool for obtaining low-rank approximations of non-negative data matrices and has been widely used in machine learning, e.g. for supporting feature extraction in high-dimensional classification tasks. In its classical form, NMF is an unsupervised method, i.e. the class labels of the training data are not used when computing the NMF. However, incorporating the classification labels into the NMF algorithms allows to specifically guide them toward the extraction of data patterns relevant for discriminating the respective classes. This approach is particularly suited for the analysis of mass spectrometry imaging (MSI) data in clinical applications, such as tumor typing and classification, which are among the most challenging tasks in pathology. Thus, we investigate algorithms for extracting tumor-specific spectral patterns from MSI data by NMF methods. RESULTS: In this article, we incorporate a priori class labels into the NMF cost functional by adding appropriate supervised penalty terms. Numerical experiments on a MALDI imaging dataset confirm that the novel supervised NMF methods lead to significantly better classification accuracy and stability as compared with other standard approaches. AVAILABILITY AND IMPLEMENTATON: gitlab.informatik.uni-bremen.de/digipath/Supervised_NMF_Methods_for_MALDI.git. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online. © The Author(s) 2018. Published by Oxford 

Physical Review Letters (2019) 122 (13)

dx.doi.org/10.1103/PhysRevLett.122.136801

Materials exhibiting reversible resistive switching in electrical fields are highly demanded for functional elements in oxide electronics. In particular, multilevel switching effects allow for advanced applications like neuromorphic circuits. Here, we report a structurally driven switching mechanism involving the so-called “dead” layers of perovskite manganite surfaces. Forming a tunnel barrier whose thickness can be changed in monolayer steps by electrical fields, the switching effect exhibits well-defined and robust resistive states.

Nano Letters (2019) 19, 5,3182-3186

https://doi.org/10.1021/acs.nanolett.9b00641

Energy Storage Materials (2019), 19, 360-369

https://doi.org/10.1016/j.ensm.2019.03.006

Aqueous rechargeable metal-ion batteries have become potentially advantageous for the integration of renewable energy sources into the electric power grid thanks to their high rate capability, low cost, environmental friendliness, and intrinsic safety. In this work, we tried to improve the electrochemical stability of CuHCF and prevent/postpone its aging upon cycling. At first we investigated the phase transformation occurring in CuHCF during intercalation of zinc using XRD, SEM and EDX. We observed that large particles are formed upon cycling, which are depleted from copper and are zinc- or iron-rich. In order to prevent this, we modified the CuHCF structure by partially substituting its transition metals with zinc ions during synthesis. We observed that CuZnHCF mixtures with Cu:Zn ratios of 93:7 exhibited an excellent cycle life up to 1000 cycles, with improved specific charge retention with respect to its CuHCF counterpart. Also in the case of CuZnHCF mixtures the formation of large particles upon cycling is observed, but less extended as in pure CuHCF. It appears that different morphologies of the particles show different compositions in term of zinc, iron and potassium.

Chemistry of Materials (2019) 31 (7), 2401-2420. 

http://dx.doi.org/10.1016/j.addma.2019.01.011

Nano Energy (2019) 57, 549-557.

https://doi.org/10.1016/j.nanoen.2018.12.070

To design and manufacture high-performance energy storagedevices with real mechanical flexibility is one of the main advantages of the solid-state battery technology. Mechanically flexible thin film, all solid-state Li-ion batteries are supposed to be the main power sources in emerging technologies such as flexible electronics, wearables, etc. However, if a flexible solid-state device is exposed to repeated external mechanical load, introducing additional aging mechanisms might be expected. In addition, externally introduced stress and strain to the battery functionalcomponents could influence lithiation kinetics of the respective electrode material. In the present study, the effect of the external mechanical load on the lithiation kinetics and the collateral mechanical fatigue of the full battery cell during dynamic bending were investigated in detail. Therefore, mechanically flexible, all solid-state MoO3/LiPON/Li battery cells were fabricated on a polymer substrate. Battery cells were exposed to static convex bending and it was ascertained that the bulk resistance of the positive electrode is largely dependent on the depth-of-discharge as well as mechanical stress state, while other processes such as charge transfer and electrolyte bulk resistance are less affected. Furthermore, battery cells were cycled galvanostatically, while they were bent repeatedly using different bending scenarios. Below a threshold bending frequency (f = 1/360 Hz), stable battery function was found, however mechanical aging of the battery cell was observed. As it was demonstrated, the metal current collector/positive electrode interface is highly prone to the physical degradation upon dynamic bending. As a result, delamination of the electrode and contact loss occur, causing capacity fading, accordingly. The present study shed light on the joint mechanical-electrochemical aging of mechanically flexible all solid-state Li-ion batteries.

Additive Manufacturing(2019) 26,161-165. 

https://doi.org/10.1016/j.addma.2019.01.011

Additive manufacturing that allows layer by layer shaping of complex structures is of rapidly increasing interest in production technology. A particularly rapid prototyping technique of additive manufacturing is laser beam melting (LBM). This 3D printing method is based on a powder bed fusion technique, using a high-powered laser to melt and consolidate metallic powders. The process needs a tightly controlled atmosphere of inert gas, which requires a confined space of a building chamber. This and more process related factors like elevated temperatures, laser radiation or the resulting light intensity caused by the melting of metals, make a closed-loop quality control very ambitious. In this paper, we propose a new in-process approach for quality control with high precision metrology based on structured light. The precise layer by layer dimensional measurement of both the printed part and the powder deposition, allows for process assessment in- or off-line.

Nature Communications (2019) 10, Article Number 180.

https://doi.org/10.1038/s41467-018-08088-8

Charge transfers resulting from weak bondings between two-dimensional materials and the supporting substrates are often tacitly associated with their work function differences. In this context, two-dimensional materials could be normally doped at relatively low levels. Here, we demonstrate how even weak hybridization with substrates can lead to an apparent heavy doping, using the example of monolayer 1H-TaS₂ grown on Au(111). Ab-initio calculations show that sizable changes in Fermi areas can arise, while the transferred charge between substrate and two-dimensional material is much smaller than the variation of Fermi areas suggests. This mechanism, which we refer to as pseudodoping, is associated with non-linear energy-dependent shifts of electronic spectra, which our scanning tunneling spectroscopy experiments reveal for clean and defective TaS₂ monolayer on Au(111). The influence of pseudodoping on the formation of many-body states in two-dimensional metallic materials is analyzed, shedding light on utilizing pseudodoping to control electronic phase diagrams.

Nano Letters (2019) 19 (1), 210-217. 

http://dx.doi.org/10.1021/acs.nanolett.8b03729