@article{62819, abstract = {{Novel oxalate-bridged heterotrinuclear complexes [A][Mn2Cr(bpy)2(H2O)2Cl2(C2O4)3] (A = (CH3)2(C2H5)NH+ (1) and (CH3)(C2H5)2NH+ (2); bpy = 2,2′-bipyridine) were synthesized using an aqueous solution of [A]3[Cr(C2O4)3] as a building block in reaction with Mn2+ ions and with the addition of the N-donor ligand bipyridine. The isostructural heterometallic complex salts were characterized by single-crystal and powder X-ray diffraction, infrared and impedance spectroscopy, thermal analysis and magnetization measurements. The trinuclear anion [{Mn(bpy)(H2O)Cl(μ-C2O4)}2Cr(C2O4)]− consists of two [Mn(bpy)(H2O)Cl]+ units bridged by the [Cr(C2O4)3]3− anion, which acts as a bidentate ligand towards each of the manganese atoms. The anions are hydrogen bonded to each other via coordinated chloride anions, water molecules and oxygen oxalate atoms, resulting in two-dimensional (2D) hydrogen bonding layers. Compounds exhibit water-assisted proton conductivity behaviour, which was investigated at different temperatures and relative humidities (RH). At 25 °C, an increase in RH from 60% to 93% resulted in an obvious proton conducting switch from 9.1 × 10−11 to 5.6 × 10−5 S cm−1 for 1 and from 7.4 × 10−10 to 1.8 × 10−6 S cm−1 for 2, corresponding to high on/off ratios of about 106 for 1 and 104 for 2. In situ powder X-ray diffraction (PXRD) analysis showed that unit cell parameters of compounds 1 and 2 slightly increase when exposed to humid conditions. This confirmed that incorporation of water molecules into structures with pores and voids causes the proton conductivity switching phenomenon. Magnetic susceptibility measurements indicate a ferromagnetic interaction between Cr3+ and Mn2+ ions bridged by the bis(bidentate) oxalate group. The prepared compounds 1 and 2 were explored as single-source precursors for the formation of spinel oxide by their thermal treatment. With increasing temperature, the spinel composition changed according to the formula Mn1+xCr2–xO4 (0 ≤ x ≤ 1), where x = 0.7 at 500 °C and x = 1 at 900 °C when tet[MnII]oct[MnIIICrIII]O4 is formed. The (micro)structure, morphology, and optical properties of spinel Mn2CrO4 were characterized by PXRD, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of this oxide in degradation of the methylene blue dye under Vis irradiation without and with the support of hydrogen peroxide was further investigated.}}, author = {{Lozančić, Ana and Burazer, Sanja and Wagner, Tobias and Molčanov, Krešimir and Pajić, Damir and Androš Dubraja, Lidija and Tiemann, Michael and Jurić, Marijana}}, issn = {{2050-7526}}, journal = {{Journal of Materials Chemistry C}}, number = {{41}}, pages = {{21179--21195}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Water-assisted proton conductivity and a magnetic study of heterotrinuclear oxalate-bridged compounds: molecular precursors for the Mn2CrO4 spinel}}}, doi = {{10.1039/d5tc02569a}}, volume = {{13}}, year = {{2025}}, } @article{62816, abstract = {{The increasing demand for advanced sensing technologies drives the development of chemical sensors using innovative materials. In gas sensing, optical sensors are often used to detect gases such as CO, NOx, and O2. Oxygen sensors typically incorporate dyes into oxygen-permeable matrices like polymers, silica, or zeolites. Alternatively, semiconductor surface chemistry can enable O2 detection. However, these approaches are often limited by slow response and recovery times and low selectivity, restricting their practical applications. The metal-organic framework MOF-76(Eu) and its yttrium-modified variant, MOF-76(Eu/Y) are reported to exhibit highly reversible and fast optical responses to varying O2 concentrations. Time-resolved emission measurements are performed over short (seconds) and long (hours) timescales using N2 and synthetic air mixtures. Cross-sensitivity to humidity is analyzed. Multichannel scaling photon-counting experiments confirm quenching at the linker level, as the emission lifetime remains nearly constant. Yttrium significantly improves stability and performance at room temperature. Structural and optical changes induced by yttrium are investigated. Additionally, MIL-78(Eu), another Eu-BTC-based MOF with a different coordination environment, is synthesized. Unlike MOF-76(Eu), MIL-78(Eu) exhibits distinct optical properties but lacks a reversible response to O2. These results highlight the potential of MOF-76-based materials for high-performance O2 sensing.}}, author = {{Zhao, Zhenyu and Weinberger, Christian and Steube, Jakob and Bauer, Matthias and Brehm, Martin and Tiemann, Michael}}, issn = {{1616-301X}}, journal = {{Advanced Functional Materials}}, publisher = {{Wiley}}, title = {{{Fast‐Responding O2 Gas Sensor Based on Luminescent Europium Metal‐Organic Frameworks (MOF‐76)}}}, doi = {{10.1002/adfm.202511190}}, year = {{2025}}, } @article{62179, author = {{Koch, Leon and Baier, Dominik and Rajput, Satyendra and König, Benedikt and Tiemann, Michael and Ebbinghaus, Simon and Nayar, Divya and Huber, Klaus}}, issn = {{1520-6106}}, journal = {{The Journal of Physical Chemistry B}}, number = {{40}}, pages = {{10213--10228}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Disaggregation at High Volume Exclusion: An “Overcrowding” Effect}}}, doi = {{10.1021/acs.jpcb.5c01245}}, volume = {{129}}, year = {{2025}}, } @article{60194, author = {{Peeters, Hendrik and Hansel, Jan-Luca and Graute, André and Fischer, Matthias and Weinberger, Christian and Neiske, Iris and Fechner, Sabine}}, journal = {{Laborpraxis}}, number = {{5-6}}, pages = {{22--25}}, title = {{{Virtual Reality trifft Künstliche Intelligenz. KI unterstützt bei virtueller Praktikumsvorbereitung}}}, year = {{2025}}, } @article{52372, abstract = {{Due to the hydrolytic instability of LiPF6 in carbonate-based solvents, HF is a typical impurity in Li-ion battery electrolytes. HF significantly influences the performance of Li-ion batteries, for example by impacting the formation of the solid electrolyte interphase at the anode and by affecting transition metal dissolution at the cathode. Additionally, HF complicates studying fundamental interfacial electrochemistry of Li-ion battery electrolytes, such as direct anion reduction, because it is electrocatalytically relatively unstable, resulting in LiF passivation layers. Methods to selectively remove ppm levels of HF from LiPF6-containing carbonate-based electrolytes are limited. We introduce and benchmark a simple yet efficient electrochemical in situ method to selectively remove ppm amounts of HF from LiPF6-containing carbonate-based electrolytes. The basic idea is the application of a suitable potential to a high surface-area metallic electrode upon which only HF reacts (electrocatalytically) while all other electrolyte components are unaffected under the respective conditions.}}, author = {{Ge, Xiaokun and Huck, Marten and Kuhlmann, Andreas and Tiemann, Michael and Weinberger, Christian and Xu, Xiaodan and Zhao, Zhenyu and Steinrueck, Hans-Georg}}, issn = {{0013-4651}}, journal = {{Journal of The Electrochemical Society}}, keywords = {{Materials Chemistry, Electrochemistry, Surfaces, Coatings and Films, Condensed Matter Physics, Renewable Energy, Sustainability and the Environment, Electronic, Optical and Magnetic Materials}}, pages = {{030552}}, publisher = {{The Electrochemical Society}}, title = {{{Electrochemical Removal of HF from Carbonate-based LiPF6-containing Li-ion Battery Electrolytes}}}, doi = {{10.1149/1945-7111/ad30d3}}, volume = {{171}}, year = {{2024}}, } @article{54419, abstract = {{Leaky mode resonances of the setae of Cataglyphis bombycina are found to enhance the thermal emission of the animals by near field coupling to the chitinous exoskeleton. This is remarkable, as the setae are also an adaption to enhance the reflectivity in the visible wavelength range. Both effects are dependent on morphology, dimensions and spatial arrangement. These parameters were experimentally characterized and simulated by finite difference time domain simulations to elucidate the optical impact of the setae in the mid infrared range and the contribution of leaky mode resonances. This mode of action and the setae’s optical properties in the visible range explain evolutionary strains that led to the actual morphology and size of the setae.}}, author = {{Schwind, Bertram and Wu, Xia and Tiemann, Michael and Fabritius, Helge-Otto}}, issn = {{2296-424X}}, journal = {{Frontiers in Physics}}, title = {{{Natural near field coupled leaky-mode resonant anti-reflection structures: the setae of Cataglyphis bombycina}}}, doi = {{10.3389/fphy.2024.1393279}}, volume = {{12}}, year = {{2024}}, } @inproceedings{55392, abstract = {{In dieser Arbeit werden Untersuchungen zur sauerstoffabhängigen Photolumineszenz von Zink-Zinn-Oxid-Partikeln präsentiert, welche perspektivisch für die optische Sauerstoffdetektion eingesetzt werden sollen. Zink-Zinn-Oxid zeigt eine sauerstoffabhängige Photolumineszenz im sichtbaren Spektralbereich und wird hier als eine photostabile Alternative zu den kommerziell verfügbaren metallorganischen Verbindungen vorgestellt. Der Fokus liegt dabei auf dem Einfluss der Temperatur auf die Sauerstoffsensitivität der Photolumineszenz. Wir zeigen, dass bereits leichte Temperaturerhöhungen zu einer signifikanten Verbesserung der Sauerstoffsensitivität der Photolumineszenz führen und gleichzeitig die Signalqualität erhöhen.}}, author = {{Kothe, Linda and Ester, Stephan and Poeplau, Michael and Wengenroth, Marc and Tiemann, Michael}}, booktitle = {{Proceedings 22. GMA/ITG-Fachtagung Sensoren und Messsysteme 2024}}, isbn = {{978-3-910600-01-0}}, pages = {{66 -- 71}}, title = {{{Stabilisierung von O2-sensitiven Photolumineszenzsignalen durch Temperaturvariation}}}, doi = {{10.5162/sensoren2024/A3.1}}, year = {{2024}}, } @article{56947, abstract = {{Pore engineering is commonly used to alter the properties of metal–organic frameworks. This is achieved by incorporating different linker molecules (L) into the structure, generating isoreticular frameworks. CPO-27, also named MOF-74, is a prototypical material for this approach, offering the potential to modify the size of its one-dimensional pore channels and the hydrophobicity of pore walls using various linker ligands during synthesis. Thermal activation of these materials yields accessible open metal sites (i.e., under-coordinated metal centers) at the pore walls, thus acting as strong primary binding sites for guest molecules, including water. We study the effect of the pore size and linker hydrophobicity within a series of Ni2+-based isoreticular frameworks (i.e., Ni2L, L = dhtp, dhip, dondc, bpp, bpm, tpp), analyzing their water sorption behavior and the water interactions in the confined pore space. For this purpose, we apply water vapor sorption analysis and Fourier transform infrared spectroscopy. In addition, defect degrees of all compounds are determined by thermogravimetric analysis and solution 1H nuclear magnetic resonance spectroscopy. We find that larger defect degrees affect the preferential sorption sites in Ni2dhtp, while no such indication is found for the other materials in our study. Instead, strong evidence is found for the formation of water bridges/chains between coordinating water molecules, as previously observed for hydrophobic porous carbons and mesoporous silica. This suggests similar sorption energies for additional water molecules in materials with larger pore sizes after saturation of the primary binding sites, resulting in more bulk-like water arrangements. Consequently, the sorption mechanism is driven by classical pore condensation through H-bonding anchor sites instead of sorption at discrete sites.}}, author = {{Kloß, Marvin and Schäfers, Lara and Zhao, Zhenyu and Weinberger, Christian and Egold, Hans and Tiemann, Michael}}, issn = {{2079-4991}}, journal = {{Nanomaterials}}, number = {{22}}, pages = {{1791}}, publisher = {{MDPI AG}}, title = {{{Water Sorption on Isoreticular CPO-27-Type MOFs: From Discrete Sorption Sites to Water-Bridge-Mediated Pore Condensation}}}, doi = {{10.3390/nano14221791}}, volume = {{14}}, year = {{2024}}, } @article{56080, abstract = {{CPO‐27 is a metal‐organic framework (MOF) with coordinatively unsaturated metal centers (open metal sites). It is therefore an ideal host material for small guest molecules, including water. This opens up numerous possible applications, such as proton conduction, humidity sensing, water harvesting, or adsorption‐driven heat pumps. For all of these applications, profound knowledge of the adsorption and desorption of water in the micropores is mandatory. The hydration and water structure in CPO‐27‐M (M = Zn or Cu) is investigated using water vapor sorption, Fourier transform infrared (FTIR) spectroscopy, density functional theory (DFT) calculations, and molecular dynamics simulation. In the pores of CPO‐27‐Zn, water binds as a ligand to the Zn center. Additional water molecules are stepwise incorporated at defined positions, forming a network of H‐bonds with the framework and with each other. In CPO‐27‐Cu, hydration proceeds by an entirely different mechanism. Here, water does not coordinate to the metal center, but only forms H‐bonds with the framework; pore filling occurs mostly in a single step, with the open metal site remaining unoccupied. Water in the pores forms clusters with extensive intra‐cluster H‐bonding.}}, author = {{Kloß, Marvin and Beerbaum, Michael and Baier, Dominik and Weinberger, Christian and Zysk, Frederik and Elgabarty, Hossam and Kühne, Thomas D. and Tiemann, Michael}}, issn = {{2196-7350}}, journal = {{Advanced Materials Interfaces}}, number = {{35}}, pages = {{2400476}}, publisher = {{Wiley}}, title = {{{Understanding Hydration in CPO‐27 Metal‐Organic Frameworks: Strong Impact of the Chemical Nature of the Metal (Cu, Zn)}}}, doi = {{10.1002/admi.202400476}}, volume = {{11}}, year = {{2024}}, } @article{55999, abstract = {{Clean hydrogen is a key aspect of carbon neutrality, necessitating robust methods for monitoring hydrogen concentration in critical infrastructures like pipelines or power plants. While semiconducting metal oxides such as In2O3 can monitor gas concentrations down to the ppm range, they often exhibit cross-sensitivity to other gases like H2O. In this study, we investigated whether cyclic optical illumination of a gas-sensitive In2O3 layer creates identifiable changes in a gas sensor´s electronic resistance that can be linked to H2 and H2O concentrations via machine learning. We exposed nanostructured In2O3 with a large surface area of 95 m2 g-1 to H2 concentrations (0-800 ppm) and relative humidity (0-70%) under cyclic activation utilizing blue light. The sensors were tested for 20 classes of gas combinations. A support vector machine achieved classification rates up to 92.0%, with reliable reproducibility (88.2 ± 2.7%) across five individual sensors using 10-fold cross-validation. Our findings suggest that cyclic optical activation can be used as a tool to classify H2 and H2O concentrations.}}, author = {{Baier, Dominik and Krüger, Alexander and Wagner, Thorsten and Tiemann, Michael and Weinberger, Christian}}, issn = {{2227-9040}}, journal = {{Chemosensors}}, keywords = {{resistive gas sensor, chemiresistor, semiconductor, metal oxide, In2O3, mesoporous, hydrogen, humidtiy, machine learning, sustainable}}, number = {{9}}, pages = {{178}}, publisher = {{MDPI}}, title = {{{Gas Sensing with Nanoporous In2O3 under Cyclic Optical Activation: Machine Learning-Aided Classification of H2 and H2O}}}, doi = {{10.3390/chemosensors12090178}}, volume = {{12}}, year = {{2024}}, } @article{45571, abstract = {{Self-templating is a facile strategy for synthesizing porous carbons by direct pyrolysis of organic metal salts. However, the method typically suffers from low yields (<4%) and limited specific surface areas (SSA<2000 m2 g−1) originating from low activity of metal cations (e.g., K+ or Na+) in promoting construction and activation of carbon frameworks. Here we use cesium acetate as the only precursor of oxo-carbons with large SSA of the order of 3000 m2 g−1, pore volume approaching 2 cm3 g−1, tunable oxygen contents, and yields of up to 15 %. We unravel the role of Cs+ as an efficient promoter of framework formation, templating and etching agent, while acetates act as carbon/oxygen sources of carbonaceous frameworks. The oxo-carbons show record-high CO2 uptake of 8.71 mmol g−1 and an ultimate specific capacitance of 313 F g−1 in the supercapacitor. This study helps to understand and rationally tailor the materials design by a still rare organic solid-state chemistry.}}, author = {{Li, Jiaxin and Kossmann, Janina and Zeng, Ke and Zhang, Kun and Wang, Bingjie and Weinberger, Christian and Antonietti, Markus and Odziomek, Mateusz and López‐Salas, Nieves}}, issn = {{0044-8249}}, journal = {{Angewandte Chemie International Edition}}, keywords = {{CO2 Adsorption, Cesium Acetate, Cesium Effect, Porous Carbons, Supercapacitor}}, publisher = {{Wiley}}, title = {{{When High‐Temperature Cesium Chemistry Meets Self‐Templating: Metal Acetates as Building Blocks of Unusual Highly Porous Carbons}}}, doi = {{10.1002/anie.202217808}}, year = {{2023}}, } @article{42679, abstract = {{The Saharan desert ant Cataglyphis bombycina is densely covered with shiny silver setae (hair-like structures). Their appearance was explained by geometric optics and total internal reflection. The setae also increase the emissivity of the ant, as they form an effective medium. This work provides additional data on microstructural details of the setae that are used to simulate the scattering of an individual seta to explain their influence on the optical properties. This is achieved by characterization of their structure using light microscopy and scanning/transmission electron microscopy. How the microstructural features influence scattering is investigated wave-optically within the limits of finite-difference time-domain simulations from the ultraviolet to the mid-infrared spectral range to elucidate the optical effects beyond ray optics and effective medium theory. The results show that Mie scattering plays an important role in protecting the ant from solar radiation and could be relevant for its thermal tolerance.}}, author = {{Schwind, Bertram and Wu, Xia and Tiemann, Michael and Fabritius, Helge-Otto}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics}}, number = {{3}}, pages = {{B49 -- B58}}, publisher = {{Optica Publishing Group}}, title = {{{Broadband Mie scattering effects by structural features of setae from the Saharan silver ant Cataglyphis bombycina}}}, doi = {{10.1364/josab.474899}}, volume = {{40}}, year = {{2023}}, } @article{43457, abstract = {{The production of hydrogen and the utilization of biomass for sustainable concepts of energy conversion and storage require gas sensors that discriminate between hydrogen (H2) and carbon monoxide (CO). Mesoporous copper–ceria (Cu–CeO2) materials with large specific surface areas and uniform porosity are prepared by nanocasting, and their textural properties are characterized by N2 physisorption, powder XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The oxidation states of copper (Cu+, Cu2+) and cerium (Ce3+, Ce4+) are investigated by XPS. The materials are used as resistive gas sensors for H2 and CO. The sensors show a stronger response to CO than to H2 and low cross-sensitivity to humidity. Copper turns out to be a necessary component; copper-free ceria materials prepared by the same method show only poor sensing performance. By measuring both gases (CO and H2) simultaneously, it is shown that this behavior can be utilized for selective sensing of CO in the presence of H2.}}, author = {{Baier, Dominik and Priamushko, Tatiana and Weinberger, Christian and Kleitz, Freddy and Tiemann, Michael}}, issn = {{2379-3694}}, journal = {{ACS Sensors}}, keywords = {{Fluid Flow and Transfer Processes, Process Chemistry and Technology, Instrumentation, Bioengineering}}, number = {{4}}, pages = {{1616 -- 1623}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Selective Discrimination between CO and H2 with Copper–Ceria-Resistive Gas Sensors}}}, doi = {{10.1021/acssensors.2c02739}}, volume = {{8}}, year = {{2023}}, } @article{44837, abstract = {{Hydrothermal carbonization (HTC) is an efficient thermochemical method for the conversion of organic feedstock to carbonaceous solids. HTC of different saccharides is known to produce microspheres (MS) with mostly Gaussian size distribution, which are utilized as functional materials in various applications, both as pristine MS and as a precursor for hard carbon MS. Although the average size of the MS can be influenced by adjusting the process parameters, there is no reliable mechanism to affect their size distribution. Our results demonstrate that HTC of trehalose, in contrast to other saccharides, results in a distinctly bimodal sphere diameter distribution consisting of small spheres with diameters of (2.1 ± 0.2) μm and of large spheres with diameters of (10.4 ± 2.6) μm. Remarkably, after pyrolytic post-carbonization at 1000 °C the MS develop a multimodal pore size distribution with abundant macropores > 100 nm, mesopores > 10 nm and micropores < 2 nm, which were examined by small-angle X-ray scattering and visualized by charge-compensated helium ion microscopy. The bimodal size distribution and hierarchical porosity provide an extraordinary set of properties and potential variables for the tailored synthesis of hierarchical porous carbons, making trehalose-derived hard carbon MS a highly promising material for applications in catalysis, filtration, and energy storage devices.}}, author = {{Wortmann, Martin and Keil, Waldemar and Diestelhorst, Elise and Westphal, Michael and Haverkamp, René and Brockhagen, Bennet and Biedinger, Jan and Bondzio, Laila and Weinberger, Christian and Baier, Dominik and Tiemann, Michael and Hütten, Andreas and Hellweg, Thomas and Reiss, Günter and Schmidt, Claudia and Sattler, Klaus and Frese, Natalie}}, issn = {{2046-2069}}, journal = {{RSC Advances}}, keywords = {{General Chemical Engineering, General Chemistry}}, number = {{21}}, pages = {{14181--14189}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Hard carbon microspheres with bimodal size distribution and hierarchical porosity via hydrothermal carbonization of trehalose}}}, doi = {{10.1039/d3ra01301d}}, volume = {{13}}, year = {{2023}}, } @article{44116, abstract = {{Faradaic reactions including charge transfer are often accompanied with diffusion limitation inside the bulk. Conductive two-dimensional frameworks (2D MOFs) with a fast ion transport can combine both - charge transfer and fast diffusion inside their porous structure. To study remaining diffusion limitations caused by particle morphology, different synthesis routes of Cu-2,3,6,7,10,11-hexahydroxytriphenylene (Cu3(HHTP)2), a copper-based 2D MOF, are used to obtain flake- and rod-like MOF particles. Both morphologies are systematically characterized and evaluated for redox-active Li+ ion storage. The redox mechanism is investigated by means of X-ray absorption spectroscopy, FTIR spectroscopy and in situ XRD. Both types are compared regarding kinetic properties for Li+ ion storage via cyclic voltammetry and impedance spectroscopy. A significant influence of particle morphology for 2D MOFs on kinetic aspects of electrochemical Li+ ion storage can be observed. This study opens the path for optimization of redox active porous structures to overcome diffusion limitations of Faradaic processes.}}, author = {{Wrogemann, Jens Matthies and Lüther, Marco Joes and Bärmann, Peer and Lounasvuori, Mailis and Javed, Ali and Tiemann, Michael and Golnak, Ronny and Xiao, Jie and Petit, Tristan and Placke, Tobias and Winter, Martin}}, issn = {{1433-7851}}, journal = {{Angewandte Chemie International Edition}}, keywords = {{General Chemistry, Catalysis}}, number = {{26}}, pages = {{e202303111}}, publisher = {{Wiley}}, title = {{{Overcoming Diffusion Limitation of Faradaic Processes: Property‐Performance Relationships of 2D Conductive Metal‐Organic Framework Cu3(HHTP)2 for Reversible Lithium‐Ion Storage}}}, doi = {{10.1002/anie.202303111}}, volume = {{62}}, year = {{2023}}, } @article{46480, author = {{Müller, Hendrik and Weinberger, Christian and Grundmeier, Guido and de los Arcos de Pedro, Maria Teresa}}, issn = {{0368-2048}}, journal = {{Journal of Electron Spectroscopy and Related Phenomena}}, keywords = {{Physical and Theoretical Chemistry, Spectroscopy, Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Radiation, Electronic, Optical and Magnetic Materials}}, publisher = {{Elsevier BV}}, title = {{{UV-enhanced environmental charge compensation in near ambient pressure XPS}}}, doi = {{10.1016/j.elspec.2023.147317}}, volume = {{264}}, year = {{2023}}, } @article{35707, abstract = {{The proton conductivity of two coordination networks, [Mg(H2O)2(H3L)]·H2O and [Pb2(HL)]·H2O (H5L = (H2O3PCH2)2-NCH2-C6H4-SO3H), is investigated by AC impedance spectroscopy. Both materials contain the same phosphonato-sulfonate linker molecule, but have clearly different crystal structures, which has a strong effect on proton conductivity. In the Mg-based coordination network, dangling sulfonate groups are part of an extended hydrogen bonding network, facilitating a “proton hopping” with low activation energy; the material shows a moderate proton conductivity. In the Pb-based metal-organic framework, in contrast, no extended hydrogen bonding occurs, as the sulfonate groups coordinate to Pb2+, without forming hydrogen bonds; the proton conductivity is much lower in this material.}}, author = {{Javed, Ali and Steinke, Felix and Wöhlbrandt, Stephan and Bunzen, Hana and Stock, Norbert and Tiemann, Michael}}, issn = {{2190-4286}}, journal = {{Beilstein Journal of Nanotechnology}}, keywords = {{Electrical and Electronic Engineering, General Physics and Astronomy, General Materials Science}}, pages = {{437--443}}, publisher = {{Beilstein Institut}}, title = {{{The role of sulfonate groups and hydrogen bonding in the proton conductivity of two coordination networks}}}, doi = {{10.3762/bjnano.13.36}}, volume = {{13}}, year = {{2022}}, } @article{33691, abstract = {{Near ambient pressure XPS in nitrogen atmosphere was utilized to investigate gas-solid interactions within porous SiO2 films ranging from 30 to 75 nm thickness. The films were differentiated in terms of porosity and roughness. The XPS N1s core levels of the N2 gas in presence of the SiO2 samples showed variations in width, binding energy and line shape. The width correlated with the surface charge induced in the dielectric films upon X-ray irradiation. The observed different binding energies observed for the N1s peak can only partly be associated with intrinsic work function differences between the samples, opening the possibility that the effect of physisorption at room temperature could be detected by a shift in the measured binding energy. However, the signals also show an increasing asymmetry with rising surface charge. This might be associated with the formation of vertical electrical gradients within the dielectric porous thin films, which complicates the assignment of binding energy positions to specific surface-related effects. With the support of Monte Carlo and first principles density functional theory calculations, the observed shifts were discussed in terms of the possible formation of transitory dipoles upon N2 physisorption within the porous SiO2 films.}}, author = {{de los Arcos, Teresa and Weinberger, Christian and Zysk, Frederik and Raj Damerla, Varun and Kollmann, Sabrina and Vieth, Pascal and Tiemann, Michael and Kühne, Thomas and Grundmeier, Guido}}, issn = {{0169-4332}}, journal = {{Applied Surface Science}}, keywords = {{Surfaces, Coatings and Films, Condensed Matter Physics, Surfaces and Interfaces, General Physics and Astronomy, General Chemistry}}, publisher = {{Elsevier BV}}, title = {{{Challenges in the interpretation of gas core levels for the determination of gas-solid interactions within dielectric porous films by ambient pressure XPS}}}, doi = {{10.1016/j.apsusc.2022.154525}}, volume = {{604}}, year = {{2022}}, } @article{33685, abstract = {{In the spatial confinement of cylindrical mesopores with diameters of a few nanometers, water molecules experience restrictions in hydrogen bonding. This leads to a different behavior regarding the molecular orientational freedom (‘structure of water') compared to the bulk liquid state. In addition to the pore size, the behavior is also strongly affected by the strength of the pore wall-to-water interactions, that is, the pore wall polarity. In this work, this is studied both experimentally and theoretically. The surface polarity of mesoporous silica (SiO2) is modified by functionalization with trimethylsilyl moieties, resulting in a change from a hydrophilic (pristine) to a hydrophobic pore wall. The mesopore surface is characterized by N2 and H2O sorption experiments. Those results are combined with IR spectroscopy to investigate pore wall-to-water interactions leading to different structures of water in the mesopore. Furthermore, the water's structure is studied theoretically to gain deeper insight into the interfacial interactions. For this purpose, the structure of water is analyzed by pairing densities, coordination, and angular distributions with a novel adaptation of surface-specific sum-frequency generation calculation for pore environments.}}, author = {{Weinberger, Christian and Zysk, Frederik and Hartmann, Marc and Kaliannan, Naveen and Keil, Waldemar and Kühne, Thomas and Tiemann, Michael}}, issn = {{2196-7350}}, journal = {{Advanced Materials Interfaces}}, keywords = {{Mechanical Engineering, Mechanics of Materials}}, number = {{20}}, publisher = {{Wiley}}, title = {{{The Structure of Water in Silica Mesopores – Influence of the Pore Wall Polarity}}}, doi = {{10.1002/admi.202200245}}, volume = {{9}}, year = {{2022}}, } @article{29376, abstract = {{The electrochemical properties of carbonaceous materials produced by hydrothermal carbonization, referred to as hydrochar, can be substantially improved by post-carbonization via pyrolysis. Although these materials have been widely studied for a variety of applications, the mechanisms underlying the pyrolysis are yet poorly understood. This study provides a comprehensive temperature-resolved characterization of the chemical composition, morphology and crystallinity of sucrose-derived hydrochar during pyrolysis. Thermogravimetric analysis, differential scanning calorimetry, and elemental analysis have shown that the dry hydrochar loses about 41% of its dry mass due to the exothermic disintegration of oxygen-containing groups until the carbonization is completed at about 850 °C with a total carbon yield of 93%. The carbonization and aromatization of the initially furanic and keto-aliphatic structure were analyzed by 13C solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The transition from an amorphous to a nanocrystalline graphitic structure was analyzed using X-ray diffraction and Raman spectroscopy. The pore formation mechanism was examined by helium ion microscopy, transmission electron microscopy, and nitrogen adsorption measurements. The results indicate the formation of oxygen-rich nanoclusters up to 700 °C, which decompose up to 750 °C leaving behind equally sized pores, resulting in a surface area of up to 480 m2/g.}}, author = {{Wortmann, Martin and Keil, Waldemar and Brockhagen, Bennet and Biedinger, Jan and Westphal, Michael and Weinberger, Christian and Diestelhorst, Elise and Hachmann, Wiebke and Zhao, Yanjing and Tiemann, Michael and Reiss, Günter and Hüsgen, Bruno and Schmidt, Claudia and Sattler, Klaus and Frese, Natalie}}, issn = {{0165-2370}}, journal = {{Journal of Analytical and Applied Pyrolysis}}, keywords = {{Analytical Chemistry, Fuel Technology}}, publisher = {{Elsevier BV}}, title = {{{Pyrolysis of sucrose-derived hydrochar}}}, doi = {{10.1016/j.jaap.2021.105404}}, volume = {{161}}, year = {{2022}}, }