Marko Bertmer | Leipzig University (Universität Leipzig) (original) (raw)

Papers by Marko Bertmer

The Journal of Physical Chemistry C

Die dynamischen Veranderungen der organische Bodensubstanz, die durch Anderungen der Umweltbeding... more Die dynamischen Veranderungen der organische Bodensubstanz, die durch Anderungen der Umweltbedingungen hervorgerufen werden, haben einen wichtigen Einfluss auf die Sorptions- und Transportvorgangen von organischen Schadstoffen. Das Verstandnis der Veranderungen innerhalb der organischen Bodensubstanz ist wichtig fur die Aufklarung der Mechanismen der Sorptions- und Transportvorgange. Die organische Bodensubstanz wird hier basierend auf einer Modellvorstellung als amorphe Matrix angesehen. Untersuchungen mit der Dynamischen Differenz Kalorimetrie (DSC) zeigten fur ausgewahlte Bodenproben ein thermisches Verhalten ahnlich dem eines Glasuberganges. Da nicht alle untersuchten Bodenproben einen solchen Ubergang aufweisen, stellt sich die Frage, welche Mechanismen zu diesen Ubergangen fuhren und inwiefern ein Zusammenhang mit der chemischen Zusammensetzung der Boden besteht. Zu diesem Zweck wurden ausgewahlte Bodenproben mit der 13C-Festkorper-NMR und der DSC charakterisiert.

Catalysts, 2021

Ru supported on mayenite electride, [Ca24Al28O64]4+(e−)4 a calcium aluminum oxide denoted as C12A... more Ru supported on mayenite electride, [Ca24Al28O64]4+(e−)4 a calcium aluminum oxide denoted as C12A7e−, are described in the literature as highly active catalysts for ammonia synthesis, especially under conditions of low absolute pressure. In this study, we investigated the application of recently reported plasma arc melting synthesized C12A7e− (aluminum solid reductant) as supports of Ru/C12A7e− catalysts in ammonia synthesis up to pressures of 7.6 MPa. Together with the plasma-arc-melting-based catalyst support, we investigated a similar plasma-synthesized C12A7e− (graphite solid reductant) and a vacuum-sintering-based C12A7e−. Complementary to the catalytic tests, we applied 2H solid-state NMR spectroscopy, DRUVVis-spectroscopy, thermal analysis and PXRD to study and characterize the reactivity of different plasma-synthesized and vacuum-sintered C12A7e− towards H2/D2 and H2O. The catalysts showed an immediate deactivation at pressures > 1 MPa, which can be explained by irreversi...

Three-dimensional methylhydrazinium (CH 3 NH 2 NH 2 + , MHy +) lead halides, related to the famou... more Three-dimensional methylhydrazinium (CH 3 NH 2 NH 2 + , MHy +) lead halides, related to the famous methylammonium (CH 3 NH 3 + , MA +) and formamidinium (CH(NH 2) 2 + , FA) perovskites, are attractive optoelectronic materials crystallizing in polar structures. In this work, temperature-dependent 1 H and 207 Pb magic-angle spinning (MAS) NMR, Raman as well as high-pressure Raman studies of CH 3 NH 2 NH 2 PbCl 3 (MHyPbCl 3) are reported. Raman spectroscopy reveals many similarities between phonon properties of MHy lead halides and the MA and FA analogues. In particular, these families of compounds show an increase in wavenumber of cage modes when large I − ions are replaced by smaller Br − and then Cl − ones. They also show strong sensitivity of the CH 3 torsional mode on size of the cavity occupied by MHy + cation that decreases with decreasing size of the halide anion. The cage modes of MHyPbCl 3 are, however, observed at significantly lower wavenumbers than similar modes of MAPbCl 3 and FAPbCl 3 , indicating higher softness of MHyPbCl 3. Temperature-dependent Raman and NMR studies demonstrate that the MHy + cations in MHyPbCl 3 are significantly less affected by the temperature-induced phase transition than the Pb−Cl framework. This suggests a displacive type of the phase transition dominated by tilting and deformation of the PbCl 6 octahedra. Analysis of the 207 Pb MAS NMR spectra reveals the presence of two differently distorted PbCl 6 octahedra and diminishing (increasing) distortion of the less (more) distorted octahedra in the high-temperature phase. Pressure-dependent Raman studies reveal the presence of a single firstorder pressure-induced phase transition between 0.72 and 1.27 GPa. Analysis of the spectra indicates that the driving forces for the pressure-induced phase transition in MHyPbCl 3 are tilting and distortion of the PbCl 6 octahedra accompanied by reorientation of MHy + cations. Raman spectra do not show evidence of any additional phase transition or amorphization up to 6.95 GPa.

Catalysts, 2020

Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hyd... more Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu2+ and Cu+), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N2-sorption, SEM) and acid/redox properties (FT-IR, TPR-H2, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NOx with ammonia (NH3-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu2+ in the double six-membered ring (6MRs). Such copper species contribute to a high NH3-SCR activity. Nevertheless, all materials show comparable activity in NH3-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction ...

Solid State Nuclear Magnetic Resonance, 2019

For the first time, 15 N NMR data are obtained for a sample of nitric oxide at various temperatur... more For the first time, 15 N NMR data are obtained for a sample of nitric oxide at various temperatures. Spectra have been obtained in the liquid and solid state. In the former, the chemical shift as well as the spin-lattice relaxation time is characterized by the dynamic equilibrium of the dimerization reaction. Only the signal of the (NO) 2 dimer is observed, while the paramagnetic NO has strong influences on the NMR parameter. From T 1 relaxation and linewidth analysis a range for the correlation time of the exchange between monomer and dimer is obtained. SQUID measurements corroborate the NMR analysis.

The Journal of Physical Chemistry C, 2018

Adsorption of nitric oxide (NO) in the metal-organic framework MIL-100(Al) is studied by solid-st... more Adsorption of nitric oxide (NO) in the metal-organic framework MIL-100(Al) is studied by solid-state NMR. Due to a modified synthesis no extra-framework btc is present on the cost of a small amount of extra-framework Al(OH) as evident from 27 Al, 1 H as well as HETCOR spectra. Five-coordinated aluminum sites represent about 50% of the aluminum in a dehydrated sample which remain open for adsorption. With increasing NO loading, a decrease of fivecoordinated aluminum with a subsequent increase of six-coordinated aluminum site intensity is found. Additionally, 1 H spin-lattice relaxation time T 1 is decreasing with increasing amount of NO which also supports NO interaction with the MOF because of the paramagnetism of NO. FTIR data further hint at Al-NO interactions.

Physical Chemistry Chemical Physics, 2019

The Zintl phase deuterides CaSiD4/3, SrSiD5/3, BaSiD2, SrGeD4/3, BaGeD5/3 and BaSnD4/3 were inves... more The Zintl phase deuterides CaSiD4/3, SrSiD5/3, BaSiD2, SrGeD4/3, BaGeD5/3 and BaSnD4/3 were investigated by nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations to reliably determine element–deuterium bond lengths.

Crystals, 2019

Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites fo... more Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and / or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like SrTr2H2 (Tr = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of LnTr2, where the lanthanide metals Ln introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases LnAl2 (Ln = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa2 forms a ternary hydride LaGa2H0.71(2). Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La3Ga2 interstitials with 67% and 4...

Inorganic Chemistry, 2018

LiSr 2 SiO 4 H is synthesized by solid-state reaction of LiH and α-Sr 2 SiO 4. It crystallizes in... more LiSr 2 SiO 4 H is synthesized by solid-state reaction of LiH and α-Sr 2 SiO 4. It crystallizes in space group P2 1 /m (a = 658.63(4) pm, b = 542.36(3) pm, c = 695.01(4) pm, β = 112.5637(9)°) as proven by X-ray and neutron diffraction, is isotypic to LiSr 2 SiO 4 F, and exhibits isolated SiO 4 tetrahedra. Hydride anions are located in Li 2 Sr 4 octahedra, which share faces to form columns, with H−H distances of 271.18(2) pm. NMR, IR, and Raman spectroscopy, density measurements, elemental analysis, and theoretical calculations confirm these results. Despite its hydridic nature, it is stable in air up to 550 K. When doped with europium, it emits bright yellow-green light with an intensity maximum at 560 nm for Li-Sr 1.98 Eu 0.02 SiO 4 H. Even after treatment in water for several hours, the solid shows luminescence. The broad emission peak is attributed to the allowed 4f 6 5d → 4f 7 transition of divalent europium. LiSr 2 SiO 4 H is the first silicate hydride, a class of compounds that might have potential as host for luminescent materials.

The Journal of Physical Chemistry C, 2019

The adsorption of the biologically important signaling molecule nitric oxide (NO) on two metal−or... more The adsorption of the biologically important signaling molecule nitric oxide (NO) on two metal−organic frameworks (MOFs), Cu 3 btc 2 and Cu 3 (NHEtbtc) 2 , has been studied by multinuclear solid-state NMR. N-Diazenium diolate (NONOate) formation as primary mode of NO adsorption in the latter MOF is concluded from 15 N, 1 H, and 13 C NMR spectra together with analysis of the 1 H spin−lattice relaxation time (T 1). Furthermore, NO adsorption at the open metal site of Cu 3 btc 2 as well as Cu 3 (NHEtbtc) 2 is also evident, indicating both physisorption and chemisorption of nitric oxide.

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Angewandte Chemie (International ed. in English), Jan 23, 2018

Through IR microimaging the spatially and temporally resolved development of the CO concentration... more Through IR microimaging the spatially and temporally resolved development of the CO concentration in a ZIF-8@6FDA-DAM mixed matrix membrane (MMM) was visualized during transient adsorption. By recording the evolution of the CO concentration, it is observed that the CO molecules propagate from the ZIF-8 filler, which acts as a transport "highway", towards the surrounding polymer. A high-CO -concentration layer is formed at the MOF/polymer interface, which becomes more pronounced at higher CO gas pressures. A microscopic explanation of the origins of this phenomenon is suggested by means of molecular modeling. By applying a computational methodology combining quantum and force-field based calculations, the formation of microvoids at the MOF/polymer interface is predicted. Grand canonical Monte Carlo simulations further demonstrate that CO tends to preferentially reside in these microvoids, which is expected to facilitate CO accumulation at the interface.

Inorganic chemistry, Jan 18, 2017

Zintl phases form hydrides either by incorporating hydride anions (interstitial hydrides) or by c... more Zintl phases form hydrides either by incorporating hydride anions (interstitial hydrides) or by covalent bonding of H to the polyanion (polyanionic hydrides), which yields a variety of different compositions and bonding situations. Hydrides (deuterides) of SrGe, BaSi, and BaSn were prepared by hydrogenation (deuteration) of the CrB-type Zintl phases AeTt and characterized by laboratory X-ray, synchrotron, and neutron diffraction, NMR spectroscopy, and quantum-chemical calculations. SrGeD4/3-x and BaSnD4/3-x show condensed boatlike six-membered rings of Tt atoms, formed by joining three of the zigzag chains contained in the Zintl phase. These new polyanionic motifs are terminated by covalently bound H atoms with d(Ge-D) = 1.521(9) Å and d(Sn-D) = 1.858(8) Å. Additional hydride anions are located in Ae4 tetrahedra; thus, the features of both interstitial hydrides and polyanionic hydrides are represented. BaSiD2-x retains the zigzag Si chain as in the parent Zintl phase, but in the hyd...

Geoderma, 2016

The impact of low water contents on the molecular mobility of soil organic matter (SOM) and its m... more The impact of low water contents on the molecular mobility of soil organic matter (SOM) and its most frequent components was investigated. Combined 1 H, 2 H, and 13 C solid-state nuclear magnetic resonance (NMR) techniques allow for an advanced insight into mechanisms of water uptake under defined atmospheres and its effect on SOM segment mobility. The major individual organic components of two peats, a gleyic podsol and a number of model substances (cutin, suberin, wood and cellulose) were distinguished with respect to their contribution to the 1 H and 13 C NMR spectra. Water molecules and mobile polymer constituents of SOM contribute to the mobile fraction in 1 H NMR wide line spectra. Poly(methylene), being most probably part of amphiphilic molecules, have been identified as SOM components that are mobilized in the presence of water. Even though being of hydrophobic nature, water acts as a plasticizer on such long chain aliphatic soil components. Differential scanning calorimetry measurements of SOM samples support this insight in terms of a thermal step transition. Based on our findings, comparison of experimental results from different soils with varying water contents and soil composition should consider mobility effects of both, aliphatic moieties as well as polar moieties of SOM.

Environmental Chemistry, 2016

Environmental context The mobility of soil organic matter and water molecules has a strong influe... more Environmental context The mobility of soil organic matter and water molecules has a strong influence on the availability of fertilisers as well as on the fate of pollutants in soil. Magnetic resonance techniques identified two regimes of mobility change on the molecular level occurring on a timescale of 1 year after initially heating the sample. The results can help to understand the effect of soil type and water content for agricultural use and soil protection. 1H wide-line solid-state NMR methods have been applied to monitor long-term mobility changes in the supramolecular network of soil organic matter and water induced by short thermal treatment. NMR line widths are a direct measure of the mobility of water molecules and organic matter components. For the first time, we obtained an insight into the long-term physical mechanisms in terms of molecular mobility governing soil organic matter–water interactions. All time series reveal a systematic, attenuated proton demobilisation on...

Microporous and Mesoporous Materials, 2015

Four new secondary amino functionalized trimesic acid ligands (H 3 RNHbtc, R ¼ Me, Et, n Pr, and ... more Four new secondary amino functionalized trimesic acid ligands (H 3 RNHbtc, R ¼ Me, Et, n Pr, and i Pr) were synthesized. When used in combination with H 3 btc these ligands lead to four new mixed-linker metalorganic frameworks (MOFs) which we call UHM-36, UHM-37, UHM-38, and UHM-39. All MOFs are isostructural to HKUST-1. We tested these MOFs as nitric oxide storage and release materials and investigate the influence of the amine groups on the NO storage capacity of the MOFs. The results were compared to the unfunctionalized HKUST-1, i.e. Cu 3 (btc) 2.

Soil organic matter (SOM) is a complex and heterogeneous matter. Characterization by solid-state ... more Soil organic matter (SOM) is a complex and heterogeneous matter. Characterization by solid-state NMR methods on 1H and 13C nuclei is therefore demanding. Our goal is to obtain information on the dynamic behaviour of soil samples and to study the influence of external parameters on both structure and dynamics. We regard water molecules to be the pivotal agent of soil dynamics by generating a network between organic matter via intermolecular hydrogen bonding, which leads to cross linking of organic matter and increases its rigidity. Although 1H solid-state NMR on non-rotating samples are not so commonly used for soil characterization, they enable the differentiation of proton mobilities via their linewidths which are resulting from differences in the dipole-dipole coupling strengths. Therefore, even weak molecular interactions such as hydrogen bonding can be differentiated and changes due to heat treatments and the short and long term behaviour followed. Though in principle a simple t...

Journal of Materials Chemistry B, 2014

Microencapsulation of cells by using biodegradable hydrogels offers numerous attractive features ... more Microencapsulation of cells by using biodegradable hydrogels offers numerous attractive features for a variety of biomedical applications including tissue engineering. This study highlights the fabrication of microcapsules from an alginate-gelatin crosslinked hydrogel (ADA-GEL) and presents the evaluation of the physico-chemical properties of the new microcapsules which are relevant for designing suitable microcapsules for tissue engineering. Alginate di-aldehyde (ADA) was synthesized by periodate oxidation of alginate which facilitates crosslinking with gelatin through Schiff's base formation between the free amino groups of gelatin and the available aldehyde groups of ADA. Formation of Schiff's base in ADA-GEL and aldehyde groups in ADA was confirmed by FTIR and NMR spectroscopy, respectively. Thermal degradation behavior of films and microcapsules fabricated from alginate, ADA and ADA-GEL was dependent on the hydrogel composition. The gelation time of ADA-GEL was found to decrease with increasing gelatin content. The swelling ratio of ADA-GEL microcapsules of all compositions was significantly decreased, whereas the degradability was found to increase with the increase of gelatin ratio. The surface morphology of the ADA-GEL microcapsules was totally different from that of alginate and ADA microcapsules, observed by SEM. Two different buffer solutions (with and without calcium salt) have an influence on the stability of microcapsules which had a significant effect on the gelatin release profile of ADA-GEL microcapsules in these two buffer solutions.