TY - GEN A1 - Efimova, Anastasia A1 - Hubrig, Grit A1 - Schmidt, Peer T1 - Thermal stability and crystallization behavior of imidazolium halide ionic liquids T2 - Thermochimica Acta N2 - The 1-butyl-3-methylimidazolium halide ionic liquids are stable up to temperatures of 246(1) °C ([BMIm]Cl), 260(1) °C ([BMIm]Br), and 238(1) °C ([BMIm]I). The thermal decomposition proceeds in thermogravimetric measurements with a total mass loss of 100%. Using evolved gas analysis (EGA) a complete degradation of [BMIm]X ionic liquids under formation of characteristic fragments CH3+, NHn+, C4Hn+, and CH3X+ (X = Cl, Br, I) has been observed. [BMIm]Cl shows enantiotropic polymorphism with a phase transition temperature at 30(1) °C, and melts at 74(1) °C (ΔHfus = 18 ± 0.5 kJ mol−1). Spontaneous e-crystallization and reversible phase transition have been found for cooling of the substance.[BMIm]Br melts at 78(1) °C (ΔHfus = 29 ± 0.5 kJ mol−1). The re-crystallization fails and thus a glassy solid is formed. The glass transition temperature is about −65 °C, the cold crystallization occurs between −30 and −20 °C. The application of both homogeneous and heterogeneous nucleation agents does not interfere the glassy state. [BMIm]I undergo solidification without crystallization. The melting effect for the amorphous substance arise at −70(5) °C with ΔHfus = 0.4 ± 0.2 kJ mol−1. KW - Ionic liquids (ILs); 1-butyl-3-methylimidazolium salts ([BMIm] salts); Thermal decomposition; Glass formation; Nucleation. Y1 - 2013 UR - http://www.sciencedirect.com/science/article/pii/S0040603113004875 U6 - https://doi.org/10.1016/j.tca.2013.09.023 SN - 0040-6031 VL - Vol. 573 SP - 162 EP - 169 ER - TY - GEN A1 - Efimova, Anastasia A1 - Pinnau, Sebastian A1 - Mischke, Matthias A1 - Breitkopf, Cornelia A1 - Ruck, Michael A1 - Schmidt, Peer T1 - Development of salt hydrate eutectics as latent heat storage for air conditioning and cooling T2 - Thermochimica Acta N2 - Sustainable air conditioning systems require heat reservoirs that operate between 4 and 20 ◦C. A systematic search for binary and ternary eutectics of inorganic salts and salt hydrates with melting temperatures in this temperature regime and with high enthalpies of fusion has been performed by means of differential scanning calorimetry (DSC). Promising results were obtained for the pseudo-ternary system Zn(NO3)2·6H2O, Mn(NO3)2·4H2O, and KNO3 with the melting temperature range 18–21 ◦C and the enthalpy of fusion of about 110 kJ kg−1. Suitable nucleating and thickening agents have been found and tested to prevent the mixture from supercooling and phase separation. KW - Phase change material (PCM); Latent heat thermal energy storage (LHTES); Cold storage; Salt hydrate eutectics Y1 - 2014 UR - http://www.sciencedirect.com/science/article/pii/S004060311300573X U6 - https://doi.org/10.1016/j.tca.2013.11.011 SN - 0040-6031 VL - 45 IS - 575 SP - 276 EP - 278 ER - TY - GEN A1 - Efimova, Anastasia A1 - Pfützner, Linda A1 - Schmidt, Peer T1 - Thermal Stability and Decomposition Mechanism of 1-Ethyl-3-Methylimidazolium Halides T2 - Thermochimica Acta N2 - The thermochemical behavior of 1-ethyl-3-methylimidazolium [EMIm] halides (Cl, Br and I) has been investigated for their crystalline and liquid states in the temperature range from −90 °C to 600 °C using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The temperatures and enthalpies of phase transitions have been determined: Tfus = 86(1) °C, ΔHfus = 14.2(0.7) kJ mol−1 ([EMIm]Cl); Tfus = 67(1) °C, ΔHfus = 19.3(0.7) kJ mol−1 ([EMIm]Br); and Tfus = 74(1) °C, ΔHfus = 16.9(0.6) kJ mol−1 ([EMIm]I). The decomposition temperatures, determined by onset of DTG at 1 K min−1 are 233(5) °C ([EMIm]Cl), 246(5) °C ([EMIm]Br), and 249(5) °C ([EMIm]I). The maximum operation temperature (MOT) has been estimated based on dynamic TGA for an operation time of 24 h: 132 °C ([EMIm]Cl), 149 °C ([EMIm]Br), 139 °C ([EMIm]I) and 8000 h: 76 °C ([EMIm]Cl), 90 °C ([EMIm]Br), 77 °C ([EMIm]I). The decomposition products of the investigated ionic liquids (ILs) after heating experiments were identified by means of TGA complemented with mass spectrometry (MS), for establishment of the mechanism of thermal decomposition of the ILs. Complete degradation of [EMIm]X ionic liquids occurs under formation of characteristic molecule fragments CH3+, NH+, and X+, CH3X+, C2H5X+ (X = Cl, Br, I). KW - Ionic liquids (ILs) KW - 1-Ethyl-3-methylimidazolium halides ([EMIm] halides) KW - Thermal decomposition mechanism KW - Differential scanning calorimetry (DSC) KW - Thermogravimetric analysis (TGA) KW - Mass spectrometry (MS) KW - Integral isoconversional method KW - Maximum operation temperature (MOT) Y1 - 2015 UR - http://www.sciencedirect.com/science/article/pii/S0040603115000350 U6 - https://doi.org/10.1016/j.tca.2015.02.001 VL - 604 SP - 129 EP - 136 ER - TY - GEN A1 - Groh, Matthias F. A1 - Breternitz, Joachim A1 - Ahmed, Ejaz A1 - Isaeva, Anna A1 - Efimova, Anastasia A1 - Schmidt, Peer A1 - Ruck, Michael T1 - Ionothermal Synthesis, Structure, and Bonding of the Catena-Heteropolycation 1∞[Sb2Se2]+ T2 - Zeitschrift für anorganische und allgemeine Chemie N2 - The reaction of antimony and selenium in the Lewis-acidic ionic liquid 1-butyl-3-methyl-imidazolium tetrachloridoaluminate, [BMIm]Cl·4.7AlCl3, yielded dark-red crystals of [Sb2Se2]AlCl4. The formation starts above 160 °C; at about 190 °C, irreversible decomposition takes place. The compound crystallizes in the triclinic space group Pequation image with a = 919.39(2) pm, b = 1137.92(3) pm, c = 1152.30(3) pm, α = 68.047(1)°, β = 78.115(1)°, γ = 72.530(1)°, and Z = 4. The structure is similar to that of [Sb2Te2]AlCl4 but has only half the number of crystallographically independent atoms. Polycationic chains 1∞[Sb2Se2]+ form a pseudo-hexagonal arrangement along [01-1], which is interlaced by tetrahedral AlCl4– groups. The catena-heteropolycation 1∞[Sb2Se2]+ is a sequence of three different four-membered [Sb2Se2] rings. The chemical bonding scheme, established from the topological analysis of the real-space bonding indicator ELI-D, includes significantly polar covalent bonding in four-member rings within the polycation. The rings are connected into an infinite chain by homonuclear non-polar Sb–Sb bonds and highly polar Sb–Se bonds. Half of the selenium atoms are three-bonded. KW - Chain structures KW - Antimony KW - Heteropolycations KW - Main-group elements KW - Selenium Y1 - 2015 UR - http://onlinelibrary.wiley.com/doi/10.1002/zaac.201400543/abstract U6 - https://doi.org/10.1002/zaac.201400543 SN - 1521-3749 VL - 641 IS - 2 SP - 388 EP - 393 ER - TY - GEN A1 - Pfister, Daniela A1 - Schäfer, Konrad A1 - Ott, Claudia A1 - Gerke, Birgit A1 - Pöttgen, Rainer A1 - Janka, Oliver A1 - Baumgartner, Maximilian A1 - Efimova, Anastasia A1 - Hohmann, Andrea A1 - Schmidt, Peer A1 - Venkatachalam, Sabarinathan A1 - Wüllen, Leo van A1 - Schürmann, Ulrich A1 - Kienle, Lorenz A1 - Duppel, Viola A1 - Parzinger, Eric A1 - Miller, Bastian A1 - Becker, Jonathan A1 - Holleitner, Alexander A1 - Weihrich, Richard A1 - Nilges, Tom T1 - Inorganic double helices in semiconducting SnIP T2 - Advanced Materials N2 - SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes. KW - Helical semiconductor Y1 - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/adma.201603135/full U6 - https://doi.org/10.1002/adma.201603135 SN - 1521-4095 VL - 28 IS - 44 SP - 9783 EP - 9791 ER - TY - GEN A1 - Efimova, Anastasia A1 - Hubrig, Grit A1 - Pfützner, Linda A1 - Schmidt, Peer T1 - Thermal Stability of Alkyl-Imidazolium-Ionic Liquids T2 - Zeitschrift für Anorganische und Allgemeine Chemie N2 - The thermochemical behavior of two groups of ionic liquids (ILs), 1-ethyl-3-methylimidazolium [EtMeIm] and 1-butyl-3-methylimidazolium [BuMeIm] halides (Cl, Br and I) was investigated for their crystalline and liquid states in the temperature range from −100 °C to 600 °C using DSC and thermogravimetric analysis (TGA). Some investigated ILs exhibit significant subcooling effect and the glass state formation [1]. The decomposition mechanism has been identified by means of TGA with coupled mass spectrometry (MS). All investigated ILs decompose with a total mass loss of about 100 % in the temperature range of Tonset from 230 to 290 °C (Fig. 1). By complete degradation of IL, dominant fragments CnH2n+1+, CnH2n+, CnHn+, NHn+, and the respective alkyl halides (X = Cl, Br, I) are formed. KW - Ionic liquid KW - Thermal stability Y1 - 2014 UR - http://onlinelibrary.wiley.com/doi/10.1002/zaac.201490026/full U6 - https://doi.org/10.1002/zaac.201490026 SN - 1521-3749 VL - 640 IS - 11 SP - 2391 ER - TY - RPRT A1 - Pinnau, Sebastian A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Identifikation technischer Salze als Latentspeichermaterialien im Temperaturbereich von 4 bis 15 °C und deren Verkapselung: Abschlussbericht N2 - Der Einsatz von thermischen Speichern erlaubt eine bessere Lastanpassung von Erzeugeranlagen zur Gebäudeklimatisierung sowie eine Optimierung des Betriebsregimes unter energetischen Gesichtspunkten. Für solche Anwendungsfälle können Latentwärmespeicher zum Einsatz kommen, bei denen üblicherweise der Schmelz- und Erstarrungsvorgang sogenannter Phasenwechselmaterialien (Phase Change Materials, PCM) ausgenutzt wird. Für die Anwendungstemperaturbereiche der Klimatisierung von etwa 4 °C bis 15 °C und für die Kühlung bis etwa 25 °C ist die Auswahl an Reinstoffen mit einer passenden Schmelztemperatur sehr begrenzt. Durch die Bildung von eutektischen Gemischen aus zwei oder mehr Komponenten – die ähnlich wie Reinstoffe einen scharfen Schmelzpunkt aufweisen – kann die Bandbreite an potentiellen PCM’s für diesen Temperaturbereich vergrößert werden. Für die genannten Temperaturbereiche werden vorzugsweise anorganische Salzhydrate als potentielle Speichermedien betrachtet, da diese gegenüber organischen Substanzen häufig größere Schmelzenthalpien und geringere Kosten aufweisen. KW - Latentwärmespeicher KW - PCM Y1 - 2013 UR - https://www.tib.eu/suchen/id/TIBKAT:786966173/ U6 - https://doi.org/10.2314/GBV:786966173 CY - Dresden ER - TY - GEN A1 - Efimova, Anastasia A1 - Varga, Janos A1 - Matuschek, Georg A1 - Saraji-Bozorgzad, Mohammad R. A1 - Denner, Thomas A1 - Zimmermann, Ralf A1 - Schmidt, Peer T1 - Thermal Resilience of Imidazolium-Based Ionic Liquids—Studies on Short- and Long-Term Thermal Stability and Decomposition Mechanism of 1-Alkyl-3-methylimidazolium Halides by Thermal Analysis and Single-Photon Ionization Time-of-Flight Mass Spectrometry T2 - Journal of Physical Chemistry B N2 - Ionic liquids are often considered as green alternatives of volatile organic solvents. The thermal behavior of the ionic liquids is relevant for a number of emerging large-scale applications at elevated temperature. Knowledge about the degradation products is indispensable for treatment and recycling of the used ionic liquids. The objective of this paper was an investigation of the short- and long-term stability of several 1-alkyl-3-methylimidazolium halides, determination of the degradation products, and the elucidation of their decomposition patterns and structure–stability relations. Short-term stability and mechanism of thermal degradation were investigated by a self-developed, innovative thermal analysis single-photon ionization time-of-flight mass spectrometry device with Skimmer coupling. The applied technology provides real-time monitoring of the forming species and allows tracing their change during the course of the decomposition. Therein, the almost fragment-free soft ionization with vacuum ultraviolet photons plays a crucial role. We have detected unfragmented molecules whose formation was only assumed by electron ionization. Nevertheless, the main decomposition products of the selected ionic liquids were alkyl imidazoles, alkenes, alkyl halides, and hydrogen halides. From the decomposition products, we have deduced the fragmentation patterns and discussed their interrelation with the length of the alkyl chain and the type of the halide anion. Our results did not suggest the evaporation of the investigated ionic liquids prior to their decomposition under atmospheric conditions. Long-term thermal stability and applicability were determined based on thermogravimetric analysis evaluated with a kinetic model. Thus, the time-dependent maximum operation temperature (MOT) for the respective ionic liquids has been calculated. As a rule, the short-term stability overestimates the long-term decomposition temperatures; the calculated MOT are significantly lower (at least 100 K) than the standardly obtained decomposition temperatures. KW - Ionic liquid KW - Thermal analysis KW - Thermal decomposition KW - Maximum operation temperature Y1 - 2018 U6 - https://doi.org/10.1021/acs.jpcb.8b06416 VL - 122 IS - 37 SP - 8738 EP - 8749 ER - TY - GEN A1 - Knies, Maximilian A1 - Kaiser, Martin A1 - Lê Anh, Mai A1 - Efimova, Anastasia A1 - Doert, Thomas A1 - Ruck, Michael T1 - Low-Temperature Ordering in the Cluster Compound (Bi₈)Tl[AlCl₄]₃ T2 - Inorganics N2 - The reaction of Bi, BiCl₃, and TlCl in the ionic liquid [BMIm]Cl·4AlCl₃ (BMIm = 1-n-butyl-3-methylimidazolium) at 180 °C yielded air-sensitive black crystals of (Bi₈)Tl[AlCl₄]₃. X-ray diffraction on single crystals at room temperature revealed a structure containing [Tl(AlCl₄)₃]∞12− strands separated by isolated Bi₈²⁺ square antiprisms. The thallium(I) ion is coordinated by twelve Cl⁻ ions of six [AlCl₄]⁻ groups, resulting in a chain of face-sharing [TlCl₁₂]¹¹⁻ icosahedra. The Bi₈²⁺ polycation is disordered, simulating a threefold axis through its center and overall hexagonal symmetry (space group P6₃/m). Slowly cooling the crystals to 170 K resulted in increased order in the Bi₈ cluster orientations. An ordered structure model in a supercell with a’ = 2a, b’ = 2b, c’ = 3c and the space group P6₅ was refined. The structure resembles a hexagonal perovskite, with complex groups in place of simple ions. KW - bismuth KW - cluster compounds KW - hexagonal perovskite KW - ionic liquids KW - low-valen KW - low-valent compounds KW - order–disorder transition KW - orientational disorder KW - polycations KW - pseudosymmetry Y1 - 2019 U6 - https://doi.org/10.3390/inorganics7040045 VL - 7 IS - 4 SP - 1 EP - 9 ER - TY - GEN A1 - Meißner, André A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Impacts of TGA furnace parameters for prediction of long-term thermal stability of ionic liquids T2 - Thermochimica Acta N2 - The concept of maximum operation temperature is established for the prediction of the time dependent thermal stability of ionic liquids based on kinetic evaluation of thermogravimetric analysis. The influence of the furnace control parameters on the maximum operation temperature (MOT) is shown using the example of 1-methyl-3-propylimidazolium iodide ([C3C1im]I) with respect to three different parameter sets of a programmed proportional integral derivative (PID) controller of the TGA. Kinetics of thermal decomposition of [C3C1im]I have been investigated with the implementation of an improved kinetic model. The activation energy obtained using the Kissinger-Akahira-Sunose equation showed variations apparently due to the decomposition degree. The model compound is decomposed by a one-step kinetics, which results from pseudo zero order relationship of the activation energy to the conversion rate. The activation energy, pre-exponential factor, and the activation energy are strongly dependent on the parameters of TGA furnace controller. KW - Ionic liquid KW - Thermal analysis KW - Thermal decomposition Y1 - 2021 UR - https://www.sciencedirect.com/science/article/pii/S0040603121000587#! U6 - https://doi.org/10.1016/j.tca.2021.178917 VL - 704 SP - 178917-1 EP - 178917-7 ER - TY - GEN A1 - Ivshin, Kamil A1 - Metlushka, Kirill A1 - Zinnatullin, Ruzal A1 - Nikitina, Kristina A1 - Pashagin, Alexander A1 - Zakharychev, Dmitry V. A1 - Efimova, Anastasia A1 - Kiiamov, Airat A1 - Latypov, Shamil A1 - Kataeva, Olga T1 - Competitive Hydrogen Bonding and Unprecedented Polymorphism in Selected Chiral Phosphorylated Thioureas T2 - Crystal Growth Design N2 - New racemic and enantiopure N-phosphorylated thioureas bearing 1-phenylethyl or tetrahydronaphthalenyl fragments were synthesized. According to NMR data assisted by DFT calculations, the preferred conformation is stabilized by an intramolecular hydrogen bond. This form in solution is in equilibrium with dimeric N–H···S hydrogen-bonded associates, the population depending on the concentration. In the crystalline phase the low-energy conformation with an intramolecular H-bond is realized only in the racemic tetrahydronaphthalenyl derivative. In most crystals various types of intermolecular hydrogen bonding are observed, accompanied by the formation of infinite linear chains or helical structures. Due to the conformational lability of compounds and competitive intermolecular H-bonding, multiple polymorphic modifications are formed. Therefore, crystallization of enantiopure 1-phenylethyl derivatives from various solvents results in concomitant polymorphs at room temperature. One of them undergoes reversible two-step phase transitions from the high-symmetry I41 space group (Z′ = 1, no disorder) via the P41 space group (Z′ = 6) to the monoclinic P21 space group (Z′ = 16) accompanied by drastic concerted conformational changes. Notably, the optimization of the crystal packing is observed upon phase transitions with a gradual reduction of the void space in the unit cell from 4.5% to 0.8%. This is a rare case of several high-Z′ polymorphs for one compound, with chirality playing an important role. KW - Crystal growth KW - Crystal structure KW - Thermal analysis KW - Polymorphism Y1 - 2021 UR - https://pubs.acs.org/doi/10.1021/acs.cgd.1c00758 U6 - https://doi.org/10.1021/acs.cgd.1c00758 SN - 1528-7505 SN - 1528-7483 VL - 21 IS - 9 SP - 5460 EP - 5471 ER - TY - GEN A1 - Vinokurova, Ekaterina A1 - Knorr, Monika A1 - Efimova, Anastasia A1 - Ovchinnikov, Alexander A1 - Schmidt, Peer A1 - Büchner, Bernd A1 - Isaeva, Anna A1 - Roslova, Maria T1 - Microstructural evolution of layered K-doped RuCl3 during annealing traced by thermogravimetric analysis and 3D electron diffraction T2 - Zeitschrift für Anorgische und Allgemeine Chemie N2 - Nanoscale phase separation was induced in the K-doped RuCl3 van der Waals material by annealing, and studied with the goal to find a natural design strategy for the formation of two-dimensional architectures as an alternative to the costly and time-consuming experimental artificial growth methods. Phase conversion was traced by means of thermogravimetric analysis combined with mass spectrometry. The local crystal structure of co-existing K3Ru2Cl9 domains with the sizes of about 100 nm was solved by 3D electron diffraction. KW - 2D layered compounds KW - Chemical vapor transport KW - Crystal growth KW - Crystal structure KW - Halides KW - Thermal analysis Y1 - 2023 UR - https://onlinelibrary.wiley.com/doi/full/10.1002/zaac.202300141 U6 - https://doi.org/10.1002/zaac.202300141 SN - 0044-2313 SN - 1521-3749 VL - 649 IS - 19 SP - 1 EP - 8 ER - TY - RPRT A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Kristallisationsverhalten von Phasenwechselmaterialien als Latentwärmespeicher (KristallLaW): Abschlussbericht N2 - Phasenwechselmaterialien (PCM) sind chemische Verbindungen oder deren Mischungen, die bei einer definierten Temperatur schmelzen bzw. erstarren. Der zyklische Einsatz von Wärmespeichern ermöglicht den Ausgleich von Überlasten für den Bedarf oder den „Abfall“ von Wärme sowie die Vergleichmäßigung von Wärmeprofilen. Bestehende anorganische Materialien weisen überwiegend Einschränkungen bezüglich der Anforderungen an eine geringe Hysterese von Aufheizung und Abkühlung auf. Das Maß der Unterkühlung der Schmelze sowie ein zyklenstabiler Wärmeaustausch kann aber durch Zusätze als Kristallisationshilfen (Keimbildner) gesteuert werden. Im vorliegenden Bericht werden die Keimbildung und Kristallisation von Phasenwechselmaterialien unter folgenden Gesichtspunkten diskutiert: Methoden der Thermischen Analyse zur Untersuchung der thermochemischen Eigenschaften von PCM, thermochemische Eigenschaften anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Salze und Salzhydrate als PCM, dominierende Kristallstrukturen und Strukturmotive anorganischer Stoffe als homogener und heterogener Keimbildner, Änderung der thermochemischen Eigenschaften von PCM bei Zusatz von Keimbildnern, geeignete Konzentrationsbereiche von Keimbildnern, Homogenität/Segregation von Phasen. KW - Latentwärmespeicher KW - PCM Y1 - 2017 UR - https://www.tib.eu/suchen/id/TIBKAT:884496287/ U6 - https://doi.org/10.2314/GBV:884496287 PB - BTU Cottbus - Senftenberg, Fachgebiet Anorganische Chemie CY - Senftenberg ER - TY - GEN A1 - Ehrling, Sebastian A1 - Senkovska, Irena A1 - Efimova, Anastasia A1 - Bon, Volodymyr A1 - Abylgazina, Leila A1 - Petkov, Petko A1 - Evans, Jack D. A1 - Attallah, Ahmed Gamal A1 - Wharmby, Michael Thomas A1 - Roslova, Maria A1 - Huang, Zhehao A1 - Tanaka, Hideki A1 - Wagner, Andreas A1 - Schmidt, Peer A1 - Kaskel, Stefan T1 - Temperature Driven Transformation of the Flexible Metal-Organic Framework DUT-8(Ni) T2 - Chemistry - a European journal N2 - DUT-8(Ni) metal-organic framework belongs to the family of flexible pillared layer materials. The desolvated framework can be obtained in the open pore form (op) or in the closed pore form (cp), depending on the crystal size regime. In the present work, we report on the behaviour of desolvated DUT-8(Ni) at elevated temperatures. For both, op and cp variants, heating causes a structural transition, leading to an new, crystalline compound, containing two interpenetrated networks. The state of the framework before transition (op vs. cp) influences the transition temperature: the small particles of the op phase transform at significantly lower temperature in comparison to the macroparticles of the cp phase, transforming close to the decomposition temperature. The new compound, confined closed pore phase (ccp), was characterized by powder X-ray diffraction and spectroscopic techniques, such as IR, EXAFS, and positron annihilation lifetime spectroscopy (PALS). Thermal effects of structural cp to ccp transitions were studied using differential scanning calorimetry (DSC), showing an overall exothermic effect of the process, involving bond breaking and reformation. Theoretical calculations reveal the energetics, driving the observed temperature induced phase transition. KW - Metal organic framework (MOF) KW - Thermal analysis KW - Crystal structure KW - Phase transition Y1 - 2022 UR - https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201281 U6 - https://doi.org/10.1002/chem.202201281 SN - 1521-3765 VL - 28 IS - 55 SP - 1 EP - 10 ER - TY - GEN A1 - Knorr, Monika A1 - Icker, Maik A1 - Efimova, Anastasia A1 - Schmidt, Peer T1 - Reactivity of Ionic Liquids: Studies on Thermal Decomposition Behavior of 1-Butyl-3-methylimidazolium Tetrafluoroborate T2 - Thermochimica Acta N2 - The Ionic Liquid 1-butyl-3-methylimidazolium tetrafluoroborate [C4C1im]BF4 serves as a commonly solvent in inorganic material synthesis and analytics. Nevertheless, its application is frequently associated with trial and error approaches. Thereupon, detailed knowledge on the thermal behavior is the key information for understanding the reactivity of [C4C1im]BF4. 1-butyl-3-methylimidazolium tetrafluoroborate behaves as a glass in the cold, its glass transition temperature being ϑg = −83 °C. During heating with 10 K·min−1 [C4C1im]BF4 appears to be stable above 350 °C with onset temperatures ϑonset, DSC = 375 °C, ϑonset, DTG = 422 °C, and ϑonset, TG = 437 °C. Thereby, thermal decomposition occurs in a single step reaction forming 1-methyl-1H-imidazole (CH3C3H3N2 or C4H6N2), but-1-ene (C4H8), fluoromethane (CH3F) and boron trifluoride (BF3) as main species, as determined by thermogravimetry coupled with mass spectrometry and FTIR spectroscopy. To be more specific in thermal behavior, the temperature and time dependent stability is evaluated here on the basis of the kinetic model of maximum operation temperature − MOT. Clearly, thermal stability rises with application time, thus being 193 °C for one hour, while reaching only 141 °C for one day, and 114 °C for one week. The incipient decomposition (≤ 1 %) at the calculated time dependent maximum operation temperature finally is verified by optical analysis, infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy. Y1 - 2020 UR - https://www.sciencedirect.com/science/article/pii/S0040603120307012?via%3Dihub#! U6 - https://doi.org/10.1016/j.tca.2020.178786 SN - 0040-6031 VL - Vol. 694 SP - 1 EP - 11 ER - TY - GEN A1 - Garai, Bikash A1 - Bon, Volodymyr A1 - Efimova, Anastasia A1 - Gerlach, Martin A1 - Senkovska, Irena A1 - Kaskel, Stefan T1 - Reversible switching between positive and negative thermal expansion in a metal–organic framework DUT-49 T2 - Journal of Materials Chemistry A N2 - Three-dimensional architectures constructed via coordination of organic ligands to metal ions (broadly termed metal–organic frameworks, MOFs), are highly interesting for many demanding applications such as gas adsorption, molecular separation, heterogeneous catalysis, molecular sensing, etc. Being constructed from heterogeneous components, such framework solids show characteristic features from both the individual components and framework-specific features. One such interesting physicochemical property is thermal expansion, which arises from thermal vibration from the organic linker and metal ions. Herein, we show a very unique example of thermal responsiveness for the DUT-49 framework, a MOF well-known for its distinctive negative gas adsorption (NGA) properties. In the guest-free form, the framework shows another counter-intuitive phenomenon of negative thermal expansion (NTE), i.e. the lattice size increases with decrease of temperature. However, in the solvated state, it shows both NTE and positive thermal expansion (i.e. lattice size decreases with lowering of temperature, PTE) based on a specific temperature range. When the solvent exists in the liquid form inside the MOF pore, it retains the pristine NTE nature of the bare framework. But freezing of the solvent inside the pores induces the strain, which causes a structural transformation through in-plane bending of the linker and this squeezes the framework by ∼10% of the unit cell volume. This effect has been verified using 3 different solvents where the structural contraction occurs immediately at the freezing point of the individual solvent. Furthermore, studies on a series of DUT-49(M) frameworks with varying metals confirm the general applicability of this mechanism. KW - Metal organic framework (MOF) KW - Thermal analysis KW - Crystal structure Y1 - 2020 UR - https://pubs.rsc.org/en/content/articlehtml/2020/ta/d0ta06830f U6 - https://doi.org/10.1039/D0TA06830F SN - 2050-7496 VL - 39 IS - 8 SP - 20420 EP - 20428 ER - TY - GEN A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Thermal Characterization of Ionic Liquids T2 - OnSet : News, Facts and Professional Solutions for Thermal Analysis N2 - Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide tempera¬ture range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl- 3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation. KW - Thermal Properties KW - Ionic Liquids Y1 - 2015 UR - https://dcyd0ggl1hia3.cloudfront.net/media/thermal-analysis/customer-magazine/OnSet_15_en_web.pdf?1454325612&Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6XC9cL2RjeWQwZ2dsMWhpYTMuY2xvdWRmcm9udC5uZXRcL21lZGlhXC90aGVybWFsLWFuYWx5c2lzXC9jdXN0b21lci1tYWdhemluZVwvT25TZXRfMTVfZW5fd2ViLnBkZj8xNDU0MzI1NjEyIiwiQ29uZGl0aW9uIjp7IkRhdGVMZXNzVGhhbiI6eyJBV1M6RXBvY2hUaW1lIjoxNTMzNzA4MDcwfX19XX0_&Signature=Q9l-r6mgKOmETHkMaU0IDzTKMH~FdduFunQKnxL6AmEhhrVMKNrbho6JK5pYF0NlM1GPkitI2SxlRwwdygr9m654DWkV5Ka4Qw0NA-BkcKczW4G0dX9WWiXbKk12lQGUe2Z1sMy6i9EJ2vW9wZtn8S-mCQHgrNV~hzE~I8BxV-Q_&Key-Pair-Id=APKAIBNUHYIJDHQEJVRQ VL - 15 SP - 14 EP - 17 ER - TY - RPRT A1 - Schmidt, Peer A1 - Efimova, Anastasia T1 - Thermal Characterization of Ionic Liquids N2 - Ionic liquids (ILs) are currently of high interest due to their high performance physicochemical properties over a wide temperature range of existence of the liquid state. Among the ionic liquids investigated, 1-alkyl-3-methylimidazolium halides were found generally preferred for their low melting points and ease of handling and preparation. KW - Thermal analysis KW - Ionic liquid Y1 - 2015 UR - https://www.netzsch-thermal-analysis.com/en/service-support/customer-magazine-onset/ SP - 14 EP - 17 PB - NETZSCH-Gerätebau GmbH CY - Selb ER - TY - GEN A1 - Jurischka, Christoph A1 - Dinter, Franziska A1 - Efimova, Anastasia A1 - Weiss, Romano A1 - Schiebel, Juliane A1 - Schulz, Christian A1 - Fayziev, Bekzodjon A1 - Schierack, Peter A1 - Fischer, Thomas A1 - Rödiger, Stefan T1 - An explorative study of polymers for 3D printing of bioanalytical test systems T2 - Clinical Hemorheology and Microcirculation N2 - Background: The 3D printing is relevant as a manufacturing technology of functional models for forensic, pharmaceutical and bioanalytical applications such as drug delivery systems, sample preparation and point-of-care tests. Objective: Melting behavior and autofluorescence of materials are decisive for optimal printing and applicability of the product which are influenced by varying unknown additives. Methods: We have produced devices for bioanalytical applications from commercially available thermoplastic polymers using a melt-layer process. We characterized them by differential scanning calorimetry, fluorescence spectroscopy and functional assays (DNA capture assay, model for cell adhesion, bacterial adhesion and biofilm formation test). Results: From 14 tested colored, transparent and black materials we found only deep black acrylonitrile-butadiene-styrene (ABS) and some black polylactic acid (PLA) useable for fluorescence-based assays, with low autofluorescence only in the short-wave range of 300-400 nm. PLA was suitable for standard bioanalytical purposes due to a glass transition temperature of approximately 60°C, resistance to common laboratory chemicals and easy print processing. For temperature-critical methods, such as hybridization reactions up to 90°C, ABS was better suited. Conclusions: Autofluorescence was not a disadvantage per se but can also be used as a reference signal in assays. The rapid development of individual protocols for sample processing and analysis required the availability of a material with consistent quality over time. For fluorescence-based assays, the use of commercial standard materials did not seem to meet this requirement. KW - Thermal analysis KW - 3D Printing Y1 - 2020 UR - https://pubmed.ncbi.nlm.nih.gov/31929149/ U6 - https://doi.org/10.3233/CH-190713 SN - 1875-8622 VL - 75 IS - 1 SP - 57 EP - 84 ER -