@misc{TaubertBalischewskiHentrichetal.2017, author = {Taubert, Andreas and Balischewski, Christian and Hentrich, Doreen and Elschner, Thomas and Eidner, Sascha and G{\"u}nter, Christina and Behrens, Karsten and Heinze, Thomas}, title = {Water-soluble cellulose derivatives are sustainable additives for biomimetic calcium phosphate mineralization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400453}, pages = {17}, year = {2017}, abstract = {The effect of cellulose-based polyelectrolytes on biomimetic calcium phosphate mineralization is described. Three cellulose derivatives, a polyanion, a polycation, and a polyzwitterion were used as additives. Scanning electron microscopy, X-ray diffraction, IR and Raman spectroscopy show that, depending on the composition of the starting solution, hydroxyapatite or brushite precipitates form. Infrared and Raman spectroscopy also show that significant amounts of nitrate ions are incorporated in the precipitates. Energy dispersive X-ray spectroscopy shows that the Ca/P ratio varies throughout the samples and resembles that of other bioinspired calcium phosphate hybrid materials. Elemental analysis shows that the carbon (i.e., polymer) contents reach 10\% in some samples, clearly illustrating the formation of a true hybrid material. Overall, the data indicate that a higher polymer concentration in the reaction mixture favors the formation of polymer-enriched materials, while lower polymer concentrations or high precursor concentrations favor the formation of products that are closely related to the control samples precipitated in the absence of polymer. The results thus highlight the potential of (water-soluble) cellulose derivatives for the synthesis and design of bioinspired and bio-based hybrid materials.}, language = {en} } @article{TaubertBalischewskiHentrichetal.2016, author = {Taubert, Andreas and Balischewski, Christian and Hentrich, Doreen and Elschner, Thomas and Eidner, Sascha and G{\"u}nter, Christina and Behrens, Karsten and Heinze, Thomas}, title = {Water-Soluble Cellulose Derivatives Are Sustainable Additives for Biomimetic Calcium Phosphate Mineralization}, series = {Inorganics : open access journal}, volume = {4}, journal = {Inorganics : open access journal}, publisher = {MDPI}, address = {Basel}, issn = {2304-6740}, doi = {10.3390/inorganics4040033}, pages = {17}, year = {2016}, abstract = {The effect of cellulose-based polyelectrolytes on biomimetic calcium phosphate mineralization is described. Three cellulose derivatives, a polyanion, a polycation, and a polyzwitterion were used as additives. Scanning electron microscopy, X-ray diffraction, IR and Raman spectroscopy show that, depending on the composition of the starting solution, hydroxyapatite or brushite precipitates form. Infrared and Raman spectroscopy also show that significant amounts of nitrate ions are incorporated in the precipitates. Energy dispersive X-ray spectroscopy shows that the Ca/P ratio varies throughout the samples and resembles that of other bioinspired calcium phosphate hybrid materials. Elemental analysis shows that the carbon (i.e., polymer) contents reach 10\% in some samples, clearly illustrating the formation of a true hybrid material. Overall, the data indicate that a higher polymer concentration in the reaction mixture favors the formation of polymer-enriched materials, while lower polymer concentrations or high precursor concentrations favor the formation of products that are closely related to the control samples precipitated in the absence of polymer. The results thus highlight the potential of (water-soluble) cellulose derivatives for the synthesis and design of bioinspired and bio-based hybrid materials.}, language = {en} } @article{UgwujaAdelowoOgunlajaetal.2019, author = {Ugwuja, Chidinma G. and Adelowo, Olawale O. and Ogunlaja, Aemere and Omorogie, Martins O. and Olukanni, Olumide D. and Ikhimiukor, Odion O. and Iermak, Ievgeniia and Kolawole, Gabriel A. and G{\"u}nter, Christina and Taubert, Andreas and Bodede, Olusola and Moodley, Roshila and Inada, Natalia M. and Camargo, Andrea S.S. de and Unuabonah, Emmanuel Iyayi}, title = {Visible-Light-Mediated Photodynamic Water Disinfection @ Bimetallic-Doped Hybrid Clay Nanocomposites}, series = {ACS applied materials \& interfaces}, volume = {11}, journal = {ACS applied materials \& interfaces}, number = {28}, publisher = {American Chemical Society}, address = {Washington, DC}, issn = {1944-8244}, doi = {10.1021/acsami.9b01212}, pages = {25483 -- 25494}, year = {2019}, abstract = {This study reports a new class of photocatalytic hybrid clay nanocomposites prepared from low-cost sources (kaolinite clay and Carica papaya seeds) doped with Zn and Cu salts via a solvothermal process. X-ray diffraction analysis suggests that Cu-doping and Cu/Zn-doping introduce new phases into the crystalline structure of Kaolinite clay, which is linked to the reduced band gap of kaolinite from typically between 4.9 and 8.2 eV to 2.69 eV for Cu-doped and 1.5 eV for Cu/Zn hybrid clay nanocomposites (Nisar, J.; Arhammar, C.; Jamstorp, E.; Ahuja, R. Phys. Rev. B 2011, 84, 075120). In the presence of solar light irradiation, Cu- and Cu/Zn-doped nanocomposites facilitate the electron hole pair separation. This promotes the generation of singlet oxygen which in turn improves the water disinfection efficiencies of these novel nanocomposite materials. The nanocomposite materials were further characterized using high-resolution scanning electron microscopy, fluorimetry, therrnogravimetric analysis, and Raman spectroscopy. The breakthrough times of the nanocomposites for a fixed bed mode of disinfection of water contaminated with 2.32 x 10(7) cfu/mL E. coli ATCC 25922 under solar light irradiation are 25 h for Zn-doped, 30 h for Cu-doped, and 35 h for Cu/Zn-doped nanocomposites. In the presence of multidrug and multimetal resistant strains of E. coli, the breakthrough time decreases significantly. Zn-only doped nanocomposites are not photocatalytically active. In the absence of light, the nanocomposites are still effective in decontaminating water, although less efficient than under solar light irradiation. Electrostatic interaction, metal toxicity, and release of singlet oxygen (only in the Cu-doped and Cu/Zn-doped nanocomposites) are the three disinfection mechanisms by which these nanocomposites disinfect water. A regrowth study indicates the absence of any living E. coli cells in treated water even after 4 days. These data and the long hydraulic times (under gravity) exhibited by these nanocomposites during photodisinfection of water indicate an unusually high potential of these nanocomposites as efficient, affordable, and sustainable point-of-use systems for the disinfection of water in developing countries.}, language = {en} } @article{FoersterDeocampoAsratetal.2018, author = {Foerster, Verena and Deocampo, Daniel M. and Asrat, Asfawossen and G{\"u}nter, Christina and Junginger, Annett and Kr{\"a}mer, Kai Hauke and Stroncik, Nicole A. and Trauth, Martin H.}, title = {Towards an understanding of climate proxy formation in the Chew Bahir basin, southern Ethiopian Rift}, series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, volume = {501}, journal = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2018.04.009}, pages = {111 -- 123}, year = {2018}, abstract = {Deciphering paleoclimate from lake sediments is a challenge due to the complex relationship between climate parameters and sediment composition. Here we show the links between potassium (K) concentrations in the sediments of the Chew Bahir basin in the Southern Ethiopian Rift and fluctuations in the catchment precipitation/evaporation balance. Our micro-X-ray fluorescence and X-ray diffraction results suggest that the most likely process linking climate with potassium concentrations is the authigenic illitization of smectites during episodes of higher alkalinity and salinity in the closed -basin lake, due to a drier climate. Whole-rock and clay size fraction analyses suggest that illitization of the Chew Bahir clay minerals with increasing evaporation is enhanced by octahedral Al-to-Mg substitution in the clay minerals, with the resulting layer charge increase facilitating potassium-fixation. Linking mineralogy with geochemistry shows the links between hydroclimatic control, process and formation of the Chew Bahir K patterns, in the context of well-known and widely documented eastern African climate fluctuations over the last 45,000 years. These results indicate characteristic mineral alteration patterns associated with orbitally controlled wet-dry cycles such as the African Humid Period (similar to 15-5 ka) or high-latitude controlled climate events such as the Younger Dryas (similar to 12.8-11.6 ka) chronozone. Determining the impact of authigenic mineral alteration on the Chew Bahir records enables the interpretation of the previously established pXRF-derived aridity proxy K and provides a better paleohydrological understanding of complex climate proxy formation.}, language = {en} } @article{ScottMuhlingFletcheretal.2011, author = {Scott, James and Muhling, Janet and Fletcher, Ian and Billia, Marco and Palin, J. Michael and Elliot, Tim and G{\"u}nter, Christina}, title = {The relationship of Palaeozoic metamorphism and S-type magmatism on the paleo-Pacific Gondwana margin}, series = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, volume = {127}, journal = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, number = {3-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0024-4937}, doi = {10.1016/j.lithos.2011.09.008}, pages = {522 -- 534}, year = {2011}, abstract = {A massive pulse of granitic magma was rapidly emplaced into the once contiguous West Antarctic and New Zealand segments of the palaeo-Pacific margin of the Gondwana supercontinent at similar to 371 Ma. In New Zealand, these Late Devonian S-type granitoids cover an areal extent of > 3400 km(2), but the tectonic setting for crustal partial melting has remained unclear because most of the exposure represents either emplacement-level, or rocks that have been reworked during Cretaceous orogenesis. New petrologic data indicate that aluminous paragneisses and orthogneisses in the Bonar Range represent a rare portion of Devonian middle crust that preserves evidence for the initiation of crustal melting. The investigated rocks outline the tail of a clockwise P-T path that involved partial melting at peak conditions (similar to 670 degrees C, 5.1 kb), deformation during the immediately following near-isothermal decompression, and then partial re-equilibration under static conditions. Syn- to post-kinematic growth of zoned monazite establishes the timing of recrystallisation to a similar to 16 Ma period that began at 373.4 +/- 4.1 Ma. This age overlaps with the initiation of regional Karamea S-type granitic magmatism. Although estimated metamorphic conditions were insufficient for large amounts of melt to have been produced from Bonar Range pelites (calculated melt volumes are <10\%), they do provide evidence consistent with widespread heating and partial melting in the deeper crust. This heating episode was contemporaneous with partial melting in Fiordland (New Zealand) and West Antarctica, although Mesozoic thermal and deformational events complicate the Palaeozoic record in both those areas. Nevertheless, the apparent 1000 s km of along-strike crustal partial melting indicates that a continental-scale tectonic plate margin re-organisation took place at this time. The cause in the New Zealand segment was most likely, but not unequivocally, an extensional tectonic regime with an elevated geothermal gradient caused by conductive heating from a shallowed lithospheric mantle.}, language = {en} } @article{EugeniaCisternaAltenbergerMonetal.2017, author = {Eugenia Cisterna, Clara and Altenberger, Uwe and Mon, Ricardo and G{\"u}nter, Christina and Gutierrez, Adolfo Antonio}, title = {The metamorphic basement of the southern Sierra de Aconquija, Eastern Sierras Pampeanas}, series = {Journal of South American earth sciences}, volume = {82}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2017.09.028}, pages = {292 -- 310}, year = {2017}, abstract = {The Eastern Sierras Pampeanas are mainly composed of Neoproterozoic-early Palaeozoic metamorphic complexes whose protoliths were sedimentary sequences deposited along the western margin of Gondwana. South of the Sierra de Aconquija, Eastern Sierras Pampeanas, a voluminous metamorphic complex crops out. It is mainly composed of schists, gneisses, marbles, calk-silicate schists, thin layers of amphibolites intercalated with the marbles and granitic veins. The new data correlate the Sierra de Aconquija with others metamorphic units that crop out to the south, at the middle portion of the Sierra de Ancasti. Bulk rock composition reflects originally shales, iron rich shales, wackes, minor litharenites and impure limestones as its protoliths. Moreover, comparisons with the northern Sierra de Aconquija and from La Majada (Sierra de Ancasti) show similar composition. Amphibolites have a basaltic precursor, like those from the La Majada (Sierra de Ancasti) ones. The analyzed metamorphic sequence reflects low to moderate weathering conditions in the sediments source environment and their chemical composition would be mainly controlled by the tectonic setting of the sedimentary basin rather than by the secondary sorting and reworking of older deposits. The sediments composition reveal relatively low maturity, nevertheless the Fe - shale and the litharenite show a tendency of minor maturity among them. The source is related to an acid one for the litharenite protolith and a more basic to intermediate for the other rocks, suggesting a main derivation from intermediate to felsic orogen. The source of the Fe shales may be related to and admixture of the sediments with basic components. Overall the composition point to an upper continental crust as the dominant sediment source for most of the metasedimentary rocks. The protolith of the amphibolites have basic precursors, related to an evolving back-arc basin. The chemical data in combination with the specific sediment association (wackes, shales, Fe-shales and minor litharenites) are characteristic for turbidity currents deposits along tectonically active region. They are also commonly associated with calcareous clays (marbles), commonly observed in the evolution of basins with slope and shelf derived carbonate turbidites. The amphibolites members are probably derived from lava-flows synchronous with the sedimentation during the basin evolution. The basin was controlled by a continental island arc possible evolving to a back-arc setting, as indicated for the mixed nature of the inferred source. The metasedimentary sequence from the Cuesta de La Chilca have petrographic, structural and strong chemical similarities, building a north-south striking belt from the north of the Sierra de Aconquija and to the south along the Sierra de Ancasti (La Majada area). The observed similarities allow to present this portion of the Eastern Sierras Pampeanas as a crustal block that records the sedimentary sequences developed along the geodynamic context of the southwestern margin of Gondwana during the Neoproterozoic and Early Palaeozoic. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{LopezAltenbergerBellosetal.2019, author = {Lopez, Jose P. and Altenberger, Uwe and Bellos, Laura I. and G{\"u}nter, Christina}, title = {The Cumbres Calchaquies Range (NW-Argentina)}, series = {Journal of South American earth sciences}, volume = {93}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2019.03.016}, pages = {480 -- 494}, year = {2019}, abstract = {The Cumbres Calchaquies Range forms part of the Famatinian metamorphic basement of the Eastern Sierras Pampeanas. The sedimentary protoliths of the metamorphic sequence were deposited in a marine basin alongside the western margin of Gondwana during the Neoproterozoic. New petrologic, geochemical and thermobarometric data give insight into the evolution of the sedimentary basin, its sediment source area, its later metamorphic overprint and its regional relationship to other parts of the Famatinian basement. The metamorphic series studied here consists of banded schists and gneisses and rare calcsilcate-rocks and migmatites that have been reworked by mid-to deep-crustal metamorphic and tectonic processes. The bulk rock compositions indicate shale, wacke, marl and litharenitic protoliths. The metamorphosed elastic sediments have major and trace element compositions indicating a continental granitoid-dominated source area with low sediment recycling. Low SiO2/Al2O3 ratios suggest a relatively low maturity of the sedimentary protoliths. Therefore, the Cumbres Calchaquies section represents a sequence of turbidity currents with progressive shallowing of the depositional environment, as indicated by quartz- and carbonate-rich sediments. The overall data are consistent with the geodynamic environment of a basin adjacent to a continental magmatic arc as the most probable scenario. Whereas the sedimentary protoliths of the metamorphic basement in the Sierra de Ancasti and Sierra de Aconquija, located ca 100-300 km south of the study area are interpreted as originating in an evolving back-arc basin, our results from the Cumbres Calchaquies region indicate a sedimentary source in a felsic continental arc with no significant influx of basic rocks. The Famatinian metamorphic evolution of the Cumbres Calchaquies rocks is of typical Barrow-type, culminating in partial melting of the metasediments. Conventional thermobarometry combined with thermodynamic models (pseudosections) reveal a prograde evolution reaching peak conditions of ca 665 degrees C/6.1 Kbar. This implies a geothermal gradient of ca 35 degrees C/km, which is slightly higher than the average for continental crust and suggests a period of crustal thinning, as known from back-arc basins, or additional heat supply by voluminous intrusions.}, language = {en} } @article{BalischewskiBhattacharyyaSperlichetal.2022, author = {Balischewski, Christian and Bhattacharyya, Biswajit and Sperlich, Eric and G{\"u}nter, Christina and Beqiraj, Alkit and Klamroth, Tillmann and Behrens, Karsten and Mies, Stefan and Kelling, Alexandra and Lubahn, Susanne and Holtzheimer, Lea and Nitschke, Anne and Taubert, Andreas}, title = {Tetrahalidometallate(II) ionic liquids with more than one metal}, series = {Chemistry - a European journal}, volume = {28}, journal = {Chemistry - a European journal}, number = {64}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-3765}, doi = {10.1002/chem.202201068}, pages = {13}, year = {2022}, abstract = {Fifteen N-butylpyridinium salts - five monometallic [C4Py](2)[MBr4] and ten bimetallic [C4Py](2)[(M0.5M0.5Br4)-M-a-Br-b] (M=Co, Cu, Mn, Ni, Zn) - were synthesized, and their structures and thermal and electrochemical properties were studied. All the compounds are ionic liquids (ILs) with melting points between 64 and 101 degrees C. Powder and single-crystal X-ray diffraction show that all ILs are isostructural. The electrochemical stability windows of the ILs are between 2 and 3 V. The conductivities at room temperature are between 10(-5) and 10(-6) S cm(-1). At elevated temperatures, the conductivities reach up to 10(-4) S cm(-1) at 70 degrees C. The structures and properties of the current bromide-based ILs were also compared with those of previous examples using chloride ligands, which illustrated differences and similarities between the two groups of ILs.}, language = {en} } @article{AltenbergerCisternaGuenteretal.2021, author = {Altenberger, Uwe and Cisterna, Clara and G{\"u}nter, Christina and Guti{\´e}rrez, Adolfo Antonio and Rosales, J.}, title = {Tectono-metamorphic evolution of the proto-Andean margin of Gondwana}, series = {Journal of South American earth sciences}, volume = {110}, journal = {Journal of South American earth sciences}, publisher = {Elsevier}, address = {Oxford}, issn = {0895-9811}, doi = {10.1016/j.jsames.2021.103305}, pages = {23}, year = {2021}, abstract = {The present work gives a detailed analysis of the metamorphic and structural evolution of the back-arc portion of the Famatinian Orogen exposed in the southern Sierra de Aconquija (Cuesta de La Chilca segment) in the Sierras Pampeanas Orientales (Eastern Pampean Sierras). The Pampeanas Orientales include from north to south the Aconquija, Ambato and Ancasti mountains. They are mainly composed of middle to high grade metasedimentary units and magmatic rocks. At the south end of the Sierra de Aconquija, along an east to west segment extending over nearly 10 km (Cuesta de La Chilca), large volumes of metasedimentary rocks crop out. The eastern metasediments were defined as members of the El Portezuelo Metamorphic-Igneous Complex (EPMIC) or Eastern block and the western ones relate to the Quebrada del Molle Metamorphic Complex (QMMC) or Western block. The two blocks are divided by the La Chilca Shear Zone, which is reactivated as the Rio Chanarito fault. The EPMIC, forming the hanging wall, is composed of schists, gneisses and rare amphibolites, calc- silicate schists, marbles and migmatites. The rocks underwent multiple episodes of deformation and a late high strain-rate episode with gradually increasing mylonitization to the west. Metamorphism progrades from a M-1 phase to the peak M-3, characterized by the reactions: Qtz + Pl + Bt +/- Ms -> Grt + Bt(2) + Pl(2) +/- Sil +/- Kfs, Qtz + Bt + Sil -> Crd + Kfs and Qtz + Grt + Sil -> Crd. The M-3 assemblage is coeval with the dominant foliation related to a third deformational phase (D-3). The QMMC, forming the foot wall, is made up of fine-grained banded quartz - biotite schists with quartz veins and quartz-feldspar-rich pegmatites. To the east, schists are also overprinted by mylonitization. The M-3 peak assemblage is quartz + biotite + plagioclase +/- garnet +/- sillimanite +/- muscovite +/- ilmenite +/- magnetite +/- apatite. The studied segment suffered multiphase deformation and metamorphism. Some of these phases can be correlated between both blocks. D-1 is locally preserved in scarce outcrops in the EPMIC but is the dominant in the QMMC, where S-1 is nearly parallel to S-0. In the EPMIC, D-2 is represented by the S-2 foliation, related to the F-2 folding that overprints S-1, with dominant strike NNW - SSE and high angles dip to the E. D-3 in the EPMIC have F-3 folds with axis oblique to S-2; the S-3 foliation has striking NW - SE dipping steeply to the E or W and develops interference patterns. In the QMMC, S-2 (D-2) is a discontinuous cleavage oblique to S-1 and transposed by S-3 (D-3), subparallel to S-1. Such structures in the QMMC developed at subsolidus conditions and could be correlated to those of the EPMIC, which formed under higher P-T conditions. The penetrative deformation D-2 in the EPMIC occurred during a prograde path with syntectonic growth of garnet reaching P-T conditions of 640 degrees C and 0.54 GPa in the EPMIC. This stage was followed by a penetrative deformation D-3 with syn-kinematic growth of garnet, cordierite and plagioclase. Peak P-T conditions calculated for M-3 are 710 degrees C and 0.60 GPa, preserved in the western part of the EPMIC, west of the unnamed fault. The schists from the QMMC suffered the early low grade M-1 metamorphism with minimum PT conditions of ca 400 degrees C and 0.35 GPa, comparable to the fine schists (M-1) outcropping to the east. The D-2 deformation is associated with the prograde M-2 metamorphism. The penetrative D-3 stage is related to a medium grade metamorphism M-3, with peak conditions at ca 590 degrees C and 0.55 GPa. The superimposed stages of deformation and metamorphism reaching high P-T conditions followed by isothermal decompression, defining a clockwise orogenic P-T path. During the Lower Paleozoic, folds were superimposed and recrystallization as well as partial melting at peak conditions occurred. Similar characteristics were described from the basement from other Famatinian-dominated locations of the Sierra de Aconquija and other ranges of the Sierras Pampeanas Orientales.}, language = {en} } @article{GoebelXieNeumannetal.2012, author = {Goebel, Ronald and Xie, Zai-Lai and Neumann, Mike and G{\"u}nter, Christina and Loebbicke, Ruben and Kubo, Shiori and Titirici, Maria-Magdalena and Giordano, Cristina and Taubert, Andreas}, title = {Synthesis of mesoporous carbon/iron carbide hybrids with unusually high surface areas from the ionic liquid precursor [Bmim][FeCl4]}, series = {CrystEngComm}, volume = {14}, journal = {CrystEngComm}, number = {15}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1466-8033}, doi = {10.1039/c2ce25064k}, pages = {4946 -- 4951}, year = {2012}, abstract = {Mesoporous carbon/iron carbide hybrid materials with surface areas reaching 800 m(2) g(-1) were synthesized via an exotemplating route using monolithic mesoporous silica as template and the ionic liquid 1-butyl-3-methylimidazolium tetrachloridoferrate(III) [Bmim][FeCl4] as carbon and iron source. After heat treatment (750 degrees C under argon) of the [Bmim][FeCl4] precursor confined within the silica matrix, the silica exotemplate was removed with HF leaving the mesoporous C/Fe3C hybrid behind. The surface areas and the pore sizes depend on the exotemplate and the surface areas a significantly larger than any other surface area reported for C/Fe3C hybrid materials so far. The approach is thus a prototype for the synthesis of high-surface area iron carbide-based hybrid materials with potential application in catalysis.}, language = {en} }