TY - JOUR A1 - König, R. A1 - Scholz, G. A1 - Pawlik, Alf A1 - Jäger, Christian A1 - van Rossumm, B. A1 - Oschkinat, H. A1 - Kemnitz, E. T1 - Crystalline Aluminium Hydroxy Fluorides: Structural Insights Obtained by High Field Solid State NMR and Trend Analyses JF - The journal of physical chemistry / C N2 - A series of crystalline aluminum hydroxy fluorides in cubic pyrochlore structure AlFx(OH)3-x·H2O with variable F-content x were investigated by solid-state NMR by applying different magnetic fields up to 21.1 T. Distinguishable octahedral species AlFx(OH)6-x (x = 1-6) were identified in the crystalline aluminum hydroxy fluorides. The subsequent analysis of the highfield 27Al MAS NMR data allows the derivation of the trend analysis graphs giving correlations between the 27Al chemical shifts and the quadrupolar frequencies and the F-content x in AlFx(OH)6-x. Clear trends were obtained for both, which are, along with the 19F MAS chemical-shift trend analysis presented earlier, valuable tools for the interpretation of MAS NMR spectra of amorphous AlFx(OX)3-x compounds (X = H, alkyl). Following the dehydration of the pyrochlores by solid-state NMR eventually reveals a remarkable influence of the incorporated solvent molecules (H2O) on the 19F chemical shift. On that basis, a new chemical-shift trend analysis for 19F chemical shifts in correlation with x in AlFx(OH)6-x units for proton-poor substances (in the Al, F, O, H system) was determined. By using this correlation, high-surface AlF3 has a mean bulk Al:F ratio similar to that found for ACF, namely, AlF2.8(O/OH)0.2. KW - Aluminium-27 KW - Crystalline aluminium hydroxy fluorides KW - Chemical shift trend analysis KW - High field solid state NMR KW - Quadrupolar nuclei PY - 2008 DO - https://doi.org/10.1021/jp804662f SN - 1932-7447 SN - 1089-5639 VL - 112 IS - 40 SP - 15708 EP - 15720 PB - Soc. CY - Washington, DC AN - OPUS4-18365 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Hannes A1 - Kemnitz, E. A1 - Hertwig, Andreas A1 - Beck, Uwe T1 - Moderate temperature sol-gel deposition of magnesium fluoride films for optical UV-applications: A study on homogeneity using spectroscopic ellipsometry JF - Physica status solidi A N2 - Thin films of MgF2 have been deposited on silicon wafers in optical quality with a novel sol-gel deposition process at temperatures as low as 100 °C. The properties of the fluoride layers are compared to bulk MgF2 with respect to the optical constants. By employing spectroscopic mapping ellipsometry, the uniformity of the thickness of fluoride layers is confirmed to be within acceptable limits for optical applications. The optical constants are close to the bulk data. High-quality low-index films of suitable and homogeneous thickness have already been produced on a laboratory scale. KW - 78.20.-e KW - 78.66.Li KW - 78.68.+m KW - 81.20.Fw PY - 2008 DO - https://doi.org/10.1002/pssa.200777856 SN - 1862-6300 SN - 0031-8965 VL - 205 IS - 4 SP - 821 EP - 824 PB - Wiley-VCH CY - Berlin AN - OPUS4-17330 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ünveren, Ercan A1 - Kemnitz, E. A1 - Oran, Umut A1 - Unger, Wolfgang T1 - Static TOF-SIMS Surface Analysis of a CCl2F2 Activated Chromia Catalyst Used for a Cl/F Exchange Reaction JF - The journal of physical chemistry / B N2 - Static TOF-SIMS results strongly underpin earlier conclusions from ESCA, XANES, and tracer studies that the accumulation of fluorine and chlorine at the surface of chromia by a heterogeneous reaction with a chlorofluorocarbon compound results in the formation of mixed chromium oxide halide species and not in the nucleation of CrCl3 and/or CrF3 phases. KW - Oberflächenanalytik KW - Katalyse PY - 2004 DO - https://doi.org/10.1021/jp046773h SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 108 SP - 15454 EP - 15456 PB - Soc. CY - Washington, DC AN - OPUS4-4718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholz, G. A1 - Emmerling, Franziska A1 - Dreger, M. A1 - Kemnitz, E. T1 - Mechanochemical synthesis and characterization of hydrated and dehydrated crystalline strontium terephtalates JF - Zeitschrift für anorganische und allgemeine Chemie = Journal of inorganic and general chemistry N2 - A successful mechanochemical synthesis of strontium terephthalate trihydrate is described for the first time. The dehydration of Sr(C8H4O4)·3H2O occurs at about 100 °C and results in a well-defined strontium terephtalate, Sr(C8H4O4), thermally stable up to 550 °C. Both compounds are not described so far in the literature. Their structures were solved by ab initio structure determination and subsequent Rietveld refinement of the powder diffraction data. Further methods like DTA-TG, MAS NMR and FT-IR spectroscopy, and BET measurements were used to characterize these compounds. KW - Mechanochemical synthesis KW - Ab initio structure determination KW - MAS NMR spectroscopy KW - Strontium PY - 2013 DO - https://doi.org/10.1002/zaac.201200550 SN - 0044-2313 SN - 1521-3749 SN - 0372-7874 SN - 0863-1786 SN - 0863-1778 VL - 639 IS - 5 SP - 689 EP - 693 PB - Wiley-VCH CY - Weinheim AN - OPUS4-29117 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - König, R. A1 - Scholz, G. A1 - Pawlik, Alf A1 - Jäger, Christian A1 - Rossum, B. van A1 - Kemnitz, E. T1 - Identification of AIFx(OR)y species in strongly disordered aluminium isopropoxide fluoride solids: a field-dependent MAS NMR study JF - The journal of physical chemistry / C KW - Ultra high-field MAS NMR (21.1T) KW - 27 Al MAS solid state NMR KW - Fluoride xerogels KW - Sol-gel process KW - Fluorolysis KW - Quadrupolar nuclei PY - 2009 DO - https://doi.org/10.1021/jp9066795 SN - 1932-7447 SN - 1089-5639 VL - 113 IS - 35 SP - 15576 EP - 15585 PB - Soc. CY - Washington, DC AN - OPUS4-20461 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pawlik, Alf A1 - König, R. A1 - Scholz, G. A1 - Kemnitz, E. A1 - Brunklaus, G. A1 - Bertmer, M. A1 - Jäger, Christian T1 - Access to local structures of HS-AIF3 and its precursor determined by high-resolution solid-state NMR JF - The journal of physical chemistry / C KW - Aluminium fluoride KW - 27Al NMR KW - MQMAS KW - Amorphous materials KW - Catalysts PY - 2009 DO - https://doi.org/10.1021/jp904626k SN - 1932-7447 SN - 1089-5639 VL - 113 IS - 38 SP - 16674 EP - 16680 PB - Soc. CY - Washington, DC AN - OPUS4-20463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kemnitz, E. A1 - Krüger, Hannes A1 - Beck, Uwe A1 - Hertwig, Andreas T1 - Nano metal fluorides: Small size but great properties T2 - Inorganic Fluorides for Chemistry and Environment, Optics and Electronics T2 - Inorganic Fluorides for Chemistry and Environment, Optics and Electronics CY - Bordeaux, France DA - 2010-04-14 PY - 2010 AN - OPUS4-20868 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - König, R. A1 - Scholz, G. A1 - Scheurell, K. A1 - Heidemann, D. A1 - Buchem, I. A1 - Unger, Wolfgang A1 - Kemnitz, E. T1 - Spectroscopic characterization of crystalline AIF3 phases JF - Journal of fluorine chemistry N2 - A comprehensive spectroscopic characterization of all known crystalline AlF3 phases (α-, β-, η-, κ-, θ-AlF3) is presented for the first time in this study. Beside their X-ray diffraction powder patterns, which were already published in the literature, 27Al and 19F MAS NMR, FT IR and XPS spectroscopic techniques were applied for all phases in a consistent manner. For all phases prepared the utilization of 27Al satellite transition (SATRAS) NMR allowed to determine the quadrupolar parameters of the aluminium sites including their distributions. In addition, η-AlF3 was isolated with high phase purity and characterized following a new preparation path different from those known so far in the literature. KW - Crystalline aluminium fluorides KW - Solid state NMR KW - FT IR KW - XPS PY - 2010 DO - https://doi.org/10.1016/j.jfluchem.2009.10.015 SN - 0022-1139 SN - 1873-3328 VL - 131 IS - 1 SP - 91 EP - 97 PB - Elsevier CY - Amsterdam AN - OPUS4-20991 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zänker, Steffen A1 - Scholz, Gudrun A1 - Krahl, Thoralf A1 - Prinz, Carsten A1 - Emmerling, Franziska A1 - Kemnitz, E. T1 - Luminescent properties of Eu3+/Tb3+ doped fluorine containing coordination polymers JF - Solid State Sciences N2 - Lanthanides doped coordination polymers (CPs) with different binding motifs were synthesized to investigate the influence of the different fluorine positions in the structure on the decay time τ of the excited states. Fluorine can be integrated into the network mechanochemically via a fluorinated organic linker, here barium tetrafluoroterephthalate Ba(p-BDC-F4)2 or directly via a metal-fluorine bond (barium terephthalate fluoride BaF(p-BDC)0.5). The CP with a metal-fluorine bond shows the highest lifetime of the excited states of lanthanides (Eu3+, Tb3+ or Eu3+& Tb3+). The excitation of the lanthanides can be performed directly via the excitation wavelength typical for lanthanides and via the excitation wavelength of the linker. This enabled the simultaneous excitation of Eu3+ and Tb3+ in one CP. In the emission spectra (λem = 393 nm) of the mixed doped CPs (Eu3+ and Tb3+) the bands of both lanthanides can be observed. The integration into the crystal lattice and the homogeneous distribution of the lanthanides in the CPs is shown by X-ray diffraction, TEM, STEM-EDS measurements and the long decay times. KW - Alkaline earth metal coordination polymers KW - Fluorine coordination polymers KW - Lanthanides doped coordination polymers KW - Luminescence PY - 2021 DO - https://doi.org/10.1016/j.solidstatesciences.2021.106614 VL - 117 SP - 106614 PB - Elsevier Masson SAS AN - OPUS4-52559 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Agirrezabal-Telleria, Iker A1 - Guo, Y. A1 - Hemmann, Felix A1 - Arias, P. L. A1 - Kemnitz, E. T1 - Dehydration of xylose and glucose to furan derivatives using bifunctional partially hydroxylated MgF2 catalysts and N2-stripping JF - Catalysis science & technology N2 - The current furfural production yield is low due to the use of non-selective homogeneous catalysts and expensive separation. In this work, partially hydroxylated MgF2 catalysts, synthesized using different water contents, were screened during xylose dehydration in water–toluene at 160 °C. The different Lewis/Brønsted ratios on the MgF2 catalysts showed that under-coordinated Mg can isomerize xylose to xylulose, whilst the surface OH-groups were responsible for the dehydration reactions. The presence of glucose as a co-carbohydrate reduced the furfural selectivity from 86 to 81%, whilst it also led to high 5-hydroxymethylfurfural selectivity. The tests catalyzed by MgF2 in combination with simultaneous N2-stripping showed that a furfural selectivity of 87% could be achieved using low xylose loadings. Moreover, the catalysts regenerated by H2O2 showed high activity during the dehydration tests in water–toluene at 160 °C. KW - Bifunctional MgF2 KW - Lewis/Bronsted KW - Carbohydrates KW - Furan derivatives KW - N2-stripping PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-305441 DO - https://doi.org/10.1039/c4cy00129j SN - 2044-4753 SN - 2044-4761 VL - 4 IS - 5 SP - 1357 EP - 1368 PB - RSC Publ. CY - Cambridge AN - OPUS4-30544 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -