TY - JOUR A1 - Monks, M.-J. A1 - Würth, Christian A1 - Kemnitz, Erhard A1 - Resch-Genger, Ute T1 - Dopant ion concentration-dependent upconversion luminescence of cubic SrF2:Yb3+, Er3+ nanocrystals prepared by a fluorolytic sol–gel method N2 - A fluorolytic sol–gel method was used for the fast and simple synthesis of small cubic-phase SrF2:Yb3+, Er3+ upconversion (UC) nanocrystals (UCNC) of different composition at room temperature. Systematic studies of the crystal phase and particle size of this Yb3+,Er3+-concentration series as well as excitation power density (P)-dependent UC luminescence (UCL) spectra, UCL quantum yields (ΦUCL), and UCL decay kinetics yielded maximum UCL performance for doping amounts of Yb3+ of 13.5% and Er3+ of 1.3% in the studied doping and P-range (30–400 W cm−2). Furthermore, ΦUCL were determined to be similar to popular β-NaYF4:Yb3+,Er3+. The relative spectral UCL distributions revealed that all UCNC show a strong red emission in the studied doping and P-range (30–400 W cm−2) and suggest that the UCL quenching pathway for unshelled cubic-phase SrF2:Yb3+,Er3+ UCNC differs from the commonly accepted population and depopulation pathways of β-NaYF4:Yb3+,Er3+ UCNC. In SrF2:Yb3+,Er3+ UCNC the 4S3/2 → 4I13/2 transition exhibits a notably stronger sensitivity towards P and reveals increasing values for decreasing Yb3+–Yb3+ distances while the 4I9/2 → 4I15/2 transition is significantly less affected by P and energy migration facilitated UCL quenching. These results emphasize the complexity of the UC processes and the decisive role of the crystal phase and symmetry of the host lattice on the operative UCL quenching mechanism in addition to surface effects. Moreover, the room temperature UCNC synthesis enabled a systematic investigation of the influence of the calcination temperature on the crystal phase of powder-UCNC and the associated UCL properties. Calcination studies of solid UCNC of optimized doping concentration in the temperature range of 175 °C and 800 °C showed the beneficial influence of temperature- induced healing of crystal defects on UCL and the onset of a phase separation connected with the oxygenation of the lanthanide ions at elevated temperature. This further emphasizes the sensitivity of the UC process to the crystal phase and quality of the host matrix. KW - Upconversion nanoparticle KW - Lanthanide KW - Photophysics KW - Synthesis PY - 2022 U6 - https://doi.org/10.1039/d2nr02337g SP - 1 EP - 10 PB - Royal Society of Chemistry AN - OPUS4-55364 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübert, Thomas A1 - Kemnitz, Erhard A1 - Usmani, Shirin A1 - Schlischka, Jörg A1 - Klutzny, Kerstin A1 - de Laval, Yvonne A1 - Plarre, Rüdiger A1 - Krahl, Thoralf A1 - Stephan, Ina T1 - Wood protection with nanoparticles: MgF2 and CaF2 N2 - The potential of alkaline earth metal Fluoride nanoparticles was tested for protection of wood against fungi and termites. These nanoparticles are ideal for wood protection. T2 - School of Analytical Sciences Poster Session CY - Berlin, Germany DA - 06.12.2016 KW - Wood preservation KW - Fluorides KW - Nanoparticles PY - 2016 AN - OPUS4-39141 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Scholz, Gudrun A1 - Emmerling, Franziska A1 - Kemnitz, Erhard T1 - Ca-Tetrafluorophthalate and Sr-isophthalate: mechanochemical synthesis and characterization in comparison with other Ca-and Sr-coordination polymers N2 - New Ca- and Sr-based coordination polymers (CPs) were mechanochemically synthesized by milling metal hydroxide samples (M = Ca, Sr) with tetrafluorophthalic acid (H2oBDC-F4) and isophthalic acid (H2mBDC). [Ca(oBDC-F4)(H2O)2] (1) exhibits a small surface area which is slightly increased after removing the crystal water. On the other hand, the hydrated sample of the nonfluorinated [Sr(mBDC)(H2O)3.4] (2) reveals a small BET surface area which remains unchanged even after the release of crystal water via thermal treatment. The new compounds 1 and 2 are similar to their Sr- and Ca-analogs, respectively. These findings are confirmed by thermal analysis, MAS NMR, and ATR-IR measurements, in addition to the Le Bail refinements for the measured powder X-ray data of 1 and 2. Ca- and Sr-CPs based on perfluorinated dicarboxylic systems and their nonfluorinated analogs diverse in structural and chemical properties depending on the geometries of the organic linkers and the presence of fluorine atoms. The fluorinations of organic ligands lead to the formation of fluorinated CPs with higher dimensionalities compared to their nonfluorinated counterparts. Conversely, the thermal stabilities of the latter are higher than those of the fluorinated CPs. KW - Mechanochemistry PY - 2018 U6 - https://doi.org/10.1039/c8dt00695d SN - 1477-9226 SN - 1477-9234 VL - 47 IS - 16 SP - 5743 EP - 5754 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-44696 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Scholz, Gudrun A1 - Emmerling, Franziska A1 - Kemnitz, Erhard T1 - Barium coordination polymers based on fluorinated and fluorine-free benzene-dicarboxylates: Mechanochemical synthesis and spectroscopic characterization N2 - A series of new Ba-based coordination polymers (CPs) were mechanochemically synthesized by milling Ba-hydroxide samples with perfluorinated and fluorine-free benzene-dicarboxylic acids, including tetrafluoroisophthalic acid (H2mBDC-F4), tetrafluorophthalic acid (H2oBDC-F4), isophthalic acid (H2mBDC) and phthalic acid (H2oBDC). The new fluorinated CPs: [Ba(mBDC-F4)$0.5H2O] (1) and [Ba(oBDC-F4)·1.5H2O] (2) are compared to their nonfluorinated counterparts: [Ba(mBDC)·2.5H2O] (3), and [Ba(oBDC)·1H2O] (4). These materials are thoroughly characterized using powder X-ray diffraction. The products obtained by milling are all hydrated but vary in their water contents. Compositions and local structures are investigated by elemental analysis, thermal analysis, MAS NMR and attenuated total reflectioninfrared spectroscopy. These materials exhibit high thermal stabilities but small surface areas that remain unchanged even after thermal treatments. KW - Mechanochemical synthesis KW - Barium KW - Fluorine KW - Coordination polymers KW - PXRD KW - MAS NMR spectroscopy PY - 2018 UR - https://www.sciencedirect.com/science/article/pii/S1293255817310798 U6 - https://doi.org/10.1016/j.solidstatesciences.2018.03.013 SN - 1293-2558 SN - 1873-3085 VL - 79 SP - 99 EP - 108 PB - Elsevier AN - OPUS4-44880 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Prinz, Carsten A1 - Scholz, Gudrun A1 - Kemnitz, Erhard A1 - Emmerling, Franziska T1 - Ca-, Sr-, and Ba-Coordination polymers based on anthranilic acid via mechanochemistry N2 - Ca-, Sr-, and Ba-Based coordination polymers (CPs) were prepared mechanochemically by milling metal-hydroxide samples with anthranilic acid (oABAH). {[Ca(oABA)2(H2O)3]}n consists of one-dimensional polymeric chains that are further connected by a hydrogen-bonding network. {[Sr(oABA)2(H2O)2]·H2O}n is a one-dimensional CP in which water molecules bridge Sr2+ ions and increase the dimensionality by building an extended network. {[Ba(oABA)2(H2O)]}n crystallizes as a two-dimensional CP comprising one bridging water molecule. The cation radii influence the inorganic connectivity and dimensionality of the resulting crystal structures. The crystal structures were refined from powder X-ray diffraction data using the Rietveld method. The local coordination environments were studied via extended X-ray absorption fine structure (EXAFS) measurements. The compounds were further characterized using comprehensive analytical methods such as elemental analysis, thermal analysis, MAS NMR, imaging, and dynamic vapor sorption (DVS) measurements. Compounds 1, 2, and 3 exhibit small surface areas which decrease further after thermal annealing experiments. All compounds exhibit a phase transformation upon heating, which is only reversible in 3. KW - Mechanochemistry KW - XRD PY - 2019 U6 - https://doi.org/10.1039/c9dt00991d SN - 1477-9226 SN - 1477-9234 VL - 48 IS - 19 SP - 6513 EP - 6521 PB - Royal Society of Chemistry AN - OPUS4-48014 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -