TY - JOUR A1 - Nguyen, Thi Yen A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Direct evidence of polyamorphism in paracetamol N2 - While polymorphism is a common phenomenon in the crystallization processes of organic compounds, polyamorphism has gained importance only recently. Using sophisticated sample environments and applying in situ scattering methods and vibrational spectroscopy, the complete crystallization process of organic compounds from solution can be traced and characterized. Diffuse scattering from amorphous intermediates can be investigated by analyzing the atomic pair distribution function (PDF) to gain further insights into molecular pre-orientation. The crystallization behavior of paracetamol was studied exemplarily under defined, surface-free conditions. Based on the choice of the solvent, the formation of different polymorphs is promoted. The thermodynamically stable form I and the metastable orthorhombic form II could be isolated in pure form directly from solution. For both polymorphs, the crystallization from solution proceeds via a distinct amorphous precursor phase. PDF analyses of these different amorphous states indicate a specific pre-orientation of the analyte molecules introduced by the solvent. The resulting crystalline polymorph is already imprinted in these proto-crystalline precursors. Direct experimental evidence for the polyamorphism of paracetamol is provided. PY - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-351366 SN - 1466-8033 VL - 17 IS - 47 SP - 9029 EP - 9036 PB - Royal Society of Chemistry CY - London, UK AN - OPUS4-35136 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarfraz, Adnan A1 - Simo, A. A1 - Fenger, R. A1 - Christen, W. A1 - Rademann, K. A1 - Panne, Ulrich A1 - Emmerling, Franziska T1 - Morphological diversity of caffeine on surfaces: needles and hexagons N2 - A systematic crystal morphology study on the pharmaceutical model compound caffeine has been conducted on different surfaces: silicon, silver, soda lime glass, and silver subsurface ion-exchanged soda-lime silicate (SIMO) glasses. The morphology of the solid caffeine deposits has been investigated using environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Needle-shaped caffeine crystals have been observed by drop-casting and also by applying the rapid expansion of supercritical solutions (RESS) technique using supercritical carbon dioxide. The aspect ratio of the crystalline needles typically vary between 10 and 100, but have been observed as large as 500. The XRD data of the RESS products indicate unambiguously the presence of the thermodynamically most stable polymorph of caffeine known as the β-form. Under defined conditions we observe a unique, surface-mediated morphology for caffeine crystals with nearly perfect hexagonal shape. The relative fraction of the hexagons was seen to strongly increase especially when SIMO glasses were used. These hexagons have a distinct upper size limit depending on the solvent and substrate being used. The size distribution analysis of the hexagons yielded an average perimeter of typically 10 µm. The mechanism of the formation process of this new hexagonal motif is explained in terms of the spinodal dewetting of the thin film of caffeine solution on the surface. KW - Caffeine KW - Silicon KW - Silver KW - Ion exchanged soda lime silicate glass KW - ESEM KW - AFM KW - X-ray diffraction KW - RESS KW - Carbon dioxide KW - Supercritical fluids PY - 2012 U6 - https://doi.org/10.1021/cg101358q SN - 1528-7483 VL - 12 IS - 2 SP - 583 EP - 588 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-25457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Meyer, Klas A1 - Panne, Ulrich A1 - Rademann, K. A1 - Maiwald, Michael T1 - Quantitative NMR Spektroskopie unter Druck - Anwendungen an fluiden und gasförmigen technischen Mischungen N2 - Die quantitative NMR-Spektroskopie (qNMR) gewinnt in den letzten Jahren immer mehr an Bedeutung, speziell hinsichtlich der Anwendung auf komplexe Fragestellungen der analytischen Chemie. Ein großer Vorteil dieser Methode ist die Möglichkeit der Relativquantifizierung durch das „Zählen von Kernspins" in der Probe. Unter der Voraussetzung eines korrekt ausgeführten NMR-Experiments ist so der direkte Vergleich von Signalflächen im Spektrum möglich, ohne dass zuvor zwingend eine Kalibrierung notwendig ist. T2 - 8. Interdisziplinäres Doktorandenseminar CY - Berlin, Germany DA - 23.02.2014 PY - 2014 SN - 978-3-9816380-1-1 SP - 20 AN - OPUS4-32090 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heyde, M. A1 - Sturm, Heinz A1 - Geuss, Markus A1 - Ritter, C. A1 - Rademann, K. T1 - Rastersondenmikroskopie als Werkzeug der Lithographie für Nanostrukturen PY - 1999 SN - 0946-641X VL - 6 IS - 3 SP - 28 EP - 33 PB - Universität CY - Berlin AN - OPUS4-6861 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Eichelbaum, M. A1 - Rademann, K. A1 - Müller, Ralf A1 - Radtke, Martin A1 - Riesemeier, Heinrich A1 - Görner, Wolf T1 - Vom Atom zum Nanodraht: Kontrolliertes Wachstum von Edelmetall-Nanokristalliten in Kalk-Natron-Silikatglas T2 - 79. Glastechnische Tagung CY - Würzburg, Deutschland DA - 2005-05-23 KW - Glas KW - Metallnanocluster KW - Optische Eigenschaften PY - 2005 SN - 3-921089-43-3 SP - 15 Seiten PB - Deutsche Glastechnische Gesellschaft CY - Offenbach AN - OPUS4-7558 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eichelbaum, M. A1 - Rademann, K. A1 - Müller, Ralf A1 - Radtke, Martin A1 - Görner, Wolf T1 - Zur Chemie des Goldes in Silicatgläsern: Untersuchungen zum nicht-thermisch aktivierten Wachstum von Goldclustern KW - Glas KW - Goldcluster KW - Nanophotonik PY - 2005 U6 - https://doi.org/10.1002/ange.200502174 SN - 0044-8249 SN - 0932-2140 SN - 1521-3757 VL - 117 IS - 48 SP - 8118 EP - 8122 PB - Wiley-VCH CY - Weinheim AN - OPUS4-7691 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -