TY - CONF A1 - Leiterer, Jork A1 - Emmerling, Franziska A1 - Radnik, J. A1 - Armbruster, U. A1 - Bentrup, U. A1 - Martin, A. A1 - Brückner, A. T1 - In Droplet Monitoring of Catalytic Precursors Preparation T2 - 27 th Bessy User's Meeting CY - Berlin, Germany DA - 2008-12-06 PY - 2008 AN - OPUS4-18516 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leiterer, Jork A1 - Emmerling, Franziska A1 - Wolf, S. E. A1 - Tremel, W. T1 - Ovalbumin Extends Dramatically the Lifespan of a Homogenous Amorphous CaCO3 Precursor - Amorphous Precursors During Formation of Calcium Carbonate Monitored via Contact-free in situ Synchrotron X-Ray Scattering Techniques T2 - Berliner Elektronenspeicherring-Gesellschaft für Synchrotonstrahlung m.b.H. (BESSY) CY - Berlin, Germany DA - 2008-12-06 PY - 2008 AN - OPUS4-18522 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leiterer, Jork A1 - Emmerling, Franziska A1 - Panne, Ulrich A1 - Christen, W. A1 - Rademann, K. T1 - In situ studies of caffeine polymorph crystal formation by droplet evaporation T2 - Tag der Chemie und Innovationskongress Chemie und Biotechnologie CY - Berlin, Germany DA - 2008-04-23 PY - 2008 AN - OPUS4-17851 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leiterer, Jork A1 - Emmerling, Franziska A1 - Panne, Ulrich A1 - Christen, W. A1 - Rademann, K. T1 - Tracing Coffee Tabletop Traces N2 - Crystallization processes under different conditions are of fundamental interest in chemistry, pharmacy, and medicine. Therefore, we have studied the formation of micro- and nanosized crystals using water-caffeine (1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione) solutions under ambient conditions as a relevant model system. When droplets of an aqueous caffeine solution evaporate and eventually dry on surfaces (glass, polystyrene, and polyester), stable “coffee tabletop” rings with a perimeter of typically 3 mm are formed after 20 to 50 min. Using a micro focus X-ray beam available at the BESSY µSpot-beamline, the fine structure of different caffeine needles can be distinguished. Unexpectedly, both crystal modifications (α- and β-caffeine) are present, but locally separated in these rings. Furthermore, AFM studies reveal the presence of even smaller particles on a nanometer length scale. To eliminate influences of surface irregularities from the crystallization process, acoustic levitation of liquid samples was employed. Such levitated droplets are trapped in a stable position and only surrounded by air. The solvent in an ultrasonically levitated drop evaporates completely, and the resulting crystallization of caffeine was followed in situ by synchrotron X-ray diffraction. In this case, the diffraction pattern is in accordance with pure α-caffeine and does not indicate the formation of the room temperature polymorph β-caffeine. Hence, our investigations open new vistas that may lead to a controlled formation of cocrystals and novel polymorphs of micro- and nanocrystalline materials, which are of relevance for fundamental studies as well as for pharmaceutical and medical applications. KW - Polymorphism KW - Crystallization KW - Acoustic levitation KW - Evaporation of droplets KW - µSpot KW - Micro spot KW - Synchrotron radiation PY - 2008 DO - https://doi.org/10.1021/la800768v SN - 0743-7463 SN - 1520-5827 VL - 24 IS - 15 SP - 7970 EP - 7978 PB - American Chemical Society CY - Washington, DC AN - OPUS4-17818 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Leiterer, Jork A1 - Emmerling, Franziska A1 - Panne, Ulrich A1 - Rademann, K. A1 - Christen, W. T1 - In situ Studies of Caffeine Polymorph Crystal Formation by Droplet Evaporation T2 - 27h Bessy Users´ Meeting CY - Berlin, Germany DA - 2008-12-06 PY - 2008 AN - OPUS4-18520 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leiterer, Jork A1 - Grabolle, Markus A1 - Rurack, Knut A1 - Resch-Genger, Ute A1 - Ziegler, J. A1 - Nann, T. A1 - Panne, Ulrich T1 - Acoustically Levitated Droplets - A Contactless Sampling Method for Fluorescence Studies N2 - Acoustic levitation is used as a newtool to study concentration-dependent processes influorescence spectroscopy. With this technique, small amounts of liquid and solid samples can be measured without the need for sample supports or containers, which often limits signal acquisition and can even alter sample properties due to interactions with the support material. We demonstrate that, because of the small sample volume, fluorescence measurements at high concentrations of an organic dye are possible without the limitation of inner-filter effects, which hamper such experiments in conventional, cuvette-based measurements. Furthermore, we show that acoustic levitation of liquid samples provides an experimentally simple way to study distance-dependent fluorescence modulations in semiconductor nanocrystals. The evaporation of the solvent during levitation leads to a continuous increase of solute concentration and can easily be monitored by laser-induced fluorescence. KW - Acoustic levitation KW - Dyes KW - Energy transfer KW - Fluorescence KW - Quantum dots KW - Nanocrystals KW - Ultrasonic trap PY - 2008 DO - https://doi.org/10.1196/annals.1430.039 SN - 0077-8923 SN - 1749-6632 SN - 0094-8500 VL - 1130 SP - 78 EP - 84 PB - New York Academy of Sciences CY - New York, NY AN - OPUS4-17658 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -