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231223s2008 xx |||||o 00| ||eng c |
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|a 10.1021/la800768v
|2 doi
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|a pubmed25n0602.xml
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|e rakwb
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|a eng
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| 100 |
1 |
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|a Leiterer, Jork
|e verfasserin
|4 aut
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| 245 |
1 |
0 |
|a Tracing coffee tabletop traces
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1 |
|c 2008
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|a Text
|b txt
|2 rdacontent
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|a ƒaComputermedien
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|a ƒa Online-Ressource
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|a Date Completed 08.09.2008
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|a Date Revised 21.11.2013
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|a published: Print-Electronic
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|a Citation Status MEDLINE
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|a 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-1 H-purine-2,6(3 H,7 H)-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 muSpot-beamline, the fine structure of different caffeine needles can be distinguished. Unexpectedly, both crystal modifications (alpha- and beta-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 alpha-caffeine and does not indicate the formation of the room temperature polymorph beta-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
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|a Journal Article
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|a Coffee
|2 NLM
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|a Solutions
|2 NLM
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|a Caffeine
|2 NLM
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|a 3G6A5W338E
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| 700 |
1 |
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|a Emmerling, Franziska
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Panne, Ulrich
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Christen, Wolfgang
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Rademann, Klaus
|e verfasserin
|4 aut
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| 773 |
0 |
8 |
|i Enthalten in
|t Langmuir : the ACS journal of surfaces and colloids
|d 1991
|g 24(2008), 15 vom: 05. Aug., Seite 7970-8
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|x 0743-7463
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|g year:2008
|g number:15
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|g month:08
|g pages:7970-8
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|u http://dx.doi.org/10.1021/la800768v
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